Anatomy and Physiology

Atrial septal defects (ASDs) are direct interatrial communications that permit the shunting of blood at the atrial level. These defects comprise the third most common congenital malformations, with an estimated incidence of 56 per 100,000 live births. Based on the site of the communication and its relation to the neighboring systemic and pulmonary veins, interatrial communications have been classified into the following groups:

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  Secundum ASDs, the most common (60% of cases), which include defects within the fossa ovalis, usually due to one or multiple defects within the septum primum. Their size may vary from a few millimeters to 2 to 3 cm.

  
  
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  Primum ASDs (approximately 20%), involving the lower (primum) portion of the atrial septum near the crux of the heart. They are located between the anteroinferior margin of the fossa ovalis and the atrioventricular (AV) valves. A primum ASD is often associated with an abnormal left AV valve (a left-sided AV valve is a trileaflet valve).

  
  
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  Sinus venosus defects (5% to 10% of cases). A superior sinus venosus defect (5%) is located in the superior portion of the atrial septum near the superior vena cava (SVC). An inferior sinus venosus defect (<1%) is located near the inferior vena cava (IVC).

  
  
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  Coronary sinus septal defects (<1%), where there is partial or complete lack of separation of the coronary sinus from the left atrium (LA).

  
  
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  Common atrium, when the entire atrial septum is absent.

Most ASDs are identified and repaired in the individual’s childhood. Small secundum ASDs may become smaller during the first years of life or may close spontaneously; however, this is not the case for the other types of ASDs. These defects produce a left-to-right atrial shunt that causes enlargement of the right cardiac chambers. Raised pulmonary artery pressure is common in patients with large shunts, but the development of pulmonary vascular disease and pulmonary hypertension over time is not as frequent.

Associated Lesions

Although the majority of cases are sporadic, ASDs are associated with numerous other congenital abnormalities (in approximately 30% of the cases). These include pulmonary valve stenosis, partial anomalous pulmonary venous connection, congenital mitral stenosis, mitral valve prolapse, ventricular septal defect (VSD), patent ductus arteriosus (PDA), and coarctation of the aorta (CoA). Specifically, primum ASDs may occur alone or in association with a small-inlet VSD and a trileaflet left AV valve. A superior sinus venosus defect is commonly associated with anomalous return of the right pulmonary vein to the right atrium (RA)/superior vena cava (SVC) junction. A coronary sinus septal defect may coexist with partial or complete anomalous pulmonary vein return as well as persistent left SVC (Raghib syndrome).

Additionally, there are well-established associations of different types of ASDs with genetic syndromes. Secundum ASDs may be present in genetic syndromes such as Holt-Oram syndrome, Noonan syndrome, or trisomy 21.

Transthoracic Echocardiography in Patients With Unrepaired Atrial Septal Defects

The goals of transthoracic echocardiography (TTE) in patients with unrepaired ASDs are

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  Determination of the anatomic site of the septal defect. The subcostal long- and short-axis views are best for the evaluation of all types of ASDs. In patients with suboptimal subcostal windows, the low left parasternal short-axis view can often provide adequate imaging of the atrial septum. However, once these defects are located, their presence should be documented by different views and confirmed by shunting and seen on color Doppler as well. Secundum ASDs are usually visualized in the midportion of the interatrial septum. The parasternal short-axis view can be used to evaluate the anteroposterior diameter of a secundum ASD. Primum ASDs are located next to the annuli of AVs and are best assessed from the apical four-chamber view and parasternal short-axis view. The low parasternal short-axis is used to visualize secundum and sinus venosus ASDs. The apical four-chamber view is not optimal for the assessment of ASDs, except for primum ASDs because the interatrial septum is parallel to the ultrasound beam, resulting in dropout. Color Doppler helps to identify the defect as well as to evaluate its size and the direction of shunt ( Fig. 6.1 ).

  
  

  
  

  
  

  

  
  

  
  

  A, Two-dimensional transthoracic echocardiogram (2D TTE) from the parasternal short-axis view at the level of the aortic valve showing a large secundum ASD (white arrows) . The RA is enlarged. B, Color Doppler showing a large left-to-right shunt (white arrows) . Ao, Aorta; ASD, atrial septal defect; LA, left atrium; RA, right atrium; RV, right ventricle.

  
  
  
  
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  Estimation of its relationship with neighboring structures (AV valves, pulmonary veins, systemic veins). The position and connection of pulmonary veins to the left atrium (LA) should always be demonstrated. Subcostal, parasternal short-axis, and high right parasternal views are helpful in detecting sinus venosus ASDs, as the connection of the right upper part of the LA, where the right pulmonary vein is normally located, with the SVC can be seen. Dilatation of the coronary sinus ostium is seen as an inferior interatrial communication close to the IVC-to-RA connection. In the patient with a dilated coronary sinus, the presence of a persistent left SVC from the suprasternal view should be identified or excluded. The morphology of the AVs should be also assessed. Primum ASDs are associated with abnormal (trileaflet) left AV valves, which are best seen from the parasternal short-axis view. Color Doppler from the parasternal long-axis, parasternal short-axis, and apical four-chamber views helps in evaluating the function of the left AV valve.

