Persistence of MB isoenzyme of creatine phosphokinase in the serum after minor iatrogenic cardiac trauma. Absence of postmortem evidence of myocardial infarction

The specificity of serum CPK MB creatine phosphokinase, the myocardial specific isoenzyme for acute myocardial infarction was examined by retrospective analysis of 401 consecutive patients admitted to a Coronary Care Unit over a 3 1/2 yr period with suspected infarction, in whom the isoenzyme was subsequently detected. 4 patients (1%) who died during the hospital admission had no autopsy evidence of acute myocardial infarction. All 4 had experienced mild iatrogenic cardiac trauma, following which serum CPK MB persisted for at least 24 hr. In one patient, a permanent pacemaker had been inserted by the transmediastinal approach. 2 patients had been subjected to closed chest cardiac massage and intracardiac puncture, and one to external cardiac massage alone. The findings suggest that persistent identification of serum CPK MB, although specific for myocardial necrosis, cannot be regarded as diagnostic of myocardial infarction. The implications of this are important in treatment of patients after cardiopulmonary resuscitation and operative trauma to the heart.