THE CARDIAC OUTPUT AND OTHER MEASUREMENTS OF THE CIRCULATION IN COARCTATION OF THE AORTA 1

Abstract

14 cases of coarctation of the aorta are presented, in nine of which measurements of the circulation were made, including: cardiac output, basal metabolic rate, arteriovenous O2 difference, cardiac output per beat, left ventricular work per beat, the blood pressure in all 4 extremities, venous pressure, vital capacity, circulation time by means of decholin, CO2 inhalation, and Mascosol, electrocardiograms and x-rays of the chest. The heart at rest maintained a normal or even increased vol. output of blood before the onset of failure. In only one case was the cardiac output decreased. In only one case was the heart enlarged to give a cardiothoracic ratio greater than 50%. This patient had a cardiac output within normal limits but it was not in proportion to the greatly enlarged heart. In all other cases the work of the heart in relation to the cardiac size was adequate. The systolic blood pressure in the arms was higher than that in the legs in all except. 1 patient. This finding was the most constant of the characteristic signs of coarctation of the aorta. In most cases there was not only an increase in the resistance to the outflow of blood at the site of coarctation and in the collateral channels, but also a generalized increase in peripheral resistance sufficient to maintain a high diastolic pressure below the level of the coarctation. The circulation time was within or near normal limits above the level of coarctation but there was a tendency to prolongation below the coarctation. Erosion of the inferior margins of the ribs posteriorly was the most common x-ray finding. This was noted in 11 of the 14 cases. Enlargement of the heart and T wave changes point to a poor prognosis.