Prospective, randomized clinical study of ischemic preconditioning as an adjunct to intermittent cold blood cardioplegia.

BACKGROUND: Ischemic preconditioning has been shown to be beneficial to myocardial preservation in a variety of models. This study was performed to determine whether ischemic preconditioning can ameliorate the postischemic myocardial dysfunction often seen in patients undergoing open heart operations. METHODS: Seventy patients were prospectively randomized to receive or not receive ischemic preconditioning before intermittent cold blood cardioplegic arrest. Ischemic preconditioning was induced by 1 minute of aortic cross-clamping followed by 5 minutes of reperfusion during normothermic cardiopulmonary bypass, immediately before cardioplegic arrest. Control patients had an extra 6 minutes of normothermic cardiopulmonary bypass before cardioplegic arrest. Hemodynamic parameters were obtained before bypass, and at 1, 6, and 12 hours after weaning from bypass. All patients were monitored for the development of postoperative complications and need for inotropic agents or intraaortic balloon pumping. RESULTS: Preconditioned patients showed marked improvement in cardiac index from a preoperative value of 2.2 +/- 0.1 L x min(-1) x m(-2) to 2.5 +/- 0.1 L x min(-1) x m(-2) at 1 hour after bypass (p < 0.01), 2.8 +/- 0.1 L x min(-1) x m(-2) at 6 hours after bypass (p < 0.0001), and 2.9 +/- 0.1 L x min(-1) x m(-2) at 12 hours after bypass (p < 0.0001). In the control group the cardiac index deteriorated significantly from 2.5 +/- 0.1 to 2.2 +/- 0.1 L x min(-1) x m(-2) at 1 hour after bypass (p < 0.05), and then only returned to baseline at 6 and 12 hours after bypass. Thirteen control patients required inotropic agents; however, none of the ischemic preconditioning group required inotropic agents (p < 0.001). There was no significant difference between the groups with respect to postoperative morbidity and mortality. CONCLUSIONS: Ischemic preconditioning significantly improves heart function in clinical cardiac operations, decreases the need for inotropic support, and could be an important adjunct to myoprotective strategies.