Background: We evaluated myocardial tissue injury by measuring serum levels of creatine kinase MB (CK-MB), myoglobin, and cardiac troponin I (cTnI) after off-pump coronary artery bypass grafting (CABG) and conventional on-pump CABG.

Methods: Thirty patients undergoing first-time elective CABG were randomly assigned to on-pump (n=15) or offpump (n=15) CABG. Blood samples were taken before surgery (m1), after induction of anesthesia (m2), 30 minutes after aortic unclamping in the on-pump CABG group or 30 minutes after the last distal anastomosis in the off-pump CABG group (m3), and at postoperative 12 hours (m4) and 24 hours (m5). Serum CK-MB activity was measured by the immunoinhibition method, and myoglobin and cTnI were measured by direct chemiluminometric technology.

Results: The mean duration of cross-clamping in the on-pump group was 74.9±17.0 minutes and the mean ischemic period due to target coronary artery occlusion in the off-pump group was 25.7±9.1 minutes. The number of grafts used was significantly higher in the on-pump CABG group (p=0.041). There were no deaths and no significant differences were observed with regard to adverse clinical events. Although serum CK-MB activity did not differ significantly in the off-pump group except for one patient, increases at m3, m4, and m5 were significant in the onpump group. The two groups differed significantly at m3 (p<0.001), m4 ( p<0.01), and m5 (p<0.01). Myoglobin activity showed significant increases at all times in both groups, but this showed significance only at m3 between the two groups (p<0.001). Serum cTnI activity reached peak values at m4 in both groups. Increases remained within the normal range in the off-pump group, whereas they were beyond normal at m3, m4, and m5 in the on-pump group, showing significant differences with the off-pump group (p<0.001).

Conclusion: Of the two techniques, off-pump CABG is associated with less myocardial tissue injury.

Keywords : Biological markers; cardiopulmonary bypass/methods/ adverse effects; coronary artery bypass; creatine kinase/blood; myocardial ischemia/blood; troponin I/blood