ABSTRACT
Reviews of stored electrograms from ICDs revealed a 5-30% incidence of short-long-short intervals preceding the onset of recurrent ventricular tachyarrhythmias. Rate stabilization by dedicated antibradycardia pacing algorithms has, therefore, been suggested to prevent onset of pause dependent tachyarrhythmias. However, the clinical efficacy of this approach has not been studied systematically. In a prospective multicenter crossover study, patients were randomized to activation or deactivation of an implemented ventricular rate stabilization algorithm (VRS) after first implant of a dual chamber ICD. After 3 months, all patients were crossed over to the alternate programming. The rate of appropriate spontaneous VA episodes was compared between VRS On and VRS Off. Stored electrograms were reviewed for evaluation of the mode of onset of tachyarrhythmias. Overall efficacy analysis was based on 309 patients enrolled in the study. Forty percent (124/309) of the patients experienced 4,973 VA episodes. Based on an intention-to-treat analysis, VRS Off and On arrhythmia incidence was 10.2 and 6.6 normalized to 3 months, respectively (risk reduction 35%; P = 0.18) On an on-treatment basis, a reduction from 9.0 episodes to 8.1 episodes (10% risk reduction, P = 0.24) was seen. In an extended Cox model adjusting for confounding variables, the relative risk for recurrent episodes was 0.92 during VRS On compared to Off (95% CI: 0.58-1.48; P = 0.74). During VRS Off, pause dependent onset was documented in only 36 (8%) of 427 visually analyzed episodes. There was no significant reduction in the incidence of recurrent ventricular tachyarrhythmias with VRS On compared to the Off programming in this prospective study.
