Definition

An atrial septal defect (ASD) is a pathological connection between the left and the right atrium. The defect may be found at different sites on the atrial septum and leads to a left-to-right shunt at the atrial level with increased pulmonary blood flow. The most common type of ASD is the ostium secundum type (ASD II), which is found at the center of the atrial septum.

Epidemiology

ASDs constitute about 10% of all congenital heart defects. Women are affected around twice as often as men. A patent foramen ovale can be found in as many as one-third of all individuals.

Pathogenesis

During embryonic development, there is a wide opening between the two atria (ostium primum). This ostium primum increasingly narrows as the septum primum develops from a cranial direction. Before it fuses at the level of the atrioventricular (AV) valves, the upper portion of the septum primum tears, resulting in the ostium secundum. The septum secundum then grows in a caudal direction from the atrial roof to the right of the septum primum at the level of the AV valves. At the overlap with the ostium secundum, a crescent-shaped slit, the foramen ovale, forms between the septa. The foramen ovale functions as a check valve that opens when the pressure comes from the right and closes when the pressure comes from the left. The fusion of the septum primum with the septum secundum results in complete separation of the atria. A patent foramen ovale is the result of incomplete fusion. Inhibited development of the septum secundum leads to an ASD II.

Classification

Various types of ASD are differentiated according to their location in the atrial septum. (Fig. 15.1):

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  Ostium secundum ASD (ASD II; 70%): ASD II is the most common form. The defect is centrally located in the region of the foramen ovale and is surrounded on all sides by remnants of the atrial septum. ASD II is rarely associated with a partial anomalous pulmonary venous connection.

  
  
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  Ostium primum ASD (ASD I; 20%): This defect is actually part of the AV canal (Chapter 15.3). The defect is located in the lower part of the atrium close to the AV valves and is almost always associated with an anomaly of the AV valves. Most common is a cleft in the anterior leaflet of the mitral valve that leads to mitral valve regurgitation.

  
  
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  Sinus venosus defect (10%): Sinus venosus defects are located at the connection of the vena cava into the right atrium and are classified as upper or lower sinus venosus defects. They are usually associated with partial anomalous pulmonary venous connections.

  
  
  
  
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    Superior sinus venosus defect: An upper sinus venosus defect is located at the connection of the superior vena cava to the atrium. The actual atrial septum is intact, but the wall between some of the right pulmonary veins and the superior vena cava is missing, so that the pulmonary venous blood passes through the superior vena cava to the right atrium. The open connection between the two atria is located near the actual confluence of the pulmonary vein (Fig. 15.2).

    
    
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    Inferior sinus venosus defect (rare): A lower sinus venosus defect is located where the inferior vena cava and the right inferior pulmonary vein connect to the atrium. This defect leads to a functional partial anomalous pulmonary venous connection.

  
  
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  Coronary sinus defect (1%): This defect is the rarest form of ASD. In this form the coronary sinus connects not only to the right atrium but also to the left atrium. It is also called “unroofed coronary sinus” as the “roof” of the coronary sinus in the region of left atrium is missing. This allows the blood from the left atrium to reach the coronary sinus and from there, the right atrium. As a result of the increased blood flow, the ostium of the coronary sinus is widened. The coronary sinus defect is almost always associated with a left persistent superior vena cava. It often occurs with a total anomalous pulmonary venous connection or heterotaxy syndromes.

  
  
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  Patent foramen ovale (PFO): A PFO can be found in almost one-third of the population. It occurs when there is incomplete fusion of the ostium primum with the ostium secundum. There is no left-to-right shunt in a PFO. The foramen ovale may open like a valve when the pressure in the right atrium exceeds the pressure of the left atrium (e.g., during Valsalva maneuver, diving, or if there is pulmonary hypertension with high right atrial pressures). In this way venous thrombi from the right atrium can pass to the left atrium and cause systemic embolism (paradoxical embolism). The risk for this seems to be higher when the atrial septum in the oval fossa is widened by an aneurysm (atrial septum aneurysm). The relationship between PFO and migraine has also been discussed, although the exact pathological mechanism is still unclear.

Hemodynamics

There is a left-to-right shunt at the atrial level. The shunt direction is determined by the pressure difference in the atria, which in turn is dependent on the compliance of the ventricles and on the resistance in the pulmonary and the systemic circulatory system. The right ventricle normally has a better diastolic elasticity than the muscular left ventricle, so the pressure in the left atrium is higher than in the right atrium. This leads to a left-to-right shunt at atrial level left-to-right shunt with an increased volume overload in the right ventricle and pulmonary circulatory system.

After the drop in pulmonary vascular resistance beyond the neonatal period, the left-to-right shunt continues to increase. In a larger shunt there is a relative pulmonary stenosis (gradient usually 15–20 mmHg higher than the gradient across the aortic valves), because more blood passes through the pulmonary valve than the aortic valve. Likewise, tricuspid insufficiency can occur due to the volume-related dilatation of the right ventricle.

Associated Anomalies

ASDs occur in isolation or in combination with almost all congenital heart defects. Of particular importance are:

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  Partial anomalous pulmonary venous connections: almost always present with sinus venosus defects, rarely with ASD II as well

  
  
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  Persistent left superior vena cava

  
  
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  Valvular or infundibular pulmonary stenosis

  
  
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  Patent ductus arteriosus (PDA)

  
  
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  Mitral valve anomalies—for example, cleft of the mitral valve associated with ASD I or a mitral valve prolapse associated with ASD II

Associated Syndromes

Lutembacher syndrome (extremely rare)

In Lutembacher syndrome there is a combination of an ASD II and an acquired or congenital mitral stenosis. Due to the mitral stenosis, the left-to-right shunt at the atrial level is more pronounced than with an isolated ASD.

Holt–Oram syndrome

Holt–Oram syndrome is a combination of a heart defect (often an ASD) and a unilateral malformation of the forearm or hand (e.g., aplasia/hypoplasia of the radius or missing thumb).

Symptoms

Most children with an ASD are asymptomatic. Often the ASD is discovered as an incidental finding or the only symptom is a heart murmur. The symptoms depend on the size of the shunt. If there is a large shunt, the typical symptoms are:

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  Recurrent pulmonary infections (often the only symptom in childhood)

  
  
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  slender body constitution and pale skin

  
  
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  signs of congestive heart failure such as failure to thrive, poor feeding, and tachypnea or impaired physical capacity with dyspnea on exertion, which occur only if there is a large left-to-right shunt and are rare before the child reaches the toddler stage

Complications

Depending on the size of the shunt, in the long term, the increasing dilatation of the right atrium and ventricle leads to atrial arrhythmia, right ventricular failure, pulmonary congestion, and pulmonary hypertension. Paradoxical embolism may also occur.

Auscultation

The typical auscultation finding is fixed splitting of the second heart sound independent of respiration (not to be confused with the physiological respiratory-dependent split second heart sound) and a relative pulmonary stenosis murmur (2/6–3/6 systolic murmur with point of maximum impulse [PMI] in the 2nd–3rd left parasternal intercostal space [ICS]).

In a very large shunt there is also a rumbling, low-frequency diastolic bruit with PMI in the 4th left parasternal ICS as a sign of a relative tricuspid valve stenosis.

In an ASD I, there is often also a systolic mitral regurgitation murmur.

ECG

Typical ECG findings:

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  Right axis deviation. However, in an ASD I there is typically a left axis deviation due to a shift in the conduction system.

  
  
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  Incomplete right bundle branch block due to increased right ventricular volume (rSR′ configuration in V₁, Fig. 15.3). This finding should not be confused with the physiological Rsr′ configuration in V₁ in infancy.

  
  
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  Signs of volume related hypertrophy of the right ventricle (slightly elevated R wave in the right precordial leads, deep and wide S wave in the left precordial leads), possibly abnormal repolarization in the right precordial leads (flattened T wave, T wave inversion, ST depression).

  
  
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  AV block I (typical for ASD I, otherwise rare).

  
  
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  An atrial rhythm with a P axis less than 30° is typical for a sinus venosus defect.

  
  
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  Atrial arrhythmias such as atrial flutter or fibrillation may occur in adults.

Chest X-ray

Depending on the size of the shunt, there is moderate cardiomegaly, increased pulmonary vascular markings, a prominent right heart silhouette due to the enlarged right atrium, and a right ventricle that forms the left border of the heart with a rounded and elevated cardiac apex.

Echocardiography

Echocardiography is the diagnostic method of choice. Larger patients may require transesophageal echocardiography.

Echocardiography should be used to detect or exclude:

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  Location and type of the atrial septal defect (Fig. 15.4)

  
  
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  Detection of a shunt using color Doppler

  
  
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  Enlargement of the right atrium, right ventricle, and pulmonary artery

  
  
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  Flattened or even paradoxical ventricular septal motion in M mode as a sign of volume overload. A paradoxical septal motion is evident when, during the systole, the ventricular septum moves away from the dorsal wall of the left ventricle and contracts in the direction of the right ventricle. The septum thus “helps” to empty the enlarged right ventricle

  
  
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  Associated anomalies—for example, mitral valve cleft in ASD I, partial anomalous pulmonary venous connections in sinus venosus defects, or persistent left superior vena cava associated with a coronary sinus defect

Echocardiography should also be used:

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  To visualize the distances of the defect borders to the adjacent structures (caudal: AV valves; cranial: superior vena cava; anterior: aorta; posterior: pulmonary vein). It is especially important to visualize the spatial relationship of the defect borders to the adjacent structures for interventional closure.

  
  
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  Caution: An superior sinus venosus defect can often be visualized only from the subcostal area. An indirect indication of a sinus venosus defect is a large right ventricle without any other obvious cause. If the right ventricle is enlarged, a partial anomalous pulmonary venous connection must also be considered as a differential diagnosis.

Cardiac Catheterization

Cardiac catheterization is not usually necessary for purely diagnostic reasons. When in doubt it is used to answer the following questions:

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  To quantify shunts

  
  
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  To exclude or detect associated anomalies (in particular anomalous pulmonary venous connections)

  
  
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  To measure pressure in pulmonary circulation, possibly testing pulmonary vascular responsiveness

Cardiac catheterization is now performed almost only as interventional therapy for a typical ASD II.

MRI

In ambiguous cases (e.g., sinus venosus defect), an MRI scan can help locate the defect and detect or rule out associated anomalies. In addition, the shunt can be quantified.

Conservative Treatment

Conservative treatment is rarely needed. Exceptional cases may need pharmacological treatment for heart failure.

Indications for ASD closure

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  Any sign of right ventricular enlargement (dilatation of the right ventricle or paradoxical septal motion in echocardiography)

  
  
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  Left-to-right shunt of more than 30% of the Q_P or Q_P: Q_S > 1.5:1

  
  
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  Signs of congestive heart failure such as reduced capacity or delayed physical development

  
  
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  Following a paradoxical embolism

An ASD is generally closed in preschool children between the ages of 3 and 5, earlier if it is symptomatic. In adults the closure can be performed electively after the diagnosis has been established.

Contraindication

Closure of an ASD is contraindicated if pulmonary resistance is massively increased. Then a right-to-left shunt is necessary to make sure that there is sufficient cardiac output for systemic circulation. Due to the increased pulmonary resistance, sufficient blood cannot pass the lung to the left atrium. Filling the left atrium and the left ventricle is dependent on a right-to-left shunt across the ASD. Because of the right-to-left shunt, however, these patients are cyanotic.

Interventional Catheterization

Interventional catheterization is the method of choice for most cases of ASD II or patent foramen ovale. Usually, a double umbrella occluder system is implanted transvenously to close the defect. The residual atrial septum defects (ASD I, sinus venosus defects, coronary sinus defects) are not eligible for interventional catheter closure due to the lack of the border required for anchoring the double umbrella system.

Surgery

If an interventional catheterization closure is not possible, the defect is closed by direct suturing or with a patch (mostly from autologous pericardium) under cardiopulmonary bypass (Fig. 15.6). A median sternotomy is performed as an access route. Other cosmetically more favorable access routes are from anterolateral (right inframammary fold) or posterior access. Here, however, there is an increased risk of complications. In some centers the operation is also performed as a minimally invasive procedure.

Definition

A ventricular septal defect (VSD) is an interventricular connection. A VSD can occur in isolation or as an accompanying anomaly with complex heart defects.

Epidemiology

A VSD is the most common congenital heart defect, constituting up to 40% of all congenital heart defects. There is an accompanying anomaly in about half of these cases. Women are affected slightly more frequently than men.

Pathogenesis

A VSD is caused by a malformation of the interventricular septum during the first 7 weeks of gestation. The exact cause is usually unknown. A VSD can also occur in association with chromosome anomalies (e.g., trisomy 13, 18, 21) or other genetic diseases (e.g., Holt–Oram syndrome). Acquired VSDs following a cardiac contusion, a gunshot or knife wound, or myocardial infarction are rare.

Classification

The ventricular septum consists of the small high membranous septum and the larger muscular septum. The muscular septum has three segments:

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  Inlet septum

  
  
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  Trabecular septum

  
  
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  Outlet septum (= infundibular septum, conus septum)

Various VSDs are described, depending on the location of the defect in the ventricular septum (Fig. 15.7). However, the nomenclature is not uniform and is complicated by numerous terms that are sometimes used synonymously. The following classification has proven useful in practice.

Perimembranous VSD

Synonyms: subaortic, infracristal, or membranous VSD. Perimembranous VSDs affect the membranous septum. They usually extend somewhat beyond the membranous septum into adjacent areas of the ventricular septum and are therefore termed perimembranous. They constitute approximately 70% of all VSDs.

The rare Gerbode defect is a special form of perimembranous VSD with a shunt between the left ventricle and right atrium (Fig. 15.8). Such a shunt is possible because part of the membranous septum separates the left ventricle from the right atrium due to the difference in levels of the AV valves.

Muscular VSD

Synonyms: trabecular, apical VSD. Muscular VSDs are in the trabecular segment of the muscular septum. These defects frequently occur in multiples (an extreme case is a Swiss cheese septum). With the improvement in diagnostic methods, the number of muscular VSDs detected, some of which are very small, has increased, but they frequently close spontaneously.

Infundibular VSD

Synonyms: outlet, subpulmonary, supracristal, doubly-committed, subarterial VSD. In an infundibular VSD, there is a gap in the outlet septum below the aortic and pulmonary valves. There is a risk that the aortic valve cusp may prolapse into the VSD, leading to aortic insufficiency. In Western nations, the incidence of infundibular VSD is only 5 to 8%, but up to 30% in Asia.

Inlet VSD

Synonym: AV canal type VSD. An inlet VSD is located in the inlet septum, that is, relatively posterior. It is limited from above by the tricuspid valve annulus. An inlet VSD occurs typically with an AV septal defect (AV canal), but can also occur in isolation. Inlet VSDs constitute 5 to 8% of all VSDs.

