Abstract P134: Total Liquid Ventilation Induced Ultrafast Cardioprotective Hypothermia during Prolonged Myocardial Ischemia in Rabbits

Abstract

Introduction: Total liquid ventilation with temperature-controlled perfluorocarbons induces an ultra-fast cardioprotective cooling when instituted during a 30-min coronary artery occlusion (CAO) in rabbits. Hypothesis: We hypothesized that ultra-fast hypothermia instituted with a short total liquid ventilation episode would be still beneficial after a prolonged CAO as compared to conventional low rate surface cooling. Methods: Anesthetized rabbits underwent a 60-min CAO followed by 4 hours of reperfusion before infarct size and no reflow evaluations. Rabbits randomly underwent either a normothermic CAO (Control group, n=7) or cooling from 5th min of CAO to the end of CAO (target left atrial temperature: 32°C). Cooling procedures were either low rate surface cooling (LRC) using ice-filled cold blankets (LRC group, n=7) or ultra-fast cooling (UFC) initiated by 20 min of hypothermic total liquid ventilation and maintained if necessary by cold blankets (UFC group, n=6). An additional group underwent a similar ultra-fast cooling protocol started at the 20th min of CAO (UFC-delayed group, n=6). After reperfusion, all hypothermic animals were rewarmed. Results: Left atrial temperature was similar in all groups at baseline (Table ). Hypothermia was modest in LRC vs UFC and UFC-delayed groups at 30-min CAO but reached similar level at the end of ischemia (i.e., 60-min CAO). Interestingly, no reflow and infarct sizes were only significantly reduced in UFC and UFC-delayed but not in LRC groups as compared to Control. Infarct size reduction was significantly better predicted by the integrated decrease in left atrial temperature throughout ischemia than by the temperature at the end of ischemia. Conclusion: Ultra-fast cooling induced by total liquid ventilation afforded cardioprotection against prolonged ischemia in rabbits, even when instituted later than a low rate surface cooling. Left atrial temperature (LAT) at different times of the protocol and infarct and no reflow sizes