  
  
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  Evaluation of the hemodynamic significance of the shunt

  
  
  
  
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    Direction of the shunt: Color Doppler is useful in determining the direction of the shunt. Since the pressure gradient between the atria is small, velocity across the defect is usually low (< 1 to 1.5 m/s) and occurs in late ventricular systole and early diastole. When the left atrial pressure is raised due to LV disease or mitral valve stenosis, flow across the defect becomes continuous and velocity increases. In patients with atrial fibrillation, left-to-right shunt is not clear on color as the increased pressure is biatrial.

    
    
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    Size of the shunt: The size of the shunt depends on the size of the defect and the compliance of the ventricles. Left-to-right shunt usually increases with age as the compliance of the LV declines.

  
  
  
  
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  Effects of shunting: Unexplained right heart enlargement and reversed septal motion—typical of right ventricular (RV) volume overload and elevated RV pressure—are suggestive of significant shunting. RV enlargement indicates a hemodynamically significant shunt, being present when the output of the right heart exceeds the left by 50% ( Q _p / Q _s >1.5).

  
  
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  Determine RV systolic pressure: Data regarding RV peak systolic pressure must be obtained as part of the examination. The best tricuspid regurgitant Doppler signal should be sought from multiple views. By applying the modified Bernoulli equation to the peak velocity of tricuspid regurgitation (TR) jet, the pressure gradient between the RV and RA is obtained. Adding on an estimated or measured mean right atrial pressure to this pressure gradient gives the estimate of right ventricular systolic pressure (RVSP) in millimeters of mercury (mm Hg). In the absence of RV outflow tract (RVOT) obstruction, RV systolic pressure is equal to pulmonary artery (PA) systolic pressure. The modified Bernoulli equation is

  
  
  <SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='RVsystolicpressure(mmHg)=[(4)×(TRvelocity{m/s})2]+RApressure(mmHg)’>RVsystolicpressure(mmHg)=[(4)×(TRvelocity{m/s})2]+RApressure(mmHg)RVsystolicpressure(mmHg)=[(4)×(TRvelocity{m/s})2]+RApressure(mmHg)
  RV systolic pressure ( mm Hg ) = [ ( 4 ) × ( TR velocity {m / s} ) 2 ] + RA pressure ( mm Hg )
  
  
  
  
  
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  Assess biventricular function: (Two-dimensional [2D] echocardiography and Doppler in the parasternal long- and short-axis views and apical four-, five-, and three-chamber views.) All conventional parameters for both ventricles can be used.

  
  
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  Identify associated lesions: The segmental analysis approach should be followed to avoid missing important defects.

Contrast Echo

Injection of a mixture of agitated saline and blood through a peripheral vein can assist in the diagnosis of ASDs. After the injection, the appearance of microbubbles in the LA and LV or a negative jet effect in the RA suggests the presence of an interatrial septal defect. Additionally, contrast echocardiography is very helpful in diagnosing a coronary sinus septal defect and persistent left SVC. In this condition, after injection via a left side peripheral vein, contrast appears first in the LA and LV and then in the RA.

Transesophageal Echocardiography During the Surgical and Interventional Closure of Atrial Septal Defects

The major indication for ASD closure, irrespective of symptoms, is the presence of a significant left-to-right shunt ( Q _p : Q _s >1.5) that causes dilation of the right heart chambers and pulmonary artery pressure less than two-thirds of the systemic pressure.

Surgical closure is the treatment of choice for primum, sinus venosus, and coronary sinus septal defects. The surgical closure of septal defects is followed by almost no mortality and very low morbidity rates. Postoperative complications such as arrhythmias are usually transient.

Percutaneous closure: This is the treatment of choice for the closure of secundum ASDs in the vast majority of cases. Among the relative contraindications for percutaneous device closure are large secundum ASDs (>36 to 40 mm), the lack of adequate septal rims for safe anchoring of the device, and interference of the device with the function of the AV valve or pulmonary vein ( Fig. 6.2 ).

A, Two-dimensional transesophageal echocardiogram at 0 degrees showing a centrally located large secundum ASD (white arrow) with anterior and posterior margins that appear sufficient for percutaneous closure. B, Color Doppler shows a left-to-right shunt through the defect (white arrow) . ASD, Atrial septal defect; LA, left atrium; RA, right atrium; RV, right ventricle.