Malalignment VSD

In a malalignment VSD there is an abnormal displacement of the outflow tract septum with the result that the semilunar valve overrides the VSD. Malalignment VSDs never occur in isolation, but are always associated with other cardiac anomalies. Typical examples are tetralogy of Fallot (aorta overrides the VSD) or truncus arteriosus (truncus valve overrides the VSD).

Hemodynamics

The hemodynamics in a VSD depends on the size of the VSD and the resistance in the systemic and pulmonary circulation. If the pressures are normal, the VSD leads to a left-to-right shunt at the ventricular level. This results in excessive pulmonary blood flow and volume overload in the left ventricle. The size of a VSD is often indicated in relation to the diameter of the aortic root:

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  Small (restrictive) VSDs are less than 50% of the diameter of the aortic root.

  
  
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  Mid-sized VSDs have 50 to 100% of the diameter of the aortic root.

  
  
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  Large VSDs constitute more than 100% of the diameter of the aortic root.

In mid-sized defects, the volume overload of the left ventricle is most significant; as the defect becomes larger, pressure overload of the pulmonary circulation and the right ventricle increase. If the diameter of the VSD exceeds 50 to 75% of the diameter of the aortic root, the pressure between the two ventricles is equalized (pressure-equalizing VSD). Then the shunt is determined only by pulmonary resistance, which increases steadily as a result of the volume overload of the pulmonary circulation. This ultimately results in the Eisenmenger reaction, which is a reversal of the shunt across the VSD. This results in a right-to-left shunt with cyanosis.

In VSDs near the aortic valve, the lack of resistance may cause the aortic valve leaflets to prolapse in the VSD, resulting in aortic insufficiency.

Associated Anomalies

VSDs often occur as an additional anomaly in almost all complex defects—for example, d-TGA, ccTGA, pulmonary atresia, pulmonary stenosis, coarctation of the aorta, AV valve anomalies, PDA, ASD, tetralogy of Fallot, or truncus arteriosus communis.

Associated Syndromes

VSDs occur frequently in many genetic syndromes (e.g., trisomy 13, 18, 21, deletions, Goldenhaar syndrome). They also occur in connection with an alcohol embryopathy, but 95% of VSDs are not associated with chromosomal anomalies or syndromes.

Symptoms

The symptoms depend on the size of the defect and the pressures in systemic and pulmonary circulation. Small, not hemodynamically relevant VSDs are asymptomatic. They are generally noticed only due to the murmur on auscultation finding.

In large hemodynamically relevant VSDs, there are signs of congestive heart failure such as tachypnea or dyspnea, intercostal retractions, hepatomegaly, increased sweating, poor feeding, and failure to thrive. A systolic thrill can also be palpated at the left sternal border. The first symptoms usually occur when pulmonary vascular resistance decreases at around age 6 to 8 weeks.

Complications

If there is a large VSD, congestive heart failure can occur in early infancy. A large left-to-right shunt with excessive pulmonary blood flow leads to pulmonary hypertension. Due to the subsequent reduction of the shunt, there then appears to be an improvement in the clinical symptoms. The time at which pulmonary hypertension develops depends not only on the volume of the shunt, but also on the associated heart defects as well. Pulmonary hypertension becomes manifest especially early in children with an AV canal, d-TGA with VSD, or truncus arteriosus.

In VSD, a stenosis can also develop occasionally in the right ventricular outflow tract (double-chambered right ventricle). This obstruction sometimes does not develop until after corrective surgery. This stenosis of the right ventricular outflow tract is also described as the Gasul transformation.

Bacterial endocarditis can occur, especially at the side of the right ventricle opposite the defect (jet lesion).

Auscultation

There is a typical rough, band-shaped holosystolic murmur with PMI in the 3rd to 4th left parasternal ICS (frequently louder than 3/6) on auscultation. If there is a large left-to-right shunt, a low-amplitude, mesodiastolic murmur can be heard over the cardiac apex as a sign of a relative mitral stenosis. A pronounced second heart sound is a sign of pulmonary hypertension and must be interpreted as an alarm signal. In addition, a diastolic decrescendo murmur at the left sternal border, which can be a sign of aortic insufficiency, should be noted.

ECG

The ECG is unremarkable if the defect is small. In larger defects, there are signs of left ventricular volume overload. There is also frequently a P sinistroatriale. When the pressure increases in the right ventricle, signs of right ventricular hypertrophy also develop.

Chest X-ray

The X-ray is unremarkable if the defect is small. In larger VSDs, cardiomegaly develops in relation to the size of the shunt with dilatation of the left atrium and ventricle. There is lateral inferior displacement of the cardiac apex. The pulmonary artery segment is prominent due to volume overload; pulmonary vascular markings are increased and can be detected up to the periphery of the lungs. Additional right ventricular hypertrophy with prominent pulmonary arteries is an important indication of pulmonary hypertension.

Echocardiography

Echocardiography including color Doppler ultrasound is the diagnostic method of choice. It usually allows the number, size, and location of the defects to be reliably determined. Associated cardiac defects can also be ruled out.

Using CW Doppler and the Bernoulli equation, it is possible to estimate the pressure gradients across the defect. The VSD is said to be restrictive if the estimated restrictive ventricular pressure via the VSD flow is normal.

The pressure can also be calculated across the VSD (BP_syst -pressure gradient across the VSD) or estimated by the degree of valve insufficiency if the tricuspid valve is insufficient. The size of the left atrium and ventricle are indirect indications of the size of the shunt.

The typical sites of the VSD in echocardiography are listed in Fig. 15.9.

Perimembranous VSD

This type can be best visualized in the parasternal long axis immediately below the aortic valve or in the parasternal short axis between the 9 and 12 o’clock positions. The apical five-chamber view also affords good visualization. These defects are sometimes concealed by a structure resembling an aneurysm. This is tissue from the septal tricuspid valve leaflet. This is sometimes called an “aneurysmal tissue tag (partially) obstructing a VSD” although the term “aneurysmal” is not correct from a pathological standpoint.

Muscular VSD

These VSDs can be readily visualized in the parasternal short axes and in the four-chamber view. With muscular defects, it is important to note whether there are one or more defects. Due to trabecularization of the right ventricle, larger muscular VSDs can appear as multiple defects in a color Doppler image.

Infundibular VSD

Infundibular VSDs are located in the parasternal short axis between the 12 and 3 o’clock positions in the vicinity of the aortic valve. A leaflet of the aortic valve can prolapse into the defect and lead to aortic insufficiency.

Inlet VSD

Inlet VSDs are located posteriorly in the area of the tricuspid valve annulus and can be readily visualized in the four-chamber view by tilting backward.

To assess the size of a VSD, its relation to the diameter of the aortic valve annulus can be used (see Hemodynamics above).

Cardiac Catheterization

Most VSDs can be reliably diagnosed using echocardiography. Cardiac catheterization is indicated only if the exact number or location of VSDs cannot be determined or there are presumed to be additional cardiac anomalies, or if the hemodynamic relevance (in particular increased pulmonary resistance) cannot be reliably assessed. Some VSDs can also be closed by interventional catheterization.

Pulse oximetry shows an increase in oxygen saturation in the right ventricle and pulmonary artery if there is a left-to-right shunt. Using the Fick principle, the shunt and the systemic-to-pulmonary blood flow ratio can be calculated. If there is a relevant VSD, there is an increase in left atrial pressure and left ventricular end-diastolic pressure. The pulmonary arterial pressure is also measured and the pulmonary vascular resistance calculated.

The VSD can be detected and precisely located in an angiography after injecting contrast medium into the left ventricle. It is important to note any potential aortic insufficiency.

In patients with elevated pulmonary vascular resistance, the examination may be supplemented by testing vasodilator responsiveness (Chapter 21).

MRI

An MRI is only rarely needed to clarify anatomical details in an isolated VSD.

Conservative Treatment

In hemodynamically relevant defects, congestive heart failure is treated pharmacologically until surgery. The conservative treatment of an Eisenmenger reaction is discussed in Chapter 22.

Indications for Closure

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  In a large left-to-right shunt with clinical symptoms (frequent pulmonary infections, failure to thrive, congestive heart failure that cannot be managed pharmacologically) the defect is closed in infancy.

  
  
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  For older asymptomatic children with normal pulmonary pressures, surgery is indicated for a left-to-right shunt of over 40% of cardiac output if the Qp/Qs ratio is over 1.5, or if the left atrium and ventricle are dilated.

  
  
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  In a VSD with secondary aortic insufficiency or aortic valve prolapse into the VSD, immediate surgery is always indicated; otherwise there is a risk that the valve may have to be replaced.

  
  
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  Incipient pulmonary hypertension is also an indication for closure.

Contraindications

VSD closure is contraindicated if there is fixed pulmonary hypertension (Eisenmenger reaction).

Surgery

The defect is usually closed with a patch; smaller defects may be closed by direct sutures. To avoid a ventriculotomy, a surgical access route across the right atrium and tricuspid valve (transtricuspid) is usually selected.

In isolated cases such as multiple defects (“Swiss cheese VSD”) or complex accompanying cardiac anomalies, or if there are contraindications to cardiopulmonary bypass surgery, pulmonary artery banding may be performed as a palliative interim measure to reduce the excessive pulmonary blood flow.

The procedure if there is a VSD combined with coarctation of the aorta or a large PDA is controversial. In infancy, the aortic coarctation or the PDA may first be corrected without cardiopulmonary bypass. The VSD surgery is performed later, for example, at the age of 2 to 3 months. If there is a large, hemodynamically relevant VSD, a one-time procedure must also be considered. For Eisenmenger reaction, heart–lung transplant is the last treatment option.

Interventional Catheterization

Interventional catheterization closure using double umbrella occluder systems or special coils can be performed only for selected defects and is not yet a routine procedure in most centers (Chapter 24).

Definition

An atrioventricular septal defect (AVSD) is a development disorder of varying degrees affecting mainly the segments of the atrial and ventricular septum near the AV valve and the AV valves themselves. These structures arise from the endocardial cushion during embryonic development.

Typical features of an AVSD:

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  Anomaly of the atrioventricular septum (segments of the atrial and ventricular septum near the AV valve)

  
  
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  Common AV valve for both ventricles with a variable number of leaflets and openings

  
  
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  Abnormal position and elongation of the ventricular outflow tract (“goose neck” deformity). In an AVSD, the aorta is located anterior to the single common AV valve, not wedged between the mitral and tricuspid valve.

  
  
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  Displacement of the AV node and excitation conduction system

Epidemiology

AVSDs constitute 4 to 5% of all congenital heart defects. The incidence is 0.2 per 1,000 live births.

Pathogenesis and Pathology

AVSD is caused by a developmental disorder of the embryonic endocardial cushion with anomaly of the segments of the atrial and ventricular septum near the AV valves (atrioventricular septum) and the AV valves including the leaflets, tendinous cords, and papillary muscles.

Only a single AV valve develops, which can, however, have one or two openings (see below: classification in partial and complete types). The AV valve usually consists of a total of five leaflets. The bridging leaflets are of particular significance. There is an anterior and a posterior bridging leaflet. These bridging leaflets bridge a defect in the segments of the atrial and ventricular septum and connect the left and right ventricular segments (Fig. 15.10). The bridging leaflets play an important role in classifying the types of AVSD (Fig. 15.11).

Classification

Partial AVSD

In a partial AVSD there is only one hole in the atrial septum near the AV valve. The defect in the ventricular septum is closed by a tissue bridge that also connects the two bridging leaflets of the common AV valve. This results in a cleft in the mitral valve. Strictly speaking, the term “mitral valve” is incorrect, as even in a partial AVSD, there is only one AV valve with no separation into a mitral and a tricuspid valve. However, this common AV valve has two openings and this “cleft” leads to a hemodynamic “mitral valve insufficiency.”

Intermediate AVSD

In an intermediate AVSD there are two separate openings in a common AV valve. The two bridging leaflets are adjoined, similar to a partial AVSD. In addition, there is a defect in the atrial septum directly above the AV valve and a ventricular septal defect in the inlet septum directly below the AV valve level. The VSD is often restrictive in an intermediate AVSD.

Complete AVSD

In a complete AVSD, there is an atrial septal defect directly above the AV valve level and a nonrestrictive VSD in the inlet septum directly below the AV valve level. The AV valve has a common opening. The left and right ventricular segments of the AV valve are connected by an anterior and a posterior bridging leaflet.

A complete AVSD is also subdivided into types A to C according to Rastelli (Fig. 15.12 and Fig. 15.13). The location and attachment of the anterior bridging leaflet are important for this classification:

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  Type A (most common type): The anterior bridging leaflet is separated immediately below the defect in the atrial and ventricular septum and is tethered to the septal crest by tendinous cords.

  
  
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  Type B (least common type): The anterior bridging leaflet is tethered by tendinous cords that straddle the septal defect from the left to the right ventricle. The anterior bridging leaflet is oriented slightly toward the right ventricle. This type is frequently associated with a hypoplastic left ventricle (unbalanced AVSD, see below).

  
  
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  Type C: A freely movable anterior bridging leaflet oriented far to the right that is attached to the anterior papillary muscle of the right ventricle.

There are also special forms of AVSD as described below.

Unbalanced AVSD

In an unbalanced AVSD, one of the two ventricles is hypoplastic. By definition, the left ventricle is hypoplastic if it is not involved in forming the cardiac apex. Biventricular correction is usually not possible in this case.

AV valve cleft

This is a minimal variant of an endocardial cushion defect. There is only a cleft in an AV valve with no atrial or ventricular septal defect.

Hemodynamics

The hemodynamic situation depends on the extent of the left-to-right shunt at the atrial and ventricular levels, on the insufficiency of the AV valve, possible pulmonary hypertension, and accompanying anomalies.

Incomplete and intermediate AVSD

Volume overload of the right atrium and ventricle and of pulmonary circulation (similar to an ASD).

Complete AVSD

Depending on the size of the defects in the atrial and ventricular septum, there is usually a large left-to-right shunt at the atrial and ventricular level with excessive pulmonary blood flow and increasing congestive heart failure in early infancy. Insufficiency of the AV valve can complicate the situation. Obstructive pulmonary diseases and hypoventilation, which are often present in children with Down syndrome, aggravate the symptoms. Pulmonary hypertension with an increase in pulmonary resistance typically develops very soon in a complete AVSD. An Eisenmenger reaction usually looms within the first 6 months in the form of obstructive pulmonary vascular changes. Once an Eisenmenger reaction has occurred, a right-to-left shunt with cyanosis develops.

