Does rapid heart rate, vagal stimulation, or acute myocardial ischemia affect the threshold for ventricular fibrillation in a canine model?
Rapid heart rate lowers the ventricular fibrillation threshold, particularly during acute myocardial ischemia, suggesting a mechanistic basis for correcting tachycardia in acute myocardial infarction.
The minimum current required to cause ventricular fibrillation was determined by electrical stimulation of the normal or ischemic canine left ventricle. The threshold for ventricular fibrillation in the normal heart decreased when the heart rate was rapid. Strong vagal stimulation did not affect the ventricular fibrillation threshold when the heart rate was fixed. The fall in the ventricular fibrillation threshold in the presence of acute myocardial ischemia was greater and more prolonged when the heart rate was rapid. These findings indicate the importance of the immediate correction of tachycardia in patients suffering from acute myocardial infarction.
James et al. (Tue,) studied this question.