A significant ASD (i.e. a pulmonary flow that is more than 50% increased when compared with systemic flow) should be repaired before the age of 10 years or as soon as possible if first diagnosed in adulthood. There is a good result from surgery unless pulmonary hypertension has developed.
Persistent ductus arteriosus (PDA)
The ductus arteriosus connects the pulmonary artery at its bifurcation to the descending aorta immediately distal to the subclavian artery. In fetal life the ductus diverts blood away from the unexpanded, and hence high-resistance, pulmonary circulation into the systemic circulation, where the blood is reoxygenated as it passes through the placenta. At birth, the high oxygen in the lungs and the reduced pulmonary vascular resistance triggers closure of the duct. If the duct is malformed, i.e. it does not contain sufficient elastic tissue, it will not close. This is more common in females and is sometimes associated with maternal rubella. Premature babies are often born with persistent ducts that are anatomically normal but are immature in that they lack the mechanism to close. Because aortic pressure exceeds pulmonary artery pressure throughout the cardiac cycle, a persistent duct produces continuous aorta-to-pulmonary artery shunting. This leads to an increased pulmonary venous return to the left heart and an increased left ventricular volume load.
If the shunt is large, the left heart volume overload results in severe left heart failure. However, there are often no symptoms until later in life when heart failure or infective endocarditis develop.
The characteristic physical sign is a continuous ‘machinery’ murmur (due to turbulent aortic-to-pulmonary artery shunting in both systole and diastole), best heard below the left clavicle in the first interspace or over the first rib. A thrill may often be felt. The peripheral pulse is large in volume (‘bounding’) because of the increased left heart blood flow and the decompression of the orta into the pulmonary artery.
The aorta and pulmonary arterial system are prominent radiologically. There is both a left atrial abnormality and left ventricular hypertrophy on the ECG. The echocardiogram shows a dilated left atrium and left ventricle.
Premature infants with a persistent duct may be treated medically with indomethacin, which inhibits prostaglandin production and stimulates duct closure. In other cases the duct can be ligated surgically with very little risk. Surgery should be performed as soon as possible and not later than 5 years.
Coarctation of the aorta
Coarctation of the aorta occurs twice as commonly in men as in women. It is also associated with Turner’s syndrome. The coarctation is a narrowing of the aorta at, or just distal to, the insertion of the ductus arteriosus . In 80% of cases coarctation of the aorta is associated with a bicuspid (and potentially stenotic) aortic valve.
Severe narrowing of the aorta encourages the formation of a collateral arterial circulation involving theperiscapular and intercostal arteries. Decreased renal perfusion can lead to the development of systemic hypertension that persists even after surgical correction.
Coarctation of the aorta is often asymptomatic for many years. Headaches and nose bleeds (due to hypertension) and claudication and cold legs (due to poor blood flow in the lower limbs) may be present. Physical examination reveals hypertension in the upper limbs, and weak, delayed (radiofemoral delay) pulses in the legs. A mid-to-late systolic murmur due to turbulent flow through the coarctation may be heard over the upper precordium or the back. Vascular bruits from the collateral circulation may also be heard.
The chest X-ray may reveal a dilated aorta indented at the site of the coarctation. This is manifested by an aorta (seen in the upper right mediastinum) shaped like a figure ‘3’. In adults, tortuous and dilated collateral intercostal arteries may erode the undersurfaces of the ribs (‘rib notching’). The ECG demonstrates left ventricular hypertrophy. Echocardiography sometimes shows the coarctation and other associated anomalies. Aortography will show the defect and digital vascular imaging allows the coarctation to be visualized after the intravenous injection of contrast. MRI will also demonstrate the coarctation.
The treatment is surgical excision of the coarctation and end-to-end anastomosis of the aorta. If the coarctation is extensive, prosthetic vascular grafts may be needed. When surgery is performed in childhood, hypertension usually resolves completely. However, when the operation is performed on adults the hypertension persists in 70% because of previous renal damage.
This is the most common cyanotic congenital heart abnormality in children who survive beyond the neonatal period. It consists of the following four features:
1 A VSD.
2 Right ventricular outflow obstruction. The level of the obstruction may be subvalvular, valvular or supravalvular. The commonest obstruction is subvalvular, either alone (50%) or in combination with valvular stenosis (25%).
3 Positioning of the aorta above the VSD (,overriding aorta’).
4 Right ventricular hypertrophy.
This combination of lesions leads to a high right ventricular pressure and right-to-left shunting of blood through the VSD. Thus the patient is centrally cyanosed.
Children with this condition may present with dyspnoea or fatigue or with hypoxic episodes (Fallot’s spells), i.e. deep cyanosis and possible syncope, on exertion. Squatting is common.
Physical signs include a parasternal heave and a systolic ejection murmur, often associated with a thrill in the second left interspace close to the sternum. The second heart sound is usually single because the pulmonary component is too soft to be heard. Central cyanosis is commonly present from birth, and finger clubbing and polycythaemia are obvious after about 1 year. Growth may be retarded.
The chest X-ray shows a large right ventricle and a small pulmonary artery. The ECG reveals right ventricular hypertrophy and the echocardiogram demonstrates discontinuity between the aorta and the anterior wall of the ventricular septum. Cardiac catheterization is performed to evaluate the size and degree of the right ventricular outflow obstruction.
Complete surgical correction of this combination of lesions is possible even in infancy. Often a palliative procedure- an anastomosis between a subclavian artery and a pulmonary artery (Blalock shunt) -is performed on very young infants.
This operation results in an incresed blood supply to the lungs. Fallot’s spells may need treatment with f3- blockade or, when severe, with diamorphine to relax the right ventricular outflow obstruction.
Adolescent congenital heart disease
As more children with structural heart disease survive into adulthood there is a need for an increased awareness amongst general physicians and cardiologists of the problems posed by these young adults. Both atrial and ventricular arrhythmias are common sequels of long-standing structural heart disease and are often quite resistant to treatment. Sudden cardiac death is not uncommon. End-stage heart failure secondary to congenital heart disease can now be managed by heart or heart-lung transplantation.