The response of regular re-entrant supraventricular tachycardia to right heart stimulation.

The study was designed to assess the effect of various forms of right atrial or ventricular stimulation on the termination of re-entrant "supraventricular" tachycardias. Standard electrophysiological techniques were used in 81 patients to study 86 stable tachycardias. All tachycardias were initiated by single or double atrial or ventricular premature stimuli or incremental atrial pacing. Eight groups of tachycardia circuit were defined in terms of the anterograde and retrograde pathways. Termination of each tachycardia was studied by atrial underdrive, ventricular underdrive, rapid atrial stimulation and single or double atrial and ventricular premature extrastimuli. Intranodal re-entrant tachycardias formed 33% of the total and WPW tachycardias as a whole formed 55% of the total number of arrhythmias. The remainder were comprised of atrial tachycardia (5%), tachycardias in association with a partial AV nodal bypass (3%) and pre-excited tachycardias (5%). A single atrial extrastimulus was most effective where the circuit involved the right atrium. Atrial underdrive was consistently less successful than a single atrial extrastimulus in all groups. Rapid atrial pacing was effective in all groups, but caused transient atrial flutter or fibrillation in a proportion of each group except one. Ventricular underdrive stimulation was most effective in those groups where the right ventricle was involved in the circuit, but tended to be less effective than programmed single or double ventricular extrastimuli. Pacemakers designed to deliver appropriately timed single or double extrastimuli may offer an important alternative to other pacing modalities.