THE EFFECT OF DIPHENYLHYDANTOIN ON CONDUCTION IN ISOLATED, BLOOD-PERFUSED DOG HEARTS

¹ Department of Pharmacology and Therapeutics, University of Manitoba Faculty of Medicine, Winnipeg, Canada

The effects of diphenylhydantoin on conduction times through the atrium and the specialized conducting tissue to the ventricular myocardium have been determined from records obtained with a bipolar surface electrode placed over the bundle of His of isolated, blood-perfused dog hearts. Diphenylhydantoin slowed conduction in the atrioventricular node to a greater extent than in any other part of the heart at all concentrations tested. Clinically effective concentrations slowed conduction only through the atrioventricular node. The conduction of atrial extrasystoles interpolated after every 10th driving stimulus was preferentially affected by diphenylhydantoin. Concentrations of diphenylhydantoin which had only minimal effects on atrioventricular nodal conduction time of the normal beat greatly increased the atrioventricular nodal conduction delay of an extrasystole.