CONTRASTING EFFECTS OF DIPHENYLHYDANTOIN AND PROCAINE AMIDE ON A-V CONDUCTION IN DIGITALIS-INTOXICATED AND NORMAL HEART

The effects of diphenylhydantoin (DPH) and procaine amide on A-V conduction in the digitalis-intoxicated and the normal heart were compared. DPH consistently converted more acetylstrophanthidin-induced ventricular tachycardia to sinus rhythm and completely restored A-V conduction to control values. In contrast, procaine amide, in doses necessary to counteract digitalis-induced ventricular tachycardia, invariably exacerbated the A-V conduction prolongation produced by the glycoside. The effect of DPH on A-V conduction makes this a unique drug in the therapy of digitalis toxicity, since it abolishes both the ventricular ectopia and A-V conduction abnormalities produced by the glycoside. The selective effects of DPH are in contrast with agents such as procaine amide which depress both ventricular ectopia as well as A-V transmission in the digitoxic heart. However, DPH is contra-indicated in complete heart block. © 1968.