Comparison of biochemical markers for the detection of minimal myocardial injury: superior sensitivity of cardiac troponin – T ELISA

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Abstract
Objectives. Patients with minimal myocardial injuries who present clinically with unstable angina, early stages of myocardial infarction or myocarditis require different therapy strategies to those without. The newer diagnostic assays for detecting myocardial lesions (cardiac Troponin T and cardiac Troponin I [cTnT, cTnI], glycogenphosphorylase – BB [GPBB]) are reported to be more sensitive and specific than common biochemical markers such as CK and myoglobin. Our study tested whether the recently developed four assays cTnT‐ELISA (in vitro), cTnT rapid bedside assay, cTnI rapid bedside assay, and GPBB (Immunoenzymetric assay) are effective in detecting minimal myocardial injuries caused by endomyocardial biopsy. We compared them with CK activity (CK‐cat), CK‐MB activity (CK‐MBcat), CK‐MB‐concentration (CK‐MB‐mass) and Myoglobin concentration (Myo‐conc.). Patients and methods. Twenty‐four patients [six female, 18 male, age (mean): 47 years (20–65)] underwent diagnostic endomyocardial biopsy. Between four and six biopsies were taken from the mid‐right ventricular aspect of the interventricular septum of the heart. Blood was drawn before catheterization (baseline), 10 min after the biopsy, in the next morning, and in the morning of the second day after (days 1 and 2). Results and Conclusion. Because of very low CKcat it was not possible to analyse CK‐MBcat with reliable precision. The assay for GPBB and cTnI rapid bedside assay did not indicate this minimal myocardial injury. The CK cat, CK‐MB mass, and myoglobin assays indicated significant increase at 10 min after biopsy but remained within reference range. cTnT rapid bedside assay indicated this minimal myocardial injury in 50% (P < 0.05). cTnT‐ELISA (in vitro) was increased above the reference limit in 54%. This increase was 3.6‐fold the upper reference limit (P < 0.01). In our study, due to superior discriminating power, cTnT‐ELISA (in vitro) was the most sensitive assay for minimal myocardial injuries.

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