Effects of off-pump versus on-pump coronary surgery on reversible and irreversible myocardial injury - A randomized trial using cardiovascular magnetic resonance imaging and biochemical markers

Background - There is biochemical evidence that off-pump coronary artery bypass grafting (OPCABG) reduces myocardial injury compared with the use of cardiopulmonary bypass (ONCABG), but the functional significance of this is uncertain. We hypothesized that OPCABG surgery would result in reduced postoperative reversible ( stunning) and irreversible myocardial injury, as assessed by cardiovascular MRI (CMRI). Methods and Results - In a single-center randomized trial, 60 patients undergoing multivessel total arterial revascularization were randomly assigned: 30 to OPCABG and 30 to ONCABG. Patients underwent preoperative and early postoperative cine MRI for assessment of global left ventricular function, and contrast-enhanced CMRI for assessment of irreversible myocardial injury. Serial troponin I measurements were obtained perioperatively and correlated with the CMRI findings. The mean preoperative cardiac index was similar in the 2 surgical groups ( 2.9 +/- 0.7 ONCABG; 2.9 +/- 0.8 OPCABG; P = 0.9). After surgery, the cardiac index was significantly higher in the OPCABG group (2.7 +/- 0.6 ONCABG; 3.2 +/- 0.8 OPCABG; P = 0.04). New irreversible myocardial injury was similar in incidence (36% ONCABG; 44% OPCABG; P = 0.8) and magnitude (6.3 +/- 3.6 g ONCABG; 6.8 +/- 4.0 g OPCABG; P = 0.9) across the 2 groups. The median area-under-the-curve (AUC) troponin I values were significantly larger in the ONCABG group ( 182 versus 135 mug/L; P = 0.02). There was a moderate correlation between the troponin I AUC values and mean mass of new myocardial hyperenhancement (r(2) = 0.4; P = 0.008). Conclusions - OPCABG results in significantly better left ventricular function early after surgery but does not reduce the incidence or extent of irreversible myocardial injury.