Myocardial injury and cardiac troponin I release after off-pump versus on-pump coronary surgery.

Release After Off-Pump Versus On-Pump Coronary Surgery In a recent study by Selvanayagam and colleagues aimed at evaluating reversible and irreversible myocardial injury in patients undergoing off-pump (OP-) versus on-pump (P-) coronary artery bypass surgery (CABG),1 the authors documented a similar incidence and magnitude of new irreversible myocardial injury in both groups, despite the greater release of cardiac troponin I (cTnI) after P-CABG. These findings raise questions about not only the clinical significance of increased cTnI levels after P-CABG, but also the higher degree of cardioprotection allegedly supplied by OP-CABG. The extent of cTnI release does not necessarily correlate with occurrence or magnitude of irrevocable myocardial injury. Although the inaccuracy of cTnI levels in the “quantification” of postsurgical myocardial infarction seems to be mainly related to the “washout phenomenon,” the lack of correlation between cTnI release and occurrence of irreversible myocardial injury may be ascribed to iatrogenic stressors, intrinsic to the P-CABG surgical approach, and not typically associated with enduring myocardial injury. Release of cTnI after P-CABG was detected in bypass patients in the absence of ischemic conditions,2 as well as associated with myocardial stunning3 (a common occurrence after P-CABG), and elevated preload, independently of cardiac ischemia.4 This release, potentially occurring in cardiopulmonary bypass together with that inevitably associated with surgical manipulations, may possibly explain higher, though benign, cTnI levels, detected in P-CABG versus OP-CABG. Reperfusion, whether pharmacologically or mechanically achieved, results in earlier and augmented cTnI release versus no reperfusion. This was substantiated by a recent study showing that P-CABG had graft patency rates significantly greater than OP-CABG, despite higher cTnI levels at 6 to 12 hours postoperatively.5 Additional studies are therefore needed to confirm whether an earlier and greater cTnI release in P-CABG patients should be paradoxically welcomed as a marker of earlier and greater reperfusion.