Ratio of high-sensitivity troponin to creatine kinase-MB in takotsubo syndrome.

BACKGROUND: Takotsubo syndrome (TT) and myocardial infarction (MI) share numerous similarities in clinical presentation, ECG modifications and biomarker elevation. We sought to determine whether the ratio of high-sensitivity cardiac troponin T (hs-TnT) to the myocardial fraction of creatine kinase (CKMB) could be a potent discriminator between TT and MI patients.

METHODS: We separately present analysis of data from retrospective files and prospectively recruited patients presenting with TT (35 retrospective and 42 prospective), NSTEMI (48 retrospective and 75 prospective) and STEMI (20 retrospective and 39 prospective). We compared ratios of hs-TnT to CKMB on admission to the hospital between TT, NSTEMI and STEMI patients. Receiver operating characteristic (ROC) curves were analysed to determine optimal cut-off values.

RESULTS: On admission, hs-TnT/CKMB ratio was significantly higher in TT patients than in NSTEMI and STEMI patients in both the retrospective phase (median and interquartile range, TT 0.024 [0.018-0.047] vs NSTEMI 0.009 [0.006-0.022], p<0.0001; TT vs STEMI 0.011 [0.006-0.016], p=0.0002) and the prospective cohort (median and interquartile range, TT 0.032 [0.018-0.040] vs NSTEMI 0.009 [0.006-0.015], p<0.0001; TT vs STEMI 0.009 [0.005-0.017], p<0.0001). A cut-off hs-TnT/CKMB ratio of 0.015 distinguished TT from MI with a sensitivity of 85.7% and a specificity of 67.6% (AUC 0.796; 95%CI: 0.71-0.89) in the retrospective phase. In the prospective phase, a ratio of 0.017 distinguished TT from MI with a sensitivity of 83.3% and a specificity of 78.1% (AUC 0.88; 95%CI: 0.83-0.94).

CONCLUSION: hs-TnT/CKMB ratio is a novel, readily available parameter that could be used alongside clinical risk scores, other biomarkers and ECG findings to discriminate between TT and MI.