title: Defibrillation thresholds in hypertrophic cardiomyopathy.
abstract: BACKGROUND
  Defibrillation threshold (DFT) testing is performed in part to ensure an adequate safety margin for the termination of spontaneous ventricular arrhythmias. Left ventricular mass is a predictor of high DFTs, so patients with hypertrophic cardiomyopathy (HCM) are often considered to be at risk for increased defibrillation energy requirements. However, there are little prospective data addressing this issue.
  
  
  OBJECTIVE
  To assess DFTs in patients with HCM and evaluate the clinical predictors of elevated DFTs.
  
  
  METHODS
  Eighty-nine consecutive patients with HCM and 600 control patients with ischemic or nonischemic cardiomyopathy underwent a uniform modified step-down DFT testing protocol. DFT was compared between the control and HCM populations. Predictors of elevated DFT were evaluated in the HCM group.
  
  
  RESULTS
  There was no difference in DFT between HCM and control groups (10.4 ± 5.8 J vs 11.2 ± 5.6 J, respectively). Among patients with HCM, clinical parameters such as left ventricular ejection fraction, interventricular septal thickness, left ventricular mass, and QRS duration were not predictive of an elevated DFT. Only 3 patients (3.4%) with HCM had a DFT >20 J.
  
  
  CONCLUSIONS
  Patients with HCM do not have elevated DFTs as compared to more typical populations undergoing implantable cardioverter-defibrillator implant; high-energy devices or complex lead systems are not needed routinely in this population.
authors.affiliation: Division of Cardiology, Medical University of South Carolina, Charleston, South Carolina 29425, USA. emattquin@gmail.com
authors.forename: Ernest M
authors.initials: EM
authors.lastname: Quin
authors.forename: Frank A
authors.initials: FA
authors.lastname: Cuoco
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Forcina
authors.forename: Jason B
authors.initials: JB
authors.lastname: Coker
authors.forename: Robert H
authors.initials: RH
authors.lastname: Yoe
authors.forename: William H
authors.initials: WH
authors.lastname: Spencer
authors.forename: Valerian L
authors.initials: VL
authors.lastname: Fernandes
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Nielsen
authors.forename: J Lacy
authors.initials: JL
authors.lastname: Sturdivant
authors.forename: Robert B
authors.initials: RB
authors.lastname: Leman
authors.forename: J Marcus
authors.initials: JM
authors.lastname: Wharton
authors.forename: Michael R
authors.initials: MR
authors.lastname: Gold
mesh_terms: D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000503:physiopathology* / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D004056:Differential Threshold; D004554:Electric Countershock / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control*