Troponin T — a reliable marker of perioperative myocardial infarction?

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Abstract
Following cardiac surgery, electrocardiography and creatine kinaseisoenzyme MB (CK-MB) activities are of limited value in diagnosing anon-transmural infarction. With the recent availability of an assay todetect serial levels of the specific cardiocyte contractile proteintroponin T the possibility has been increased of closing a diagnostic gapamong cardiosurgical patients. Ninety patients with severe diffusethree-vessel disease undergoing myocardial revascularization were groupedby their postoperative electrocardiographic (ECG) findings (groupI--unchanged ECG; group II--new Q-waves representing perioperativemyocardial infarction (PMI)). Serial levels of troponin T and the activityof CK-MB were measured 6, 12, 24 and 48 h after aortic unclamping. Thecourse of CK-MB activity was compared to a profile and values derived frompatients with unchanged (n = 1312) or new Q-wave ECGS (n = 89). In 72patients (80.0%) with unchanged postoperative ECG (group I) serial troponinT levels remained constantly low and reached a median peak value of 0.37microgram/l (quartile 0.13-0.50 microgram/l) after 24 h. Serial CK-MBactivities demonstrated the typical non-ischemic course with amonoexponential decline from an initial median peak value of 15.5 U/l(quartile 12.0-21.0 U/l) to 7.0 U/l (quartile 6.0-9.0 U/l). In sevenpatients (7.8%) with new Q-waves and a pathologic CK-MB profile (group II)troponin T reached median levels of 10.47 micrograms/l (quartile 6.34-12.50micrograms/l) (P ≪ 0.001 I vs II). Four of five patients with a newright bundle branch block demonstrated low troponin T levels below 1microgram/l and a normal CK-MB profile. Among six patients with unchangedQRS- configuration and elevated troponin T levels between 0.84 and 4.99micrograms/l CK-MB activity showed a characteristic PMI pattern in twopatients. Troponin T is characterized by a very narrow margin of normalvalues represented by a maximum third quartile of 0.50 microgram/l. Asingular value of troponin after 6 h or 24 h may be sufficient evidence toconfirm the diagnosis of a PMI.