title: Analysis of implantable cardioverter defibrillator therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial.
abstract: BACKGROUND
  The implantable cardioverter defibrillator (ICD) is commonly used to treat patients with documented sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia recurrence rates in these patients are high, but which patients will receive a therapy and the forms of arrhythmia recurrence (VT or VF) are poorly understood.
  
  
  RESULTS
  The therapy delivered by the ICD was examined in 449 patients randomized to ICD therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. Events triggering ICD shocks or antitachycardia pacing (ATP) were reviewed for arrhythmia diagnosis, clinical symptoms, activity at the onset of the arrhythmia, and appropriateness and results of therapy. Both shock and ATP therapies were frequent by 2 years, with 68% of patients receiving some therapy or having an arrhythmic death. An appropriate shock was delivered in 53% of patients, and ATP was delivered in 68% of patients who had ATP activated. The first arrhythmia treated in follow-up was diagnosed as VT (63%), VF (13%), supraventricular tachycardia (18%), unknown arrhythmia (3%), or due to ICD malfunction or inappropriate sensing (3%). Acceleration of an arrhythmia by the ICD occurred in 8% of patients who received any therapy. No physical activity consistently preceded arrhythmias, nor did any single clinical factor predict the symptoms of the arrhythmia.
  
  
  CONCLUSIONS
  Delivery of ICD therapy in AVID patients was common, primarily due to VT. Inappropriate ICD therapy occurred frequently. Use of ICD therapy as a surrogate endpoint for death in clinical trials should be avoided.
authors.affiliation: Cardiology Division, University of Utah Health Sciences Center and VA Medical Center, 50 N. Medical Drive, Salt Lake City, UT 84132, USA. richard.klein@hsc.utah.edu
authors.forename: Richard C
authors.initials: RC
authors.lastname: Klein
authors.forename: Merritt H
authors.initials: MH
authors.lastname: Raitt
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Wilkoff
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Beckman
authors.forename: James
authors.initials: J
authors.lastname: Coromilas
authors.forename: D George
authors.initials: DG
authors.lastname: Wyse
authors.forename: Peter L
authors.initials: PL
authors.lastname: Friedman
authors.forename: James B
authors.initials: JB
authors.lastname: Martins
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Epstein
authors.forename: Alfred P
authors.initials: AP
authors.lastname: Hallstrom
authors.forename: Robert B
authors.initials: RB
authors.lastname: Ledingham
authors.forename: Karen M
authors.initials: KM
authors.lastname: Belco
authors.forename: H Leon
authors.initials: HL
authors.lastname: Greene
mesh_terms: D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D017147:Defibrillators, Implantable / Q000009:adverse effects / Q000592:standards*; D004554:Electric Countershock; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*
chemical_list: D000889:Anti-Arrhythmia Agents