[Usefulness of creatine phosphokinase isoenzyme, CK-MB, in the diagnosis of myocardial necrosis (author's transl)].

With the objective of evaluating the clinical usefulness of a new immunologic method (Merck-1-Test CK-MB), in the determination of the CK-MB activity, 48 patients admitted to the Coronary Unit for angina pectoris were studied. Samples of blood were gathered upon admission and every 4 hours for 48-72 hours, determining in each one of them the total CPK, SGOT, LDH, and CK-MB; electrocardiograms (ECG) were taken and all possible causes for the increase in the enzymatic activity were recorded. Results were analyzed in order to study the following aspects: in the patients in which an acute myocardial infarction was diagnosed the CK-MB activity was studied, also the relation of CK-MB to the remaining parameters, each parameter's sensitivity and specificity and the relationship of the CK-MB to the prognosis of the patients. The usefulness of CF-MB in the differential diagnosis of myocardial necrosis and variations in the total CKP curve in the clinical course of acute myocardial infarction unrelated to myocardial necrosis were evaluated too. The following conclusions were drawn from the analysis of the data. The immunological method has the advantages of its sensitivity and easily and quickly performance (15 minutes), but it has the disadvantage that it detects CK-BB (elevated in cebrovascular disorders). Twenty-four hours after the onset of symptoms, the negativity of CK-MB does not exclude the diagnosis of a myocardial necrosis. CK-MB is more sensitive than total CPK in diagnosing the extent of the area of necrosis. CK-MB is very specific for myocardial necrosis but less sensitive than other parameters. A positive CK-MB upon the patient's admission confirmed the diagnosis of necrosis in 60 percent of the cases, but in 18 percent error was induced because of false positives. CK-MB permitted confirmations of the diagnosis of myocardial infarction in 33 percent of cases in which there was only a suggestion of necrosis by the ECG. The variation in the curve of total CPK in the course of an acute myocardial infarction is subjected to such a great number of factors intercurrent with time, that caution should be exercised in trying to relate a specific elevation of total CPK to an unsuccessful maneuver or to a possible extension of the area of necrosis.