Hemodynamics and energy balance of the left ventricle during low flow venoarterial bypass and venoarterial counterpulsation with an oxygenator in experimental animals.

Abstract

The effects of partial venoarterial continuous flow and counterpulsating bypass with an oxygenator on the hemodynamics and energy balance of the left ventricle were studied in 8 anesthetized closed-chest dogs. A mean blood flow of 35%, and 48% of the animals's cardiac output was pumped via an extracorporeal circuit. 1. with continuous flow by means of a roller pump, and 2. with ECG-synchronized counterpulsation by means of a one-chambered electropneumatically driven ventricle pump. Central venous shunt blood was oxygenated with a double oxygenator and returned into the descending aorta. A bypass of 48% of cardiac output both with continuous and counter-pulsating flow resulted in a significant decrease of the maximal rise in left ventricular pressure (dp/dt max, 32% and 30% respectively) and of the calculated myocardial oxygen requirement (10% and 16% respectively). The improved myocardial energy balance during diastolic counterpulsation was due to a significant decrease in systolic aortic pressure (11%). During bypass of 35% of cardiac output with continuous flow the hemodynamics and energy balance of the left ventricle remained essentially unchanged. However, during bypass with counterpulsating flow a significant decrease in systolic pressure (7%) dp/dt max. (19%), and myocardial requirement oxidend (9%) was obtained. The results indicate that, if combined with counterpulsation, partial venoarterial bypass of only 35% of cardiac output can be an effective method of supporting the failing heart. Low flow venoarterial counterpulsation may therefore be of value for transitory use up to 72 hours in postoperative low-output syndrome or myocardial infarction whenever intraaortic balloon pumping alone is not sufficient or combined right and left heart failure is present.