Acute myocardial infarction and MB creatine phosphokinase. Relationship between onset of symptoms of infarction and appearance and disappearance of enzyme.

Sixty-six patients admitted to the coronary care unit within 12 hours of the onset of symptoms of acute myocardial infarction (AMI) were subjected to blood sampling at one- to two-hour intervals for analysis of creatine phosphokinase (CPK) and lactic dehydrogenase (LDH) enzymes and isoenzymes. Complete MB CPK curves were obtained in 27 patients, and these were analyzed for optimum times for sampling and minimum number of analyses for detection of AMI. The present study indicates that (1) optimum detection of AMI can be achieved by analysis for MB CPK in a minimum of two samples obtained at 12 and 24 hours after onset of symptoms of AMI; (2) negative results of analyses for MB CPK in samples obtained before 12 hours or after 24 hours should not be used to exclude the diagnosis of AMI; and (3) a total CPK value within the normal range is not a reliable screening test to exclude analysis of MB CPK.