Objective: To assess the safety and efficacy of myocardial protection of the donor heart during transplantation with the use of blood cardioplegia, a prospective randomized clinical trial was undertaken between January 1997 and March 1998. Methods: Forty-seven consecutive patients were assigned either to crystalloid (27 patients; group 1) or blood cardioplegia (20 patients; group 2), Comparison of recipient age (54 +/- 11 years vs 55 +/- 7 years; P = .9), sex (89% vs 90% male patients; P = .9), diagnosis (63% vs 65% dilated cardiomyopathy; P = .8), elevated pulmonary vascular resistance (30% vs 30%; P = .9), prior cardiac operations (22% vs 30%; P = .5), need for urgent heart transplantation (7% vs 20%; P = .2), donor age (32 +/- 11 Sears vs 31 +/- 13 years; P = .7), cause of death (33% vs 40% vascular; P = .5), and global myocardial ischemia (176 +/- 51 minutes vs 180 +/- 58 minutes; P = .5) showed no difference. Hemodynamically unstable donors (15% vs 45%; P = .02) were more prevalent in group 2, Results: Operative mortality rates (4% vs 5%; P = .8), high-dose inotropic support (41% vs 30%; P = 0.6), and postoperative mechanical assistance (11% vs 10%; P = 0.9) mere comparable in the 2 groups. Prevalence of acute right heart failure (27% vs 0: P = .02) and of temporary complete atrioventricular block (52% vs 20%; P = .02) were greater in group 1, Spontaneous sinus rhythm recovery was more prevalent in group 2 (11% vs 40%; P = .02), Higher peak creatine kinase (1429 +/- 725 u/L vs 868 +/- 466 u/L: P = .01) and creatine kinase MB (144 +/- 90 u/L vs 102 +/- 59 u/L; P = .06) levels suggested more severe ischemic injury in group I. Conclusion: Use of blood cardioplegia was associated with a lower prevalence of right heart failure, cardiac rhythm dysfunction, and laboratory evidence of ischemia.