Single-Point Cardiac Troponin T at Coronary Care Unit Discharge after Myocardial Infarction Correlates with Infarct Size and Ejection Fraction

Background: One of the major concerns in replacing creatine kinase MB (CK-MB) with cardiac troponins is the lack of evidence of the ability of troponins to estimate the size of acute myocardial infarction (AMI). We investigated the ability of a single measurement of cardiac troponin T (cTnT) at coronary care unit (CCU) discharge to estimate infarct size and assess left ventricular (LV) function in AMI patients. Methods: We studied 65 AMI patients in whom infarct size was estimated by CK-MB peak concentrations and gated single-photon emission computed tomography (SPECT) myocardial perfusion using technetium-99m sestamibi and LV function by SPECT imaging. Measurements of cTnT and SPECT were performed 72 h (median) after admission (range, 40–160 h). SPECT was also repeated 3 months later. Results: We found a significant correlation between cTnT and both the peak CK-MB concentrations (r = 0.76; P <0.001) and the perfusion defect size at SPECT (r = 0.62; P <0.001). cTnT was inversely related to LV ejection fraction (LVEF) assessed both early (r = −0.56; P <0.001) and 3 months after AMI (r = −0.70; P <0.001). cTnT >2.98 μg/L predicted a LVEF <40% at 3 months with a sensitivity of 86.7%, specificity of 81.4%, and a likelihood ratio for a positive test of 4.7 (95% confidence interval, 4.0–5.4). Conclusions: A single cTnT measurement at CCU discharge after AMI is useful as a noninvasive estimate of infarct size and for the assessment of LV function in routine clinical setting.