Myocardial Protection Of HTK Cardioplegia On Isolated Rabbit Heart

Objective: This study was designed to determine whether Histidine- Tryptophan-Ketoglutarate (HTK) cardioplegic solution is as effective for preservation of the immature myocardium during ischemia as it is for the mature myocardium and to evaluate the myocardial protective effects of St.Thomas'II (STH) cardioplegic solution and HTK cardioplegic solution on the immature myocardium. Methods: Hearts from immature (3-4 weeks, 440 to 540 mg, n=24,) and mature (4-5 months, 1.84-2.01 kg, group A: HTK cardioplegia in mature rabbits, n=12) New Zealand White rabbits were studied, the immature rabbits were divided into two groups randomly (groupB: HTK cardioplegia in immature rabbits, n=12 and groupC: STH cardioplegia in immature rabbits, n=12). Animals were anesthetized and given heparin. The hearts were rapidly excised and placed in 37 ℃ bicarbonate buffer, within 2 minutes the heart was cannulated via the aorta and perfused by Langendorff perfusion apparatus. Aortic perfusion pressures were as follow: immature hearts: 60 cmH2O; mature hearts: 100 cmH2O. All hearts were perfused by the 37 ℃ oxygenated (O2:CO2 = 95%:5%) KH solution and surrounded by a water jacket at 37℃. 2 hearts from every group randomly were removed from the perfusion apparatus to observe the myocardial ultra-structure after 30minutes. For others, control values for coronary flow(CF), systolic and diastolic left ventricle end pressure(LVPSP and LVEDP), heart rate(HR) were recorded, and when perfused 30 minutes, 2 ml coronary effluent was collected for the determination of CK and CK-MB leakage, After 30 minutes, aortic line was clamped and cardioplegic solution was infused into the coronary vasculature, the perfusion pressure was as same as aortic perfusion pressure. Group A & B were infused by Histidine- Tryptophan- Ketoglutarate (HTK) cardioplegic solution, Group C was infused by St.Thomas'II (STH) cardioplegic solution at interval of 30 minutes. Global ischemia maintained for 2 hours at 25℃. Following this period, the hearts were reperfused by 37℃ KH solution for 30 minutes, during which time the recovery of cardiac function was assessed. At the conclusion of each experiment the hearts were removed from the perfusion apparatus, some myocardium tissue was taken to observe the myocardial ultra-structure and some...