A history of cyanosis is always present, although it depends on the amount of mixing. Quiet tachypnea and a single S2 are typically present. If the ventricular septum is intact, there may be no murmur.
Children with transposition and a large VSD have improved intracardiac mixing and less cyanosis. They may present with signs of heart failure. The heart is hyperdynamic, with palpable left and right ventricular impulses. A loud VSD murmur is heard. S2 is single.
ECG findings typically include right axis deviation and right ventricular hypertrophy. The chest x-ray reveals increased pulmonary vascularity, and the cardiac shadow is classically an egg on a string created by the narrow superior mediastinum. Echocardiography shows the transposition of the great arteries, the sites and amount of mixing, and any associated lesions.
Figure 144-3 Tricuspid atresia with ventricular septal defect. AO, Aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium.
Initial medical management includes prostaglandin E1 to maintain ductal patency. If significant hypoxia persists on prostaglandin therapy, a balloon atrial septostomy improves mixing between the two circulations. Complete surgical repair is most often an arterial switch. The arterial switch usually is performed within the first 2 weeks of life, when the left ventricle can still maintain systemic pressure.
Tricuspid atresia accounts for approximately 2% of all congenital heart defects (Fig. 144-3). The absence of the tricuspid valve results in a hypoplastic right ventricle. All systemic venous return must cross the atrial septum into the left atrium. A PDA or VSD is necessary for pulmonary blood flow and survival.
Infants with tricuspid atresia are usually severely cyanotic and have a single S2. If a VSD is present, there may be a murmur. A diastolic murmur across the mitral valve may be audible. Frequently there is no significant murmur.
The ECG shows left ventricular hypertrophy and a superior QRS axis (between 0° and –90°). The chest x-ray reveals a normal or mildly enlarged cardiac silhouette with decreased pulmonary blood flow. Echocardiography shows the anatomy, associated lesions, and source of pulmonary blood flow.
Management initially depends on the presence of a VSD and the amount of antegrade blood flow to the lungs. If there is no VSD, or it is small, prostaglandin E1 maintains pulmonary
Figure 144-4 Truncus arteriosus. AO, Aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle.
blood flow until surgery. Surgery is staged with an initial subclavian artery-to-pulmonary shunt (BlalockTaussig procedure)typically followed by a two-stage procedure: bidirectional cavopulmonary shunt (bidirectional Glenn) and Fontan procedure. These surgeries direct systemic venous return directly to the pulmonary arteries.
Truncus arteriosus occurs in less than 1% of all cases of congenital heart disease (Fig. 144-4). It results from the failure of septation of the truncus during the first 3 to 4 weeks of gestation. A single arterial trunk arises from the heart with a large VSD immediately below the truncal valve. The pulmonary arteries arise from the single arterial trunk either as a single vessel that divides or individually from the arterial trunk to the lungs.