THE CONTRACTION STATE OF MYOFIBRILS DURING GLOBAL-ISCHEMIA AND AFTER REPERFUSION FOLLOWING DIFFERENT FORMS OF CARDIAC-ARREST - CORRELATION WITH METABOLIC PARAMETERS IN THE CANINE HEART

This study was undertaken in order to obtain information on the mode o f reaction of the contractile apparatus after different forms of cardi ac arrest, global ischemia and reperfusion, as well as on possible cor relations between the contraction state of myofibrils and biochemical parameters. During the survival time, before the level of 3 mumol/g(ww ) creatine phosphate (CP) is reached, the contraction state shows only minor changes. During the revival time in which ATP tissue concentrat ions decay to 4 mumol/g(ww), the contribution of ATP, lactate, anorgan ic phosphate (Pa) and acidosis to the degree of relaxation depends on the method of cardiac arrest. At defined biochemical values, the degre e of relaxation is comparable after aortic cross clamping (ACC) and St . Thomas perfusion, but significantly different compared to HTK perfus ion. Thus, during the revival time, the relaxation of sarcomeres depen ds predominantly on the composition of the solutions used for cardiac arrest. The re-entry of contraction below 3 mumol/g(ww) ATP is correla ted with the ATP concentration, independent of the form of cardiac arr est. Reperfusion after HTK or St. Thomas cardioplegia and reversible i schemia leads to the focal formation of contraction bands, which do no t occur during ischemia. This contraction state is significantly more pronounced after reperfusion of St. Thomas arrested hearts. Thus, the contraction state of myofibrils is influenced not only by alterations in metabolite concentrations, but also by the composition of cardiople gic solutions and by the characteristic conditions (sufficient energy, oxygen and Calcium) during reperfusion.