title: Ventricular tachycardia/fibrillation early after defibrillator implantation in patients with hypertrophic cardiomyopathy is explained by a high-risk subgroup of patients.
abstract: BACKGROUND
  Implantable cardioverter-defibrillator (ICD) studies in patients with coronary artery disease report higher risk of ventricular tachycardia/fibrillation (VT/VF) early post-implant, potentially related to local proarrhythmic effects of ICD leads.
  
  
  OBJECTIVE
  To characterize early and long-term risk of ICD discharge for VT/VF in a large hypertrophic cardiomyopathy (HCM) cohort.
  
  
  METHODS
  By using HCM multicenter registry data, we compared long-term risk of VT/VF subsequent to an early post-implant period (a priori defined as within 3 months of implant) between patients with or without VT/VF within 3 months after ICD implantation.
  
  
  RESULTS
  Over a median follow-up of 4.3 years, 109 of 506 (22%) patients with HCM who received ICDs received at least 1 ICD discharge for VT/VF. Risk of first ICD discharge for VT/VF was highest in the first year post-implant (10.8% per person-year; 95% confidence interval 7.9-13.8) and particularly in the first 3 months (17.0% per person-year; 95% confidence interval 9.8-24.3). Patients with early VT/VF (≤3 months post-implant) were older, and more commonly had secondary prevention ICDs following cardiac arrest or systolic dysfunction (end-stage HCM with ejection fraction<50%). Only 2 of 247 (0.7%) patients with primary prevention ICDs and preserved systolic function had early VT/VF. Patients with VT/VF early post-implant (≤3 months) had more than 5-fold higher risk for future VT/VF during long-term follow-up compared with patients without early VT/VF (adjusted hazard ratio 5.4; 95% confidence interval 2.3-12.6).
  
  
  CONCLUSIONS
  High-risk patients with HCM and VT/VF early after ICD implantation are particularly prone to subsequent VT/VF throughout follow-up. Early ICD interventions for VT/VF are largely confined to patients with prior cardiac arrest or systolic dysfunction and therefore more likely driven by higher arrhythmic risk rather than lead-related proarrhythmia.
authors.affiliation: Cardiac Arrhythmia Service, Heart and Vascular Institute, Sheikh Khalifa Medical City, Abu Dhabi, United Arab Emirates. aalsheikhali@alum.mit.edu
authors.forename: Alawi A
authors.initials: AA
authors.lastname: Alsheikh-Ali
authors.forename: Mark S
authors.initials: MS
authors.lastname: Link
authors.forename: Christopher
authors.initials: C
authors.lastname: Semsarian
authors.forename: Win-Kuang
authors.initials: WK
authors.lastname: Shen
authors.forename: N A Mark
authors.initials: NA
authors.lastname: Estes
authors.forename: Martin S
authors.initials: MS
authors.lastname: Maron
authors.forename: Tammy S
authors.initials: TS
authors.lastname: Haas
authors.forename: Francesco
authors.initials: F
authors.lastname: Formisano
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boriani
authors.forename: Paolo
authors.initials: P
authors.lastname: Spirito
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Maron
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001315:Australia; D002312:Cardiomyopathy, Hypertrophic / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*; D016001:Confidence Intervals; D016208:Databases, Factual; D016757:Death, Sudden, Cardiac / Q000209:etiology*; D017147:Defibrillators, Implantable / Q000009:adverse effects*; D004554:Electric Countershock / Q000009:adverse effects; D005060:Europe; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D018709:Statistics, Nonparametric; D016019:Survival Analysis; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*; D016896:Treatment Outcome; D014481:United States; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*