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

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.