PARTIAL CONSTRICTION of the descending thoracic aorta is necessary in pulmonary arteryaortic anastomosis for cyanotic heart disease and complete occlusion in resectional therapy for aneurysm. Previous studies from our laboratory have shown that protection of the kidneys and the spinal cord from ischemic change during crossclamping of the aorta may be afforded by bypass flows of approximately 15 to 20 cc/kg/min.1 The purpose of the present investigation was to study physiological events occurring proximal to the constricted aorta. Left ventricular performance was evaluated when the aorta was partially and completely occluded and when graded bypass flows were carried out.
Ventricular function was determined by a modification of the method of Sarnoff and Berglund.2 Twenty healthy mongrel dogs weighing 13 to 18 kg were studied. Ten animals were operated on and caval blood was diverted into an extracorporeal circuit by gravity-siphon drainage. The pulmonary artery was ligated.