RANDOMIZED CROSS-OVER EVALUATION OF 2 ADAPTIVE PACING ALGORITHMS FOR THE TERMINATION OF VENTRICULAR-TACHYCARDIA

Objective: In a randomized, cross-over study we evaluated the efficacy of rate adaptive constant cycle length (BURST) and autodecremental (RAMP) pacing for termination of sustained monomorphic ventricular tachycardia. Methods: An external device capable of delivering the same types of antitachycardia pacing as the newer generation implantable cardioverter defibrillators was used. Thirty-one patients with ischemic and nonischemic cardiomyopathy and documented clinical ventricular tachycardia or ventricular fibrillation were examined during routine invasive electrophysiological studies. RAMP and BURST pacing were each attempted in 54 matched pairs of induced ventricular tachycardia. After a therapy was applied, the tachycardia was reinitiated and the other therapy applied during the second episode so that a total of 108 ventricular tachycardia episodes were studied. Results: Overall efficacy of ventricular tachycardia pace termination was 69% and the time required to stop ventricular tachycardia was 14.1 +/- 11.3 seconds. The ability to terminate ventricular tachycardia by RAMP (72%) or BURST (65%) pacing was not significantly different. However, time to terminate ventricular tachycardia by RAMP (11.8 +/- 8.5 sec) was significantly shorter than by BURST (16.4 +/- 13.5), P < 0.001. Acceleration of ventricular tachycardia was uncommon with both pacing modes, 7/108 (7%). The ability to pace terminate ventricular tachycardia was cycle length dependant. The highest success was with ventricular tachycardia cycle length between 300 and 350 msec. The success rate decreased with faster and also slower ventricular tachycardia. Conclusions: 1. Rate adaptive pacing methods for ventricular tachycardia termination are effective and safe. 2. Autodecremental RAMP pacing afford quicker ventricular tachycardia termination than constant cycle length BURST pacing. 3. The ability to terminate ventricular tachycardia is cycle length dependent with cycle length range of 300-350 msec being most responsive to pace termination.