BACKGROUND Excessive myocardial necrosis following coronary artery bypass grafting is associated with adverse outcome. The present study was designed to assess the extent of myocardial injury after conventional coronary artery bypass grafting with cardio pulmonary bypass (ONCAB) compared with off-pump coronary artery bypass (OPCAB). METHODS Measurements of serum cardiac troponin T (TnT) were obtained in 137 consecutive, unselected patients who underwent coronary artery bypass grafting. Serial blood sampling was performed at 3 time intervals after surgery: immediately postoperatively, 6 to 12 hours postoperatively, and 18 to 24 hours postoperatively. RESULTS ONCAB patients totaled 122, and OPCAB patients numbered 15. Ten patients in the ONCAB group suffered perioperative complications, compared with no patients in the OPCAB group. At each time point examined, OPCAB patients exhibited significantly less release of TnT than ONCAB patients (immediately postoperative TnT, 1.99 +/- 4.75 ng/mL versus 0.20 +/- 0.32 ng/mL, P =.004; 6- to 12-hour TnT, 2.28 +/- 3.66 ng/mL versus 0.37 +/- 0.32 ng/mL, P =.001; and 18- to 24-hour TnT 1.59 +/- 3.49 ng/mL versus 0.30 +/- 0.32 ng/mL, P =.01). When ONCAB patients with perioperative ischemic complications were excluded, the differences between the 2 groups remained. The OPCAB patients still demonstrated less TnT release, typically 5- to 6-fold less than for ONCAB patients. CONCLUSIONS The nearly 6-fold reduction of postoperative TnT associated with OPCAB suggests that off-pump surgery may offer superior cardioprotection than coronary artery bypass grafting with conventional cardiopulmonary bypass. \par