The procedure is considered safe in experienced centers with a very low rate of minor or major complications (between 1% and 6%). The most common complications include

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  Atrial arrhythmias

  
  
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  Vascular complications

  
  
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  Transient heart block

  
  
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  Stroke

  
  
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  Device thrombosis

  
  
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  Device erosion through the atrial wall or aortic root

  
  
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  Device embolization

Before ASD closure, three-dimensional (3D) transesophageal echocardiography is useful for

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  Determining suitability for percutaneous closure.

  
  
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  Assessment of the shape, diameter, and number of defects as well as the rims of the septum surrounding the ASD. (The midesophageal [ME] bicaval, modified ME AV short-axis, ME four-chamber, and ME two-chamber views are best for demonstrating ASDs.)

3D TEE is an effective imaging modality for assessing the dimensions and location of ASDs as well as their spatial relations to adjacent atrial structures. This is a potential alternative to 2D TTE for the identification and characterization of ASDs ( Figs. 6.3 and 6.4 ).

A, Two-dimensional transesophageal echocardiogram (2D TEE) at 90 degrees shows two secundum ASDs—a larger one posteriorly (upper white arrow) and a smaller one anteriorly (lower white arrow) . B, Color Doppler shows the two separate flow jets through the ASDs. C, 3D TEE clearly shows the two separate ASDs. ASD, Atrial septal defect; LA, left atrium; RA, right atrium.

Images from a patient with a large atrial septal defect and pulmonary arterial hypertension after closure with a fenestrated device.

A, Three-dimensional transesophageal echocardiogram (3D TEE) imaging showing a fenestrated device closing the atrial septal defect (ASD); the blue arrow points to the fenestration on the ASD closure device. B, Two-dimensional transthoracic echocardiography (2D TTE) from the parasternal short-axis view; color Doppler demonstrates a left-to-right shunt through the fenestration (blue arrow) . Ao, Aorta; LV, left ventricle; RA, right atrium; RV, right ventricle.

Intraprocedural guidance in cases of percutaneous or surgical closure of defects : 3D TEE is especially useful in assessing the exact shape of the defect and providing accurate measurements of the size of the defect and the surrounding structures. The stretched diameter of the defect during balloon inflation can also be measured. 3D TEE is also very useful for recognizing periprocedural complications such as residual shunts, device malpositioning, or fractures.

After ASD closure, either with a device or surgical, echocardiographic assessment aims to

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  Exclude residual shunts: 2D color Doppler from the subcostal long- and short-axis views and parasternal short-axis view.

  
  
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  Assess RV remodeling: Changes in RV dimensions and RV systolic function, which can be assessed by RV fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE), and tissue Doppler velocity of the tricuspid annulus (the 2D apical four-chamber view, M-mode, and tissue Doppler imaging [TDI]).

  
  
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  Assess pulmonary venous and systemic venous connections and flow: 2D color Doppler from the subcostal long- and short-axis views, apical four-chamber view.

Anatomy and Physiology

A complete AVSD consists of

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  Ostium primum ASD

  
  
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  VSD of the inlet septum

  
  
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  Common five-leaflet AV valve with an anterior bridging leaflet, a posterior bridging leaflet, a left mural leaflet, a right mural leaflet, and a right anterosuperior leaflet. This valve is all at the same level within the ASD and VSD. The AV valve is usually equally committed to both ventricles but may be primarily committed to a single ventricle. Further description of the AV valve is based on the extent and location of attachments of the superior bridging leaflet. The following Rastelli classification is helpful for the decision on surgical intervention :

  
  
  
  
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    Type A. The superior bridging leaflet is divided at the level of the ventricular septum.

    
    
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    Type B. Division of the superior bridging leaflet occurs to a RV papillary muscle in the RV.

    
    
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    Type C. The superior bridging leaflet is undivided or “free floating” (it has no chordal attachments).

  
  

A partial AVSD (ostium primum ASD) consists of the following:

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  An AV valve divided into right- and left-sided orifices by a band of tissue connecting the superior and posterior bridging leaflets. In this case, the AV valve is displaced downward (but both sides are still at the same level) into the ventricle and anchored to the crest of the septum, eliminating the VSD component.

  
  
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  A trileaflet left AV.

  
  
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  An intermediate AVSD is characterized by a primum ASD, a small, restrictive VSD, and separate right and left (trileaflet) AV valves.

Associated Anomalies

Complete AVSD is common in patients with trisomy 21. It is frequently associated with left or right isomerism. Secundum ASD, tetralogy of Fallot (TOF), transposition complexes, and double orifice or parachute type of left AV valve may also be present.

Transthoracic Echocardiography in Unoperated Patients

The goals of the TTE include

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  Establishing the diagnosis of AVSD: Define the components of the AV septal defect (subcostal long-axis, parasternal long- and short-axis, apical four-chamber views). The apical and subcostal four-chamber views are best for evaluating the inlet portion of the heart. They show the ASD and VSD well. In some instances, the VSD may be closed by chordal attachments or tricuspid valve (TV) tissue.

