Figure 143-4 Atrioventricular canal defects. AO, Aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle.
ECG and chest x-ray findings are normal with small PDAs. Moderate to large shunts may result in a full pulmonary artery silhouette and increased pulmonary vascularity. ECG findings vary from normal to evidence of left ventricular hypertrophy. If pulmonary hypertension is present, there is also right ventricular hypertrophy.
Spontaneous closure of a PDA after a few weeks of age is uncommon in full-term infants. Moderate and large PDAs may be managed initially with diuretics, but eventually require closure. Elective closure of small, hemodynamically insignificant PDAs is controversial. Most PDAs can be closed in the catheterization laboratory by either coil embolization or a PDA closure device.
Endocardial cushion defects, also referred to as atrioventricular canal defects, may be complete or partial (Fig. 143-4).Failure of the septum to fuse with the endocardial cushion results in abnormal atrioventricular valves as well. The complete defect results in a primum ASD, a posterior or inlet VSD, and clefts in the anterior leaflet of the mitral and septal leaflet of the tricuspid valves. In addition to left-to-right shunting at both levels, there may be atrioventricular valve insufficiency.
The symptoms of heart failure usually develop as the pulmonary vascular resistance decreases over the first 6 to 8 weeks of life. Symptoms may be earlier and more severe with significant atrioventricular valve insufficiency. Pulmonary hypertension resulting from increased pulmonary circulation often develops early. The presence of murmurs varies depending on the amount of shunting at both atrial and ventricular levels. If there is a large VSD component, S2 will be single. Growth is usually poor. Complete endocardial cushion defects are most commonly seen in children with Down syndrome.
The diagnosis usually is made with echocardiography. A chest radiograph reveals cardiomegaly with enlargement of all chambers and the presence of increased vascularity. An ECG reveals left axis deviation and combined ventricular hypertrophy and may show combined atrial enlargement.
Initial management includes diuretics (± digoxin) and after-load reduction for treatment of heart failure. Surgical repair of the defect ultimately is required.
Pulmonary stenosis accounts for approximately 10% of all congenital heart disease and can be valvular, subvalvular, or supravalvular in nature. Pulmonary stenosis results from the failure of the development, in early gestation, of the three leaflets of the valve, insufficient resorption of infundibular tissue, or insufficient canalization of the peripheral pulmonary arteries.
Symptoms depend on the degree of obstruction present. Mild pulmonary stenosis is asymptomatic. Moderate to severe stenosis results in exertional dyspnea and easy fatigability. Newborns with severe stenosis may be more symptomatic and even cyanotic because of right-to-left shunting at the atrial level.
Pulmonary stenosis causes a systolic ejection murmur at the second left intercostal space which radiates to the back. A thrill may be present. S2 may be widely split with a quiet pulmonary component. With more severe pulmonary stenosis, an impulse at the lower left sternal border results from right ventricular hypertrophy. Valvular stenosis may result in a click that varies with respiration. Worsening stenosis causes an increase in the duration of the murmur and a higher frequency of the sound. The systolic ejection murmurs of peripheral pulmonary stenosis are heard distal to the site of obstruction in the pulmonary circulation, including radiation to the back.