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(Circulation Research. 2006;99:1141.)
© 2006 American Heart Association, Inc.

Clinical Research

Time Course of Degradation of Cardiac Troponin I in Patients With Acute ST-Elevation Myocardial Infarction

The ASSENT-2 Troponin Substudy

Lene H. Madsen, Geir Christensen, Terje Lund, Victor L. Serebruany, Chris B. Granger, Ingvild Hoen, Zanina Grieg, John H. Alexander, Allan S. Jaffe, Jennifer E. Van Eyk, Dan Atar

From the Department of Cardiology and Endocrinology (L.H.M.), Frederiksberg University Hospital, Copenhagen, Denmark; Center for Heart Failure Research (L.H.M., G.C., D.A.), University of Oslo, Norway; Institute for Experimental Medical Research (G.C., I.H., Z.G.), Ullevål University Hospital, Oslo, Norway; Hormone Laboratory (T.L.), Aker University Hospital, Oslo, Norway; HeartDrug Research Laboratories (V.L.S.), Towson, Md; Duke University Medical Center (C.B.G., J.H.A.), Durham, NC; Division of Cardiology and Laboratory Medicine (A.S.J.), Mayo Clinic and Graduate Medical School, Rochester, Minn; Division of Cardiology (J.E.V.E.), Johns Hopkins University, Baltimore, Md; and Division of Cardiology (D.A.), Aker University Hospital, University of Oslo, Norway.

Correspondence to Lene Helleskov Madsen, MD, Frederiksberg University Hospital, Department of Cardiology and Endocrinology, Ndr. Fasanvej 57-59, 2000 Frederiksberg, Denmark. E-mail lhm{at}dadlnet.dk

Although measurement of troponin is widely used for diagnosing acute myocardial infarction (AMI), its diagnostic potential may be increased by a more complete characterization of its molecular appearance and degradation in the blood. The aim of this study was to define the time course of cardiac troponin I (cTnI) degradation in patients with acute ST-elevation myocardial infarction (STEMI). In the ASSENT-2 substudy, 26 males hospitalized with STEMI were randomized to 2 different thrombolytic drugs within 6 hours after onset of symptoms. Blood samples were obtained just before initiation of thrombolysis and at 30 minutes intervals (7 samples per patient). Western blot analysis was performed using anti-cTnI antibodies and compared with serum concentrations of cTnI. All patients exceeded the cTnI cutoff for AMI during the sampling period; at initiation of therapy, 23 had elevated cTnI values. All patients demonstrated 2 bands on immunoblot: intact cTnI and a single degradation product as early as 90 minutes after onset of symptoms. On subsequent samples, 15 of 26 patients showed multiple degradation products with up to 7 degradation bands. The appearance of fragments was correlated with higher levels of cTnI (P<0.001) and time to initiation of treatment (P=0.058). This study defines for the first time the initial time course of cTnI degradation in STEMI. Intact cTnI and a single degradation product were detectable on immunoblot as early as 90 minutes after onset of symptoms with further degradation after 165 minutes. Infarct size and time to initiation of treatment was the major determinant for degradation.

Key Words: myocardial infarction • troponin • troponin degradation • diagnostics

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