COMPARATIVE SENSITIVITY OF CARDIAC TROPONIN-I AND LACTATE-DEHYDROGENASE ISOENZYMES FOR DIAGNOSING ACUTE MYOCARDIAL-INFARCTION

Criteria for the retrospective diagnosis of acute myocardial infarctio n rely heavily on increases in lactate dehydrogenase (LD) isoenzymes. However, increases of LD isoenzyme activities are not specific for myo cardial injury. Recently, increased concentrations of cardiac troponin I (cTnI) have been shown to be highly specific for myocardial damage and to have sensitivity comparable with that of creatine kinase MB iso enzyme for detecting cardiac injury. Furthermore, increases of cTnI pe rsist in plasma for at least several days. The present study was desig ned to determine the relative sensitivities of cTnI and LD isoenzymes over time for the diagnosis of infarction. The results indicate that c TnI values are at least as sensitive as LD isoenzymes: 90% of patients with myocardial infarction had above-normal concentrations of cTnI on the 4th day after admission to the coronary care unit, Criteria based on cTnI should improve the accuracy of retrospective diagnoses of acu te myocardial infarction.