A clinical trial of nifedipine, a calcium antagonist, in cardioplegic solution was performed based on previous laboratory data demonstrating improved postischemic performance in dogs. During a 12 month interval, 47 patients at increased risk had cardiac operations under a protocol in which a standard cardioplegic solution was used or the same solution with the addition of 275 μg/L of nifedipine. The protocol included formal criteria for entrance into the study, serial radionuclide ventriculograms, 24 hour Holter electrocardiographic (ECG) recordings, creatine kinase MB isoenzyme (CK-MB) analyses, technetium 99 myocardial pyrophosphate scans, and intraoperative and postoperative hemodynamic assessment. Thirty of the 47 received nifedipine and 17 received cardioplegic solution only. The two groups were similar for symptoms, anginal and left ventricular function classifications, sex, age, preoperative hemodynamic status, rate of premature ventricular contractions (PVCs), ischemic time-myocardial temperature integrals, and distribution by operation. The results show a difference (p