Comparison of the effect of blood cardioplegia to crystalloid cardioplegia on myocardial contractility in man

Abstract

The myocardial protection achieved by blood cardioplegia was compared to that achieved by crystalloid cardioplegia in a randomized prospective series of patients having coronary bypass operations. Group BCP (n = 15) was protected with 10 degrees C blood containing potassium, 30 mEq/L; Group KCP (n = 9) by an electrolyte solution at 4 degrees C with mannitol, 25 gm/L, and potassium, 26 mEq/L, and group MgKCP (n = 9) by an electrolyte solution at 4 degrees C containing magnesium, 30 Meq/L, and potassium, 19.6 mEq/L. The three groups were comparable in regard to age, sex, preoperative left ventricular function, symptoms, propranolol use, previous myocardial infarction, number of vessels bypassed, and duration of ischemic arrest. In each patient cardiac output, left ventricular end-diastolic pressure (LVEDP), and maximum contractile element velocity (Vpm) were recorded before and after the ischemic period. All operations were performed in an identical manner with one continuous period of aortic cross-clamping averaging 52.9 minutes. No significant alterations in myocardial function were observed after ischemia within the BCP or KCP groups. However, patients receiving MgKCP had significant (p = 0.02) depression in Vpm from 2.86 +/- 7.8 to 2.04 +/- 3.6 second-1 and increase (p < 0.05) in LVEDP from 9.4 +/- 2.2 to 13.4 +/- 5.2 mm Hg. Analysis of variance between groups showed that Vpm decreased significantly (p < 0.05) and LVEDP increased significantly (p < 0.05) in the MgKCP group by comparison to the BCP group. Patients receiving BCP experienced spontaneous defibrillation more frequently (p < 0.02) and received nitroprusside postoperatively more often (p < 0.05) than patients in the other two groups. From these results we conclude that blood cardioplegia provides excellent protection during myocardial ischemia, probably better than one of the two crystalloid solutions tested but no better than the other crystalloid solution. Because the three solutions differed from one another in several respects, no conclusion can be reached about the efficacy of any one ingredient.