Cardiac troponin I in diagnosis of perioperative myocardial infarction after cardiac surgery

Abstract

Objective: The diagnosis of perioperative myocardial infarction (PMI) after cardiac surgery remains an important issue. The present study was designed to determine the relevance of the measurement of serum cardiac troponin I (cTnI), a biochemical marker with high cardiospecificity. Therefore, cTnl was compared with creatine kinase-MB (CK-MB) mass and to the other classical signs of myocardial infarction after cardiac surgery.Design: A prospective study.Setting: A university hospital.Participants: Forty-one patients undergoing coronary artery bypass grafting (CABG) (n = 17) or valvular replacement (n = 24). These patients were separated into three groups according to postoperative complications: group 1, Q-wave PMI (n = 5); group 2, nonspecific changes (non-Q wave) on the electrocardiogram (ECG) and/or need of inotropic support (n = 12); group 3, no postoperative complication (n = 24).Interventions: Postoperative follow-up consisted of serial determination of different biochemical markers (CK, CK-MB, cTnl), ECGs, and echocardiography. Blood samples were drawn before (HO) and 3 (H3),12 (H12),20 (H20),24 (H24), and 48 (H48) hours after the onset of cardiopulmonary bypass (CPB).Measurements and Main Results: In all patients in group 3, CK-MB and cTnI concentrations increased, and peaked at H12 after CPB (13.4 ± 7.7 and 7.1 ± 4.1 μg/L for CK-MB and cTnl, respectively). In group 1, cTnI concentrations were significantly higher than in group 3 from H12 until H48 (p < 0.002), peaked later (H24; 59.0 ± 38.8 μg/L), and remained in plateau. In group 2, cTnl peak concentrations were significantly different than in groups 1 and 3 (26.2 ± 14.8 μg/L) and occurred at H24 (as in patients with Q-wave PMI).Conclusion: A cTnl concentration less than 15 μg/L (mean + 2 standard deviations [Sds] of peak cTnl in group 3) within 24 to 48 hours after cardiac surgery is highly suggestive of the absence of perioperative myocardial necrosis. Because of its higher cardiospecificity than CK-MB mass, and its prolonged release after myocardial necrosis, cTnI might be a useful tool in the diagnosis of PMI after cardiac surgery.