  
  
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  Defining the direction and level of shunting (interatrial and interventricular) (2D and color Doppler subcostal long-axis, parasternal long- and short-axis, apical four-chamber views): Doppler is helpful in defining the levels of intracardiac shunting and the degree of AV valve regurgitation. The precise hemodynamics depend on the level of the shunt. Shunting predominately at the atrial level produces hemodynamics typical of a primum ASD. Shunting at both atrial and ventricular levels occurs with complete AVSD.

  
  
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  Defining the morphology (single orifice or two separate orifices) and chordal attachments of the leaflets of the AV valve (subcostal short-axis view, parasternal short-axis view, apical four-chamber view): The parasternal short-axis view at the level of the left AV valve is helpful in determining whether one or two orifices are present and how well they line up with the ventricles. If two orifices are present, the left AV valve is usually trileaflet. This is best seen in looking at the motion of the anterior leaflet, which separates in the middle as the valve opens in diastole. Additionally, a color Doppler map will show the location of the regurgitant jet originating from the closure line.

  
  
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  Estimating the size and function of the right and left ventricles

  
  
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  Estimating the presence of LV outflow tract (LVOT) or RVOT obstruction and its severity: Color Doppler and pulse-wave (PW) Doppler can be applied sequentially to assess the level of obstruction, while color-wave (CW) Doppler is applied to evaluate the severity of obstruction. Apical three- and five-chamber views are best for the evaluation of LVOT obstruction. Parasternal long-axis (RV outflow view) and parasternal short-axis views are the best for evaluating RVOT obstruction. Outflow tract obstruction can be due to a muscular obstruction or chordae crossing the outflow tract and inserting into the septum, especially on the left side.

  
  
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  RVSP: Right ventricular systolic pressure is estimated from TR velocity with CW Doppler (parasternal long axis–RV inflow view, parasternal short-axis view, and apical four-chamber view). In patients with large shunts at the ventricular level, there is risk of early development of irreversible pulmonary vascular disease unless the pulmonary circulation is protected by RVOT obstruction.

  
  
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  Excluding other coexisting anomalies.

Transesophageal Echocardiography

TEE is a very useful imaging tool that can provide a detailed evaluation of the AV valve prior to surgical repair.

Three-Dimensional Transthoracic Echocardiography

3D TTE—with en-face views as well as the capacity for image acquisition from different angles—can provide more detailed information regarding the size of the AV defect, the surrounding structures, and the AV valve ( Fig. 6.5 ).

A, Three-dimensional transthoracic echocardiography (3D TTE) image of a complete atrioventricular septal defect (AVSD); the white arrow points to the ventricular component, and the black arrow the atrial component of the AVSD. B, 3D TTE image of a common AV valve viewed from apex to valve. The black arrow points to the common AV valve. AV, Atrioventricular; LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.

Specifically, 3D TTE can

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  Provide detailed imaging of the five leaflets of the AV valve and its function. This information is important for Rastelli-type classification.

  
  
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  Provide information on the morphology of the left AV.

  
  

  In addition, 3D color Doppler is useful in assessing the severity of AV valve regurgitation.

Transthoracic Echocardiography in Operated Patients

Common complications in operated patients include

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  Left and right AV valve regurgitation and/or stenosis

  
  
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  Left ventricular outflow tract (LVOT) obstruction

  
  
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  Residual shunt at atrial and/or ventricular level

  
  
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  Pulmonary vascular disease (in patients who underwent a late repair)

  
  
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  Endocarditis.

  
  
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  Complete heart block and arrhythmias (atrial or/and ventricular) are common late complications.

TTE assessment should include

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  Detection of residual shunts: (2D and color Doppler subcostal long-axis, parasternal long- and short-axis, apical four-chamber views.)

  
  
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  Detection of AV valve regurgitation: (2D and color Doppler and spectral Doppler from the subcostal short-axis view, parasternal short-axis view, apical four-chamber view.)

  
  
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  Estimation of the presence of LVOT or RVOT obstruction and their severity: (Color Doppler and PW Doppler, CW Doppler from the apical three- and five-chamber views, parasternal long-axis [RV outflow] and parasternal short-axis views.)

  
  
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  Estimation of the presence of pulmonary arterial hypertension: estimated from TR velocity with CW Doppler (parasternal long-axis –RV-inflow view, parasternal short-axis view and apical four-chamber view).

Anatomy and Physiology

VSDs are among the most common congenital cardiac anomalies, accounting for approximately 40% of these. They are characterized by the location of the defect on the interventricular septum, which includes membranous and muscular portions.

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  The membranous septum is thin and relatively small. It is bounded by the AV superiorly at the junction of the right and noncoronary cusps and inferiorly by the muscular septum.

  
  
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  The muscular component comprises the majority of the septum and is divided into three regions.

