Cardiac Troponin T at 96 Hours After Acute Myocardial Infarction Correlates With Infarct Size and Cardiac Function

OBJECTIVES: In clinical practice, myocardial infarct size can be estimated non-invasively by nuclear imaging techniques or contrast-enhanced magnetic resonance imaging (CE-MRI). Due to limited availability and high costs, serologic tests are frequently used as an alternative. BACKGROUND: We examined the ability of a single value of cardiac troponin T (cTnT) 96 h after onset of ST-/non-ST-segment elevation myocardial infarction (STEMI/NSTEMI) to estimate absolute infarct mass. METHODS: Functional and CE-MRI were conducted on a 1.5-T whole-body system 4 days after STEMI/NSTEMI using gadolinium (0.2 mmol/kg/bw). Infarct sizes were measured employing a specified software (Philips Medical Systems, Best, the Netherlands) and correlated with TnT measurements 96 h after onset of STEMI/NSTEMI. RESULTS: We enrolled 23 STEMI and 21 NSTEMI patients. Median time delay from onset of symptoms to balloon angioplasty was 6.25 and 9.9 h for STEMI/NSTEMI patients, respectively. Contrast-enhanced magnetic resonance imaging (median 4 days) revealed an absolute mean infarct size of 16.2 g (7.7 to 30.1 g) with a mean ejection fraction of 58% (53% to 63%) and mean stroke volume of 84 ml (75 to 107 ml). Absolute infarct sizes and median cTnT values were larger in STEMI than in NSTEMI (29.3 g interquartile range (IQR) 16.0 to 53.0 and 1.88 microg/l IQR 0.7 to 2.57 vs. 8.8 g IQR 3.3 to 16.4 and 0.83 microg/l IQR 0.4 to 1.3, both p < 0.02). Linear regression analysis was excellent for STEMI (r = 0.910) and moderate albeit still significant for NSTEMI (r = 0.575). CONCLUSIONS: A single 96-h cTnT value provides an accurate estimate of absolute infarct mass in myocardial infarction. The ability to quantify and the potential to distinguish effects of novel drug regimens on infarct size make cTnT attractive for routine practice and as a clinical end point.