Late results of the ‘warm heart trial’: the influence of nonfatal cardiac events on late survival

Background — The Warm Heart Trial randomized 1732 CABG patients to receive warm or cold blood cardioplegia. In the warm cardioplegia patients, nonfatal perioperative cardiac events were significantly decreased and the mortality rate was nonsignificantly decreased (1.4% versus 2.5%, P=0.12). The purpose of the present study was to evaluate the late results of these trial patients.

Methods and Results — Randomization was stratified according to surgeon and urgency of the operation. Seven hundred sixty-two patients recruited from 1 of the centers were followed through the hospital clinic for late events. Late survival (including perioperative deaths) at 72 months was nonsignificantly greater in the warm cardioplegia patients (94.5±1.7%, mean±SEM) than in the cold cardioplegia patients (90.9±2.6%). Independent predictors of mortality by Cox proportional hazards model were redo CABG, diabetes mellitus, renal insufficiency, and increasing age. The influence of nonfatal perioperative events (perioperative myocardial infarction according to computerized ECG readings or low output syndrome as determined by an outcome committee) on late survival was also analyzed. Late survival at 84 months was significantly reduced in the group who experienced nonfatal perioperative outcomes (94.5±1.7% versus 84.9±4.5%, P<0.001) and remained a significant predictor after adjustment for other important variables (risk ratio 6.4, 95% CI 1.87 to 8.73, P<0.0001).

Conclusions — Effective myocardial protection through either cold or warm blood cardioplegia is essential, because late survival is significantly reduced in patients with nonfatal perioperative cardiac outcomes.