Diagnostic utility of cardiac biomarkers in discriminating takotsubo cardiomyopathy from acute myocardial infarction

Background: Takotsubo cardiomyopathy (TC) mimics acute myocardial infarction (AMI). We postulated that ventricular dysfunction in TC in the absence of significant myocardial necrosis would produce higher B-type natriuretic peptide (BNP)/troponin T (TnT) and BNP/creatine kinase MB fraction (CKMB) ratios than in AMI. Methods and Results: We studied 58 consecutive TC (age 65.8 ± 12.9) and 97 AMI patients (age 59.8 ± 13.4). The ratios of BNP/TnT and BNP/CKMB were calculated with the use of first simultaneously drawn laboratory values. Receiver operating characteristic curves were used to distinguish TC from AMI with 95% specificity based on cardiac biomarker ratios. Median BNP/TnT and BNP/CKMB ratios were, respectively, 1,292 [interquartile range 443.4-2,657.9] and 28.44 [13.7-94.8] in the TC group and 226.9 [69.91-426.32] and 3.63 [1.07-10.02] in the AMI group (P .001). TC can be distinguished from AMI with 95% specificity with the use of BNP/TnT ratio 1,272 (sensitivity 52%) and BNP/CKMB ratio ≥29.9 (sensitivity 50%). Conclusions: The value of BNP is significantly higher in TC than in AMI. Early BNP/TnT and BNP/ CKMB ratios help to differentiate TC from AMI with greater accuracy than BNP alone.