Single-Beat Stimulation and Train of Stimuli Method for Prevention of Reentrant Tachycardia

Abstract

Eleven patients with an atrioventricular accessory pathway were studied by programmed electrical stimulation to determine if reentrant tachycardia can be prevented in these patients by delivery of a single atrial extrastimulus, applied at a critical time after the tachycardia-initiating stimulus (or stimuli), or by delivery of a train of stimuli. In all 11 patients, reentrant tachycardia could reproducibly be induced from high right atrium with a single premature beat, and in all patients initiation of tachycardia could be prevented from the same site by a second premature beat. This second extrastimulus was effective if delivered within a zone which began 10 ms outside the effective refractory period of the tachycardia-initiating stimulus, and averaged 61 ms in width. It was termed the “preventive zone”. In 7 patients the effect of train stimulation to the high right atrium was studied. In all 7, results were concordant with those obtained by single-beat stimulation. Any train to achieve single atrial capture within the preventive zone was effective in preventing tachycardia. Prevention was always possible with a single atrial extrastimulus or with single-capture train stimulation, whereas termination of an ongoing tachycardia required at least 2 atrial extrastimuli, or stimulation from the right ventricle.