Determination of Troponin I Release After CABG Surgery

Abstract  Background: Troponin I is used to diagnose myocardial infarction (MI). Its use and pattern of elevation is not well defined in coronary artery bypass graft (CABG) surgery. This study assessed the timing of troponin I elevation in patients undergoing urgent CABG. Method: Patients undergoing urgent isolated‐CABG with cardiopulmonary bypass were studied prospectively. Blood samples were taken to measure CK, CK‐MB, and troponin I: preoperatively, 7 hours postoperatively, 14 to 18 hours postoperatively, 30 to 48 hours postoperatively, and on postoperative day 4. Electrocardiograms and in‐hospital course were recorded. Perioperative MI (PMI) was defined by either (i) ECG criteria of new Q‐waves in the presence of CK‐MB elevation >50 μg/L or (ii) CK‐MB > 100 μg/L. Results: Of the 50 patients studied, 6 met the criteria for PMI (12%); 2 by criteria (i) and 4 by criteria (ii). In patients not meeting the criteria for MI the troponin I level peaked at 7 hour post‐op with a mean of 20.97 μg/L (95% CI, 17.11 to 24.83). At this time, patients who met the criteria for MI had a mean troponin I level of 46.85 μg/L (95% CI, 36.40 to 57.30). Of variables investigated for the 44 patients who did not meet MI criteria, only preoperative troponin I level impacted peak postoperative troponin I. Conclusions: CABG elevates troponin I far beyond current diagnostic benchmarks without the clinical occurrence of a MI and appears to peak during the second postoperative day. An elevated preoperative troponin I may predict an elevated peak postoperative troponin I in patients who do not have a PMI.