Heart transplantation from non-heart-beating donors; future transplantation

Background Heart transplantation is an alternative treatment for cardiac failure. However, increasing demand for donor hearts has lead to extension of donor criteria. Thus, our final purpose is to achieve heart transplantation from non-heart-beating donors (NHBDs). However, cardiac function of NHBDs is uncertain due to severe myocardial damage, resulting in primary graft failure. To utilize NHBDs for heart transplantation, it is critically important to minimize cardiac damage with many myocardial protections and also to evaluate resuscitated hearts from NHBDs before transplantation. We developed isolated myocardial perfusion system to resuscitate the NHBD hearts and attempted to predict functional recovery of 60-min warm ischemic hearts by analyzing systolic and diastolic functions. Methods Hypoxic cardiac arrest was induced in eight mongrel dogs without any pretreatments. After 60-min ischemia, intracoronary microthrombi were flushed out by retrograde blood cardiopledia with tissue-type plasminogen activator. Coronary arteries were initially perfused from the aortic root with tepid hyperkalemic blood (20 mmol/L) at low pressure (20 mm Hg) for the first 60 min and then with normothermic blood for the next 60 min. After 120 min of reperfusion, preload was increased for ejection against an 80 mm Hg of afterload. Pressure-volume loops were recorded to obtain end-systolic pressure-volume relationship (ESPVR) and end-diastolic pressure-volume relationship (EDPVR). Stroke volume at given preload was calculated from averaged ESPVR, EDPVR and afterload identical to averaged baseline value. Frank-Starling relationship was obtained and cardiac status was classified by Forrester's hemodynamic subset. Results End-systolic elastance was significantly decreased to about 60% of the baseline and time constant of isovolumic relaxation was significantly prolonged by about 20%. Cardiac index was decreased to about 50% and cardiac status was classified in Forrester's III or IV subset. Conclusions An extent of functional recovery of NHBD hearts is predictable by cardiac output. Although 120 min of recovery time may be short for 60-min ischemic damage, this system may be feasible to predict posttransplant cardiac function before transplantation.