Myocardial protection during aortocoronary bypass operations. Comparison of two different operative procedures: cold chemical cardioplegia versus intermittent cross-clamping of the aorta.

Myocardial injury was studied in 40 randomized coronary patients operated on electively with coronary bypass grafting using two different techniques, (A) cardioplegic arrest and continuous cross-clamping of aorta, and (B) ischaemic arrest and intermittent cross-clamping of aorta. The released quantity of the MB isoenzyme of creatine kinase was used as an indicator of myocardial injury. Of the whole group, 3 patients (8%) suffered a myocardial infarction as judged by ECG. The CK-MB release was not significantly different in the two groups. The total period of aortic cross-clamping was markedly longer in the cardioplegic group than in the intermittent clamping group. A significant correlation between the duration of aortic clamping and the amount of CK-MB release was found in the cardioplegic group. Our results indicate that the beneficial effects of cardioplegic arrest are outweighed by an unavoidable longer period of total aortic clamping as compared with the intermittent clamping technique.