  
  
  
  
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    Inlet portion between the mitral and TVs

    
    
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    Outlet (infundibular) portion between the aortic and pulmonic valves

    
    
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    Trabecular portion, the largest, extending from the membranous septum to the apex

  
  

VSDs commonly include

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  Perimembranous defects (70% to 80% of cases). These defects lie inferiorly of the TV, resulting in fibrous continuity between the tricuspid and mitral valves.

  
  
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  Outlet defects (5% to 8% of cases). This is also referred to as supracrystal, conal, subarterial, subpulmonic, or doubly committed VSD. Part of the rim is formed by the annulus of the pulmonary and aortic valves. The right cusp of the aortic valve may herniate into the defect, creating progressive aortic regurgitation ( Fig. 6.6 ).

  
  

  
  

  
  

  

  
  

  
  

  A and B, Two-dimensional transesophageal echocardiogram (2D TEE) permits accurate assessment of the size and spatial relationships of this muscular-outlet VSD. The blue arrow shows the location of the VSD. The + symbols indicate the size of the VSD. C, Color Doppler demonstrates a left-to-right shunt through the VSD (white arrow) . Ao, Aorta; LA, left atrium; LV, left ventricle; RV, right ventricle; VSD, ventricular septal defect.

  
  
  
  
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  Inlet defects (5% to 8% of cases). These are located posterior and inferior to the perimembranous defect and may be part of an AV septal defect ( Fig. 6.7 ).

  
  

  
  

  
  

  

  
  

  
  

  A, Two-dimensional transthoracic echocardiography (2D TTE) from the apical four-chamber view showing a perimembranous inlet VSD (white arrow) . B, Color Doppler shows the left-to-right shunt through the VSD (white arrow) . LA, Left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle; VSD, ventricular septal defect.

  
  
  
  
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  Muscular defects often occur within the trabecular portion of the septum and may be multiple (5% to 20% of the cases); they may also be located at the outlet septum ( Fig. 6.8 ).

  
  

  
  

  
  

  

  
  

  
  

  Two-dimensional transthoracic echocardiography (2D TTE) from parasternal short axis view showing a muscular trabecular ventricular septal defect (VSD) (blue arrow) . LV, Left ventricle; RV, right ventricle.

  
  

Most VSDs seen in an adult population are either small, with no significant shunt, or large, with pulmonary hypertension or Eisenmenger physiology. In a few patients the VSDs result in significant left-to-right shunt but without concomitant pulmonary vascular resistance; in such cases closure of the VSD is indicated.

Associated Lesions

VSDs can present as isolated lesions. However, sometimes they are part of other more complex cardiac malformations, like tetralogy of Fallot (TOF), congenitally corrected transposition of the great arteries (ccTGA), anomalies of the LVOT or RVOT, coarctation of the aorta (CoA), and interrupted aortic arch.

Transthoracic Echocardiography in Unoperated Patients

The goals of the examination are to

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  Determine the anatomic location and size of the defect within the septum: Outlet subarterial VSDs are best seen from the parasternal long-axis view. They are characterized by the absence of septal tissue between the superior margin of the VSD and the hinge of the right coronary cusp. Prolapse of the aortic valve cusp into the defect is well seen from this view. With a minimal medial angulation, perimembranous VSDs can also be viewed. By tilting the transducer to pulmonary outflow tract, outlet VSD with malalignment of outlet septum can be demonstrated.

The parasternal short-axis view is very useful for clarifying different types of VSDs. At the aortic root level, perimembranous VSDs are seen between 9 and 11 o’clock and outlet VSDs between 11 and 12 o’clock. Doubly committed subarterial VSDs will be seen between 12 o’clock and hinge of the pulmonary valve and characterized by the absence of septal tissue between the AV and pulmonary valve cusps. Upon sweeping downward toward the LV apex, a muscular VSD can be seen at various location of the septum. Inlet VSDs can be viewed in the apical four-chamber view or from the parasternal short-axis view at the level of the mitral valve.

The size of the defect is very important because this determines the hemodynamic consequences. VSDs are classified as small when their size is less than one-third of the diameter of the aorta, moderate when their size is between one to two-thirds of the aortic diameter, and large when their diameter is more than two-thirds of the aortic diameter.

The echocardiographic examination should exclude the presence of additional VSDs as well as any coexisting conditions that may need to be taken into consideration before making the decision for closure, such as a straddling AV valve apparatus or prolapse of the AV cusps into the VSD.

