Cardiac troponin I: Its contribution to the diagnosis of perioperative myocardial infarction and various complications of cardiac surgery

Objective: To study the value of assaying cardiac troponin I (cTnI) for the early diagnosis of perioperative myocardial infarction (PMI) and various c omplications of cardiac surgery. Design: A prospective observational clinical study. Setting. Biochemical laboratory, anesthesia, and cardiac surgery department of Hopital Broussais. Patients. Two hundred and sixty consecutive patients undergoing cardiac sur gery. Interventions. All patients underwent coronary artery bypass grafting and/o r valvular surgery under extracorporeal circulation. Per-operative and post operative follow-up consisted of electrocardiogram, echocardiography (mainl y by the transesophageal approach), and serial determinations of biochemica l markers such as creatinine kinase-MB isoenzyme (CK-MB) and cTnI. PMI, new ST segment changes, and ventricular arrhythmias were considered postoperat ive adverse cardiac outcome. Measurements and Main Results. CTnI was measured before cardiopulmonary byp ass (T-0) and 12 and 24 hrs after (T-12, T-24). CK-MB was measured on arriv al in the intensive care unit and on the first postoperative day (D1). Pati ents were divided into three groups according to the type of surgery: coron ary artery bypass graft (CABG), valvular surgery (VS), or both procedures. The plasma CK-MB and cTnI concentrations were high in all patients after ex tracorporeal circulation because of aortic clamping or cardioplegia. The CK -MB and cTnI values were higher in the VS group than in the CABG group. Val ues peaked at T-12 and fell by T-24, except when PMI occurred. Eight patien ts developed a PMI. Patients with PMI had significantly higher cTnI levels at T-12 and T-24, and higher CK-MB values at DI than patients without PMI. Cutoff values of cTnI for diagnosing PMI were > 19 mug/L at T-12 with 100% sensitivity and 73% specificity, and > 36 mug/L at T-24, with 100% sensitiv ity and 93% specificity. Lower cTnI values were highly suggestive of the ab sence of PMl after CABG and/or VS. Other complications such as ST segment c hanges, ventricular arrhythmias and cardiac failure were indicated by high cTnI levels at T-12 and T-24, Myocardial protective measures were associate d with a nonsignificant increase in cTnI values. Conclusions. CTnI is more sensitive and specific than CK-MB for diagnosing PMI and other forms of heart failure after cardiac surgery.