Diagnosis of acute myocardial infarction. Relative efficiency of serum enzyme and isoenzyme measurements.

Total serum enzyme activity for creatine phosphokinase (CPK), alpha-hydroxybutyric dehydrogenase (HBDH), lactic dehydrogenase (LDH), and serum glutamic oxaloacetic transaminase (SGOT), as well as the isoenzymes of CPK and LDH, were measured on admission and for ten subsequent days in 100 patients admitted consecutively to a coronary care unit. On discharge, patients were classified by a cardiologist as either having or not having suffered an acute myocardial infarction (MI) on the basis of clinical and electrocardiographic criteria--without knowledge of the enzyme studies. The combined use of CPK and LDH isoenzyme levels provided the greatest laboratory discrimination between the two clinical groups (MI vs non-MI). The routine use of HBDH and SGOT levels can be abandoned in the setting of a coronary care unit if CPK and LDH isoenzyme assays are available.