Cold cardioplegia versus hypothermia for myocardial protection. Randomized clinical study

17 of 34 consecutive patients undergoing coronary artery bypass grafting were randomly assigned to one of two methods of myocardial preservation. With the cold cardioplegic method (group A), a 4°C. asanguineous solution with 30 mEq. of potassium per liter was infused into the aortic root for about 2 minutes immediately after aortic cross-clamping and again after about 45 minutes or when myocardial temperature rose above 19°C. External cardiac cooling was provided by constant infusion of 4°C. Ringer's solution into the pericardium. 17 Patients were assigned to simple cardiac cooling by hypothermic systemic perfusion before aortic cross-clamping plus external cardiac cooling (Group B). Electromechanical activity ceased within 1 to 2 minutes in Group A but continued throughout the ischemic period in 14 patients in Group B. Myocardial temperature (mean for all observations) during aortic cross-clamping was 17.2 ± 0.44°C. in Group A and 24.0 ± 0.70°C. in Group B. Operating conditions were better in Group A. Cardiac function early postoperatively was good in both groups clinically and according to measurements, but only in the cold cardioplegic group (A) was cardiac index not adversely affected by longer cross-clamp time. Myocardial necrosis occurred in both groups but was probably less in the cold cardioplegic group. 13 Patients (76%) in Group A had no electrocardiographic evidence of myocardial injury, compared with 8 (47%) in Group B (p = 0.08). 11 (65%) of Group A had no or short-lived appearance of creatine phosphokinase isoenzyme (CK-MB), compared with 6 (35%) of Group B (p = 0.08). Time-related CK-MB and SGOT mean levels were consistently lower in Group A.