[Importance of metabolic disorders and endocardial viability ratio in the prognosis of open-heart operations. Experimental study of the pig heart protected by potassium cardioplegia in hypothermia].
The aim of this study was to investigate the protective efficacy of potassium cardioplegia in general moderate hypothermia, in five pigs, after 90 minutes of myocardial ischemia induced by extracorporeal circulation (ECC) and aortic clamping. The behaviour of subendocardial supply demand ratio (DPTI/TTI), of CSBF (coronary sinus blood flow) and numerous hemodynamic parameters was evaluated in addition to lactate myocardial metabolism changes, at rest, after 90 minutes of total ECC and during a 60 minutes reperfusion period. The reperfusion period included two phases: during the first (15-20 minutes) the animals were in ECC with unclamped aorta; spontaneous circulation was instituted during the second one (40 minutes). A marked increase in CSBF was observed at aortic clamp removal during the first phase (post ischemic reactive hyperemia). Coronary sinus lactate release was also noted, probably due to wash-out of previously sequestered acid metabolites during aortic clamping (90 minutes). At the onset of the second phase a depressed left ventricular performance and low DPTI/TTI values were shown. A rapid return (20 minutes) to normal values of this parameter was then noted. DPTI/TTI normalization results strictly correlated to the progressive improvement in myocardial performance. Hypothermic potassium cardioplegia seems therefore to prevent the irreversible myocardial damage and favour a fast recovery of cardiac function.