title: Defibrillation thresholds with right pectoral implantable cardioverter defibrillators and impact of waveform tuning (the Tilt and Tune trial).
abstract: OBJECTIVE
  Assess defibrillation thresholds (DFTs) with right active pectoral implantable cardioverter defibrillator (RICDs). Defibrillation thresholds in patients receiving RICDs are regarded as 'high' and potentially improved by waveform optimization (tuning). However, this has not been systematically tested.
  
  
  RESULTS
  Patients receiving RICDs [Single chamber (VVI) = 16, DDD = 32, cardiac resynchronization therapy (CRT) = 43] were randomized to either 50/50% fixed tilt (FT) or tuned waveform (3.5 ms time constant based). Defibrillation threshold was tested with a binary search protocol in single coil anodal configuration. Then RICDs were compared with left-sided placements. Baseline patient characteristics in FT (n = 54) and tuned (n = 37) were similar (65 ± 14 years, 71% male, Left ventricular ejection fraction 31 ± 13%; and proportions VVI/DDD/Cardiac resynchronization therapy defibrillator). Tuning reduced Phase 1 by 15% and Phase 2 by 45%. For FT vs. tuned: high voltage impedance was 61.9 ± 13.2 vs. 64.5 ± 12.7 Ω (P = 0.33) and mean DFT 14.2 ± 8.8 vs. 14.9 ± 9.2 J (P = 0.8). When high voltage impedance was >62 Ω (mean 73.6 ± 8.6 Ω), DFT was identical [FT 13.0 ± 7.9 J vs. tuned 12.0 ± 5.9 J (P= 0.7)]. Defibrillation thresholds exceeded 20 J (600 V) in >20% of patients [FT 11/54 (20.4%) vs. tuned 12/37 (32%) patients]. Defibrillation threshold with RICD was greater and exhibited wider dispersion compared with left ICDs (n = 54) under similar conditions.
  
  
  CONCLUSIONS
  This first randomized trial investigating DFTs with right ICDs confirms relatively higher DFTs with RICDs than reported for left pectoral ICDs. However, DFTs were generally unaffected by 3.5 ms time constant-based waveform tuning compared with a 50% tilt waveform. