Early diagnosis of myocardial infarction by timed sequential enzyme measurements.

Serum samples from patients admitted to a coronary care unit with a history of acute chest pain suggestive of myocardial infarction in the previous 12 h were obtained on admission and at 6 and 12 h, thereafter. Creatine kinase (CK), CK-MB isoenzyme, CK-MM sub-bands, myoglobin, and lactate dehydrogenase (LD) isoenzymes were examined. Changes were evaluated in relation to the diagnosis obtained from clinical examination, serial electrocardiography and 'routine' cardiac enzymes (CK, aspartate transaminase and alpha-hydroxy butyrate dehydrogenase daily for 3 days following admission). The slope of the logarithms of CK, CK-MB activity and CK-MB concentration in the early post infarct period fully distinguished between infarct and non-infarct patients. Measurement of myoglobin and lactate dehydrogenase isoenzymes was less sensitive. Serial estimation of CK-MM sub-band patterns allowed the time from infarction to be estimated. Serial estimation of CK in the 12 h following admission can be substituted for conventional daily enzyme estimations for the diagnosis of acute myocardial infarction in patients with onset of chest pain within the previous 12 h. This could reduce laboratory and in-patient costs.