Sensitivity and specificity of triphenyl tetrazolium chloride in the gross diagnosis of acute myocardial infarcts

Objective. - Myocardial infarction is the most common cause of sudden death in the United States. However, the identification of early myocardial infarcts at necropsy is frequently difficult, since unequivocal gross changes of infarcts do not become apparent for 24 to 48 hours following myocardial ischemic injury. The use of dyes, such as nitro-blue tetrazolium and 2,3,5 triphenyl tetrazolium chloride (TTC), that identify the dehydrogenase- deficient infarcted myocardium has been shown, largely by animal studies, to be very helpful in the macroscopic diagnosis of such cases. Such animal studies could not be directly extrapolated to human autopsy studies, however, because of the assumption that autolysis may invalidate the histochemical assessment of myocardial enzymatic changes after death. This study was carried out to evaluate the sensitivity and specificity of TTC in the gross diagnosis of acute myocardial infarction in the human population. Design. - The TTC stain reactions were correlated with histologic findings in the hearts of 638 consecutive adult autopsies. Results. - Of the 638 hearts examined by TTC, 174 hearts stained positive for acute infarction; histology confirmed myocardial infarction in 140 hearts. Histologic examination revealed acute infarcts in 41 of the remaining 464 cases that had stained negatively with TTC. The use of TTC in the macroscopic diagnosis of acute myocardial infarcts in the human population was found to have a diagnostic sensitivity of 77.4% and a specificity of 92.6%. The predictive value of a positive test was 80.5%, and that of a negative test was 91.2%. Conclusions. - The overall diagnostic efficiency of the TTC test (ie, number of patients correctly identified) was 88%. These results show that the TTC test is a reliable, sensitive, and specific adjunct in the examination of the human heart at necropsy.