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

Background. The metabolic changes, possible myocardial damage, and influence on the vascular endothelium during off-pump coronary artery bypass grafting have been investigated. Methods. Coronary sinus and arterial blood samples were obtained before coronary arterial occlusion, after 10 minutes of ischemia, and after 1 and 10 minutes of reperfusion in 9 patients who had an anastomosis performed to the left anterior descending coronary artery off-pump bypass Results. The mean ischemic time was 14 ± 1 minutes. The arteriovenous difference in lactate decreased during ischemia to reach a minimum at 1 minute of reperfusion (−0.15 ± 0.06 μmol/L compared to 0.21 ± 10 μmol/L before ischemia; p< 0.01). Myocardial lactate extraction decreased from 14.2 ± 6.8 μmol/min before ischemia to −10.9 ± 6.5 μmol/min after 1 minute of reperfusion (p< 0.01). Simultaneously, the arteriovenous difference in 6-keto-PGF1α, the stable metabolite of prostacyclin, decreased from −30 ± 26 pg/mL to −258 ± 80 pg/mL at 1 minute of reperfusion (p< 0.05), and the 6-keto-PGF1α 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 procedures causes changes in the myocardium and endothelial influence. Coronary bypass surgery performed on the beating heart may not be superior in preventing cardiac ischemia and endothelial disturbance, compared with conventional bypass surgery.