[Comparative study of myocardial protection by coronary perfusion in deep hypothermia (10 degrees C) with or without potassium cardioplegia. Clinical, electrocardiographic, enzymatic results; biochemical and histological controls].

A technique of coronary perfusion with diluted blood, giving homogenous myocardial cooling (10-12 degrees C) under lignocaine perfusion, with or without potassium (K) cardioplegia is presented. The first 75 operated cases were used to adjust the optimal lignocaine (5 mg/min) and K (2 meq/min in continuous coronary perfusion, 5 meq/min in discontinuous coronary perfusion) dosage in the myocardial protection circuit. Then, 123 operated patients (78 aortic valve replacement, 30 mitro-aortic double valve replacement, 15 other operations on the ascending aorta) were classified into four groups prospectively: 1. Continuous coronary perfusion 10 degrees C, 2. Continuous coronary perfusion 10 degrees C with associated K cardioplegia, 3. Discontinuous coronary perfusion 10 degrees C, 4. Discontinuous coronary perfusion 10 degrees C with K cardioplegia. The best return of cardiac activity was observed in Group 1 and this was statistically significant with a high percentage of spontaneous heart beating after declamping the aorta (average 10 minutes), immediate efficacity of left ventricular contraction, and absence of arrhythmias, especially the transient conduction defects observed with K cardioplegia. In Group 1, during mitro-aortic valve replacement, after over 60 minutes aortic clamping, no significant reduction of ATP or myocardial phosphocreatinine or changes of hexosemonophosphates were observed, contrary to the findings after 15 minutes aortic clamping at 28 degrees C in a control group of mitral valve replacements (n = 10). Myocardial changes on electron microscopy in the subendocardial region of the left ventricle were minimal or absent, especially with respect to the mitochondria. The early post-operative course was the same in all four groups: of the 123 patients operated, early mortality was 2.4 p. 100 (1.6 p. 100 from intercurrent causes), severe arrhythmias were observed in 1.6 p. 100, supraventricular arrhythmias in 4.9 p. 100, myocardial infarction in 0.8 p. 100, electrocardiographic ischaemia in 0.8 p. 100, and atrioventricular block in 0.8 p. 100. The average enzyme level (CPK, SGOT, LDH) in the early postoperative period were low, with no correlation with the duration of aortic clamping.