Specificity of cardiac markers troponin I and T in excluding postoperative myocardial infarction.

Abstract

Creatine kinase MB isoenzyme (CK-MB) determinations are often regarded as the reference standard for diagnosis of myocardial cell damage. However, the presence of CK-MB in non-cardiac muscular tissue and its short duration of increase in serum during the course of myocardial infarction both limit its diagnostic value.' The diagnosis of myocardial infarction is especially difficult in the postoperative period following aortic surgery. Conventional serum markers of myocardial damage are often useless because of the muscular damage provoked by surgery. The surgical procedure studied here consisted of a graft replacement of diseased abdominal aorta and required abdominal aortic cross-clamping. Aortic cross-clamping increases left ventricular afterload which is a well-known factor for postoperative myocardial infarction (POMI). For this reason, this diagnosis is of major concern. Further, aortic cross-clamping induces muscular ischaemia which results in increased serum levels of conventional biochemical markers and interferes with the diagnosis of POMI based on these parameters. Because of their extraordinarily high specificity for myocardial damage, cardiac troponin T (TnT) and cardiac troponin I (cTnl)1.2 have attracted particular interest in recent years. cTnl is present exclusively in cardiac muscle, and the latest immunoassays show no cross reactivity with skeletal muscle TnI or other cardiac proteins. The aim of this study was to assess the specificity of biochemical markers, including TnT and cTnl, during abdominal aortic surgery in a control group of patients without POMI. Eleven patients scheduled for infrarenal aortic surgery were included in this study, which was conducted in accordance with the Helsinki