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Patent Ductus Arteriosus


The ductus arteriosus (see fig 23) connects the descending aorta (distal to the left subclavcan artery takeoff from the aorta to supply the left arm) to the left pulmonary artery. The ductus arteriosus serves in the fetus to shunt blood from the pulmonary artery (avoiding the unexpanded lungs) to the descending aorta for oxygenation in the placenta of the womb. It closes normally soon after birth. However, in some babies it does not close spontaneously, and there is continuous flow from the aorta to the pulmonary artery (i.e. left to right shunting) (see figure). This abnormality accounts for 10% of congenital heart disease cases, and is higher than average in pregnancies associated with persistent perinatal hypoxemia (reduced oxygen levels) or maternal rubella (German measles) and among babies born at high altitude or prematurely. Diagnosis includes the following: 1)physical examination especially looking for a "machinery" at the second left anterior intercostal space (between the second and third ribs) murmur occurring throughout the cardiac cycle. 2) EKG 3) Chest X ray showing heart enlargement, dilated pulmonary arteries, and a prominent ascending aorta. The right ventricle may enlarge if high pressure occurs the pulmonary arteries. 4) Echocardiography with doppler may visualize the ductus and show continuous flow in the pulmonary artery. 5) Heart catheterization and angiography allow determination of the size of the shunt, pulmonary vascular resistance and visualization of the ductus arteriosus itself. A small patient ductus is usually asymptomatic and a person with such a small defect can have a normal life span. But the area can become infected and lead to infected blood clots being thrown into the lungs. A moderate sized defect may cause symptoms of fatigue, shortness of breath, and palpatations in childhood or adulthood. In addition, the ductus may enlarge as an aneurysm and rupture. Larger shunts may cause left heart failure. Finally, pulmonary hypertension may occur, and cause the shunts to reverse direction into the descending aorta. One third of patients with a patent ductus arteriosus which is not surgically repaired, die of heart failure, pulmonary hypertension, or endarteritis by the age of 40 years and two thirds die by the age of 60 years. Surgical ligation of the patent ductus arteriosus, often done without cardiopulmonary bypass, has an associated mortality of less than 0.5%. But if there is an aneurysm or calcification of the ductus, resection with cardiopulmonary bypass may be required. The risk of endarteritis (inflammation of the arteries) associated with unrepaired patent ductus arteriosus and the low risk associated with ligation, it is recommended that even a small patent ductus be ligated surgically or occluded with a percutaneously placed closure device. The onset of severe pulmonary vascular obstructive disease is a contraindication to surgical ligation or occlusion.

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