Associated Anomalies

The following cardiac defects occur frequently in conjunction with an AVSD:

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  Patent ductus arteriosus (10%)

  
  
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  Tetralogy of Fallot (10%)

  
  
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  Double-outlet right ventricle

  
  
• 
  

  Coarctation of the aorta (frequently associated with an unbalanced AVSD, almost never with Down syndrome)

  
  
• 
  

  Heterotaxy syndromes

  
  
• 
  

  Rarely: total anomalous pulmonary venous connection, persistent left superior vena cava

Associated Syndromes

An AVSD is the typical heart defect associated with trisomy 21 (Down syndrome). It is also frequently found with microdeletion of 22q11 or with the Ellis–van Creveld syndrome.

Symptoms

Partial and intermediate AVSD without mitral valve insufficiency

The hemodynamic and clinical situation is similar to that of a large ASD with a large left-to-right shunt. The defect is usually asymptomatic in childhood, but later, congestive heart failure and in adulthood pulmonary hypertension can develop.

An exception is when there is a hypoplastic left ventricle and hypoplastic mitral valve annulus. In this case, there is a pronounced left-to-right shunt with excessive pulmonary blood flow and hypoperfusion in the systemic circulation early on so that congestive heart failure develops sooner.

Partial and intermediate AVSD with mitral valve insufficiency

Congestive heart failure develops sooner in these patients because the regurgitation volume across the insufficient mitral valve leads to additional overload of the left ventricle.

Complete AVSD

After the drop in pulmonary vascular resistance in the 2nd to 8th week of life, these patients rapidly develop congestive heart failure. There is frequently pronounced pulmonary blood flow. Problems are caused by pulmonary hypertension, failure to thrive, and recurrent pulmonary infections. Cyanosis during activity and later also at rest is a sign of pulmonary hypertension or an incipient Eisenmenger reaction.

Auscultation

Partial AVSD

In a partial AVSD, the auscultation finding is largely consistent with that of an atrial septal defect: 2/6–3/6 systolic murmur with PMI in the 2nd left parasternal ICS as a sign of relative pulmonary stenosis. This is because a larger volume has to flow across the actually normal pulmonary valve as a result of the left-to-right shunt at the atrial level. There may also be a diastolic murmur due to the relative tricuspid valve stenosis. In addition, if there is mitral valve insufficiency, a clear bubbling (pouring) murmur can be heard over the cardiac apex. There is a fixed split second heart sound.

Intermediate and complete AVSD

A loud holosystolic murmur can be heard with PMI in the 4th left parasternal ICS as a result of the left-to-right shunt across the septum and AV valve insufficiency. The second heart sound is loud as a sign of excessive pulmonary blood flow or hypertension. While the left-to-right shunt and therefore the intensity of the systolic murmur decreases as pulmonary hypertension increases, the second heart sound becomes steadily louder.

Complications

Irreversible pulmonary hypertension develops unusually early in patients with an AVSD, and in patients with trisomy 21, sometimes as soon as during the 6th to 12th month of life.

ECG

There are indicative ECG findings associated with an AVSD that are enough to raise suspicion of the condition. Typical findings are:

• 
  

  Left axis deviation: Left axis deviation arises due to displacement of the conduction system. Sometimes the axis “deviates” further up to right axis deviation. Moderate right axis deviation in an AVSD is found almost exclusively in connection with pulmonary hypertension or a pulmonary stenosis.

  
  
• 
  

  I AV block: The PQ interval is frequently prolonged. Strictly speaking, this is not an AV block, since there is no delayed conduction in the AV node itself, but rather delayed intra-atrial conduction that leads to the extended PQ interval in the superficial ECG.

  
  
• 
  

  Signs of right heart hypertrophy in the precordial leads (high R waves in V₁ + V₂ and a low S wave in V₅ +V₆): The signs of right heart hypertrophy can also be masked by left heart hypertrophy if there is simultaneous mitral valve insufficiency.

  
  
• 
  

  Incomplete right bundle branch block (rsR′ or rR′ in V₁ + V₂): An incomplete right bundle branch block is found frequently, especially with a partial AVSD.

  
  
  
  

  Note

  
  

  A left axis deviation in the ECG should always make one think of an AVSD.

Chest X-ray

Typical X-ray findings are cardiomegaly with a prominent pulmonary segment and increased pulmonary vascular markings as a result of excessive pulmonary blood flow.

Echocardiography

The following findings are typical for an AVSD and should be investigated:

• 
  

  Absence of the atrioventricular septum (defect in the lower segment of the atrial septum immediately above the AV valve and VSD in the inlet septum immediately below the level of the AV valve): In a partial AVSD, no shunt is found in the ventricular septum; in an intermediate AVSD the VSD is generally small and restrictive, and there is usually a large VSD in a complete AVSD.

  
  
• 
  

  Assessment of the AV valve: Instead of two staggered valves, there is a common AV valve with all the leaflets at one level. In a partial or intermediate AVSD, there are two separate AV valve openings; in a complete AVSD only one valve opening is detected. In addition, the extent and location of AV valve insufficiencies must be investigated. The location and size of a cleft must also be determined.

  
  
• 
  

  Assessment of ventricle sizes: It is also necessary to clarify whether the AVSD is balanced or unbalanced. If the left ventricle is not involved in forming the cardiac apex, there is a hypoplastic left ventricle by definition.

  
  
• 
  

  Visualization of the bridging leaflets and attachments of the valve leaflets: Straddling tendinous cords and a single papillary muscle in the left ventricle should be noted.

  
  
• 
  

  Assessment of the extent, site, and direction of the shunt at the atrial and ventricular level.

  
  
• 
  

  Assessment of the left ventricular outflow tract: The “goose-neck” configuration due to the anterior and superior displacement of the aortic valve is typical. It should also be investigated whether there is a subaortic stenosis, which can be caused by a mitral valve leaflet.

  
  
• 
  

  The pressure in pulmonary circulation should be estimated by Doppler ultrasonography to quantify the extent of pulmonary hypertension.

  
  
• 
  

  Exclusion of additional anomalies, in particular PDA, tetralogy of Fallot, and coarctation of the aorta.

Cardiac Catheterization

Echocardiography is generally sufficient for diagnosing and assessing the individual anatomy. Cardiac catheterization is used primarily for the precise assessment of pulmonary vascular resistance, possibly including testing the responsiveness of the pulmonary vascular bed. Typical findings in an AVSD are:

• 
  

  The left ventricle is easier to visualize than the right. The catheter reaches the left atrium and practically “falls” into the left ventricle after being advanced through the inferior vena cava and the right atrium.

  
  
• 
  

  Large left-to-right shunt with elevated pressures in the pulmonary circulation.

  
  
• 
  

  Angiography shows the “goose-neck” deformity due to the anterior displacement of the aortic valve in front of the common AV valve.

MRI

An MRI is not generally needed. In special cases, it can be used to clarify anatomical details and quantify shunts.

Conservative Treatment

Digoxin, diuretics, beta blockers, and ACE inhibitors can be used as interim measures to treat congestive heart failure. A feeding tube may be inserted for a high-calorie diet to promote the child’s growth until the operation. Oxygen should not be administered due to excessive pulmonary blood flow.

Indications for Surgery

There is practically always an indication for surgery. The timing of the operation is usually between the 3rd and 6th month of life for a complete AVSD. Early onset of obstructive pulmonary vascular changes and frequently pronounced congestive heart failure necessitate rapid corrective surgery.

For asymptomatic partial and intermediate AVSDs, the operation is generally performed between 2 and 4 years of age. If there are clinical symptoms of congestive heart failure, a pronounced shunt, or relevant AV valve insufficiency, the timing for operation may be earlier. In older patients, the operation is performed as an elective procedure after the diagnosis has been established.

Contraindications for an operative correction

Operative correction is contraindicated after irreversible pulmonary hypertension (Eisenmenger reaction) has developed.

Surgery

The standard procedure is a patch closure of the atrial and ventricular septal defects using the one or two patch technique and reconstruction of the AV valve.

In an unbalanced AVSD, it is usually possible to perform only palliative operations for a univentricular heart in the sense of a Fontan procedure.

Pulmonary artery banding to protect against excessive pulmonary blood flow is performed only in exceptions as a palliative measure or as an interim measure until the definitive correction can be made, for example, if definitive surgery is not yet possible in very small premature infants with treatment-refractory congestive heart failure.

Definition

A patent ductus arteriosus (PDA) is a pathological persistence of the physiological prenatal shunt between the bifurcation of the pulmonary artery and the descending aorta (Fig. 15.14).

Epidemiology

Approximately 10% of all congenital heart defects are PDAs. Girls are affected about twice as often as boys. Among mature neonates, the incidence of PDA is about 0.1 per 1,000 live births, but is considerably more frequent in premature neonates and following perinatal asphyxia. Almost half of all premature infants with a birth weight of less than 1750 g have a PDA. PDA is also more common among individuals living at high altitudes. This is probably due to the lower partial pressure of oxygen at high altitudes.

Pathogenesis

Prenatally, the ductus arteriosus exists as a shunt between the pulmonary artery and the descending aorta to bypass pulmonary circulation. The blood flows from the right ventricle through the pulmonary artery via the ductus arteriosus into the descending aorta, finally reaching the placenta via the umbilical artery. Intrauterine synthesis of endogenous prostaglandin E₂ maintains the patency of the ductus. If the mother takes prostaglandin synthesis inhibitors such as aspirin or ibuprofen during pregnancy, this can lead to premature intrauterine closure of the ductus, resulting in severe right ventricular pressure overload in the child.

Within the first hours of life, the increase in the partial pressure of oxygen and release of vasoactive substances normally results in the functional closure of the ductus. The actual anatomical closure from persistent contraction of the spiral arrangement of smooth muscle fibers and thickening of the intima usually takes several days to weeks. After the obliteration of the ductus, the remaining connective tissues are called ligamentum Botalli, which remains for the entire lifetime.

In neonates, all situations in which there is an inadequate postnatal increase in the partial pressure of oxygen are a risk factor for patent ductus arteriosus (PDA). Practically relevant are perinatal asphyxia and pulmonary diseases (e.g., meconium aspiration, pulmonary hypoplasia).

For some cardiac defects, there is no chance of survival after birth without a patent ductus arteriosus. This situation is termed ductal-dependent systemic circulation (e.g., associated with a critical aortic stenosis) or ductal-dependent pulmonary circulation (e.g., with critical pulmonary stenosis or pulmonary atresia). In patients with an obstruction of the right ventricular outflow tract (e.g., pulmonary atresia, tetralogy of Fallot) the ductus generally has an unusually tortuous course. This is probably due to the fact that there is retrograde blood supply to the pulmonary artery via the ductus arteriosus and not antegrade supply via the right ventricle as in a normal anatomical situation. The different flow direction in the ductus results in the unusual course of the ductus in cardiac defects with right heart obstruction.

Rarely occurring variants are a double ductus, an aneurysm of the ductus (particularly in Marfan patients), or a right-sided PDA.

Hemodynamics

When pulmonary vascular resistance drops after birth, there is a reversal of the shunt in the PDA. In an isolated PDA occurring without other cardiac anomalies, the fetal right-to-left shunt reverses to a left-to-right shunt through which blood from the descending aorta flows along the pressure gradient into the pulmonary artery. The blood flows though the pulmonary vessels and finally reaches the pulmonary circulation, the left atrium, and the left ventricle (volume overload from pulmonary circulation, left atrium and ventricle, and ascending aorta). The extent of the shunt depends on the width and length of the ductus and the resistance in the pulmonary and systemic circulation.

Classification

An isolated PDA is classified according to its hemodynamic relevance.

• 
  

  Silent PDA: This is a very small, not hemodynamically relevant ductus that is detected as an incidental finding in a color Doppler examination and causes no heart murmur.

  
  
• 
  

  Not hemodynamically relevant PDA: The PDA causes a typical continuous to-and-fro murmur, but does not lead to relevant volume overload of the left ventricle or pulmonary circulation. No pulmonary hypertension is present.

  
  
• 
  

  Hemodynamically relevant PDA: In these cases, there is a moderate to large shunt across the ductus that causes symptoms of left ventricular and pulmonary volume overload.

Associated Anomalies

The PDA is a structure whose presence can be important for survival of patients having heart defects with:

• 
  

  restrictive or absent pulmonary arterial flow (e.g., critical pulmonary stenosis, pulmonary atresia)

  
  
• 
  

  restrictive or absent systemic arterial flow (e.g., critical aortic stenosis, critical aortic coarctation, interrupted aortic arch, hypoplastic left heart syndrome)

Associated Syndromes

A PDA frequently occurs in connection with the following syndromes:

• 
  

  Congenital rubella syndrome

  
  
• 
  

  Fetal alcohol syndrome

Symptoms

The symptoms of a PDA depend primarily on the shunt volume and age of the patient. A PDA in a premature infant is a special case with respect to the symptoms and therapy and is therefore discussed in a separate section (Chapter 15.5).

The effects of a large shunt across the PDA are perceptible in infancy. The symptoms of heart failure (tachypnea/dyspnea, feeding problems, failure to thrive, increased sweating) predominate. The peripheral pulses are noticeably strong (pulsus celer et altus, water hammer pulse) due to diastolic run-off of blood from the aorta into the pulmonary artery. The fontanelle pulse may be visible in infants. The pulse pressure is high. If the shunt is very large, a systolic or continuous thrill may be perceptible in the 1st to 3rd parasternal left ICS or in the suprasternal notch.

If elevated pulmonary resistance develops postnatally (e.g., associated with persistent fetal circulation due to asphyxia), there is a right-to-left shunt over the PDA with lower oxygen saturation in the lower half of the body distal to the junction of the ductus (differential cyanosis).

If the shunt is smaller, the children do not develop symptoms until later or not at all. Usually, the diagnosis in these cases is made only from an asymptomatic incidental finding. Increased susceptibility to infections can be the only symptom.

Complications

Depending on the size of the shunt, pulmonary hypertension may develop as a result of the excessive pulmonary blood flow, which is initially reversible but later becomes irreversible (Eisenmenger reaction). There is probably a slightly increased risk of endarteritis in the area around the PDA even if the shunt is not hemodynamically relevant. The development of a PDA aneurysm is extremely rare but involves the risk of a rupture.

Auscultation

In neonates, a purely systolic murmur with PMI in the 2nd to 3rd parasternal left ICS radiating into the back can usually be heard.

After pulmonary resistance drops (2nd to 8th week of life) the typical systolic–diastolic continuous machinery murmur is heard with PMI in the 1st to 2nd infraclavicular left ICS. The murmur can be heard both in systole and diastole because the pressure in the aorta is higher than in the pulmonary artery in systole and diastole. The maximum intensity of the murmur occurs simultaneously with the second heart sound and is softer again in the diastole (crescendo-decrescendo murmur).

If the ductus is very small, the murmur is clearer during inspiration and physical exertion. A silent ductus—as the name indicates—causes no conspicuous auscultation finding.

