Cardiac Specific Creatine Phosphokinase

The specificity and sensitivity of serum creatine phosphokinase cardiac specific isoenzyme (MB) in the diagnosis of acute myocardial infarction (AM I) was evaluated. An ion-exchange chromatographic technique was used to isolate MB. Sera layered on mini-columns of DEAE-Sephadex were eluted with Tris-buffered sodium chloride. Quantification of isolated MB was performed by creatine phosphokinase (CPK) assay (Rosalki method) of column effluents. MB was expressed as a percentage of the simultaneously determined total serum CPK. MB was determined in 100 consecutive admissions to the Coronary Care Unit. Acute myocardial infarction was diagnosed by accepted criteria. In 47 patients with proven AMI, including three with normal total CPK, peak MB was greater than 4% of total CPK. In 49 patients without AMI, including 15 with elevated total CPK (due to trauma, injections, cardioversion), peak MB was less than 2% of total CPK. MB was elevated, but did not peak, in four patients without AMI but with chronic atrial fibrillation. Isolation and quantification of MB by this technique is rapidly and easily performed and provides a specific and extremely sensitive tool for the diagnosis of AMI.