Friedman Paul A, Jalal Sohail, Kaufman Scott, Villareal Rollo, Brown Scott, Hahn Stephen J, Lerew Darin R
Mayo Clinic, Rochester, Minnesota 55902, USA.
Heart Rhythm. 2006 May;3(5):573-80. doi: 10.1016/j.hrthm.2006.01.021. Epub 2006 Feb 28.
Rate 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.
The 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.
Five 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.
Of 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.
Rate smoothing does not result in a reduction in ventricular arrhythmias in a heterogeneous population of patients receiving ICDs.
一些起搏器和植入式心脏复律除颤器（ICD）具备心率平滑功能，已被用于预防长QT综合征患者发生尖端扭转型室速。其在预防一般性室性心律失常方面的疗效尚未确定。
室性心律失常抑制试验（VAST）的目的是前瞻性研究心率平滑功能能否显著降低大量广泛的ICD患者发生室性快速心律失常的发生率。
569例患者在57个参与中心入组，并植入市售的Guidant ICD。采用单盲交叉设计，每位患者在植入时随机分为两种治疗顺序之一：先开启心率平滑功能（RS On），然后关闭（RS Off）；或先关闭，然后开启。这种模式顺序是随机确定的，并按1:1的比例使用随机排列的区组按站点分配。每种模式持续6个月。心率平滑功能的编程规定在RS On期间，下降12%和上升12%。
入组患者中，281例随机分为先RS Off后RS On，288例随机分为先RS On后RS Off。开启RS On时，75例（23%）患者心律失常减少，76例（23%）患者心律失常增加，其余176例（54%）无差异。未发现开启RS On与关闭RS Off时心律失常频率有显著差异（P = 0.58）。
在接受ICD治疗的异质性患者群体中，心率平滑功能不会降低室性心律失常的发生率。