Differential diagnoses of a PDA based on the auscultation finding:

• 
  

  “Venous hum” is a continuous murmur in the jugular veins with a maximum in early diastole. The murmur becomes softer during inspiration. It disappears when the jugular veins are compressed or the head is turned.

  
  
• 
  

  An aortopulmonary window is sometimes difficult to distinguish from a PDA even using echocardiography. An aortopulmonary window always affects the ascending aorta and does not originate in the descending aorta like a PDA.

  
  
• 
  

  In pulmonary agenesis a loud systolic–diastolic murmur is heard. The echocardiography finding with a typically massively dilated main pulmonary artery is indicative.

  
  
• 
  

  Coronary fistulas originate in the coronary arteries and usually drain into the pulmonary artery or right ventricle.

  
  
• 
  

  Arteriovenous fistulas are sometimes very difficult to distinguish using echocardiography. The exact visualization of the origin and drainage is important.

  
  
• 
  

  Peripheral pulmonary stenoses often cause a murmur similar to PDA. The diagnosis is made using echocardiography.

  
  
• 
  

  The perforation of a sinus of Valsalva into the right atrium or ventricle can sound similar to PDA on auscultation. The shunt in the region of the ruptured sinus to the right atrium or ventricle can be visualized using color Doppler.

  
  
• 
  

  In Bland–White–Garland syndrome (anomalous origin of the left coronary artery from the pulmonary artery), a continuous murmur can only rarely be auscultated owing to a pronounced retrograde flow into the pulmonary artery. However, there are often changes in the ECG typical of ischemia. The anomalous origin of the coronary artery can sometimes be visualized in echocardiography.

ECG

A mid-sized left-to-right shunt will display signs of left heart hypertrophy. If there is a large shunt with pulmonary hypertension, the ECG will have signs of biventricular hypertrophy. When pulmonary hypertension becomes the prominent symptom later on (Eisenmenger reaction), signs of right heart hypertrophy will predominate.

Chest X-ray

If the shunt is large, there is cardiomegaly with left heart enlargement and dilatation of the ascending aorta. Pulmonary vascular markings are increased due to pulmonary recirculation. However, in pulmonary hypertension, only the central pulmonary vessels are dilated, while the peripheral vessels are narrow.

Echocardiography

Echocardiography including color Doppler is the method of choice to confirm the diagnosis and estimate the hemodynamic relevance of the PDA.

A PDA can generally be readily visualized in the parasternal short axis at the level of the 2nd left ICS; at the bifurcation of the pulmonary artery, the PDA can be visualized as a third vessel (“pulmonary trifurcation”) in addition to the two pulmonary artery branches. By tilting the transducer in a posterior direction, the course of the ductus can be followed up to the descending aorta.

A color jet in the main pulmonary artery can be detected in the color Doppler scan. In a left-to-right shunt, a red color jet is directed toward the pulmonary valve.

Using CW Doppler, the pressure gradients across the ductus can be estimated—the ductus is restrictive if the pressure across the ductus is reduced by more than half of the systemic pressure (= systolic blood pressure).

Enlargement of the left atrium and left ventricle is an indication of hemodynamic relevance. A ratio left atrium/descending aorta of over 1.5 in the M mode is a sign of probable hemodynamic relevance.

In premature infants and neonates, the Doppler examination of the peripheral arteries (medial cerebral artery, celiac trunk) is the most sensitive method for evaluating the hemodynamic relevance of a PDA. An antegrade diastolic flow that is about one-third of the peak systolic flow (the diastolic flow is caused by the Windkessel function of the aorta) can normally be detected in these vessels. If there is a hemodynamically relevant PDA (i.e., requiring treatment), there is zero diastolic flow or negative diastolic flow in the peripheral vessels as a result of Windkessel leakage (Fig. 15.15).

Cardiac Catheterization

Diagnostic cardiac catheterization is needed only if noninvasive findings are inconclusive, additional cardiac anomalies are present, or there are indications of an increase in pulmonary pressure. Typically, blood oximetry shows an increase in oxygen saturation in the pulmonary artery. It is usually possible to probe the ductus and the descending aorta directly. The catheter position is characteristic and is shaped like a treble clef. The pressure in the pulmonary artery is determined and pulmonary vascular response to vasoactive substances such as oxygen or NO may be tested.

However, cardiac catheterization is usually performed only for the interventional closure of a PDA.

MRI

An MRI is rarely indicated, but may be useful for providing anatomical details if there are associated anomalies or for quantifying a shunt.

Interventional Catheterization

Interventional catheterization for closure using an umbrella system or coils is the therapy of choice for a PDA. Children who weigh as little as 2 to 3 kg can now be successfully treated by interventional catheterization. At lower weights, the anatomical conditions are usually still too small for the relatively large catheter systems.

For patients without heart failure, preschool age is the preferred time for closure of the ductus (spontaneous closure is unlikely at this age). Older patients can be treated electively after the diagnosis is established.

Surgery

Surgical PDA closure is performed in small premature infants after the failure of pharmacological closure or if pharmacological closure is contraindicated. In older patients, the ductus is closed surgically if the PDA is so large that interventional catheter closure is unsuitable (e.g., a large window ductus).

Closure is made using a clip and ligation with or without transection via a lateral thoracotomy. It can sometimes be performed by thoracoscopy. It should be noted that prolonged treatment with prostaglandins makes the ductus tissue brittle and can complicate the operation.

Conservative Treatment

In premature infants and neonates, an attempt can be made to close a hemodynamically relevant PDA pharmacologically in the first days of life with prostaglandin synthesis inhibitors (indomethacin, ibuprofen, diclofenac).

Indications

The indications for a pharmacological closure of the ductus are still controversial. In clinical practice, the following indications have been established:

• 
  

  Premature infants under 1,000 g: In ventilated premature infants under 1,000 g, early treatment starting on the 2nd to 3rd day of life is recommended for a PDA with discrete symptoms.

  
  
• 
  

  Premature infants over 1,000 g: Only hemodynamically significant or symptomatic PDAs should be treated. A PDA is considered hemodynamically significant or symptomatic if the following criteria are present:

  
  
  
  
  • 
    

    Clinical signs of congestive heart failure

    
    
  • 
    

    Substantial respiratory deterioration

    
    
  • 
    

    Reduced, zero or retrograde diastolic flow in the cerebral arteries or the celiac trunk

    
    
  • 
    

    Resistance Index (RI) in the anterior cerebral artery of over 0.9 (caution: RI alone is not a sufficient criterion).

Contraindications

Contraindications for ductus closure are:

• 
  

  Ductal-dependent defect (must be ruled out by echocardiography before the ductus is closed)

  
  
• 
  

  Persistent pulmonary hypertension in the neonate

  
  
• 
  

  Oliguria (< 1 mL urine/kg/h in the last 8 h), creatinine > 1.7 mg/dL

  
  
• 
  

  Thrombocytopenia < 60,000/μL, pathological plasmatic coagulation

  
  
• 
  

  Fresh cerebral, intestinal, or pulmonary hemorrhage

  
  
• 
  

  Septic shock

  
  
• 
  

  Necrotic enterocolitis

  
  
• 
  

  Recent surgery

General measures associated with a PDA

The following general measures must be noted for premature infants with a PDA:

• 
  

  Exact fluid balance: A mild restriction of fluids is often propagated, but it should be noted that this impairs renal perfusion and increases the side effects of indomethacin treatment.

  
  
• 
  

  Anemia (target Hct 0.45), hypoxemia, and hypocapnia must be avoided.

  
  
• 
  

  Furosemide should be avoided, as it can have an unfavorable effect on the closure of the ductus by promoting renal synthesis of prostaglandin.

Pharmacological Closure

Ibuprofen and indomethacin, sometimes diclofenac as well, are used for pharmacological closure. The closure rate for ibuprofen and indomethacin is similar (65–80%). The frequency of side effects regarding bleeding, necrotic enterocolitis, and bronchopulmonary dysplasia is comparable for both substances. However, gastrointestinal, cerebral, and renal perfusion are affected less negatively by ibuprofen than by indomethacin. Based on the evidence from trials, the prophylactic treatment with indomethacin does not improve the respiratory situation or the neurological outcome but does lower the rate of cerebral hemorrhages. Ibuprofen is currently considerably more expensive than indomethacin.

Ibuprofen

Ibuprofen is administered in three single doses:

• 
  

  1st single dose: 10 mg/kg as a bolus infusion over 30 min

  
  
• 
  

  2nd single dose (24 h after the 1st single dose): 5 mg/kg as a bolus infusion over 30 min

  
  
• 
  

  3rd single dose (24 h after the 2nd single dose): 5 mg/kg as a bolus infusion over 30 min

If the patient fails to respond to treatment, the ibuprofen cycle can be repeated or indomethacin therapy started.

Indomethacin

Indomethacin is also administered in three single doses:

• 
  

  1st single dose: 0.2 mg/kg as a bolus infusion over 6 h

  
  
• 
  

  2nd single dose (12 h after the start of the 1st single dose): 0.2 mg/kg as a bolus infusion over 6 h

  
  
• 
  

  3rd single dose (12 h after the start of the 2nd single dose): 0.2 mg/kg as a bolus infusion over 6 h

Bolus infusions over 6 hours cause fewer renal side effects than 30-minute infusions.

The target indomethacin level 12 hours after the third single dose is 0.7 to 1 μg/mL.

After an initial treatment success with indomethacin, maintenance therapy for 3 to 5 days is currently recommended: 0.1 (to 0.2) mg/kg as a bolus infusion once a day for 6 hours. Maintenance therapy is started 24 hours after the start of the last single dose.

Side effects of indomethacin and ibuprofen

The most important adverse effects of indomethacin and ibuprofen are:

• 
  

  Kidney failure/oliguria (more frequent with indomethacin than with ibuprofen)

  
  
• 
  

  Microhematuria

  
  
• 
  

  Occult blood in stool, bowel perforation

  
  
• 
  

  Increased risk of necrotic enterocolitis (especially in association with oliguria)

  
  
• 
  

  Thrombocytopenia, platelet aggregation disorder

Operative Treatment

If pharmacological treatment is not successful, surgical closure of the ductus is indicated. In many hospitals, it is performed via a left lateral thoracotomy in the incubator on the intensive ward for premature infants.

Definition

In a partial anomalous pulmonary venous connection (PAPVC) one or more of the pulmonary veins drains into the right atrium or a systemic venous vessel connected to the right atrium instead of into the left atrium. The result is a hemodynamic situation comparable with an ASD.

Epidemiology

Partial anomalous pulmonary venous connections constitute less than 1% of all congenital heart defects. They seldom occur in isolation, but usually in combination with other cardiac anomalies.

Pathogenesis

During embryonic development, the blood supply and drainage of the lungs takes place via the splanchnic plexus. During the course of development, the common pulmonary vein bulges out of the left atrium and connects to the splanchnic plexus. The persistence of primitive connections that were previously responsible for venous drainage of the lung buds leads to partial anomalous pulmonary venous connections.

Classification

The partial anomalous pulmonary venous connections are classified according to the connections of the pulmonary veins. Many possible anomalies are conceivable. The clinically most important ones are described below.

Connection of the right pulmonary veins to the superior vena cava

In this type, the right superior pulmonary veins typically drain into the superior vena cava below the azygos vein (Fig. 15.17). The pulmonary vein of the middle lobe usually drains into the right atrium at the level of the junction of the superior vena cava. The right inferior pulmonary veins drain normally into the left atrium. An upper sinus venosus defect is almost always associated with this type of partial anomalous pulmonary venous connection. The superior vena cava is dilated below the azygos vein due to volume overload.

Connection of the right pulmonary veins to the right atrium

In this case, all right pulmonary veins generally drain directly into the right atrium. There is almost always an ASD.

Connection of the right pulmonary veins to the inferior vena cava

In this type, typically all of the right pulmonary veins (but sometimes only some of the right pulmonary veins) drain into the inferior vena cava. This anomaly is also called the scimitar syndrome (Fig. 15.17) and is associated with other pulmonary anomalies such as hypoplasia of the right lung and lung sequestration. Aortopulmonary collaterals (connections between systemic arterial vessels and pulmonary veins) occur frequently with the scimitar syndrome. Often one or more segments of the right lobe of the lung are supplied via a collateral vessel from the descending aorta. The heart is displaced to the right by the right lung hypoplasia. The anomalous pulmonary vein proceeds downward parallel to the right atrium, passes through the diaphragm, and finally drains into the inferior vena cava. A direct connection with the right atrium is very rare. In more than one-third of cases, other heart defects are associated with a scimitar syndrome (e.g., ASD, PDA, VSD, tetralogy of Fallot, pulmonary stenosis, aortic coarctation).

The name scimitar syndrome stems from the curved opacity next to the cardiac silhouette in the chest X-ray, similar to a Turkish scimitar, made by the anomalous pulmonary vein (Fig. 15.16).

Connection of the left pulmonary veins to the left innominate vein

Left anomalous pulmonary venous connections usually drain through a vertical vein into the left innominate vein (Fig. 15.17). There is usually an ASD. Left pulmonary veins rarely drain anomalously into the superior or inferior vena cava, the coronary sinus, the left subclavian vein, or directly into the right atrium vein.

Hemodynamics

The hemodynamics of the partial anomalous pulmonary venous connection corresponds with that of an ASD. The oxygenated blood from the anomalous pulmonary veins flows into the right atrium, reaches the left ventricle and finally the pulmonary circulation. This results in volume overload and dilatation of the right cardiac chambers and pulmonary recirculation. The size of the shunt depends on the number of anomalous pulmonary veins and on the resistance of the pulmonary vascular bed. An associated ASD increases the volume overload and excessive pulmonary blood flow even further.

Associated Anomalies

Partial anomalous pulmonary venous connections are frequently associated with an ASD. Sinus venosus defects are practically always associated anatomically or functionally with a partial anomalous pulmonary venous connection. Anomalous pulmonary venous connections are also common in patients with a heterotaxy syndrome, especially left isomerism. They occur less frequently in combination with a tetralogy of Fallot.

Associated Syndromes

Anomalous pulmonary venous connections have frequently been described in conjunction with Turner and Noonan syndromes.

Symptoms

The symptoms of a partial anomalous pulmonary venous connection are usually similar to those of an uncomplicated ASD. The majority of children with a partial anomalous pulmonary venous connection are asymptomatic. They may have breathing problems during exertion.

Patients with a scimitar syndrome frequently suffer from dyspnea, cyanosis, and pulmonary infections as a result of the associated bronchopulmonary anomalies.

Auscultation

If there is a simultaneous ASD, there is a fixed, split second heart sound independent of respiration. If the atrial septum is intact (very seldom) the second heart sound is unremarkable. A soft systolic murmur in the 2nd left parasternal ICS can be a sign of a relative pulmonary stenosis as a result of increased pulmonary circulation. A diastolic murmur in the right parasternal area generally corresponds with a relative stenosis of the tricuspid valve.

