title: Risk Markers and Appropriate Implantable Defibrillator Therapy in Hypertrophic Cardiomyopathy.
abstract: BACKGROUND
  Risk stratification of sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM) is mainly based on evaluations from patients at highly specialized centers.
  
  
  OBJECTIVE
  To evaluate risk markers for appropriate implantable cardioverter defibrillator (ICD) therapy in an unselected, nationwide cohort of HCM.
  
  
  METHODS
  Patients with an ICD due to HCM were identified from the Swedish ICD Registry since its start in 1995, merged with Patient Register data, and medical records were retrieved. Risk markers for ventricular arrhythmias leading to appropriate ICD therapy were analyzed using Cox proportional hazard ratio (HR).
  
  
  RESULTS
  Of 321 patients (70.1% males), at least one appropriate therapy occurred in 77 (24.0%) during a mean follow-up of 5.4 years (5.3% per year; primary prevention 4.5%, secondary prevention 7.0%). Cumulative incidences at 1 year, 3 years, and 5 years were 8.1%, 15.3%, and 21.3%, respectively. Cardioversion effectively restored rhythm in 52% of the first episode and antitachycardia pacing was sufficient in the remaining. For the whole cohort, ejection fraction (EF) <50% (HR 2.63; P < 0.001) was associated with appropriate ICD therapy. In primary prevention, patients with established risk markers experienced appropriate therapy; atrial fibrillation (AF; HR 2.54; P = 0.010), EF < 50% (HR 2.78; P = 0.004), and nonsustained ventricular tachycardia (HR 1.80; P = 0.109) had the highest HR, and wall thickness ≥ 30 mm, syncope, exercise blood pressure response, or family history of SCD had weaker associations.
  
  
  CONCLUSIONS
  ICD therapy successfully terminates ventricular arrhythmias in HCM. In addition to conventional risk markers, a history of AF or EF < 50% may be considered in risk stratification.
authors.affiliation: Cardiology Research Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital/Solna, Stockholm, Sweden.|Centre for Research and Development, Uppsala University/Region Gävleborg, Gävle, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Magnusson
authors.affiliation: Cardiology Research Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital/Solna, Stockholm, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Gadler
authors.affiliation: Centre for Research and Development, Uppsala University/Region Gävleborg, Gävle, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Liv
authors.affiliation: Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden.
authors.forename: Stellan
authors.initials: S
authors.lastname: Mörner
mesh_terms: D002312:Cardiomyopathy, Hypertrophic / Q000401:mortality* / Q000628:therapy*; D015984:Causality; D015897:Comorbidity; D016757:Death, Sudden, Cardiac / Q000453:epidemiology / Q000517:prevention & control; D017147:Defibrillators, Implantable / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011379:Prognosis; D012042:Registries; D012307:Risk Factors; D015996:Survival Rate; D013548:Sweden / Q000453:epidemiology; D017180:Tachycardia, Ventricular / Q000401:mortality* / Q000517:prevention & control*; D016896:Treatment Outcome
keywords: epidemiology; hypertrophic cardiomyopathy; implantable cardioverter defibrillator; risk stratification; sudden death