Ischemic Preconditioning Improves Protection with Cold Blood Cardioplegia

Abstract

This prospective randomized study was undertaken to test the hypothesis that ischemic preconditioning could improve myocardial protection with cold blood cardioplegia in patients undergoing valve replacement and to investigate the mechanism of ischemic preconditioning in human myocardium. After the institution of cardiopulmonary bypass, 20 patients undergoing double valve replacement were preconditioned with 2 cycles of 3 minutes of aortic crossclamping and 2 minutes of reperfusion before cardioplegic arrest. A further 20 patients served as controls. The hearts were arrested with blood cardioplegic solution at 4°C. In the perioperative period, blood samples were collected from the coronary sinus, samples of right atrial myocardial tissue were obtained, and cardiac function was measured. Ischemic preconditioning reduced oxygen free radial production, calcium overload, and myocardial ultrastructural damage, while the myocardial production of calcitonin gene-related peptide was increased to 95.3 ± 3.8 μg·L−1 compared with 61.2 ± 4.9 μg·L−1 in the controls. Cardiac index was also higher in the preconditioned patients at 2.8 L·min−1·m−2 compared to 2.3 L·min−1·m−2 in the controls. It was concluded that ischemic preconditioning enhanced cardioplegic protection in valve replacement patients by increasing the level of calcitonin gene-related peptide and decreasing oxygen free radicals.