ECG

The ECG can be normal or similar to the finding of an uncomplicated ostium secundum ASD—incomplete right bundle branch block of the volume overload type (rSR′ in V₁). Signs of right atrial and right ventricular hypertrophy usually occur only in older patients.

Chest X-ray

Typical findings are an enlarged right ventricle and increased pulmonary vascular markings. Depending on the location of the anomalous pulmonary venous connection, the superior vena cava or the innominate vein may be dilated.

In the scimitar syndrome, there is typically a curved streaky opacity at the right of the heart. There is also hypoplasia of the right lung that displaces the cardiac silhouette to the right.

Echocardiography

It is difficult to visualize anomalous pulmonary vein connections. Every sign of right ventricular volume overload (dilated right atrium and ventricle) is suggestive of a partial anomalous pulmonary venous connection. Especially if an ASD is detected, a search must be made specifically for partial anomalous pulmonary venous connections. In a routine echocardiography, the connections of all pulmonary veins should always be visualized. If there is an anomalous pulmonary venous connection, the systemic veins distal to the anomalous connections are dilated; a color Doppler recording shows a conspicuously strong flow in this area.

When in doubt, a transesophageal echocardiography can be helpful, especially in larger patients.

MRI

MRI is now an ideal method for accurately diagnosing anomalous pulmonary venous connections. The 3D reconstruction of the pulmonary veins displays the anomalous connection(s) (Fig. 15.18).

Cardiac Catheterization

Cardiac catheterization is not routinely needed to diagnose a partial anomalous pulmonary venous connection. It is indicated in individual cases if pulmonary hypertension is assumed to be the result of increased lung perfusion. Pulse oximetry shows a sudden increase in oxygen saturation in the vicinity of the connection.

Interventional catheterization to close aortopulmonary collaterals may be possible if there is a scimitar syndrome.

Definition

A total anomalous pulmonary venous connection (TAPVC) is an anomalous connection of all pulmonary veins. The pulmonary veins drain into the right atrium or a vein connected to the right atrium instead of into the left atrium.

Epidemiology

Total anomalous pulmonary venous connections constitute approximately 1% of all congenital heart defects. Boys are more often affected by an infracardiac-type total anomalous pulmonary venous connection; the other types affect both genders equally.

Pathogenesis

During embryonic development, a common pulmonary vessel develops into which all pulmonary veins drain. This pulmonary venous confluence normally fuses with the left atrium. In a total anomalous pulmonary venous connection, there is a faulty connection of the pulmonary venous confluence to a systemic vein instead of to the left atrium.

Classification

There are four types depending on the site of the anomalous connection (Fig. 15.20), but there are also many anatomical variants:

• 
  

  Supracardiac type (55%): The pulmonary venous blood collects in a common confluence of all pulmonary veins behind the left atrium. The confluence is connected with the innominate vein via a vertical vein running in cranial direction. The pulmonary venous blood flows through the innominate vein into the superior vena cava.

  
  
• 
  

  Cardiac type (30%): The pulmonary veins drain via a short common trunk or with separate openings from posterior into the right atrium or the coronary sinus, which then drains the pulmonary venous blood into the right atrium.

  
  
• 
  

  Infracardiac type (13%): The pulmonary venous blood flows through a common trunk behind the left atrium in a caudal direction through the diaphragm and then through the portal vein system or ductus venosus into the inferior vena cava. In the infracardiac type of total anomalous pulmonary venous connection, there is almost always a pulmonary venous obstruction that determines the hemodynamics.

  
  
• 
  

  Mixed type: This type features various anomalous connections. This type is very rare and has a poor prognosis.

  
  
  
  

  Note

  
  

  Of particular significance in a total anomalous pulmonary venous connection is whether a pulmonary venous obstruction is also present. An obstruction is practically always present in the infracardiac type. Pulmonary venous obstructions can develop in up to 10% of cases even after corrective surgery due to intimal proliferation in the area of surgery and the veins themselves.

Hemodynamics

The pulmonary veins usually join in the retrocardiac area in a venous confluence located behind the left atrium from where the oxygenated pulmonary venous blood flows to the right atrium via various venous connections. There is a 100% left-to-right shunt that leads to volume overload in the right atrium and ventricle and in the pulmonary circulation system. Therefore, the right atrium and ventricle and the pulmonary artery are dilated; the left atrium is small. The only flow into the left ventricle comes through an ASD via a right-to-left shunt that is necessary for survival. The systemic circulation therefore receives mixed blood, but cyanosis may not be particularly pronounced due to the strong pulmonary recirculation.

The excessive pulmonary blood flow leads to pulmonary hypertension that can be additionally aggravated by a pulmonary venous obstruction and lead to pulmonary edema. Possible causes of such an obstruction are external compression (e.g., when passing through the diaphragm or from compression of the vertical vein between the left main bronchus and left pulmonary artery), intimal proliferation, or stenosis of the vein.

Associated Anomalies

A total anomalous pulmonary venous connection frequently occurs in isolation without any other cardiac anomalies. It can also occur in combination with what can be complex heart defects—for example, d-TGA, tetralogy of Fallot, truncus arteriosus communis, hypoplastic left heart syndrome, tricuspid atresia, coarctation of the aorta, AVSD, pulmonary atresia.

Associated Syndromes

A total anomalous pulmonary venous connection occurs frequently with heterotaxy syndromes. It has also been described in patients with a cat eye syndrome.

Symptoms

The presence or absence of a pulmonary venous obstruction is the most significant aspect of the clinical symptoms.

Total anomalous pulmonary venous connection without pulmonary venous obstruction

In these types, the initial course is often relatively asymptomatic; at birth the children are usually unremarkable at first glance. Cyanosis is frequently not pronounced and not readily visible due to pulmonary recirculation; cyanosis should however be detected during routine neonatal pulse oximetry screening. Signs of heart failure (tachypnea, tachycardia, hepatosplenomegaly, delayed growth) develop in most children within the first weeks of life. Frequent respiratory infections are the result of excessive pulmonary blood flow.

Total anomalous pulmonary venous connection with pulmonary venous obstruction

In these patients, pronounced cyanosis and dyspnea develop within the first hours of life. Pulmonary edema follows (“white” lung in an X-ray) with respiratory failure, rapidly developing cardiac failure, and metabolic acidosis.

Complications

The main feature of a pulmonary venous obstruction is rapidly developing pulmonary edema. However, if untreated, even patients without a pulmonary venous obstruction develop elevated pulmonary vascular resistance in the first months of life as a result of excessive pulmonary blood flow, which can make surgical correction impossible.

Auscultation

The auscultation finding is often nonspecific. The first heart sound is usually loud; there is a fixed split second heart sound that is also loud because of the volume overload of the right heart. There may be a functional pulmonary stenosis murmur or tricuspid regurgitation murmur.

ECG

The ECG shows signs of right atrial (P pulmonale) and right ventricular overload (e.g., of the volume overload type with rsR′ configuration in V₁, positive T wave in V₁ beyond the first days of life).

Chest X-ray

There is cardiomegaly due to the enlargement of the right atrium and ventricle with increased pulmonary vascular markings. If there is a pulmonary venous obstruction, there will already be signs of pulmonary congestion up to pulmonary edema (bilateral ground glass or fine reticular opacity extending to the periphery of the lungs) in the neonate.

In older children with a supracardiac anomalous pulmonary venous connection, the typical “snowman” or “figure 8” can often be seen, caused by the dilatation of veins (vertical vein, right superior vena cava).

Echocardiography

The diagnosis can usually be made easily by electrocardiography. Indicative findings are a conspicuously enlarged right atrium and ventricle and a right-to-left shunt at the atrial level. The left atrium is small. A venous confluence (3rd vessel in addition to the vena cava and aorta) can usually be visualized behind the left atrium. In a supracardiac anomalous pulmonary venous connection, massive flow can be seen in a dilated superior vena cava. In an anomalous pulmonary venous connection to the coronary sinus, the sinus is dilated. In the infracardiac type, dilated hepatic veins can be seen. Doppler ultrasonography is used to detect a pulmonary venous obstruction. Associated cardiac anomalies must be ruled out.

Cardiac Catheterization

A firm diagnosis can generally be made using echocardiography. Cardiac catheterization is needed only in isolated cases, for example, if there are associated complex cardiac anomalies. A typical finding in pulse oximetry is clearly elevated oxygen saturation in the right atrium with levels between 80% and 95%. Pressure is elevated in the right atrium, right ventricle, and pulmonary artery. If there is a pulmonary venous obstruction, high pulmonary capillary wedge pressure and generally suprasystemic right ventricular pressure are found. In a contrast medium angiography of the pulmonary artery, the flow path demonstrates the anomalous pulmonary venous connection.

MRI

An MRI can be used in individual cases to visualize unclear anatomical details. It is particularly valuable for assessing pulmonary vein stenoses that sometimes develop, even postoperatively.

Definition

An aortopulmonary window is a pathological nonrestrictive connection between the ascending aorta and the main pulmonary artery. Unlike a truncus arteriosus communis, there are always two distinct semilunar valves (aortic and pulmonary valves) (Fig. 15.21).

Epidemiology

This is a rare condition that constitutes about 0.2% of all congenital heart defects.

Pathogenesis

An aortopulmonary window is caused by an anomalous separation of the embryonic truncus arteriosus communis, from which the ascending aorta and the main pulmonary artery develop.

Classification

Depending on the site and the extent of the pathological connection between the ascending aorta and the main pulmonary artery, three types are distinguished (Fig. 15.22):

• 
  

  Type I (most common): This is a small defect midway between the semilunar valves and the bifurcation of the pulmonary arteries.

  
  
• 
  

  Type II: The defect is further distal and includes the bifurcation of the pulmonary arteries. In this type the right pulmonary artery often originates directly from the aorta.

  
  
• 
  

  Type III (very rare): This involves a large defect that affects almost the entire aortopulmonary septum, thus encompassing types I and II.

Hemodynamics

Like a PDA, the connection between the aorta and pulmonary artery leads to a left-to-right shunt with volume overload of the left heart and excessive pulmonary blood flow. If untreated, the defect leads to pulmonary hypertension, which can become irreversible within the first years of life.

Associated Cardiac Anomalies

There are associated cardiac anomalies in around half of the cases. The most common are VSDs, ASDs, PDA, anomalies of the aortic arch (interrupted aortic arch, coarctation of the aorta), tetralogy of Fallot, and a right aortic arch.

Coronary anomalies are also significant. An origin of the coronary arteries in the area of the aortopulmonary window has been described. Occasionally, individual coronary arteries can even originate from the pulmonary artery.

Associated Syndromes

Like all conotruncal anomalies, an aortopulmonary window is frequently associated with microdeletion of 22q11.

Symptoms

The symptoms of a large left-to-right shunt with excessive pulmonary blood flow develop when the pulmonary resistance drops, usually within the first weeks of life (tachypnea, dyspnea with intercostal retractions, failure to thrive). Similar to a PDA, there are strong pulses and a wide pulse pressure as a result of diastolic run-off into the pulmonary artery. Precordial activity is also increased depending on the volume of the shunt.

Complications

Large defects can quickly lead to pulmonary hypertension.

If there is a simultaneous interrupted aortic arch, closure of the PDA can lead to the development of cardiac shock with no pulses in the lower limbs and metabolic acidosis.

Auscultation

The auscultation finding depends on the size of the defect. A continuous systolic–diastolic machinery murmur, as in a PDA, is typical. In larger defects, a loud systolic ejection murmur is generally heard. A mid-systolic murmur at the cardiac apex is a sign of a relative stenosis of the mitral valve associated with increased pulmonary blood flow. A prominent second heart sound is indicative of pulmonary hypertension.

ECG

If the shunt is small, the ECG is unremarkable. Signs of biventricular overload can be seen if the shunt is large, in neonates, or if there is pulmonary hypertension.

Chest X-ray

Depending on the size of the shunt, there is cardiomegaly with enlarged left atrium and ventricle and increased pulmonary vascular markings. The pulmonary artery appears prominent, the aortic knob rather narrow.

Echocardiography

The defect can generally be diagnosed reliably using echocardiography. As a result of the left-to-right shunt, the left atrium and ventricle are enlarged and the pulmonary artery and its branches are dilated. The defect itself can be identified using color Doppler. Antegrade diastolic flow can be detected in the pulmonary artery. When rotating to visualize the intersecting great arteries, the 2D image shows an interruption of the contours of the vessels. Aside from the size of the defect, the relation to the branches of the pulmonary arteries should also be noted. Similar to a hemodynamically relevant PDA, there may be diastolic flow reversal in the abdominal aorta or celiac trunk.

Associated cardiac anomalies (in particular an interrupted aortic arch) must be ruled out.

PDA and truncus arteriosus communis should be considered as a differential diagnosis. However, a PDA does not originate from the ascending aorta. In truncus arteriosus communis, there is only one large semilunar (truncal) valve overriding a malalignment VSD.

Cardiac Catheterization

Cardiac catheterization is generally not required, but an isolated small aortopulmonary window can possibly be closed by interventional catheterization.

Definition

An arteriovenous fistula (AV fistula) is an abnormal connection between an artery and a vein that bypasses the capillary bed. There is either a direct connection between the two vessels or a network existing between them with a larger vascular lumen that offers lower resistance than the capillary bed. AV fistulas are generally congenital in children, but can be acquired (e.g., as a complication following a vein puncture).

The most common AV fistulas occurring in the brain, the liver, and the lungs are discussed here. Other typical sites are the thorax (usually proceeding from the mammary artery), neck (usually the external carotid artery or subclavian artery), limbs, and kidneys. AV fistulas can be isolated or occur in multiples. Multiple arteriovenous anomalies occur frequently in patients with Osler-Weber-Rendu syndrome.

Fistulas of the coronary arteries are described in Chapter 15.30.

Epidemiology

These anomalies occur rarely.

Pathology

AV fistulas occur either as a direct connection between an artery and a vein or consist of a tangle of vessels of varying sizes (nidus) supplied by one or more arteries and drained by several veins. The reduced vascular resistance can lead to an increase in stroke volume with a large pulse pressure, increase in heart rate, cardiac volume overload, and if the shunt is large, to congestive heart failure. Blood flow can be reduced distal to the fistula. In neonates, cyanosis develops if the systemic vascular resistance is lower than the pulmonary vascular resistance and a right-to-left shunt develops across a still patent foramen ovale or PDA. In patients with cardiac failure, cyanosis can also be a sign of reduced peripheral blood flow that leads to cyanosis due to extraction.

