Is a left ventricular vent necessary for coronary artery bypass operations performed with cardioplegic arrest?

The need for ventricular venting with hypothermic cardioplegic arrest is controversial. We report an evaluation of the need for left ventricular venting in a canine model that closely simulates conditions during routine coronary artery bypass grafting (CABG). Thirty-five dogs were placed on cardiopulmonary bypass for 60 minutes of hypothermic cardioplegic arrest (18 vented, 17 nonvented) and then reperfused for 30 minutes. Myocardial temperature and left atrial pressure (LAP) were recorded continuously. Before and 30 minutes after hypothermic cardioplegic arrest, left ventricular function curves were generated (six vented, six nonvented), and biopsy specimens of the left ventricle were taken for adenosine triphosphate (ATP) determinations (11 vented, 10 nonvented) and semiquantitative grading of mitochondrial ultrastructure (six vented, six nonvented). LAP in nonvented dogs was 7.4 mm Hg during hypothermic cardioplegic arrest and 5.0 mm Hg during reperfusion. Temperature during hypothermic cardioplegic arrest was 12.3 degrees C in vented dogs and 11.3 degrees C in nonvented dogs (p = 0.5). There were no differences in left ventricular function or preservation of mitochondrial ultrastructure between vented and nonvented dogs. ATP after hypothermic cardioplegic arrest was 96.6% of control (4.30 microM/gm) in vented dogs and 94.6% (4.37 microM/gm) in nonvented dogs (p = 0.7). The absence of left ventricular venting did not lead to ventricular distention or more rapid rewarming. These data in vented dogs and nonvented dogs strongly support the belief that left ventricular venting is not necessary during routine CABG.