If the ductus arteriosus does not close after birth, the higher pressure in the aorta than in the pulmonary artery causes the blood to flow from the aorta, through the patent ductus into the pulmonary artery thus resulting in left to right shunt. This results in increased work load on the left side of the heart, increased vascular pressure in the pulmonary tree and increased blood flow in the ascending aorta.
The clinical features depend upon the size of the ductus and the amount of shunting. The defect is discovered only on routine examination of a classic "machinery murmur" which occurs during systole as well as diastole.
The mild symptoms may include growth retardation, dyspnoea on exertion, palpitation, easy fatigability and recurrent respiratory infection. Other clinical symptoms may include heart rate over 150/minute, gallop rhythm due to rapid filling of the ventricle, bounding pulses due to increased systolic pressure and wide pulse pressure. In severely affected cases congestive heart failure may be present.
Radiologic examination and electrocardiogram shows enlargement of left ventricle and left atrium. The ascending aorta is dilated and there is increased pulmonary vascularity. Echocardiogram is normal and the cardiac catheterization if necessary shows increased pressure in right ventricle and pulmonary artery and oxygenated blood in pulmonary artery.