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, cTnI 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, cTnI), ECGs, and echocardiography. Blood samples were drawn before (H0) 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 micrograms/L for CK-MB and cTnI, 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 micrograms/L), and remained in plateau. In group 2, cTnI peak concentrations were significantly different than in groups 1 and 3 (26.2 +/- 14.8 micrograms/L) and occurred at H24 (as in patients with Q-wave PMI).

Conclusion: A cTnI concentration less than 15 micrograms/L (mean + 2 standard deviations [SDs] of peak cTnI 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.