VENTRICULAR PACING-INDUCED VENTRICULAR-TACHYCARDIA IN PATIENTS WITH IMPLANTABLE CARDIOVERTER-DEFIBRILLATORS

Appropriately timed noncompetitive ventricular pacing potentially may initiate ventricular tachycardia in patients prone to these arrhythmia s. The combination of bradycardia pacing and stored electrograms in a currently available cardioverter defibrillator provides an opportunity to evaluate the occurrence of such pacing induced ventricular tachyca rdia. During a surveillance period of 18.7 +/- 11.4 months, stored ele ctrograms documented 302 episodes of ventricular tachycardia in 77 pat ients. Five patients (6.5%) demonstrated 25 episodes (1-16 per patient ) of ventricular tachycardia that were immeadiately preceded by an app ropriately paced ventricular beat (8.3% of all episodes of ventricular tachycardia). All five patients had prior myocardial infarctions and a history of monomorphic ventricular tachycardia occurring both sponta neously and in response to programmed electrical stimulation. Antitach ycardia pacing terminated pacing induced ventricular tachycardia in 22 episodes; in one episode antitachycardia pacing accelerated ventricul ar tachycardia. In two cases shock therapy was aborted for nonsustaine d ventricular tachycardia. We conclude that, in selected postinfarctio n patients with recurrent sustained monmorphic ventricular tachycardia treated with implantable cardioverter defibrillators, appropriately t imed ventricular pacing may induce ventricular tachycardia.