Nonparoxysmal atrioventricular junctional rhythm. A clinical and electrophysiologic study.

The patient, a 74-year-old man, developed a persistent nonparoxysmal junctional accelerated rhythm at rate of 60-75 beats min-1 because of chronic depressed sinus node function. Intravenous atropine resulted in no change of junctional pacemaker rate but i.v. isoproterenol significantly accelerated it suggesting that autonomic neural imbalance might underlie the mechanism of nonparoxysmal junctional rhythm. Intravenous verapamil (10 mg) induced no change in the junctional pacemaker rate and postpacing pauses suggesting that the slow inward current did not play an important role in the nonparoxysmal junctional rhythm.