Definition

In dextro-transposition of the great arteries (d-TGA), the two great vessels (aorta, pulmonary artery) are “switched” (Fig. 15.24 and Fig. 15.25). There is an anomalous origin of the aorta from the right ventricle and of the pulmonary artery from the left ventricle (ventriculoarterial discordance). The positions of the atria and ventricles relative to each other are normal (atrioventricular concordance). The result is a parallel and not connected circuit of systemic and pulmonary circulation. Deoxygenated blood is pumped from the right ventricle through the aorta back into the systemic circulation, while oxygenated blood from the left ventricle reaches the lungs. This leads to severe hypoxemia if no mixing of venous and arterialized blood can take place via additional connections (e.g., patent foramen ovale, PDA, VSD).

Epidemiology

A d-TGA constitutes about 5% of all congenital heart defects and is the second most common cyanotic defect after the tetralogy of Fallot. The incidence is approximately 20 to 30 per 100,000 live births. Boys are affected around twice as often as girls.

Pathogenesis

The details leading to a d-TGA are not fully understood. The cause may be a development disorder in the embryonic truncal septum that separates the originally common trunk into the aorta and pulmonary artery, or in the distal infundibulum (arterial cone).

Classification

A simple or complex TGA is distinguished depending on the presence of other cardiac anomalies:

• 
  

  Simple d-TGA: The term “simple d-TGA” (d-TGA simplex) describes a d-TGA in which there are no other cardiac anomalies aside from a patent foramen ovale and PDA. Two-thirds of cases are d-TGA simplex.

  
  
• 
  

  Complex d-TGA: In a complex d-TGA, additional cardiac anomalies such as a VSD or coronary anomalies are present.

Hemodynamics

The aorta arises from the right ventricle. It usually passes in front of the pulmonary artery, which arises behind the aorta from the left ventricle. Both vessels proceed upward parallel to each other and do not intersect. Generally, this means that the aorta is at the right (hence dextro-TGA, d-TGA) and in front of the pulmonary artery. Both circulations are arranged in parallel and are completely separate from each other. The right ventricle supplies the systemic circulation and the coronary arteries; the left ventricle supplies the pulmonary circulation. This can be survived only if there is a connection that results in oxygenated blood entering the aorta and thus systemic circulation. This connection is a defect at the atrial level that allows oxygenated blood from the left atrium to flow into the right atrium across a left-to-right shunt (Fig. 15.26). The oxygenated blood then flows through the right ventricle into the aorta.

The pulmonary blood flow is increased by a PDA, leading to an increase in pressure in the left atrium, which encourages a left-to-right shunt at the atrial level. A VSD can have the same effect. It is important to understand that systemic circulation can generally be supplied with oxygenated blood only through a left-to-right shunt at the atrial level. A PDA or a VSD encourages a left-to-right atrial-level shunt by increasing pulmonary blood flow and thus increasing left atrial pressure.

An exception may be if there is a very large ASD with pressure equalization in both atria, where true intracirculatory mixing of oxygenated and deoxygenated blood occurs at the atrial level. When the pulmonary vascular resistance is still elevated, a bidirectional shunt may form at the ductus level and also results in mixing oxygenated and venous blood. However, when the pulmonary vascular resistance drops, only a shunt from the systemic to pulmonary circulation occurs across the ductus.

In clinical practice, “poor mixers” are occasionally seen, in whom there is no satisfactory explanation for pronounced undersaturation despite a large atrial communication.

Associated Anomalies

Associated cardiac anomalies occur in around one-third of patients with a d-TGA (complex d-TGA) that sometimes have a considerable effect on the hemodynamics or consequences for the surgical procedure:

• 
  

  A ventral septal defect (VSD) increases pulmonary blood flow and leads to an increase in left atrial pressure so the left-to-right shunt at atrial level is improved. In addition, if there is a very large VSD with equalization of the pressure in both ventricles, the left ventricle remains “fit,” which can have a favorable effect on a later switch procedure.

  
  
• 
  

  Coronary anomalies are frequent and are particularly significant for surgical correction. The most frequent coronary anomaly is an origin of the circumflex branch from the right coronary artery; less frequently, there is a single coronary ostium or an intramural course of the coronary arteries in the aortic wall. A coronary anomaly may make a switch procedure impossible, as the coronary arteries would have to be transplanted as part of the correction procedure.

  
  
• 
  

  A valvular or subvalvular pulmonary stenosis becomes a functional aortic stenosis after a switch procedure. If there is a relevant pulmonary stenosis, a Rastelli procedure must be performed (see Chapter 15.10.3).

  
  
• 
  

  The leading symptom of a d-TGA with coarctation of the aorta or interrupted aortic arch is dissociated cyanosis: the upper half of the body is cyanotic while the lower half is rosy. This occurs because the lower half of the body is supplied with oxygenated blood through the patent PDA.

  
  
• 
  

  An obstruction of the left ventricular outflow tract is usually a dynamic stenosis caused by the protrusion of the ventricular septum into the left ventricle.

  
  
• 
  

  Mitral valve anomalies: After a switch procedure, a previously existing mitral valve cleft can lead to severe mitral valve incompetence, so anomalies in the mitral valve must be diagnosed preoperatively and treated during the operation.

Associated Syndromes

A d-TGA is only rarely associated with genetic syndromes or extracardiac anomalies.

Symptoms

The clinical symptoms depend on the type and size of the shunt between the parallel circulatory systems and associated cardiac anomalies. Neonates are initially unimpaired in the immediate postnatal period and generally have a normal birth weight, as an intrauterine d-TGA has only a minimal hemodynamic effect.

The leading symptoms are severe central cyanosis that develops in the first hours or days of life that does not respond to oxygen and metabolic acidosis. This finding is in contrast to the relatively unremarkable auscultation finding of a d-TGA simplex.

In a d-TGA with large VSD, cyanosis may be less pronounced. Progressive heart failure is the main clinical symptom, which develops when pulmonary resistance drops and leads to increasing excessive pulmonary blood flow. In these cases, the symptoms of heart failure (poor feeding, tachypnea, tachycardia, hepatomegaly, and failure to thrive) are predominant.

Complications

The main problems are the developing severe systemic hypoxia and metabolic acidosis. Excessive pulmonary blood flow (d-TGA with large VSD) leads to increasing cardiac failure. In patients with a d-TGA and VSD, pulmonary vascular resistance develops sooner than in other defects associated with excessive pulmonary blood flow—often in infants as young as 3 to 4 months. The reasons are not yet fully understood.

Auscultation

A murmur is usually not heard in a d-TGA with no additional cardiac anomalies. After the drop in pulmonary vascular resistance, there may be a left parasternal systolic ejection murmur, which is a sign of a relative pulmonary stenosis associated with increased pulmonary blood flow. Because of the anterior position of the aorta, the second heart sound is prominent and seems to be unsplit because the closing sound of the pulmonary artery located to the posterior is not heard.

If there is a simultaneous VSD, a typical band-shaped holosystolic murmur with PMI in the 3rd or 4th left parasternal ICS can be heard after the drop in pulmonary vascular resistance.

ECG

The ECG has signs of (initially physiological, later pathological) right heart hypertrophy (moderate right axis deviation, high R waves in V₁/V₂, possibly a positive T wave in V₁ after the 1st day of life) and possibly signs of right atrial overload (P pulmonale).

If there is a large VSD or pulmonary stenosis, signs of biventricular hypertrophy develop.

Chest X-ray

The cardiac silhouette is generally slightly enlarged. The typical configuration of the cardiac silhouette is described as “egg on its side,” an egg-shaped heart lying sideways in the thorax. The mediastinal vascular band is narrow; the pulmonary segment is absent. The pulmonary vascular markings are increased.

Echocardiography

A reliable diagnosis can be made using echocardiography. The following typical d-TGA findings should be assessed for every d-TGA:

• 
  

  The parasternal long view shows the aorta arising from the right ventricle, which is in an anterior position. In the parasternal short axis view, the aorta lies anterior and to the right of the pulmonary artery. The two vessels run parallel to one another and do not intersect.

  
  
• 
  

  The right ventricle is usually enlarged and compresses the banana-shaped left ventricle. The right ventricle normally curves around the left ventricle.

  
  
• 
  

  Visualization of the coronary artery anatomy (Fig. 15.27): The coronary arteries practically always originate from the “facing sinus,” that is, from the two sinuses of Valsalva of the aorta located directly opposite the pulmonary artery. In a d-TGA, the right coronary artery usually originates in the right “facing sinus 1” and the left coronary artery with the circumflex branch arises from the left “facing sinus 2.”

  

  
  
• 
  

  Visualization of the atrial communication (patent foramen ovale, ASD II): A sufficiently large atrial shunt is necessary for survival. A protrusion of the atrial septum to the right and accelerated flow across the defect are signs of a restrictive atrial shunt.

  
  
• 
  

  Visualization of the PDA: It is necessary to investigate whether the PDA is sufficiently wide or is occluded. The shunt direction must also be assessed. There is usually a bidirectional shunt until the drop in pulmonary vascular resistance, after which the flow is generally from the aorta to the pulmonary artery.

  
  
• 
  

  Exclusion or detection of additional cardiac anomalies: especially VSD, valvular or subvalvular pulmonary stenosis, left ventricular outflow tract obstruction, coarctation of the aorta, and mitral valve cleft.

Cardiac Catheterization

The diagnosis can usually be reliably made using echocardiography. Cardiac catheterization is indicated only to perform a Rashkind balloon atrial septostomy for a restrictive atrial connection (see Chapter 15.10.3) or in individual cases for the reliable visualization of the coronary arteries and associated cardiovascular anomalies.

MRI

A preoperative MRI is not usually needed, but can explain specific anatomical details. It is often performed postoperatively in older patients after an atrial baffle procedure (see Chapter 15.10.3).

Conservative Treatment

Immediately after the diagnosis is made, prostaglandin E infusion should be started to keep the ductus arteriosus patent (initial dose: 50 [to 100] ng/kg/min). The dose can usually later be reduced considerably (5–10 ng/kg/min) or discontinued depending on the symptoms and the echocardiography findings.

Oxygen therapy should be given with caution. On the one hand, oxygen can provoke the closure of the ductus arteriosus and on the other hand, pulmonary resistance is also lowered when oxygen is given, which can result in an increase in the pulmonary blood flow and systemic saturation. After a successful balloon atrial septostomy, the pulse oximetry oxygen saturation should be over 70% without additional oxygen therapy or prostaglandin infusion to maintain the patency of the PDA.

The indication for volume treatment (e.g., fractionated 5 – 10 – 15 mL/kg IV) should be made generously, but volume overload must be avoided. If there are clear signs of excessive pulmonary blood flow (e.g., d-TGA with a large VSD), diuretics are indicated.

Interventional Catheterization

Rashkind balloon atrial septostomy

If there is a restrictive atrial connection and systemic oxygen saturation below 70% despite a PDA, a Rashkind balloon atrial septostomy (Fig. 15.28) is indicated. A special balloon catheter is inserted through the foramen ovale into the left atrium, filled with 2.5 to 3 mL of fluid, and retracted forcefully. This tears the atrial septum and enlarges the atrial connection. This procedure can generally also be performed in the intensive care unit under echocardiography guidance.

In older children with a rigid atrial septum, an alternative is blade atrial septostomy, which is performed using a special catheter with a blade at the tip.

Stent implantation in the ductus arteriosus is only rarely indicated to keep it patent for a long period.

Surgery

In principle, correction is possible at the atrial level (Mustard/Senning procedure), ventricular level (Rastelli procedure), or level of the great arteries (arterial switch operation). Today, the arterial switch procedure, which most closely approaches normal anatomy and gives the best long-term results, is generally preferred. Until the mid-1980s, before the more complicated switch procedure became routine, atrial baffle procedures were performed in most patients. The greatest surgical challenge in the switch operation is transplanting the coronary arteries.

Arterial Switch Operation (Jatene procedure)

Indication

Therapy of choice in the first 4 weeks of life, unless associated cardiac anomalies make this treatment option impossible.

Method

After transecting the aorta and pulmonary artery, the great vessels must be transposed (Fig. 15.29). In addition, the coronary arteries are excised with a “vascular cuff” and transplanted to the neo-aorta (coronary transfer). Usually the bifurcation of the pulmonary artery is relocated anterior to the aortic arch (Lecompte maneuver) to reduce the risk of tension in the pulmonary artery and its branches.

Timing of the operation

After the patient has reached the age of 2 months the operation can no longer be easily performed without preparation of the left ventricle, which is no longer in adequate condition to function as a systemic ventricle after the drop in pulmonary resistance. If the operation has to be performed at a later time, pulmonary artery banding may be necessary as preparation, which leads to an increase in the muscular mass of the left ventricle.

Exception: If there is a large VSD, the left ventricle retains sufficient muscle strength due to the equalization of pressure between the right and left ventricles and may later be converted to a systemic ventricle, even without preparation.

Mustard or Senning Atrial Baffle Operation

Indication

An atrial baffle operation may still be indicated today, especially when coronary anomalies make a coronary transfer impossible.

Method

The blood from the superior and inferior vena cava is directed through a trousers-shaped baffle made of pericardial (Mustard) or atrial tissue (Senning) through the atria to the mitral and subpulmonary valve. After the removal or modification of the atrial septum, the oxygenated blood from the pulmonary veins flows around the atrial baffle to the tricuspid and systemic valve (Fig. 15.30).

Rastelli Procedure

Indication

The Rastelli procedure is indicated for a d-TGA with VSD and severe pulmonary stenosis.

Method

The pulmonary artery is transected at the trunk and the VSD is closed with a patch so that the left ventricle drains into the aorta (Fig. 15.31). It may be necessary to enlarge the VSD prior to closure. The right ventricle is incised and connected with the pulmonary artery by a valved conduit.

Damus-Kaye-Stansel Procedure

Indication

For a d-TGA with VSD and a relevant subaortic stenosis, a Damus–Kaye–Stansel procedure with implantation of an extracardiac conduit from the right ventricle to the pulmonary artery may be necessary. However, this operation is very rarely needed for d-TGA.

Method

After transecting the main pulmonary artery, the pulmonary artery is anastomosed end-to-side with the ascending aorta (Damus–Kaye–Stansel anastomosis) and the VSD is also closed. The blood from the left ventricle then flows through the anastomosis via the main pulmonary artery into the aorta. The right ventricle is then connected with the pulmonary artery using an extracardiac conduit (Fig. 15.32).

