932-90 Transient Adenosine Infusion and Washout Before Ischemia Protects the Heart Against Metabolic Damage During Ischemia and Reperfusion, but Does not Attenuate Stunning in Pigs – Comparison with Ischemic Preconditioning

Recent studies indicate that ischemic preconditioning (IP) may be mediated by adenosine (ADO) receptor stimulation. This study compared the effects of adenosine pretreatment on myocardial metabolism and function with those of IP. Control hearts (C) underwent 15 min LAD occlusion (occl) followed by 120 min reperfusion (R). ADO (200/μg/kg/min) was infused into left atrium for 15 min starting at 20 min before LAD occl. IP was elicited by two cycles of 5 min occl & 5 min R. Tissue levels of ATP. creatine phosphate (CP) and pH in the area at risk were measured by 31 P-MRS, and %segment shortening (%SS) by sonomicrometry Results ADO infusion decreased blood pressure (–26%) and heart rate (–13%), and increased three times regional myocardial blood flow (RMBF). However, within 5 min after stopping ADO infusion, hemodynamic parameters returned to baseline. During sustained ischemia and reperfusion, there were no differences in hemodynamic parameters or RMBF among three groups. 15 min occl 120 min R 120 min R Groups ATP CP pH ATP CP %SS C(n = 10) 64 ± 7% 7 ± 6% 6.3 ± 0.2 71 ± 7% 105 ± 12% 39 ± 16% ADO (n = 10) 76 ± 6% * 9 ± 6% # 6.5 ± 0.1 * 90 ± 8% * 101 ± 6% # 29 ± 6% IP(n = 10) 74 ± 9% * 18 ± 6% * 6.6 ± 0.1 * 91 ± 90% 126 ± 7% 32 ± 16% ATP, CP and %SS values; % of baseline * p l 0.05 vs C # p l 0.05 vs IP Conclusion ADO pretreatment and IP had similar effects on ATP and pH, but not on CP. In spite of the protective effects on myocardial metabolism during ischemia and reperfusion, neither of the interventions improved %SS after ischemia.