Cardiac troponin I plasma levels for diagnosis and quantitation of perioperative myocardial damage in patients undergoing coronary artery bypass surgery

Abstract

Objective: The definition of a reliable and generally accepted diagnostic standard for perioperative myocardial damage is desirable. Cardiac troponin I (cTnI) is highly specific for myocardial tissue and can be measured rapidly. The aim of our study was to evaluate the diagnostic potential of cTnI for myocardial lesions in patients undergoing coronary artery bypass surgery (CABG).

Methods: A total of 119 patients with diffuse coronary artery disease were operated on using blood cardioplegia. Serial blood samples drawn before and after surgery were analyzed for the activity of creatine kinase MB isoenzyme (CKMB) and the concentrations of CKMB mass, cardiac troponins T and I. On the basis of the biochemical results (except cTnI) and the findings of electrocardiography/echocardiography, patients were classified and cTnI was studied for each group separately: group I, minor myocardial damage; group II, non-transmural infarction; group III, transmural infarction; and group IV, preoperative non-transmural infarction.

Results: In 87 patients of group I (73.1%) cTnI levels remained low; 19 patients (16.0%) were assigned to group II, 8 patients (6.7%) to group III, and 5 patients (4.2%) to group IV. For discrimination of patients without and with perioperative myocardial infarction (PMI) by one cTnI determination, the use of cutoff values of 6.5 ng/ml at 8 h, 9.8 ng/ml at 12 h, and 11.6 ng/ml at 24 h after aortic unclamping resulted in a diagnostic efficiency of 88, 94 and 98%). Especially, a cTnI value at 24 h had a sensitivity of 100% and a specificity of 97%. Cardiac troponin levels at 24 h were found to correlate closely with the well-recognized 2-48 h area-under-the-curve (P < 0.0001; R = 0.993), making serial determinations unnecessary.

Conclusions: cTnI qualifies as a marker for diagnosis of PMI and quantitation of the amount of myocardial damage, because of the availability of a quick diagnostic test with high specificity, the high diagnostic efficiency, and especially the sufficient information gained by a single determination 24 h after aortic unclamping.