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  Characterize the hemodynamic significance of the shunt: Color and spectral Doppler in the parasternal long- and short-axis views as well as the apical and subcostal four-chamber views can be used for evaluation of the direction and hemodynamic significance of the shunt. In patients with normal RV systolic pressure and normal pulmonary vascular resistance, there is high-velocity left-to-right shunting across the VSD. Flow velocity across the VSD greater than 4 m/s in most pediatric patients suggests that it is restrictive. In adult patients, this may not always be the case owing to their higher blood pressure compared with that in the pediatric population with systemic hypertension. Flow across the defect may become continuous when LV diastolic pressure exceeds RV diastolic pressure. With larger defects, large left to right shunt and elevated pulmonary artery systolic pressure, shunt velocity is lower, but pulmonary vascular resistance may still be normal or only mildly elevated. When RV systolic pressure and pulmonary vascular resistance significantly are raised, flow across VSD becomes bidirectional with low velocity indicating Eisenmenger physiology.

  
  
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  Assess the hemodynamic effects of shunting: Small restrictive VSDs usually are characterized by turbulent flow in color Doppler imaging and high-velocity systolic signal on CW Doppler (peak instantaneous RV pressure calculated using the flow velocity across VSD is less than two-thirds of systemic systolic pressure). They are usually not associated with LA or LV dilation or pulmonary hypertension. LA and LV enlargement is usually present when the left-to-right shunt volume exceeds the systemic flow ( Q _p / Q _s >1.5). In a minority of patients with small, restrictive VSDs, a dilated left heart with reduced function can be seen, suggesting independent ventricular disease. Large nonrestrictive VSDs are usually characterized by a laminar flow in color Doppler signal with low velocity on CW Doppler (peak instantaneous gradient <25 mm Hg across the defect).

  
  
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  Assessment of RV systolic pressure: RVSP should always be assessed in patients with VSD because large defects could be associated with pulmonary hypertension. RV pressures can be estimated using the gradient across the VSD by the following formula.

Measurement of peak VSD velocity can be problematic if the jet is deflected by the TV, septal aneurysm, or muscle bundle. Failure to direct the CW beam parallel to the VSD jet may result in underestimation of the pressure difference. Because of this, the TR velocity jet usually gives a more accurate estimate of peak RV systolic pressure. The estimate of the RV pressure from VSD velocity must correlate with that determined by the TR velocity. Any significant disparity needs to be resolved.

Estimated RVSP based on the VSD flow or TR jet velocities should be compared with a simultaneous measurement of the systemic systolic blood pressure. It is also important not to mistake VSD jet velocity for TR velocity when the VSD shunt is partially or completely directed to the RA.

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  Double-chamber right ventricle (DCRV): This may develop in patients with small VSDs and result in significant obstruction (2D color Doppler from the parasternal short-axis view and apical five-chamber view with further anterior angulation). In this situation, VSD usually opens to a high-pressure chamber and flow velocity across the VSD becomes low. There may be minimal or no gradient across VSD. High-flow velocity is usually detected at the RVOT, and RV hypertrophy is commonly associated. The pressure gradient calculated using TR reflects the pressure in the high-pressure chamber of the RV and not the pulmonary artery pressure ( Fig. 6.9 ).

  
  

  
  

  
  

  

  
  

  
  

  A, Two-dimensional transthoracic echocardiography (2D TTE) from apical five-chamber view showing a perimembranous VSD (horizontal white arrow) with DCRV (vertical white arrow) . B, Color Doppler showing the flow acceleration from the high- to low-pressure chambers of the RV (white arrow) . Ao, Aorta; DCRV, double-chamber right ventricle; LA, left atrium; LV, left ventricle; RV, right ventricle; VSD, ventricular septal defect.

  
  
  
  
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  Aortic regurgitation: Prolapse of the aortic cusp with progressive aortic regurgitation is usually seen in perimembranous and outlet VSDs (2D color Doppler in the parasternal long- and short-axis and four- and five-chamber views). A deformed and dilated aortic sinus (usually the right aortic sinus) prolapsing into the VSD can result in partial or complete closure of the defect and is best seen in the parasternal long-axis view. The residual VSD can be very small and shunt through the VSD is hard to obtain using CW Doppler. A deformed sinus wall can be very thin and may rupture; perforation of the sinus of Valsalva may also occur.

Assess for LVOT obstruction: In some cases, posterior deviation of the outlet septum may result in LVOT obstruction. This can be also caused by a discrete subaortic ridge. The parasternal long-axis view and apical five-chamber view with color and spectral Doppler are best in assessing the anatomy and severity.

Transthoracic Echocardiography in Operated Patients

The most common complications after VSD closure are

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  Residual VSD

  
  
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  Damaged aortic or TV with regurgitation

  
  
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  LVOT obstruction

  
  
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  LV dysfunction after long-standing LV volume overload (in cases of late repair)

  
  
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  Conduction disturbances

  
  
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  Development of pulmonary vascular disease or Eisenmenger syndrome

The goals of the echocardiography examination are to

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  Assess for residual VSDs: The presence of residual VSD is usually detected at the margins of the closure patch.

  
  
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  Presence of aortic or TR: Interrogation of the tricuspid and aortic valves for the presence of regurgitation should always be performed postoperatively (2D color Doppler in the parasternal long-, short-axis, and apical views).

