Troponin-I concentration 72 hours after myocardial infarction correlates with infarct size and presence of microvascular obstruction

John F Younger ¹, Sven Plein ¹, Julian Barth ², John P Ridgway ¹, Stephen G Ball ¹ and John P Greenwood ^2*

¹ Leeds University, United Kingdom
² Leeds General Infirmary, United Kingdom

^* To whom correspondence should be addressed. E-mail: j.greenwood{at}leeds.ac.uk.

Accepted 20 March 2007

Abstract

Objectives The aim of this study was to use late gadolinium hyper-enhancement cardiac magnetic resonance (LGE-CMR) imaging to determine if a 72 hour troponin-I (72h-troponin-I) measurement would provide a more accurate estimation of infarct size and microvascular obstruction (MVO) than serial CK or early troponin-I values.

Methods LGE-CMR was performed 3.7 ± 1.4 days after medical treatment for acute ST elevation or non ST elevation myocardial infarction. Infarct size and MVO were measured and correlated with serum troponin-I concentrations which were sampled at 12 hours and at 72 hours after admission, in addition to serial creatine kinase (CK) levels.

Results Ninety-three patients, of whom 71 had received thrombolysis for ST elevation myocardial infarction, completed the CMR study. Peak CK, 12h-troponin-I, and 72h-troponin-I were related to infarct size by LGE-CMR (r=0.75, p<0.0001; r=0.56, p=0.0003; r=0.62, p<0.0001 respectively). Serum biomarkers demonstrated higher values in the group with MVO compared to those without MVO (Peak CK 3085 ± 1531 vs. 1471 ± 1135, p<0.001; 12h-troponin-I 58.3 ± 46.9 vs. 33.4 ± 40.0, p=0.13; 72h-troponin-I 11.5 ± 9.9 vs. 5.5 ± 4.6, p<0.005). The correlation between the extent of MVO and 12h-troponin-I was not significant (r=0.16), in contrast to the other serum biomarkers (peak CK r=0.44, p<0.0001; 72h-troponin-I r=0.46, p=0.0002).

Conclusion A single measurement of 72h-troponin-I is similar to serial CK measurements in the estimation of both myocardial infarct size and extent of MVO and is superior to 12h-troponin-I measurements.

Keywords: Acute Myocardial Infarction, Coronary Heart Disease, Magnetic Resonance Imaging, Troponin

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