title: Use of a discrimination algorithm to reduce inappropriate shocks with a subcutaneous implantable cardioverter-defibrillator.
abstract: BACKGROUND
  The subcutaneous implantable cardioverter-defibrillator system (S-ICD) uses a novel detection algorithm previously shown to discriminate induced tachyarrhythmias (ventricular vs supraventricular) effectively.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the role of the S-ICD discrimination algorithm in reducing the incidence of spontaneous inappropriate shocks.
  
  
  METHODS
  A total of 314 subjects underwent implantation with an S-ICD system as part of the S-ICD Clinical Investigation (IDE Trial). Subjects were grouped according to programming at discharge to either a single shock zone or 2 shock zones, with a discrimination algorithm in the lower rate zone.
  
  
  RESULTS
  This cohort had 226 subjects (72%) with dual zone programming and 88 subjects (28%) with single zone programming. Over a mean follow-up period of 661 ± 174 days, inappropriate shocks occurred in 23 subjects from the dual zone subgroup (10.2%) and 23 subjects from the single zone subgroup (26.1%, P < .001), with 2-year inappropriate shock-free rates of 89.7% vs. 73.6%;,respectively (hazard ratio 0.38, P = .001). Freedom from appropriate shocks did not differ between subgroups (92.2% vs. 90.3%, hazard ratio 0.82, P = .64). Moreover, mean time to appropriate therapy did not differ between subgroups, and there was only 1 episode of arrhythmic syncope in the cohort.
  
  
  CONCLUSIONS
  The addition of a second shock zone with an active discrimination algorithm was strongly associated with a reduction in inappropriate shocks with the S-ICD system and did not result in prolongation of detection times or increased syncope. These data support the use of dual zone programming as a standard setting for S-ICD patients.
authors.affiliation: Medical University of South Carolina, Charleston, South Carolina. Electronic address: goldmr@musc.edu.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Gold
authors.affiliation: Ohio State University, Columbus, Ohio.
authors.forename: Raul
authors.initials: R
authors.lastname: Weiss
authors.affiliation: Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Dominic A M J
authors.initials: DA
authors.lastname: Theuns
authors.affiliation: Auckland City Hospital, Auckland, New Zealand.
authors.forename: Warren
authors.initials: W
authors.lastname: Smith
authors.affiliation: Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Angel
authors.initials: A
authors.lastname: Leon
authors.affiliation: Northwestern University, Chicago, Illinois.
authors.forename: Bradley P
authors.initials: BP
authors.lastname: Knight
authors.affiliation: Boston Scientific Corporation, Natick, Massachusetts.
authors.forename: Nathan
authors.initials: N
authors.lastname: Carter
authors.affiliation: Boston Scientific Corporation, Natick, Massachusetts.
authors.forename: Michael
authors.initials: M
authors.lastname: Husby
authors.affiliation: University of Chicago, Chicago, Illinois.
authors.forename: Martin C
authors.initials: MC
authors.lastname: Burke
mesh_terms: D000465:Algorithms; D017147:Defibrillators, Implantable / Q000592:standards*; D004554:Electric Countershock / Q000379:methods* / Q000592:standards; D004562:Electrocardiography; D004868:Equipment Failure; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D017180:Tachycardia, Ventricular / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome
keywords: Inappropriate shock; Inappropriate therapy; Oversensing; Rhythm discrimination; Subcutaneous implantable-defibrillator; Supraventricular tachyarrhythmia