  
  
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  Assess for LVOT obstruction: subAS after the placement of the VSD patch may occur (parasternal long axis view, parasternal short axis view, apical five-chamber view with color and spectral Doppler).

  
  
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  Assess LV size and function. LV dimension as well as regional and global function should be assessed postoperatively, especially in cases of late repair after long-standing LV volume overload.

  
  
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  Determine pulmonary artery systolic or mean pressure. These should be estimated from TV regurgitation velocity, pulmonary regurgitation (PR), Doppler or shunt through residual VSDs.

Three Dimensional Echocardiography

With 3D TTE, the size, location, and spatial relation of the VSD with the adjacent structures can be more precisely assessed. An en-face view of the defect obtained by 3D TTE can help to determine the best therapeutic approach, whether surgical or percutaneous.

Moreover, 3D TEE can be a valuable tool intraoperatively and during transcatheter device closure in assisting on the optimal sizing and positioning of the closure device.

Anatomy and Physiology

The ductus arteriosus is a vascular structure that connects the main pulmonary artery (MPA) with the descending aorta or the subclavian artery (SA). When a right aortic arch is present, the ductus arteriosus may connect the MPA with the right-sided descending aorta (right-sided ductus arteriosus) or the MPA with the left SA (left-sided ductus arteriosus) or the MPA with both (bilateral ductus arteriosus). Shortly after birth, once flow through the lungs is established, the ductus normally closes. Failure to close results in a left-to-right shunt through the ductus. Patent ductus arteriosus (PDA) accounts for 5% to 10% of all congenital malformations and is more common in premature infants. Usually PDA presents as an isolated lesion. Clinical presentations in adults vary according to size. PDA can be an incidental finding, during echocardiographic assessment for other indications or during clinical examination. It produces an audible ejection systolic or continuous murmur radiating to the back.

The consequences of the left-to-right shunt from a PDA depend on its size and pulmonary vascular resistance. Medium and large shunts cause congestive heart failure (CHF) due to increased pulmonary blood flow and volume overload of the left heart. If uncorrected, pulmonary hypertension develops and the shunt becomes bidirectional, with cyanosis of the lower but not the upper extremities (differential cyanosis).

Transthoracic Echocardiography in Unoperated Patients

The goals of the examination are to

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  Determine the anatomic location, size, and course of the PDA: The PDA is demonstrated from the ductal view, which can be gained by sliding the transducer superiorly from the parasternal short axis into a high left parasternal window and rotating it clockwise, at which point the pulmonary artery bifurcation can be seen. From this view of the branch pulmonary arteries, counterclockwise rotation of the transducer toward the 12 o’ clock long axis of the PDA, located between the descending aorta and left pulmonary artery, can be demonstrated. Ductal flow can be seen in the high parasternal long-axis view of the pulmonary trunk. Color Doppler demonstrates the flow of the PDA toward the transducer. From the suprasternal view the PDA could also be found by focusing on the descending aorta opposite the left subclavian and swinging toward the left PA ( Fig. 6.10 ).

  
  

  
  

  
  

  

  
  

  
  

  A, Two-dimensional transthoracic echocardiography (2D TTE) from the parasternal short-axis view showing a PDA (white arrow) . B, Color Doppler shows left-to-right shunt through the PDA (white arrows) . Ao, aorta; D.Ao, descending aorta; MPA, main pulmonary artery; PDA, patent ductus arteriosus.

  
  

A PDA is usually cone-shaped with a smaller orifice at the PA end. According to the shape, PDAs are classified into five categories (Kirchenko classification). Thus they can be short or long and straight or tortuous, making complete visualization difficult.

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  Characterize the hemodynamic significance of the shunt: With color and spectral Doppler in the parasternal long- and short-axis views, the suprasternal views can be used to evaluate the direction and hemodynamic significance of the shunt. The flow profile is characterized by near continuous left-to right-flow with a peak velocity in early systole, when PA pressure is less than the systemic pressure ( Fig. 6.11 ).

  
  

  
  

  
  

  

  
  

  
  

  A, Coarctation of aorta (CoA). Two-dimensional transthoracic echocardiography (2D TTE) suprasternal view of the aortic arch. A discrete narrowing is seen distal to the SA (white arrow) . B, Continuous-wave (CW) Doppler recording through the CoA in the descending aorta. Note the high peak systolic flow velocity with a long diastolic tail characteristic of significant CoA. SA, Subclavian artery.

  
  

With large defects and significant pulmonary hypertension (Eisenmenger physiology), there is a low-velocity bidirectional shunt. A right-to-left shunt (from the MPA to the descending aorta) occurs at early systole and a left-to-right shunt (from the descending aorta to the MPA) occurs at late systole and throughout diastole. In cases of Eisenmenger syndrome with reduced shunt, a PDA can be easily missed by 2D echocardiography. Careful examination at the ductal view with a reduced color Doppler velocity scale may help to identify the PDA.

