title: Short-long sequences prior to ventricular tachycardia onset: analysis of VAST trial electrograms.
abstract: BACKGROUND
  The recently published Ventricular Arrhythmia Suppression Trial (VAST) found no effect of rate-smoothing (RS) algorithm on frequency of ventricular tachycardia (VT) episodes in patients with implantable defibrillator. A similar recent trial reported an opposite result. In order to determine possible reasons for the discrepancy between the trials and achieve better understanding of events preceding VT onset, we analyzed stored device electrograms preceding 162 VT episodes from 50 VAST trial patients with dual-chamber devices.
  
  
  RESULTS
  In this analysis, short-long sequences were more common prior to polymorphic VTs than before monomorphic VTs. The proportion of VT episodes preceded by short-long sequences was lower during randomization to RS ON (5.3% vs 31.3%, P < 0.001). For patients with multiple episodes of monomorphic VT, there was higher interpatient than intrapatient variability in preceding RR intervals. When adjusting for this similarity of RR interval sequences preceding VT onset in individual patients, the difference in proportion short-long sequences between RS ON and RS OFF programming was no longer significant.
  
  
  CONCLUSIONS
  Episodes of VT were preceded by stereotypic, patient-specific sequences of RR intervals in several VAST trial patients. RS reduced the percentage of VTs preceded by short-long sequences, but did not change overall VT incidence.
authors.affiliation: Cardiovascular Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15206, USA. limidus@hotmail.com
authors.forename: Jan
authors.initials: J
authors.lastname: Nemec
authors.forename: Aiman
authors.initials: A
authors.lastname: El-Saed
authors.forename: Darin R
authors.initials: DR
authors.lastname: Lerew
authors.forename: Stacey
authors.initials: S
authors.lastname: Neuman
authors.forename: Samuel
authors.initials: S
authors.lastname: Asirvatham
authors.forename: Samir F
authors.initials: SF
authors.lastname: Saba
authors.forename: Win-Kuang
authors.initials: WK
authors.lastname: Shen
authors.forename: Paul A
authors.initials: PA
authors.lastname: Friedman
mesh_terms: D000465:Algorithms; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology*