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

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.