Determination of the threshold of cardiac troponin I associated with an adverse postoperative outcome after cardiac surgery: a comparative study between coronary artery bypass graft, valve surgery, and combined cardiac surgery

INTRODUCTION The objective of the present study was to compare postoperative cardiac troponin I (cTnI) release and the thresholds of cTnI that predict adverse outcome after elective coronary artery bypass graft (CABG), after valve surgery, and after combined cardiac surgery. METHODS Six hundred and seventy-five adult patients undergoing conventional cardiac surgery with cardiopulmonary bypass were retrospectively analyzed. Patients in the CABG (n = 225) and valve surgery groups (n = 225) were selected after matching (age, sex) with those in the combined surgery group (n = 225). cTnI was measured preoperatively and 24 hours after the end of surgery. The main endpoint was a severe postoperative cardiac event (sustained ventricular arrhythmias requiring treatment, need for inotropic support or intraaortic balloon pump for at least 24 hours, postoperative myocardial infarction) and/or death. Data are presented as the median and the odds ratio (95% confidence interval). RESULTS Postoperative cTnI levels were significantly different among the three groups (combined surgery, 11.0 (9.5-13.1) ng/ml versus CABG, 5.2 (4.7-5.7) ng/ml and valve surgery, 7.8 (7.6-8.0) ng/ml; P < 0.05). The thresholds of cTnI predicting severe cardiac event and/or death were also significantly different among the three groups (combined surgery, 11.8 (11.5-14.8) ng/ml versus CABG, 7.8 (6.7-8.8) ng/ml and valve surgery, 9.3 (8.0-14.0) ng/ml; P < 0.05). An elevated cTnI above the threshold in each group was significantly associated with a severe cardiac event and/or death (odds ratio, 4.33 (2.82-6.64)). CONCLUSION The magnitude of postoperative cTnI release is related to the type of cardiac surgical procedure. Different thresholds of cTnI must be considered according to the procedure type to predict early an adverse postoperative outcome.