The influence of prearrest factors on the preservation of left ventricular function during cardiopulmonary bypass

Uniformly excellent myocardial protection during global ischemia in cardiac procedures requiring cessation of aortic root perfusion remains an elusive goal. This study establishes the importance of the preischemic inotropic state of the left ventricle and the arterial blood glucose concentration ([glucose]) immediately prior to an elective period of myocardial ischemia. Thirty-one experiments were performed on dogs subjected to 90 minutes of global ischemia on cardiopulmonary bypass at 28 degrees C with perfusion pressure constantly maintained at 90 mm Hg. The maximum rate of development of left ventricular pressure (LVdp/dtmax) at constant arterial and left atrial (LAP) pressures was used as a measure of contractility prior to ischemia. In a group of 18 of these dogs undergoing anoxic cardiac arrest, arterial blood [glucose], in conjunction with the preischemic LVdp/dtmax and the cross-clamp to asystole time interval (metabolic supply/demand index), significantly predicted (p less than 0.01) the functional result following the standard ischemic insult. In 13 other dogs with [glucose] greater than 120 mg/100 ml and treated with potassium cardioplegia, "normal" preischemic LVdp/dtmas (N = 7) was associated with a good functional result, but an elevated preischemic LVdp/dtmax (N = 6) produced severe functional impairment following ischemia. Optimum myocardial protection thus involves minimizing metabolic demands and maximizing metabolic supply immediately prior to and during the period of aortic cross-clamping.