To the Editor: The recent Special Article by Drs. Stephen Epstein,

45: 1273, 1972) has raised interesting and clinically important questions concerning the effects of heart rate on the incidence and severity of cardiac arrhythmias. These authors question the prevailing view that bradyeardia after acute myocardial infarction is asso-ciated with an increased incidence of severe cardiac arrhythmias, and express some disagreement with the interpretation of experiments by Han et al. who have indicated that slowing the heart rate increases temporal dispersion of refractoriness, lowers fibrillation threshold, and increases the likelihood of severe ventricular arrhythmias and fibrillation. ' In opposition to this view, Dr. Epstein refers to his own experiments which indicate that in the conscious dog factors which tend to increase heart rate will increase the incidence an