Relevance of Cardiac Troponin in Predicting Postoperative Myocardial Infarction

Introduction: The aim of this study was to assess the validity of using early cardiac troponin (cTn) levels for the identification of postoperative myocardial infarction (MI) in patients undergoing off-pump coronary artery bypass (OPCAB) graft surgery, identify influencing factors, and determine optimal cut-off values for early identification. Materials and Methods: Patients undergoing OPCAB by a single surgical unit from January 2018 to January 2020 were included in this prospective study. Their preoperative and intraoperative characteristics were noted. The cTn was collected at 12 h and the in-hospital outcome was studied. Results: A total of 370 patients were included in the study. Eleven patients had MI determined by other criteria (2.9%), but 220 patients (60%) were identified using cTn consensus cut-off value, as per the universal definition of MI. This indicated significant mislabelling of coronary artery bypass graft-related MI and need for the recalculation to have a realistic cut-off value. The optimal cut-off levels at for identifying postoperative MI was found to be 1.8 ng/ml at 12 h, with a higher negative predictive value to exclude mislabeling. Using a cTn range, rather than a single cut-off value, would be more helpful. The factors causing significant mislabeled elevation of postoperative cTn were found to be preoperative high levels and intraoperative findings of iatrogenic hematoma secondary to suction stabilizer, surgical maneuvers for intramyocardial target vessels. Conclusion: The cTn levels were affected by the various patient and operative factors and measurements using higher cut-offs were needed to rule out MI. Certain factors peculiar to OPCAB were found to be significantly responsible. It will help identify patients needing earlier invasive re-intervention or focused intensive care.