title: Implantable cardioverter-defibrillators and prevention of sudden cardiac death in hypertrophic cardiomyopathy.
abstract: BACKGROUND
  Recently, the implantable cardioverter-defibrillator (ICD) has been promoted for prevention of sudden death in hypertrophic cardiomyopathy (HCM). However, the effectiveness and appropriate selection of patients for this therapy is incompletely resolved.
  
  
  OBJECTIVE
  To study the relationship between clinical risk profile and incidence and efficacy of ICD intervention in HCM.
  
  
  METHODS
  Multicenter registry study of ICDs implanted between 1986 and 2003 in 506 unrelated patients with HCM. Patients were judged to be at high risk for sudden death; had received ICDs; underwent evaluation at 42 referral and nonreferral institutions in the United States, Europe, and Australia; and had a mean follow-up of 3.7 (SD, 2.8) years. Measured risk factors for sudden death included family history of sudden death, massive left ventricular hypertrophy, nonsustained ventricular tachycardia on Holter monitoring, and unexplained prior syncope.
  
  
  METHODS
  Appropriate ICD intervention terminating ventricular tachycardia or fibrillation.
  
  
  RESULTS
  The 506 patients were predominately young (mean age, 42 [SD, 17] years) at implantation, and most (439 [87%]) had no or only mildly limiting symptoms. ICD interventions appropriately terminated ventricular tachycardia/fibrillation in 103 patients (20%). Intervention rates were 10.6% per year for secondary prevention after cardiac arrest (5-year cumulative probability, 39% [SD, 5%]), and 3.6% per year for primary prevention (5-year probability, 17% [SD, 2%]). Time to first appropriate discharge was up to 10 years, with a 27% (SD, 7%) probability 5 years or more after implantation. For primary prevention, 18 of the 51 patients with appropriate ICD interventions (35%) had undergone implantation for only a single risk factor; likelihood of appropriate discharge was similar in patients with 1, 2, or 3 or more risk markers (3.83, 2.65, and 4.82 per 100 person-years, respectively; P = .77). The single sudden death due to an arrhythmia (in the absence of advanced heart failure) resulted from ICD malfunction. ICD complications included inappropriate shocks in 136 patients (27%).
  
  
  CONCLUSIONS
  In a high-risk HCM cohort, ICD interventions for life-threatening ventricular tachyarrhythmias were frequent and highly effective in restoring normal rhythm. An important proportion of ICD discharges occurred in primary prevention patients who had undergone implantation for a single risk factor. Therefore, a single marker of high risk for sudden death may be sufficient to justify consideration for prophylactic defibrillator implantation in selected patients with HCM.
authors.affiliation: Hypertrophic Cardiomyopathy Center of the Minneapolis Heart Institute Foundation, Minneapolis, Minnesota 55407, USA. hcm.maron@mhif.org
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Maron
authors.forename: Paolo
authors.initials: P
authors.lastname: Spirito
authors.forename: Win-Kuang
authors.initials: WK
authors.lastname: Shen
authors.forename: Tammy S
authors.initials: TS
authors.lastname: Haas
authors.forename: Francesco
authors.initials: F
authors.lastname: Formisano
authors.forename: Mark S
authors.initials: MS
authors.lastname: Link
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Epstein
authors.forename: Adrian K
authors.initials: AK
authors.lastname: Almquist
authors.forename: James P
authors.initials: JP
authors.lastname: Daubert
authors.forename: Thorsten
authors.initials: T
authors.lastname: Lawrenz
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boriani
authors.forename: N A Mark
authors.initials: NA
authors.lastname: Estes
authors.forename: Stefano
authors.initials: S
authors.lastname: Favale
authors.forename: Marco
authors.initials: M
authors.lastname: Piccininno
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Winters
authors.forename: Massimo
authors.initials: M
authors.lastname: Santini
authors.forename: Sandro
authors.initials: S
authors.lastname: Betocchi
authors.forename: Fernando
authors.initials: F
authors.lastname: Arribas
authors.forename: Mark V
authors.initials: MV
authors.lastname: Sherrid
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Buja
authors.forename: Christopher
authors.initials: C
authors.lastname: Semsarian
authors.forename: Paolo
authors.initials: P
authors.lastname: Bruzzi
mesh_terms: D000328:Adult; D000368:Aged; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000628:therapy*; D016757:Death, Sudden, Cardiac / Q000209:etiology / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012042:Registries; D018570:Risk Assessment; D017180:Tachycardia, Ventricular / Q000150:complications / Q000628:therapy*; D014693:Ventricular Fibrillation / Q000150:complications / Q000628:therapy*