Clinical studies of myocardial protection rarely identify differences in hard clinical outcomes after surgery, either early or late, because most trials lack sufficient statistical power to deal with low-frequency events.
Prospectively collected data concerning all isolated coronary bypass operations from November 1989 to February 2000 were analyzed to determine the effects of cold blood cardioplegia and warm or tepid blood cardioplegia on early and late outcomes after surgery. Warm blood cardioplegia was used in 4532 patients, whereas cold blood cardioplegia was used in 1532. The allocation of patients to receive warm blood cardioplegia and cold blood cardioplegia was random in 749 cases and according to surgeon preference in the remainder. Most patients in the cold blood cardioplegia group had surgery earlier in the time course of the study, and most in the warm blood cardioplegia group underwent surgery later.
Perioperative death, myocardial infarction, and death or myocardial infarction were all more common in the cold blood cardioplegia group than in the warm blood cardioplegia group (death 2.5% vs 1.6%, P =.027, adjusted odds ratio 1.45, 95% confidence interval 0.95-2.22, P =.09; myocardial infarction 5.4% vs 2.4%, P