ACUTE CORONARY SYNDROMES

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

John F Younger^1,2, Sven Plein^1,2, Julian Barth³, John P Ridgway^1,4, Stephen G Ball^1,2 and John P Greenwood^1,2

¹ Cardiac Magnetic Resonance Unit, Leeds General Infirmary, Leeds, UK
² Academic Unit of Cardiovascular Medicine, University of Leeds, Leeds, UK
³ Department of Clinical Biochemistry, Leeds General Infirmary, Leeds, UK
⁴ Department of Medical Physics, Leeds General Infirmary, Leeds, UK

Correspondence to:
Dr J Greenwood, Senior Lecturer in Cardiology, Academic Unit of Cardiovascular Medicine, G Floor, Jubilee Wing, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK; j.greenwood{at}leeds.ac.uk

Objectives: The aim of this study was to use late gadolinium hyper-enhancement cardiac magnetic resonance (LGE-CMR) imaging to determine if a 72-h troponin-I measurement would provide a more accurate estimation of infarct size and microvascular obstruction (MVO) than serial creatine kinase (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 12 h and 72 h after admission, in addition to serial CK levels.

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

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

Abbreviations: AMI, acute myocardial infarction; CK, creatine kinase; LGE-CMR, late gadolinium hyper-enhancement cardiac magnetic resonance; LV, left ventricular; MVO, microvascular obstruction; NSTEMI, non-ST elevation myocardial infarction; PCI, percutaneous coronary intervention; STEMI, ST elevation myocardial infarction

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