Complex Congenital Heart Disease
Matthew A. Cavender
Richard A. Krasuski
I. TETRALOGY OF FALLOT (TOF).
TOF is the most common form of cyanotic heart disease. It occurs in approximately 1 in 3,000 live births and accounts for 10% of congenital heart disease in infants. It is also the most common congenital heart disease requiring surgical correction in the first year of life. The earliest description of TOF dates back to the 17th century; however, Fallot is credited with describing the classic features of the disease in 1888. Surgical treatment for TOF did not become available until well into the 20th century, and it dramatically improved life expectancy. The current reparative approach has shifted from palliative shunt procedures to primary surgical repair, most recently with valve-sparing techniques and usually performed in infancy. Without surgical intervention, only about 10% of patients survive beyond the age of 20 years. Adults with TOF usually have undergone surgical repair or palliation. A wide and complex spectrum of TOF exists including association with pulmonary atresia, absent pulmonary valve, and atrioventricular (AV) canal defects. Classic “simple” TOF is discussed here.
A. Anatomy
1. Anterocephalad deviation of the outlet septum results in four defining features:
Right ventricular (RV) outflow tract obstruction
Nonrestrictive ventricular septal defect (VSD)
Aortic override of the ventricular septum (> 50% over the right ventricle)
Right ventricular hypertrophy (RVH)
2. Associated defects. Anomalous origin of the left anterior descending coronary artery from the right coronary artery (5%) or a prominent conal branch from the right coronary artery can occur. These vessels cross the RV outflow tract. This anatomic feature is important to surgeons because infundibular resection or future conduit placement may be needed in this location and can lead to inadvertent arterial damage. Right aortic arch occurs in 25% of cases. A secundum atrial septal defect (ASD) occurs in 15% of cases, completing the pentalogy of Fallot. Persistent left superior vena cava is found in 5% of patients. Among adult patients, aortic insufficiency can occur naturally from long-term dilation of the aortic root, after endocarditis or as a postoperative sequela. Rare complications include pulmonary hypertension, supravalvular mitral stenosis, and subaortic stenosis. There is an association with deletion in the chromosome 22q11 region, which is also present in DiGeorge syndrome and/or velocardiofacial syndrome.
B. Clinical presentation
1. Patients who have not undergone surgical repair have variable clinical features depending on the amount of RV outflow tract obstruction, degree of aortic override, and, to a lesser extent, systemic vascular resistance, all of which dictate the amount and direction of shunting across the VSD.
a. With severe RV outflow tract obstruction, patients have central cyanosis and clubbing by 6 months of age. Hypoxic “spells” may be seen and are characterized by tachypnea, dyspnea, cyanosis, or even loss of consciousness or
death. If the obstruction is mild, however, the shunt through the VSD may be left-to-right, resulting in “pink tet” with minimal symptoms.
death. If the obstruction is mild, however, the shunt through the VSD may be left-to-right, resulting in “pink tet” with minimal symptoms.
b. On physical examination, the patient is usually cyanotic and clubbed. A prominent RV impulse may be appreciated because of equalization of right and left ventricular pressures. A lift may be palpated under the right sternoclavicular junction in patients with a right-sided arch. The first heart sound (S1) is usually normal, but the second heart sound (S2) is often single because of an inaudible P2. Auscultation is notable for a prominent systolic ejection murmur at the left upper sternal border, possibly with an associated thrill. The shorter the murmur, the more severe the infundibular pulmonary stenosis. The murmur of aortic insufficiency may be audible along with an aortic click resulting from a dilated overriding aorta. Continuous murmurs may be heard due to aortopulmonary collateral vessels. The presence of these vessels is more likely in the setting of pulmonary atresia, but they can also be acquired if RV outflow tract stenosis develops gradually.
2. Most adult congenital patients will have undergone surgical repair with or without a prior palliative procedure. The term “palliation” (as opposed to “repair”) in these patients refers to a surgical procedure that consists of a systemic-topulmonary artery shunt (modified Blalock-Taussig shunt, classic Blalock-Taussig shunt, Potts shunt, or Waterston shunt; Table 32.1). These procedures are initially performed to supplement the deficiency of antegrade pulmonary
blood flow and are taken down at the time of complete repair. The latter two procedures have been abandoned owing to associated uncontrolled pulmonary blood flow and the subsequent development of pulmonary hypertension.
blood flow and are taken down at the time of complete repair. The latter two procedures have been abandoned owing to associated uncontrolled pulmonary blood flow and the subsequent development of pulmonary hypertension.
TABLE 32.1 Index of Postoperative Anatomy among Adult Patients with Congenital Heart Disease | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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a. Patients who have undergone palliative repair alone have variable clinical findings depending on the type of palliation performed. In those who have undergone a classic Blalock-Taussig shunt, the brachial pulse on that side may be diminished or absent. If patent, shunts can produce a continuous murmur. Continuous murmurs can also result from aortopulmonary collaterals. Branch pulmonary artery stenosis at prior shunt insertion sites can produce unilateral systolic or continuous murmurs. Systolic ejection murmurs may be audible depending on the degree of antegrade flow across the outflow tract.
