Ventricular fibrillation threshold in acute myocardial infarction and its relation to myocardial infarct size.

The effect of myocardial infarct size on ventricular fibrillation threshold (VFT) was evaluated by determining changes in VFT during acute myocardial infarction and relating those changes to infarct size. Infarct size was estimated from gross measurement and from serial changes in serum CPK activity in 25 dogs. VFT reduction correlated well with gross infarct size (r=0.92). This suggests that the severity of electrical instability during AMI is related to the size of the developing infarct, and that appropriate therapeutic interventions to reduce infarct size during this time may also render the heart more electrically stable.