title: A prospective randomized trial of defibrillation thresholds from the right ventricular outflow tract and the right ventricular apex.
abstract: BACKGROUND
  Right ventricular outflow tract (RVOT) pacing has been suggested to improve hemodynamics and to help prevent pacing-induced cardiomyopathy. Pacing from the RVOT is feasible and equivalent in terms of sensing and stimulation threshold. However, physicians have been reluctant to use RVOT pacing because of concerns that defibrillation efficacy might be adversely affected. To date, there have been no randomized-controlled trials published comparing the defibrillation threshold in leads implanted in the RVOT and the right ventricular apex (RVA).
  
  
  OBJECTIVE
  The purpose of this study was to compare defibrillation thresholds (DFT) in the RVOT and RVA. Ventricular sensing and stimulation thresholds were also compared.
  
  
  METHODS
  This prospective, randomized, multicenter study included 87 patients (70 males, age 69 +/- 11 years). At implantation, the patient's ventricular implantable cardioverter-defibrillator (ICD) lead position was randomized to either the RVOT or RVA. A four-shock Bayesian up-down method was used to determine the DFT. Patients were followed for 3 months postimplant.
  
  
  RESULTS
  DFTs were not significantly different in leads implanted in the RVOT (median 8.8 J [6.28, 12.9] vs. 7.9 J [6.20, 12.6], P = 0.65). Threshold and impedance measurements were stable in both RVOT and RVA groups from implant to follow-up. All ICD leads remained stable chronically at the 3-month follow-up.
  
  
  CONCLUSIONS
  DFTs in leads placed in the RVOT and RVA are comparable. RVOT ICD lead placement is safe and exhibits similar lead stability, threshold, and impedance measurements as the traditional RVA location.
authors.affiliation: St Thomas Research Institute, and University of Tennessee College of Medicine, Cardiology Section, Nashville, Tennessee 37203, USA. gcrossley@stthomasheart.com
authors.forename: George H
authors.initials: GH
authors.lastname: Crossley
authors.forename: Ker
authors.initials: K
authors.lastname: Boyce
authors.forename: Marc
authors.initials: M
authors.lastname: Roelke
authors.forename: Joseph
authors.initials: J
authors.lastname: Evans
authors.forename: Dalal
authors.initials: D
authors.lastname: Yousuf
authors.forename: Zaffer
authors.initials: Z
authors.lastname: Syed
authors.forename: Ralph
authors.initials: R
authors.lastname: Vicari
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004056:Differential Threshold; D005260:Female; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D011446:Prospective Studies; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000517:prevention & control*; D016896:Treatment Outcome