Definition

As in dextro-transposition of the great arteries (d-TGA), in congenitally corrected transposition of the great arteries (ccTGA), the aorta also arises from the right ventricle and the pulmonary artery from the left ventricle. However, there is a simultaneous “reversal” of the ventricles (ventricular inversion). The left ventricle is positioned in the position of the right ventricle (anterior and right) and vice versa. The right ventricle is thus connected to the left atrium and the left ventricle to the right atrium (Fig. 15.33). The venous blood from the right atrium flows through the morphologic left ventricle into the pulmonary artery and arterialized blood flows from the left atrium through the morphologic right ventricle into the aorta. This is termed a discordant atrioventricular and ventriculoarterial connection. If no other cardiac anomalies are present, the hemodynamic features of a ccTGA are normal. Typically, in this heart defect the aorta runs to the left of the pulmonary artery. This characteristic has led to the designation l-TGA as a synonym for this heart defect (l is for levo = left).

The term “l-TGA” has been established as a synonym for the heart defect described above. Strictly speaking, l-TGA means only that the aorta runs to the left of the pulmonary artery (l-transposition) and the term says nothing about the relationship of the atria to the ventricles or the ventricles to the major arteries. An l-transposition of the great vessels may also be found in association with other congenital heart defects—frequently with a double-inlet left ventricle, for example.

Pathogenesis

The cause is a faulty rotation of the left heart tube during embryonic development. This leads to a situation where the morphologic right ventricle is positioned to the left of the morphologic left ventricle.

Epidemiology

A ccTGA is a rare congenital anomaly and accounts for less than 1% of all congenital heart defects. Males are affected slightly more often than females.

Hemodynamics and Pathological Anatomy

The hemodynamic status in a ccTGA is normal if there are no other cardiac anomalies: the blood of the venous system flows through the right atrium into the left ventricle and from there through the pulmonary artery into the lungs. The blood flows through the pulmonary veins into the left atrium and from there through the right ventricle into the aorta.

The spatial relations are important. In a ccTGA, the morphologic left ventricle (subpulmonary) is usually located at the right and the morphologic right ventricle (subaortic) is located at the left of the chest. The ventricle with the characteristics of a right ventricle is called a morphologic right ventricle: The atrioventricular valve has three leaflets, the myocardium is clearly trabecular, and the inflow and outflow valves are separated by a muscle band (crista supraventricularis). The left ventricle has the following morphological features: The atrioventricular valve has two leaflets, the myocardium has a fine trabecular structure, and the inflow and outflow valves are merged (fibrous continuity).

In ccTGA, as in d-TGA, the aorta is located anterior to the pulmonary artery, but to the left of it. The ventricular septum is often located in the vertical/sagittal plane in a ccTGA. In 95% of cases there is a normal arrangement (situs solitus). Dextrocardia is found in around 20% of cases.

Clinically important is the fact that the AV node is located further anterior and superior than usual and that the bundle of His is a conspicuously long segment. These anatomical features may predispose to AV conduction disorders. In addition, accessory pathways are often found.

Associated Anomalies

In around 90% of cases, there are accompanying cardiac anomalies that have a major effect on the clinical course. Most common are:

• 
  

  Tricuspid valve anomalies (up to 90%): mostly tricuspid regurgitation, the Ebsteinlike anomaly of the tricuspid valve is also relatively common (in ccTGA, the tricuspid valve is found on the left side and functions as a systemic AV valve)

  
  
• 
  

  VSD (75%)

  
  
• 
  

  Subvalvular or valvular pulmonary stenosis (30–50%)

  
  
• 
  

  Pulmonary atresia (10%)

  
  
• 
  

  Preexcitation syndromes

  
  
• 
  

  AV conduction problems

Less common are:

• 
  

  Coarctation of the aorta, interrupted aortic arch

  
  
• 
  

  Mitral valve anomalies

  
  
• 
  

  Double-outlet right ventricle

Associated Syndromes

No frequent association with specific genetic syndromes has been described.

Symptoms

The clinical symptoms depend mainly on the accompanying cardiac anomalies. If there are no additional anomalies, patients may initially be completely free of symptoms. If there is a large VSD, the main symptom is excessive pulmonary blood flow and development of heart failure (tachypnea, hepatomegaly, poor feeding, failure to thrive). Patients with a relevant tricuspid regurgitation may also develop symptoms of heart failure, depending on its extent.

Patients with a ccTGA combined with a VSD and pulmonary stenosis may present with cyanosis as in tetralogy of Fallot.

Of particular importance is bradycardia. Due to the anatomical features of the AV node and the conduction system, one-third to almost one-half of the patients eventually develop a complete AV block.

Complications

Even with an isolated ccTGA, most patients develop clinical symptoms of heart failure—but often not until adulthood. These symptoms are due to the fact that the morphologic right ventricle is not suitable for the strains of a systemic ventricle. Increasing insufficiency of the tricuspid valve, which functions as a systemic AV valve, can have an unfavorable impact. Complete AV blocks make it necessary to implant a pacemaker. Supraventricular tachycardias can be the result of an accessory conduction pathway.

Auscultation

Due to the anterior location of the aorta, there is a single, loud second heart sound because the closing sound of the pulmonary artery can usually not be heard from its posterior location. A holosystolic left parasternal murmur can be caused by tricuspid regurgitation or a VSD. A systolic ejection murmur on the left upper sternal border suggests a pulmonary stenosis.

ECG

The inversion of Q waves that represent the left ventricle is a typical ECG finding. Normally, the Q waves are present in the left precordial leads (V₅, V₆)—however, in ccTGA, Q waves can be detected in the right precordial leads.

Chest X-ray

A typical finding is an aorta that forms the upper left border. Cardiomegaly can be the result of tricuspid regurgitation or a VSD. The pulmonary blood flow is dependent on additional anomalies (VSD, pulmonary stenosis). Atrial dilatation or pulmonary edema is found if there is relevant tricuspid regurgitation. Dextrocardia is present in approximately 20% of cases.

Echocardiography

The diagnosis can be made reliably using echocardiography. In any event, accompanying cardiac anomalies must be noted. The following findings are typical:

• 
  

  In the four-chamber view, the left AV valve (in this case, the tricuspid valve) is located further apical than the right one.

  
  
• 
  

  The left ventricle has typical signs of a morphologic right ventricle (discontinuity between the AV valve and the semilunar valve from a muscle band, strong trabeculation, moderator band, attachment of the tendinous cords of the AV valve in the ventricular septum).

  
  
• 
  

  The position of the great vessels in relation to each other can be visualized in the parasternal short axis. The aorta is located anterior and to the left of the pulmonary artery. The two vessels are parallel and do not intersect.

  
  
• 
  

  The course of the ventricular septum is unusual in ccTGA with a rather vertical orientation.

  
  
• 
  

  For the further procedure, it is important to assess the coronary arteries, which usually arise from the “facing sinus” as in a d-TGA (Fig. 15.27).

  
  
• 
  

  Associated cardiac anomalies must be ruled out or identified, especially VSD, tricuspid anomalies, and obstructions of the outflow tracts.

  
  
  
  

  Note

  
  

  Every Ebstein anomaly of a left AV valve suggests a ccTGA.

Cardiac Catheterization

Cardiac catheterization is generally indicated only if there are additional anomalies. In these cases, cardiac catheterization can answer questions, for example, as to the size of the shunt and whether pulmonary hypertension is present in a VSD. In the angiography, the connection between the right atrium and the morphologic left ventricle as well as the connection of the left atrium to the morphologic right ventricle can be visualized. The aorta is located anterior and to the left.

MRI

In an MRI, detailed and often complex anatomical spatial relations and additional cardiac anomalies can be visualized. In addition, the shunt in a VSD can be quantified and function and size of the systemic ventricle can be evaluated.

Conservative Treatment

If necessary, heart failure can be treated pharmacologically. If there is tricuspid regurgitation, ACE inhibitors are used to reduce the afterload.

Surgical Treatment

The surgical procedure for a ccTGA is made difficult by the specific anatomy including abnormal location of the AV node and the unusual orientation of the ventricular septum.

Two different surgical options are available. In a conventional surgical intervention, the individual associated cardiac anomalies are corrected or are treated palliatively. In an anatomical correction, associated heart anomalies are corrected in addition to a correction of the left ventricle so that it later functions as a systemic ventricle. This requires the complex double switch procedure, which is expected to give a better long-term prognosis.

Conventional surgical procedures

The following conventional surgical procedures may be indicated:

• 
  

  VSD closure: Postoperatively there is a high risk of a complete AV block. Due to the specific anatomy, closure via a transatrial access can be difficult. To minimize the risk of a complete AV block, the sutures of the VSD patch should be placed from the morphologic right ventricle. However, in a ccTGA, the morphologic right ventricle is located on the left side so that it can be more readily reached via an access through the aortic valve.

  
  
• 
  

  Banding the pulmonary artery: If there is a large VSD, banding the pulmonary artery may be useful as an interim measure to reduce excessive pulmonary blood flow.

  
  
• 
  

  Tricuspid valve reconstruction or replacement: depending on the severity of tricuspid regurgitation, a tricuspid valve reconstruction or replacement may be necessary.

  
  
• 
  

  Tricuspid valve annuloplasty.

  
  
• 
  

  Aortopulmonary anastomosis (modified Blalock–Taussig shunt): In a VSD with severe pulmonary stenosis, an aortopulmonary anastomosis can be indicated as an interim measure to ensure pulmonary perfusion. At a later stage, a VSD patch closure and implantation of a valved conduit can be performed.

  
  
• 
  

  Univentricular palliation (modified Fontan procedure): If there is significant hypoplasia of the right systemic ventricle, a univentricular palliative Fontan procedure may be needed in individual cases.

Double switch procedure

The aim of the double switch operation is to transform the left ventricle into a systemic ventricle. This is possible using a combination of an atrial baffle procedure with an arterial switch operation (Fig. 15.34). In the atrial baffle procedure, the blood of the systemic veins is conducted to the morphologic right ventricle and the blood of the pulmonary veins is conducted to the morphologic left ventricle. In order to allow the blood of the systemic veins to reach the aorta from the morphologic left ventricle, an additional arterial switch procedure to transplant the great vessels must be performed.

In a ccTGA with VSD and severe pulmonary stenosis, it is also possible to perform a double switch procedure in which, instead of the arterial switch, a Rastelli procedure is performed with implantation of a conduit between the morphologic right ventricle and the pulmonary artery (Fig. 15.35). Details of the individual surgical procedures are found in Chapter 15.10.

Pacemaker

Implantation of a pacemaker is indicated if there is a complete AV block or symptomatic bradycardia.

Cardiac transplant

A cardiac transplant is the last treatment option for progressive failure of the systemic ventricle.

Definition

In a double-outlet right ventricle (DORV), the pulmonary artery as well as the aorta arises completely, or at least mainly, from the right ventricle. A VSD is practically always present. When both great arteries originate entirely in the right ventricle, a VSD is the only outlet from the left ventricle.

The hemodynamic status depends primarily on the location of the VSD in relation to the great vessels and the presence or absence of a pulmonary stenosis.

The definition of DORV is not always consistent. For some authors, a sufficient criterion is that one artery originates entirely and the other originates at least predominantly from the right ventricle (50% rule), but this definition is not correct from an embryological standpoint.

Another definition requires the presence of a bilateral conus. A conus (synonym for infundibulum) is a muscular ring or a tunnel located below the semilunar valve. Normally only the right ventricle has a conus or a muscular infundibulum. Therefore, in normal anatomy, a muscular infundibulum is found only below the pulmonary artery. By contrast, it is typical for a DORV that such a muscular conus is found below the pulmonary valve as well as below the aortic valve. This results in muscle tissue being present between the two semilunar valves (conus septum). There is also a typical discontinuity between the mitral valve and the adjacent semilunar valve. By contrast, in normal anatomy there is fibrous continuity between the mitral valve and the aortic valve, which means that the aortic valve and the mitral valve merge into each other and are not separated by a muscle band.

Epidemiology

DORVs constitute 1 to 1.5% of all congenital heart defects. The incidence is 0.1 per 1,000 live births.

Pathogenesis

The cause is probably a development disorder of the embryonic conotruncal septation.

Classification

DORVs are classified depending on the location of the VSD in relation to the great vessels, which is crucial for the hemodynamics (Fig. 15.36):

• 
  

  DORV with subaortic VSD (50%): The VSD is located just below the aortic valve. It is often associated with a pulmonary stenosis (Fallot-type DORV). The pulmonary stenosis is usually a subvalvular stenosis caused by the conus septum.

  
  
• 
  

  DORV with a subpulmonary VSD (25%): This is also called Taussig–Bing anomaly. The VSD is located just below the pulmonary artery. This form is often associated with a subaortic stenosis caused by the conus septum. The subaortic stenosis leads to impaired development of the aortic arch so that an interrupted aortic arch or coarctation of the aorta often occurs.

  
  
• 
  

  DORV with a doubly committed VSD (5%): The VSD is connected to both great vessels.

  
  
• 
  

  DORV with an uncommitted (remote) VSD (20%): The VSD has no direct connection to the great vessels.

Hemodynamics and Pathology

DORV does not present a uniform clinical picture. The major differences in the hemodynamic situation depend on the location of the VSD in relation to the great vessels and the presence or absence of a pulmonary stenosis.

In principle, the aorta and the pulmonary artery may have any spatial relation to each other. Most common is the side-to-side position, where both vessels originate next to each other from the heart and have a parallel course, with the aorta usually at the right of the pulmonary artery. Other possibilities are a normal position (rare), a d-malposition (the aorta originates from the pulmonary artery and runs parallel to the pulmonary artery at its right), and an l-malposition (the aorta originates from the pulmonary artery and runs parallel to the pulmonary artery at its left).

The correct term used for a DORV is malposition, not transposition of the great vessels, because the pulmonary artery always originates from the “correct” right ventricle.

Aortic and pulmonary valves are located at the same level and are typically separated by the conus septum. There is typically also a bilateral conus.

Hemodynamically, the different types of DORV are similar to three defects:

• 
  

  Tetralogy of Fallot (leading symptom: cyanosis)

  
  
• 
  

  Large VSD (leading symptom: excessive pulmonary blood flow / heart failure)

  
  
• 
  

  d-TGA with VSD (leading symptoms: cyanosis, excessive pulmonary blood flow / heart failure)

A pulmonary stenosis is commonly associated with a subaortic stenosis and, very rarely, associated with a subpulmonary VSD (Taussig–Bing anomaly). In a subpulmonary VSD, there is often a subaortic stenosis caused by the conus septum, which may lead to incomplete development of the aortic arch resulting in aortic coarctation or an interrupted aortic arch.

Subaortic VSD with a pulmonary stenosis (Fallot type)

The hemodynamic situation is similar to tetralogy of Fallot: The oxygenated blood flows from the left ventricle through the VSD primarily into the aorta, while the deoxygenated blood passes from the right ventricle to the pulmonary artery. Because of pulmonary stenosis, the pulmonary blood flow is reduced, causing cyanosis, depending on the extent of pulmonary stenosis.

