Diagnostic value for acute myocardial infarction of creatine kinase and lactate dehydrogenase isoenzymes compared with total enzymes. Creatine kinase isoenzyme specificity for myocardial damage.

The diagnostic value of creatine kinase (CK) and lactate dehydrogenase isoenzymes was investigated in a prospective study of 201 patients with suspected acute myocardial infarction (AMI). The isoenzymes were analyzed with a column chromatographic method. The patients' final diagnoses were made according to the WHO criteria without knowledge of the isoenzyme results. The prevalence of AMI was 50%. The diagnoses were predicted with significantly greater reliability with the isoenzyme than with the total enzyme determinations in most of the patients. However, the greater diagnostic reliability had sufficient therapeutic consequence to justify the extra analytical cost only in patients for whom the diagnosis must be based mainly on the enzyme results. The CK isoenzyme specificity for myocardial damage was studied in populations with low prevalence of heart disease. In a group of 39 patients who had elevated total CK due to noncardiac disease there were five with elevated isoenzyme values, but since among 69 young healthy persons none had elevated isoenzymes, this was taken to indicate that the isoenzymes may be leaked into the blood from other organs than the heart.