Myocardial outflow of prostacyclin in relation to metabolic stress during off-pump coronary artery bypass grafting

Background. The metabolic changes, possible myocardial damage, and influenc e on the vascular endothelium during off-pump coronary artery bypass grafti ng have been investigated. Methods. Coronary sinus and arterial blood samples were obtained before cor onary arterial occlusion, after 10 minutes of ischemia, and after 1 and 10 minutes of reperfusion in 9 patients who had an anastomosis performed to th e left anterior descending coronary artery off-pump bypass. Results. The mean ischemic time was 14 +/- 1 minutes. The arteriovenous dif ference in lactate decreased during ischemia to reach a minimum at 1 minute of reperfusion (-0.15 +/- 0.06 mu mol/L compared to 0.21 +/- 10 mu mol/L b efore ischemia; p < 0.01). Myocardial lactate extraction decreased from 14. 2 +/- 6.8 mu mol/min before ischemia to -10.9 +/- 6.5 mu mol/min after 1 mi nute of reperfusion (p < 0.01). Simultaneously, the arteriovenous differenc e in 6-keto-PCF1 alpha, the stable metabolite of prostacyclin, decreased fr om -30 +/- 26 pg/mL to -258 +/- 80 pg/mL at 1 minute of reperfusion (p < 0. 05), and the 6-keto-PGF(1 alpha) extraction over the heart decreased -556 /- 466 pg/min to -18,560 +/- 5,683 pg/min (p < 0.01). Conclusions. The localized myocardial ischemia associated with these proced ures causes changes in the myocardium and endothelial influence. Coronary b ypass surgery performed on the beating heart may not be superior in prevent ing cardiac ischemia and endothelial disturbance, compared with conventiona l bypass surgery. (Ann Thorac Surg 2000;70:206-11) (C) 2000 by The Society of Thoracic Surgeons.