Patient initiated implantable pacemakers for paroxysmal supraventricular tachycardia.

Seven patients with recurrent paroxysmal supraventricular tachycardia (PSVT) resistant to standard drug therapy were treated with patient initiated implantable pacemakers. All patients had required frequent hospital admissions and cardioversions prior to pacemaker implantation. Two patients had Wolff-Parkinson-White (WPW) syndrome on their surface ECGs and five patients had no ECG evidence of preexcitation. All patients had detailed electrophysiological studies. Three patients had junctional tachycardia, one patients had reciprocating atrial tachycardia and in three, including one with normal surface ECG, retrogradely conducting accessory atrio-ventricular connections (AAVC) formed a part of the tachycardia circuit. Initiation and termination of tachycardia were re-checked at subsequent studies. On the basis of these studies, two patients with WPW syndrome had right ventricular endocardial leads and custom-built, magnet actuated pacemakers capable of delivering right ventricular coupled stimuli at fixed, present intervals of 200 and 400 ms. Both these pacemakers provided inconsistent reversions and proved unsatisfactory. In the remaining five patients, a unipolar tined J-shaped right atrial (RA) lead (Medtronic 6991) and a radiofrequency (RF) receiver (Medtronic 5998T) were implanted and enabled patients to overdrive ranged from 14 to 20 months. Several episodes of PSVT have been consistently reverted and none have required hospitalisation or cardio-version. Two patients had transient atrial fibrillation following the application of RF pacemaker. Three have required no antiarrhythmic drugs and in two the drug therapy has been greatly reduced and simplified. The Medtronic 6991 lead provided satisfactory RA stimulation without dislodgement. In carefully selected patients with PSVT, RF pacemakers provide a useful mode of treatment.