All patients underwent acute echocardiography, and the peak troponin I level was determined. The troponin-ejection fraction product (TEFP) was derived by multiplying the peak troponin I level and the echocardiographically derived left ventricular ejection fraction. Comparing the SC and STEMI groups, the mean left ventricular ejection fraction at the time of presentation was 30 ± 9% versus 44 ± 11%, respectively (p less than 0.001), and the peak troponin I was 7.6 ± 18 versus 102.2 ± 110.3 ng/dl, respectively (p less than 0.001). The mean TEFP was thus 182 ± 380 and 4,088 ± 4,244 for the SC and STEMI groups, respectively (p less than 0.001). Receiver operating characteristic curve analysis showed that a TEFP value greater than or equal to 250 had a sensitivity of 95%, a specificity of 87%, a negative predictive value of 94%, a positive predictive value of 88%, and an overall accuracy of 91% to differentiate a true STEMI from SC (C-statistic 0.91 ± 0.02, p less than 0.001). In conclusion, for patients not undergoing emergent angiography, the TEFP may be used with high accuracy to differentiate SC with nonobstructive coronary artery disease from true STEMI due to coronary occlusion.
For information on the electrocardiographic differentiation see here.