THE JouRNAL OF ExTRA-CORPOREAL TECHNOLOGY Myocardial Recovery During Mechanical Circulatory Support After Acute Myocardia/Ischemia

Irreversible myocardial failure due to severe ischemia is a challenging problem in clinical practice. The present study was performed to evaluate the potential benefit of mechanical circulatory support in a bovine model with prolonged, acute myocardial ischemia. Seven calves (74+6 kg) underwent 6 hours of regional ischemia by temporary (6h) ligation of the left circumflex coronary artery. Ventricular assist was started 10 minutes after occlusion of left circumflex coronary artery. Ventricular fibrillation occurred in all animals after a mean interval of 4.0±2.4 hours. Defibrillation was attempted immediately and every hour thereafter. Successful defibrillation was achieved in 6/7 animals after 4.1±2.5 hours of ventricular fibrillation during mechanical circulatory support. Weaning from biventricular assist was attempted after 24 hours and was successful in 5 I 6 animals. Hence timely mechanical circulatory support in acute, prolonged ischemia with subsequent "irreversible" cardiac failure allows not only maintainence of acceptable hemodynamics for bridging to heart transplantation but also significant myocardial recovery if coronary artery blood flow is restored within 6 hours. Introduction Irreversible myocardial failure due to severe ischemia is a challenging problem in clinical practice. Since the introduction of percutaneous cardiopulmonary support (CPS), even desperately ill patients with sudden ischemic myocardial failure can be candidates for surgical revascularization of the myocardium. As percutaneous cardiopulmonary support cannot be used for prolonged periods if post-cardiotomy cardiac failure occurs, these patients are also potential candidates for mechanical circulatory support with pulsatile devices. In our hands1, mechanical cirAddress correspondence to: Ludwig K. von Segesser, MD Clinic for Cardiovascular Surgery University Hospital CH-8091 Zurich, Switzerland 39 culatory support with pulsatile devices for post-cardiotomy myocardial failure showed primary success in 16/20 cases (80%: weaned 14/20, transplanted 2/20). Thirty-day survival was 55% (11 /20). Hence, myocardial recovery can be achieved with uniand/ or biventricular mechanical circulatory support in a significant number of cases. The present study was performed to evaluate the potential benefit of mechanical circulatory support in prolonged, acute myocardial ischemia in a bovine model of regional ischemia and reperfusion. Materials and Methods Animals Seven calves with a mean bodyweight of 74±6 kg were studied. Following standardized premedication, general anesthesia was started with thiopental sodium and after