[31-phosphor-NMR spectroscopy for determining optical preservation temperature during long-term myocardial ischemia]

The ideal level of hypothermia during myocardial preservation for cardiac transplantation remains unknown. Therefore 31P-NMR spectroscopy was applied to assess the effect of different preservation temperatures (15 degrees C in group 1, 4 degrees C in group 2) on time dependent changes of myocardial high energy phosphorous compounds during prolonged global ischemia (5 hours in group 1, 8 hours in group 2) and subsequent reperfusion of isolated rat hearts preserved with modified St. Thomas Hospital solution. ATP-depletion during ischemia was slower in group 2 leading to a significant difference in myocardial ATP-concentrations between both groups after 3 hours of ischemia. The drop of intracellular pH during ischemia was significantly less pronounced in hearts preserved at 4 degrees C compared to 15 degrees C. Postischemic recovery of both left ventricular (LV) peak systolic pressure and its +dP/dt max. was superior in group 2, although the ischemic time was 3 hours longer than in group 1. Hypothermia at 4 degrees C appears favourable for prolonged myocardial protection compared to 15 degrees C with regard to preservation of ATP, prevention of intracellular acidosis and postischemic hemodynamic recovery.