title: Elevated defibrillation thresholds in patients undergoing biventricular defibrillator implantation: incidence and predictors.
abstract: BACKGROUND
  The biventricular implantable cardioverter-defibrillator (ICD) is an important therapy for select patients with severe heart failure. Given reported risk factors for elevated defibrillation thresholds (DFTs), patients undergoing biventricular ICD placement would be suspected of having a higher incidence of elevated DFT.
  
  
  OBJECTIVE
  The purpose of this study was to examine the clinical predictors and mortality risk of elevated DFTs in patients receiving a biventricular ICD.
  
  
  METHODS
  Characteristics of patients undergoing biventricular ICD placement with an elevated DFT were compared to those without an elevated DFT.
  
  
  RESULTS
  An elevated DFT was found in 14 (12%) of 121 patients. Mean QRS duration was 210 +/- 50 ms in the elevated DFT group and 171 +/- 36 ms in the normal DFT group (P = .01). Patients with a QRS duration >or=200 ms were more likely to have an elevated DFT than those with a duration <200 ms (odds ratio 13.4, 95% confidence interval 3.1-66.7, P <.01). No other clinical characteristics were associated with an elevated DFT. More than 90% of patients with an elevated DFT achieved an adequate safety margin through system modification or manipulation of their drug regimen. An elevated DFT did not have an impact on 2-year mortality.
  
  
  CONCLUSIONS
  Patients with a biventricular ICD had a 12% incidence of elevated DFT in our sequential patient cohort. QRS duration prior to biventricular ICD placement is the most powerful predictor of patients at risk for an elevated DFT. An elevated DFT does not have an impact on mortality, perhaps because of successful implementation of system modifications to ensure an adequate defibrillation safety margin.
authors.affiliation: Department of Medicine, Electrophysiology Section, Division of Cardiovascular Medicine, University of Pennsylvania School of Medicine, Philadelphia, 19104, USA.
authors.forename: Sumeet K
authors.initials: SK
authors.lastname: Mainigi
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Cooper
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Russo
authors.forename: Hemal M
authors.initials: HM
authors.lastname: Nayak
authors.forename: David
authors.initials: D
authors.lastname: Lin
authors.forename: Sanjay
authors.initials: S
authors.lastname: Dixit
authors.forename: Edward P
authors.initials: EP
authors.lastname: Gerstenfeld
authors.forename: Henry H
authors.initials: HH
authors.lastname: Hsia
authors.forename: David J
authors.initials: DJ
authors.lastname: Callans
authors.forename: Francis E
authors.initials: FE
authors.lastname: Marchlinski
authors.forename: Ralph J
authors.initials: RJ
authors.lastname: Verdino
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017147:Defibrillators, Implantable; D005260:Female; D006333:Heart Failure / Q000150:complications*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010414:Pennsylvania / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D014693:Ventricular Fibrillation / Q000150:complications / Q000453:epidemiology* / Q000209:etiology / Q000401:mortality / Q000628:therapy*