Subaortic VSD without pulmonary stenosis (rare)

The hemodynamic situation is similar to a large VSD: Due to the large VSD, the pressure between the two ventricles is usually equalized. There is excessive pulmonary blood flow, leading to heart failure, and a risk of pulmonary hypertension developing.

Subpulmonary VSD (Taussig–Bing anomaly) without pulmonary stenosis

The hemodynamic situation is similar to d-TGA with VSD: The oxygenated blood from the left ventricle crosses the VSD to reach the pulmonary artery, while the deoxygenated blood from the right ventricle flows primarily into the aorta and from there into the systemic circulation. There is excessive pulmonary blood flow due to the VSD. Initially, cyanosis is not pronounced, but heart failure and pulmonary hypertension can develop rapidly.

Subpulmonary VSD (Taussig–Bing anomaly) with pulmonary stenosis (very rare)

The hemodynamic situation and clinical features are similar to tetralogy of Fallot. There is often severe cyanosis and ductal-dependent pulmonary blood flow.

Doubly committed VSD without pulmonary stenosis

The hemodynamic situation is similar to large VSD.

Doubly committed VSD with pulmonary stenosis

The hemodynamic situation is similar to tetralogy of Fallot.

Uncommitted VSD without pulmonary stenosis

The hemodynamic situation is similar to large VSD.

Uncommitted VSD with pulmonary stenosis

The hemodynamic situation is similar to tetralogy of Fallot.

Associated Anomalies

Associated cardiac anomalies are common with DORV. A VSD is almost always present. Subvalvular obstruction of the outflow tract occurs mostly through displacement of the conus septum. The most important associated anomalies, which often also have an effect the surgical procedure, are listed below:

• 
  

  VSD (almost always present)

  
  
• 
  

  Malposition of the great vessels (typically side-to-side position of the great vessels, rarely also l- or d-malposition)

  
  
• 
  

  Anomalies of the AV valves (AV canal, often with unbalanced ventricles as well)

  
  
• 
  

  Pulmonary stenosis (usually subpulmonary and caused by conus tissue, hemodynamically relevant)

  
  
• 
  

  Pulmonary atresia (ductal-dependent pulmonary blood flow)

  
  
• 
  

  Mitral stenosis/atresia with hypoplasia of the left ventricle

  
  
• 
  

  “Straddling” mitral valve (mitral valve chordae pass through the VSD into the right ventricle)

  
  
• 
  

  Subaortic stenosis, coarctation of the aorta, interrupted aortic arch (especially with a Taussig–Bing anomaly in which the subaortic region may be obstructed by the conus septum)

  
  
• 
  

  Coronary anomalies: single origin of both coronary arteries, origin of the anterior interventricular branch from the right coronary artery

  
  
• 
  

  Anomalies of the conduction system (AV nodes, bundle of His)

Associated Syndromes

DORV occurs more frequently in children born to diabetic mothers and a more frequent occurrence in association with certain chromosomal diseases (CHARGE association, trisomy 13, trisomy 18, tetrasomy 8p, microdeletion of 22q11) has also been described. DORV also occurs often in heterotaxy syndromes.

Symptoms

There are various clinical manifestations corresponding with the different hemodynamic features described above:

• 
  

  Fallot type: leading symptom is cyanosis depending on the severity of the pulmonary stenosis

  
  
• 
  

  VSD type: mainly signs of heart failure due to excessive pulmonary blood flow (primarily poor feeding, failure to thrive, increased sweating, tachypnea/dyspnea, hepatomegaly)

  
  
• 
  

  TGA with VSD type: leading clinical findings are signs of heart failure due to excessive pulmonary blood flow; due to pulmonary recirculation, cyanosis is initially usually relatively mild

If there is also aortic coarctation or an interrupted aortic arch, the pulses are absent in the lower limbs after the closure of the ductus arteriosus, and heart failure develops.

Auscultation

The second heart sound is loud if there is excessive pulmonary blood flow or an anterior position of the aorta. If there is pulmonary stenosis, there is a rough holosystolic murmur with PMI in the 2nd left intercostal space. A band-shaped holosystolic murmur with PMI in the 4th left intercostal space is a sign of a VSD. A low-frequency diastolic murmur over the cardiac apex indicates a relative tricuspid stenosis associated with excessive pulmonary blood flow.

ECG

There is almost always a right axis deviation, sometimes a marked right axis deviation. Often there is a first degree AV block. If pulmonary stenosis is present, there are signs of a right ventricular hypertrophy, often a complete right bundle branch block, and a P dextrocardiale. Signs of biventricular hypertrophy are predominant if no pulmonary stenosis is present. Isolated signs of left ventricular hypertrophy are rare in these cases. Typically left axis deviation occurs if there is an associated AV canal.

Chest X-ray

The radiological appearance of the different types of DORV varies depending on the hemodynamics:

• 
  

  DORV with pulmonary stenosis: usually normal-sized cardiac silhouette and decreased pulmonary vascular markings depending on the extent of the pulmonary stenosis

  
  
• 
  

  DORV without pulmonary stenosis: usually significantly enlarged cardiac silhouette, prominent pulmonary artery segment, and increased pulmonary vascular markings

  
  
• 
  

  Taussig–Bing anomaly: similar to TGA (“egg lying on its side”), but with a wider waist

Echocardiography

The diagnosis can usually be reliably made using echocardiography. The examination shows the following typical findings or can clarify the following questions:

• 
  

  In the parasternal long axis, the posterior great artery overrides the VSD by more than 50%; the anterior artery arises entirely from the right ventricle

  
  
• 
  

  No fibrous continuity between the anterior mitral leaflet and the adjacent semilunar valve (substantiating evidence)

  
  
• 
  

  Assessment of the position of the great vessels to each other (side-to-side position), l- or d-malposition (i.e., the aorta is located anterior to and at the left or the right of the pulmonary artery)

  
  
• 
  

  Location and size of the VSD (subaortic, subpulmonary, doubly committed, uncommitted)

  
  
• 
  

  Subpulmonary or subaortic obstruction of the outflow tract

  
  
• 
  

  Visualization of the conus septum (muscle tissue between the two great arteries shaped like a teardrop or the head of a match)

  
  
• 
  

  Size of the left ventricle

  
  
• 
  

  Presence of a PDA (especially important if there is a pulmonary stenosis: ductal-dependent pulmonary blood flow?)

  
  
• 
  

  Assessment of the aortic arch: detection or exclusion of hypoplasia of the aortic arch, an interrupted aortic arch, or coarctation of the aorta (especially important if there is a Taussig–Bing anomaly)

  
  
• 
  

  Visualization of the coronary arteries (origin, course)

Cardiac Catheterization

Cardiac catheterization is indicated when important questions remain unanswered despite echocardiography, for example:

• 
  

  Measurement of pressure, flow and resistance in the pulmonary circulation

  
  
• 
  

  Assessment of the pressure gradient across an outflow tract stenosis

  
  
• 
  

  Exclusion of associated anomalies

  
  
• 
  

  Visualization of the origin and course of the coronary arteries

MRI

An MRI can provide a detailed visualization of the anatomy. It is used in individual cases, for example, to clarify the relationship between the VSD and great arteries. Shunt and flow volumes can be quantified.

Conservative Treatment

If the patient has progressive cardiac failure, anticongestive treatment may bridge the time until surgery. If there is a critical pulmonary stenosis, pulmonary atresia, severe aortic coarctation, or an interrupted aortic arch, prostaglandin E (initially 50 ng/kg/min, later possibly reduced) may be necessary to ensure pulmonary and systemic perfusion.

Interventional Catheterization

If there are hemodynamic features of a TGA and a restrictive atrial shunt, a Rashkind maneuver (balloon atrial septostomy) may be required. In individual cases, balloon dilation of a pulmonary stenosis can also be indicated.

Surgical Treatment

Due to the many variations and different hemodynamic features, the surgical procedure must always be decided on a case-by-case basis depending on:

• 
  

  Location of the VSD with respect to the great arteries

  
  
• 
  

  Position of the great arteries with respect to each other

  
  
• 
  

  Presence or absence of a pulmonary stenosis

  
  
• 
  

  Associated anomalies (coronary anomalies, coarctation of the aorta, interrupted aortic arch)

Palliative Measures

Today, primary correction is generally attempted. Palliative surgery is considered on a case-by-case basis, for example, to achieve more favorable conditions for corrective surgery. The palliative procedures include banding the pulmonary artery if there is excessive pulmonary blood flow and creating an aortopulmonary shunt if there is insufficient pulmonary blood flow.

Corrective Surgery

The surgical procedure depends mainly on the location of the VSD in relation to the great arteries (Table 15.2). Sometimes a subaortic VSD can be corrected, similar to tetralogy of Fallot. Extensive surgeries are necessary for a subpulmonary VSD (Taussig–Bing anomaly). The aim in these cases is to perform an arterial switch operation including a VSD closure. In cases with a great distance between the VSD and the great vessels (uncommitted VSD), a biventricular correction is often not possible. The situation frequently becomes more favorable after the children are more than 2 years old.

Subaortic VSD

Intraventricular tunnel

The correction is similar to that for tetralogy of Fallot. The VSD is closed with a tunnel patch so that the left ventricle drains through the aorta. Under certain circumstances, the VSD must be enlarged (complication: AV block). If there is pulmonary stenosis, the right ventricular outflow tract must be widened.

Without pulmonary stenosis, this procedure must be performed as early as in the first year of life—sometimes even in the neonatal period—due to the risk of increased pulmonary resistance. In children with pulmonary stenosis, the timing of the surgical procedure is based on the degree of cyanosis.

Rastelli procedure

This operation is necessary if the patient has a severe subvalvular or valvular pulmonary stenosis. The right ventricle is connected to the pulmonary artery by a conduit. Blood from the left ventricle flows into the aorta through an intracardiac patch tunnel. The patch also closes the VSD (Fig. 15.37).

“Réparation à l’étage ventriculaire” (REV)

This surgical procedure is an alternative procedure for DORV with a severe valvular or subvalvular pulmonary stenosis. In an REV, the pulmonary artery is directly anastomosed to the right ventricle through a ventricular incision (Fig. 15.38). The pulmonary artery bifurcation is brought forward anterior to the aorta (Lecompte maneuver).

Subpulmonary VSD

The arterial switch procedure including closure of the VSD is the treatment of choice. This procedure is usually performed in the neonatal period. Additional anomalies such as coronary anomalies or obstructions of the left outflow tract make other surgical procedures necessary. An associated hypoplasia of the aortic arch, aortic coarctation, or an interrupted aortic arch is usually corrected in the same session.

Switch procedure and VSD closure

If the coronary anatomy is more favorable and no outflow obstruction is present, an arterial switch procedure can be performed as for a d-TGA. In addition, the VSD is closed with a tunnel patch so that the left ventricle drains into the aorta (Fig. 15.39).

Mustard or Senning atrial baffle

If a switch procedure is not possible owing to a coronary anomaly or the relationship of the great arteries to each other, a Mustard or Senning atrial baffle procedure operation must be considered (Fig. 15.40). In this procedure, foreign material (Mustard) or atrial tissue (Senning) is excised to allow systemic venous blood to flow through the trousers-shaped atrial tunnel into the left ventricle and from there into the pulmonary artery. The pulmonary venous blood flows past the tunnel into the right ventricle (see Chapter 15.10). In addition, the VSD is closed with a tunnel patch that conducts the blood from the left ventricle to the pulmonary artery.

Damus–Kaye–Stansel (DKS) procedure with VSD patch closure and implantation of a conduit between the right ventricle and the main pulmonary artery

A severe subaortic stenosis may require this elaborate procedure. In this operation, the main pulmonary artery trunk is anastomized with the aortic root (DKS anastomosis). The former pulmonary valve becomes the neoaortic valve. In addition, the VSD is closed with a patch so that the left ventricle drains in the neo-aortic valve (former pulmonary valve). Pulmonary blood flow is ensured by the implantation of a conduit between the right ventricle and the distal end of the main pulmonary artery (Fig. 15.41).

Definition

In a truncus arteriosus communis, only one large arterial vessel with a semilunar valve (truncus valve) arises from the heart. This vessel supplies the systemic, pulmonary, and coronary circulation. The truncus overrides a high VSD (malalignment VSD) that is almost always present. The truncus valve generally has three or four dysmorphic, thickened leaflets and is frequently insufficient.

Epidemiology

This is a relatively rare defect, constituting 1% to 2% of all congenital heart defects.

Pathogenesis

The intrauterine separation of the embryonic truncus into the aorta and pulmonary artery by the aortopulmonary septum in the 4th to 5th week of gestation fails to occur or is only partial. The infundibular septum of the right ventricular outflow tract and pulmonary valve tissue are also absent.

Classification

The anatomy of the pulmonary vessels depends on the stage when the separation of the embryonic truncus came to a halt. There are two commonly used classifications:

Classification by Collet and Edwards

This classification comprises three types (Fig. 15.42):

• 
  

  Type I (approx. 60%): Aorta and pulmonary artery arise from a common trunk. The pulmonary artery branches into a left and a right branch shortly after its origin.

  
  
• 
  

  Type II (approx. 20%): The right and left pulmonary arteries arise jointly or separately from the posterior wall of the trunk.

  
  
• 
  

  Type III (approx. 10%): Both pulmonary arteries originate independently of one another from the lateral aspect of the trunk.

Earlier, a type IV was also defined. In this type, both pulmonary arteries are absent. The lungs are perfused exclusively via aortopulmonary collaterals. In terms of pathogenesis, this cardiac defect (“truncus IV” in medical jargon) is not a truncus arteriosus, but a pulmonary atresia with VSD (Chapter 15.26).

Classification by van Praagh

Van Praagh divides the different truncus types into the main classes A and B (Fig. 15.43). Class A has a VSD; class B has an intact ventricular septum. Since an intact ventricular septum has been described only in a few isolated cases of truncus arteriosus, class B has little practical relevance. The van Praagh and the Collet and Edwards classifications overlap in some areas:

• 
  

  A1: Corresponds with type I by Collet and Edwards (see Classification by Collet and Edwards).

  
  
• 
  

  A2: Corresponds with type II by Collet and Edwards (see Classification by Collet and Edwards).

  
  
• 
  

  A3: Only one pulmonary artery arises from the truncus, the other pulmonary artery is supplied via a ductus arteriosus or from collaterals from the aorta (“hemitruncus”).

  
  
• 
  

  A4: There are additional anomalies of the aortic arch (coarctation of the aorta, atresia of the aortic arch, interrupted aortic arch). The lower half of the body is supplied with blood via a PDA.

  
  
  
  

  Note

  
  

  The most common form of a truncus arteriosus communis is a mixture of types I and II or of A1 and A2. In most cases, there is a short pulmonary artery, which makes it difficult to distinguish between types I and II or types A1 and A2 (known as “type 1.5”).

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