Time course of creatine kinase release after termination of sustained ventricular dysrhythmias

Differentiation between primary and secondary (caused by acute myocardial infarction) ventricular fibrillation has important therapeutic and prognostic implications. The diagnosis of myocardial infarction is based on clinical, ECG, and creatine kinase MB isoenzyme (MBCK) activity. Enzymatic criteria might not be able to confirm the diagnosis of myocardial infarction after recent cardioversion. The routine use of electrophysiologic studies involving the induction and termination of ventricular dysrhythmias provides a setting in which enzyme release as a result of cardioversion alone can be examined. Therefore a systematic investigation of the magnitude and time course of creatine kinase (CK) and MBCK release was performed after termination of ventricular dysrhythmias in 57 patients undergoing electrophysiologic studies. Of patients requiring external cardioversion, only 50% had an elevation in CK and MBCK activity. Elevation when present corrected with the number of shocks and cumulative energy delivered. The magnitude of MBCK release exceeded 10% of the total CK activity in 9% of observations. Pace-termination of ventricular tachycardia did not result in enzyme release. Arrhythmia characteristics, coronary artery disease, and left ventricular function did not affect the magnitude of the time course of enzyme release. These data suggest that cardioversion with multiple shocks may result in a component of MBCK release, and thus a false positive diagnosis of primary acute myocardial infarction may be made by relying exclusively on the enzyme release pattern.