Acute myocardial infarct size estimated by serum CK-MB determinations: clinical accuracy and prognostic relevance utilizing a practical modification of the isoenzyme approach.

The clinical reliability and relevance of a practical enzymatic method to estimate infarct size (IS) were evaluated in patients with acute myocardial infarction (AMI). The technique utilized was that of relatively few sequential determinations of serum heart specific isoenzyme CK-MB, as corroborated by studies of numerous CK-MB measurements. Isoenzyme IS was determined in 321 consecutively admitted patients with AMI. Autopsies were performed in 22 of the 43 decedents for quantification of myocardial necrosis by histochemical and histologic techniques. A highly significant correlation (r = 0.83 p less than 0.001, SEE = 28%) was observed between IS values calculated from serum CK-MB and IS defined by necropsy examination. The CK-MB median IS was significantly increased in decedents compared to survivors (p less than 0.005), with IS ranges having substantial overlap between the two groups. The present study demonstrates that a practical and reliable estimation of IS in vivo is obtainable by serum CK-MB. While such estimated IS is of relatively moderate value for predicting in-hospital prognosis in single patients, the isoenzyme method appears particularly well suited for clinical evaluation of potentially beneficial interventions anticipated to limit myocardial necrosis in groups of AMI patients.