THE EFFECTS OF THE PATENT DUCTUS ARTERIOSUS ON THE CIRCULATION 1

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Abstract
Studies of the circulation made on 6 patients before and after surgical closure of an uncomplicated patent ductus arteriosus show that: When the ductus arteriosus is open the blood flow is from the aorta to the pulmonary artery. There is no flow of blood from pulmonary artery to aorta; therefore, these patients do not have arterial unsaturation and are not cyanotic. The vol. of blood flowing from aorta to pulmonary artery varied from 4 to 19 liters per min., which is 45-75% of all the blood pumped into the aorta by the left ventricle. These flows occurred in patients with large ducti and under temporary conditions which are known to elevate the output of the heart. The left ventricle expelled from 2 to 4 times the vol. of blood expelled by the right ventricle in a given period of time. Adjustment of the circulation to the patent ductus may be made by an increase in the output of the left ventricle. If this is not sufficient to compensate completely for the leak through the ductus, there may be, in addition, a diminution in the blood flow to the periphery. Comparable studies in dogs with an artificial aorta-pulmonary artery fistula showed similar circulatory adjustments. These studies of the circulation supply direct evidence of the beneficial effects of operative closure of the ductus in improving the peripheral circulation in some of the patients and in reducing the work of the heart in all of them.