Patent Ductus Arteriosus Information
What is Patent Ductus Arteriosus
The embryonic ductus arteriosus fails to close normally and persists as a shunt connecting the left pulmonary artery and aorta, usually near the origin of the left subclavian artery. Prior to birth, the ductus is kept patent by the effect of circulating prostaglandins; in early infancy, a patent ductus can often be closed by administration of indomethacin (0.2 mg/kg intravenously). If the defect is not closed, blood flows continuously from the aorta through the ductus into the pulmonary artery in both systole and diastole; the defect is a form of arteriovenous fistula, increasing the work of the left ventricle. If it remains open, obliterative changes in the pulmonary arterioles can cause pulmonary hypertension, with reversal of the direction of shunting. Then the shunt is bidirectional or right-to-left (Eisenmenger's syndrome). This complication does not correlate with shunt size.
Clinical Findings of Patent Ductus Arteriosus
Symptoms and Signs of Patent Ductus Arteriosus
There are no symptoms unless left ventricular failure or pulmonary hypertension develops. The heart is of normal size or slightly enlarged, with a hyperdynamic apical impulse. The pulse pressure is wide, and diastolic pressure is low. A continuous rough "machinery" murmur, accentuated in late systole at the time of S2, is heard best in the left first and second interspaces at the left sternal border. Thrills are common.
Prognosis & Treatment of Patent Ductus Arteriosus
Large shunts cause a high mortality rate from cardiac failure early in life. Smaller shunts are compatible with long survival, congestive heart failure being the most common complication. Infective endocarditis or endarteritis may also occur, and antibiotic prophylaxis is required. A small percentage of patients develop pulmonary hypertension and reversal of shunt (right- to-left shunting), such that the lower legs, especially the toes, appear cyanotic and clubbed in contrast to normally pink fingers. At this stage, the patient is inoperable.