Rate- and Site-Dependent Effects of Propafenone, Dofetilide, and the New<i>I</i>_Ks-Blocking Agent Chromanol 293b on Individual Muscle Layers of the Intact Canine Heart

Abstract

At the heart rates applied, the in vivo canine heart does not exhibit regional differences in electrophysiological properties. Given the homogeneity of antiarrhythmic drug effects, induction of local gradients of refractoriness is obviously not a common mechanism of proarrhythmia in normal hearts.