WARM AND COLD BLOOD CARDIOPLEGIA - COMPARISON OF MYOCARDIAL-FUNCTION AND METABOLISM USING P-31 MAGNETIC-RESONANCE SPECTROSCOPY

Background Standard myocardial protection during cardiac surgery uses hypothermic arrest, but warm heart surgery, recently introduced, is no w used in many centers. We hypothesized that warm continuous blood car dioplegia (WCBC) would provide better myocardial preservation than col d continuous blood cardioplegia (CCBC). Methods and Results In isolate d cross-perfused canine hearts, left ventricular (LV) function and myo cardial O-2 consumption (MVo(2)) were measured at constant LV volume, coronary perfusion pressure, and heart rate before and after 75 minute s of arrest at 37 degrees C or 10 degrees C. Metabolism was evaluated by P-31 nuclear magnetic resonance spectroscopy. LV resting tone incre ased transiently after arrest by CCBC but not WCBC (38+/-3.9 versus 2. 9+/-0.5 mm Hg, P<.0005). Myocardiai ATP changed over time differently in the groups (P<.001), declining at the outset of CCBC and returning to control levels during the recovery period after CCBC or WCBC. Intra cellular pH rose from 7.17+/-0.03 to 7.85+/-0.05 during CCBC (P<.0005 versus WCBC), MVo(2) declined dramatically during arrest at either tem perature but to a lower value during CCBC (P<.0005). LV pressure recov ered to 86.1+/-5.1% of its prearrest value after CCBC and to 97.2+/-7. 8% following WCBC (P=NS). After CCBC but not WCBC, there were small bu t significant increases in LV end-diastolic pressure (by 1.3 mm Hg, P< .05) and in the LV relaxation constant, tau (from 37.3+/-1.5 to 42.3+/ -2.4 milliseconds, P<.05). Conclusions The increase in intracellular p H during CCBC is largely accounted for by physicochemical factors. Gro up differences in ATP over time may be related to rapid cooling contra cture during CCBC. The data suggest that CCBC mildly impairs LV functi on but that WCBC preserves function and metabolism at or near prearres t levels.