3. Complete (or total) repair consists of patch closure of the VSD and variable degrees of RV outflow tract resection and reconstruction. It may involve pulmonary valvotomy, RV outflow tract patch augmentation, transannular patch enlargement, or placement of a right ventricle—to—pulmonary artery conduit (i.e., bioprosthetic or homograft). Distal branch pulmonary artery stenosis may have been repaired, or residual lesions may be present. These patients typically have first undergone a palliative shunt procedure, but the current surgical approach has shifted to primary complete repair in infancy.
a. Patients are often asymptomatic. They may present with late symptoms such as dyspnea, exercise intolerance, palpitations, signs of right heart failure, or syncope.
b. The jugular venous pressure is usually normal unless there is RV dysfunction, in which case elevated jugular venous pressure with a prominent a wave is seen. The brisk pulse of aortic insufficiency may also be appreciated. On palpation, there may be an RV lift or a lift under the right sternoclavicular junction when the arch is right-sided. Some degree of turbulence almost always remains across the RV outflow tract and produces a variable systolic ejection murmur at the left upper sternal border, with radiation to the back and peripheral lung fields. Of importance is the presence of associated pulmonary insufficiency. This, even if severe, may occasionally be inaudible due to low-pressure hemodynamics. It is generally appreciated at the left upper sternal border, sometimes producing a to-and-fro murmur together with the outflow tract murmur. A high-frequency systolic murmur at the left lower sternal border suggests the presence of a residual VSD (often due to a small leak in the VSD patch). Continuous murmurs from collateral formation or prior shunts may be appreciated. The diastolic murmur of aortic insufficiency may also be heard.
C. Laboratory examination
1. Chest radiographic findings depend on the surgical history. The presence of a right aortic arch may be confirmed. A concave deficiency of the left heart border reflects various degrees of pulmonary arterial hypoplasia. Upturning of the apex from RVH causes the classic finding of a “boot-shaped” heart. Pulmonary vascular markings may vary throughout the lung fields, depending on associated branch pulmonary artery stenosis and relative blood flow. Calcification or aneurysmal dilation of surgical conduits or RV outflow tract repair may be visible on plain radiographs.
2. An electrocardiogram usually demonstrates sinus rhythm with RVH. Both atrial and ventricular rhythm disturbances can be present. The QRS axis is usually normal or rightward. If left axis deviation is present, an associated AV canal defect should be suspected. A patient who has undergone surgical repair typically has right bundle branch block. A QRS duration of > 180 milliseconds is a predictor of sustained ventricular tachycardia and sudden cardiac death.
D. Diagnostic testing
1. Echocardiography
a. For a child or young adult, transthoracic echocardiography may be the only modality necessary for diagnosis. For adults or patients who have undergone surgical intervention, catheterization or magnetic resonance imaging (MRI) may be necessary in order to identify the presence and location of residual lesions.
(1) Adequate views are obtained of the right heart, RV outflow tract, and proximal pulmonary arteries. Helpful views to identify a residual VSD or the presence of aortic insufficiency include the parasternal long-axis, parasternal short-axis, and apical four-chamber views. Further definition of residual lesions in the branch pulmonary arteries may be possible with a high parasternal short-axis view.
(2) Palliative shunts are often best visualized in the suprasternal notch view where the subclavian arteries course distally.
(3) Continuous flow is typically demonstrated with color Doppler techniques. Less common shunts may be difficult to image in adult patients. Aortopulmonary collateral vessels are extremely difficult to visualize, but may be seen in suprasternal notch views of the descending aorta.
b. Transesophageal echocardiography may allow improved imaging of the intracardiac anatomic structures in adults, but limitations often remain with regard to the distal pulmonary arteries, and additional testing is frequently necessary.
2. Cardiac magnetic resonance (CMR) imaging is considered the gold standard for evaluating the right ventricle and quantitating pulmonary insufficiency in these patients. It can demonstrate the presence of scar, distal pulmonary arterial anatomy, and RV aneurysms, as well as other associated defects. It can also provide hemodynamic information about residual lesions. Previously placed shunts and possibly aortopulmonary collateral vessels can be identified as well. The anatomic information may be sufficient to proceed with surgical treatment or to guide the interventional cardiologist in planning a transcatheter procedure.
3. Cardiopulmonary testing should be performed as a baseline study and with progression of symptoms. It is useful in determining the timing for reintervention in the setting of RV volume overload secondary to free pulmonary insufficiency.
4. Quantitative pulmonary flow scans are useful to determine discrepancies in pulmonary flow that may be caused by branch pulmonary artery stenosis. These scans also provide objective baseline clinical information when obtained after surgical or transcatheter intervention.
5. The role of cardiac catheterization is decreasing with the advent of other imaging modalities, but can be helpful in assessing residual shunts and pulmonary hypertension.
a. Right heart catheterization. Residual shunts are actively sought at the atrial and ventricular levels. The pulmonary arteries and branches are evaluated extensively in search of peripheral pulmonary stenosis. Findings at right heart catheterization and their clinical significance are as follows:
(1) RV pressure is generally systemic in a patient who has not undergone surgical repair.
(2) After surgical repair, elevated RV pressure suggests the presence of residual obstructive lesions, the levels of which are to be documented.
(3) Careful pullback recordings are performed from the branch pulmonary arteries to the right ventricle because stenosis at each level is possible.
(4) The presence of stenosis at a prior shunt site is expected.
(5) RV end-diastolic pressures may be elevated in the setting of pulmonary insufficiency.
b. Left heart catheterization is performed if noninvasive studies suggest residual VSD.
(1) Angiography includes a cranialized right ventriculography and possibly selective pulmonary arterial injections if hemodynamic findings suggest stenosis.
(2) Left ventriculography better demonstrates residual VSD in the presence of subsystemic RV pressures.
(3) Aortic root injection
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