Chronic nonparoxysmal junctional tachycardia.

We describe an adult with chronic (three years' duration) acquired nonparoxysmal junctional tachycardia, a previously undescribed rhythm. Ambulatory monitoring revealed junctional rates ranging from 75 to 110 beats/min. Electrophysiologic studies demonstrated intact atrioventricular and ventriculoatrial conduction with a normal H-V interval (43 msec) and narrow QRS. Underlying sinus node function appeared to be normal (recovery time of 900 msec). Junctional rate increased with administration of atropine and isoproterenol, suggesting that the junctional pacemaker was located in the proximal His bundle. Electrocardiographic and electrophysiologic observations suggested that this case of chronic nonparoxysmal junctional tachycardia was benign, not necessitating therapy.