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  Assess the hemodynamic effects of shunting: LV enlargement is usually consistent with hemodynamically significant shunt through the PDA. The Q _p / Q _s should be measured.

  
  
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  Assess RV systolic pressure: RVSP should always be assessed. The pressure gradient, calculated using Doppler velocity across the PDA or TR velocity, provides information about RV and PA systolic pressure. As with a VSD, the TR velocity may provide a more accurate estimate of PA systolic pressure. When bidirectional shunt is present, it is characterized by a right-to-left shunt in early systole followed by a left-to-right flow in late systole and diastole. This indicates significantly elevated pulmonary vascular resistance and Eisenmenger physiology.

Transthoracic Echocardiography in Operated Patients

The goals of the examination are to

• •
  

  Show that the device is well positioned in patients after device closure: (2D and color-flow Doppler in the suprasternal and parasternal long- and short-axis views.)

  
  
• •
  

  Assess for residual ductal flow: Residual flow may be traced by color flow and spectral Doppler in the suprasternal and parasternal long- and short-axis views.)

  
  
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  Exclude LPA stenosis: (2D color-flow, and spectral Doppler in the suprasternal and parasternal short-axis views.)

  
  
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  Assess LV function

  
  
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  Assess for residual pulmonary hypertension

Three-Dimensional Echocardiography

3D TTE may provide more accurate information on the size of the duct. Additionally, it can provide a more comprehensive analysis of left atrial and ventricular dimensions and volumes. 3D TEE can be used perioperatively to determine the optimal device position, the presence of residual shunts through the duct, and/or the probable obstruction of the left PA after the placement of the closure device.

Anatomy and Physiology

Coarctation of the aorta (CoA) is the fifth most common congenital heart defect, present in approximately 6% to 8% of live births with CHD and is more common in males than in females. It is commonly located opposite the ductus arteriosus or ligamentous arteriosum and appears as a shelflike narrowing into the aorta just below the left SA. Long tubular narrowing, a hypoplastic aortic arch, or a small general arterial tree are also seen. In two-thirds of the cases the clinical manifestation occurs early after birth; in one-third of the cases the diagnosis is made in adulthood.

The etiology of CoA is not clear; however, the role of genetic factors is increasingly being identified. Almost 12% of patients with Turner syndrome present with CoA, and an association of CoA with the presence of a chromosome 22q11 microdeletion has been demonstrated.

Associated Lesions

Associated defects other than bicuspid aortic valve (which occurs in 22% to 42% of cases) are rare. Aortic atresia or interrupted aortic arch is the extreme anatomic manifestation of coarctation, with the descending aorta supplied by the ductus arteriosus or collateral vessels. Other associating anomalies include VSDs, mitral valve anomalies, and intracranial anomalies.

Most adult patients with CoA are diagnosed owing to the presence of long-standing systemic hypertension and a difference in blood pressure between upper and lower extremities. Some may present with heart failure, aortic rupture, and endocarditis.

Transthoracic Echocardiography in Unoperated Patients

The goals of echocardiographic assessment are to

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  Confirm the presence of CoA and assess its severity: (2D color Doppler, and spectral Doppler from the suprasternal window.) A study of the dimensions of the ascending aorta, aortic arch, descending and abdominal aorta should be performed by 2D echo. Color Doppler is useful to locate the site of coarctation. In patients with severe coarctation, a CW Doppler tracing through the aortic isthmus shows a characteristic pattern of high-velocity systolic amplitude (4 to 5 m/s) with continuous antegrade flow through diastole (diastolic tail). Doppler gradients from the peak systolic velocity ( V ₂ ) alone tend to overestimate the catheter-measured gradient. A better correlation has been shown when the velocity proximal to the coarctation ( V ₁ ) is included in the expanded Bernoulli equation <SPAN role=presentation tabIndex=0 id=MathJax-Element-3-Frame class=MathJax style="POSITION: relative" data-mathml='(P=4[V22−V12])’>(P=4[V22−V21])(P=4[V22−V12])
  ( P = 4 [ V 2 2 − V 1 2 ] )
  . This may not be necessary if the proximal aortic flow is less than 1 m/s. The coarctation is considered significant when the peak pressure gradient across the coarctation site is more than 30 mm Hg with the presence of anterograde diastolic flow. In rare cases of severe coarctation (near atretic aorta), Doppler may detect only low velocity (<1 m/s) but continuous flow across the narrowed segment. Low-velocity continuous flow in the abdominal aorta (spectral Doppler from the subcostal view) may be helpful in the diagnosis of severe coarctation. In cases in which multiple obstructive lesions are in series, there is tubular hypoplasia of the aortic arch, or the peak flow velocity proximal to the coarctation exceeds 1 m/s, the expanded Bernoulli equation should be used:

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