Efficacy of antitachycardia pacing confirmed by stored electrograms. A retrospective analysis of 613 stored electrograms in implantable defibrillators.

The implantable defibrillator (ICD) is an established therapy in the prevention of sudden cardiac death by defibrillation of ventricular fibrillation. Another specific feature of the ICDs is antitachycardia pacing (ATP) of ventricular tachycardia. Several studies report success rates of ATP in 83 to 98% of cases. In clinical practice the success of terminating ventricular tachycardia is estimated only by automatic device analysis. Therefore the objective of this study was to confirm the efficacy of ATP based on the evaluation of stored electrograms. From the German Ventritex MD-register stored electrograms of 613 monomorphic ventricular tachycardias in 44 patients were analyzed retrospectively. The cycle length of the ventricular tachycardias was between 265 and 560 ms. The success rate of ATP-induced termination of the episodes reached 89.3%; another 2.3% of the ventricular tachycardias were accelerated by antitachycardia pacing into ventricular fibrillation. Left ventricular function did not influence the success rate, but the success rate was lower for fast ventricular tachycardias > 200/min (63.9%). For ventricular tachycardias < 150 bpm there was no restriction of ATP effectiveness. Of the episodes 72.9% were terminated by the first ATP burst. In these cases the duration of tachycardia was very short (11.9 +/- 2.8 s). Fifty-eight ventricular tachycardias (9.5%) had to be terminated by means of a shock, and only one case required 2 shocks. In patients with more than 10 episodes an individual therapy success > 90% was recorded for 80% of them. The very high success rate of the first ATP attempt in ICD therapy can be achieved with uniform programming, and is confirmed for ventricular tachycardias analyzed on the basis of stored electrograms.