Biochemical markers of myocardial ischemic after off- and on-pump coronary artery bypass surgery

Background Recently, coronary artery bypass grafting (CABG) on the beating heart with avoidance of extracorporeal circulation (off-pump CABG technique) has been gaining increasing importance in modern cardiac surgery. The object of this prospective study was to compare postoperative kinetic and patterns of cardiac troponin I (cTnI), T (cTnT), and creatine kinase MB (CKMB) activities after off-pump CABG versus conventional on-pump CABG. Methods We studied 106 patients who underwent first-time elective on-pump (group 1, n = 69, 56 male, 13 female, mean age: 64.3 +/- 9.9 years, mean ejection fraction: 56 +/- 15%) or off-pump (group 11, n = 3 7, 24 male, 13 female, mean age: 68.4 +/- 9.1 years, mean ejection fraction: 57 +/- 13%) CABG surgery via median sternotomy. CTn I and cTnT levels, total creatine kinase (CK) and CK-MB activities in the serum were measured before operation, up on arrival at the ICU and 6, 12, 24, 48 and 120 hours later. Serial 12-lead ECGs were recorded preoperatively and on days 1, 2 and 5. Results Serum concentrations of cardiac troponins in all patients were preoperatively either not detectable or in the normal range and significantly increased after surgery. In group 1, one patient developed a Q wave myocardial infarction, one patient a non-Q wave infarction and two patients a new left bundle branch block on the ECG. One patient of group 11 developed a new Q-wave myocardial. infarction and another patient permanent atrial fibrillation associated with a continuous arrhythmia. All patients with a myocardial infarction in the ECG showed significant elevation of concentrations or activities of these biochemical markers. The median postoperative peak values for cTnI were measured at 24 h in both groups (2.7 mug/l, 95%-CI: [2.2,3.2] in group I and 1.1 mug/l, 95%-CI:[0.5,1.3] in group 11). CTnT postoperatively presented an earlier median peak of 0.128 mug/l at 12 h in group II (95%-CI:[0.041,0.146]) than in group I at 48 h (0.298 mug/l, 95%-CI: [0.254,0.335]). Conclusions All patients undergoing CABG surgery with or without extracorporeal circulation postoperatively showed an increase of cardiac troponin levels. After uncomplicated coronary revascularization, patients with the off-pump CABG technique continuously presented lower serum cardiac troponin concentrations than those with the on-pump CABG technique. CTnI showed the same patterns of release in both groups with different median postoperative peak values at 24 h. The patterns off cTnT release following CABC surgery with or without extracorporal circulation were different: CTnT reaches its postoperative peak value in patients with the off-pump CABG technique earlier than those with the on-pump CABG technique (12 h postoperatively versus 48 h).