Verapamil-induced ventricular regularity in atrial fibrillation. Effects of exercise, isoproterenol, atropine and conversion to sinus rhythm.

The effects of physical exercise, isoproterenol and atropine upon the ventricular rate and regularity were studied in 12 patients with atrial fibrillation (AF) during verapamil-induced regular ventricular rhythm. Physical exercise, isoproterenol and atropine all caused a gradual loss of ventricular regularity during AF. Verapamil caused a reduction of exercise heart rate during AF and, to a minor extent, even during sinus rhythm. The regular ventricular rhythm induced by verapamil during AF is interpreted as a total AV-nodal block with nodal escape rhythm. Possible clinical benefits of this rhythm are discussed.