• Paul A Friedman, Sohail Jalal, Scott Kaufman, Rollo Villareal, Scott Brown, Stephen J Hahn, and Darin R Lerew.
• Mayo Clinic, Rochester, Minnesota 55902, USA. friedman.paul@mayo.edu
• Heart Rhythm. 2006 May 1;3(5):573-80.

BackgroundRate smoothing, which is available in some pacemakers and implantable cardioverter defibrillators (ICDs), has been used to prevent Torsades de Pointes in patients with long QT syndrome. Its efficacy in general ventricular arrhythmia prevention has not been determined.ObjectivesThe purpose of the Ventricular Arrhythmia Suppression Trial (VAST) was to prospectively investigate whether rate smoothing could significantly reduce the incidence of ventricular tachyarrhythmias in a large, broad population of patients with ICDs.MethodsFive hundred sixty-nine patients were enrolled at 57 participating centers and implanted with a commercially available Guidant ICD. A single-blinded crossover design was used in which each patient was randomized at implant to one of two treatment sequences: either rate smoothing on (RS On) followed by rate smoothing off (RS Off), or RS Off followed by RS On. This mode sequence was randomly determined and assigned in a 1:1 fashion using randomized permuted blocks by site. Each mode was followed for 6 months. Programming of rate smoothing was prescribed as 12% Down and 12% Up for the duration of the RS On period.ResultsOf enrolled patients, 281 were randomized to RS Off followed by RS On, and 288 to RS On followed by RS Off. With RS On, 75 (23%) patients experienced a reduction in arrhythmias, 76 (23%) saw an increase in arrhythmias, and the remaining 176 (54%) had no difference. No significant difference (P = .58) in frequency of arrhythmias with RS On vs RS Off was found.ConclusionRate smoothing does not result in a reduction in ventricular arrhythmias in a heterogeneous population of patients receiving ICDs.

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