title: Do traditional VT zones improve outcome in primary prevention ICD patients?
abstract: OBJECTIVE
  We reviewed outcomes in our primary prevention implantable cardioverter defibrillator (ICD) population according to whether the device was programmed with a single ventricular fibrillation (VF) zone or with two zones including a ventricular tachycardia (VT) zone in addition to a VF zone.
  
  
  METHODS
  This retrospective study examined 137 patients with primary prevention ICDs implanted at our institution between 2004 and 2006. Device programming and events during follow-up were reviewed. Outcomes included all-cause mortality, time to first shock, and incidence of shocks.
  
  
  RESULTS
  Eighty-seven ICDs were programmed with a single VF zone (mean >193 ± 1 beats per minute [bpm]) comprising shocks only. Fifty ICDs had two zones (mean VT zone >171 ± 2 bpm; VF zone >205 ± 2 bpm), comprising antitachycardia pacing (100%), shocks (96%), and supraventricular (SVT) discriminators (98%) . Discriminator "time out" functions were disabled. Mean follow-up was 30 ± 0.5 months and similar in both groups. All-cause mortality (12.6% and 12.0%) and time to first shock were similar. However, the two-zone group received more shocks (32.0% vs 13.8% P = 0.01). Five of 16 shocks in these patients were inappropriate for SVT rhythms. The single-zone group had no inappropriate shocks for SVTs. Eighteen of 21 appropriate shocks were for ventricular arrhythmias at rates >200 bpm (three VF, 15 VT). This suggests that primary prevention ICD patients infrequently suffer ventricular arrhythmias at rates <200 bpm and that ATP may play a role in terminating rapid VTs.
  
  
  CONCLUSIONS
  Patients with two-zone devices received more shocks without any mortality benefit.
authors: Department of Cardiology, Barts and the London NHS Trust, London, UK.
authors: Edward
authors: E
authors: Duncan
authors: Glyn
authors: G
authors: Thomas
authors: Neville
authors: N
authors: Johns
authors: Cameron
authors: C
authors: Pfeffer
authors: Gautham
authors: G
authors: Appanna
authors: Nirav
authors: N
authors: Shah
authors: Ross
authors: R
authors: Hunter
authors: Malcolm
authors: M
authors: Finlay
authors: Richard J
authors: RJ
authors: Schilling
authors: Simon
authors: S
authors: Sporton
mesh_terms: D000368:Aged; D009202:Cardiomyopathies / Q000150:complications / Q000628:therapy; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000628:therapy; D011322:Primary Prevention / Q000295:instrumentation*; D012189:Retrospective Studies; D013318:Stroke Volume; D013617:Tachycardia, Supraventricular / Q000175:diagnosis / Q000401:mortality / Q000517:prevention & control / Q000628:therapy; D017180:Tachycardia, Ventricular / Q000209:etiology / Q000401:mortality / Q000517:prevention & control*; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000517:prevention & control / Q000628:therapy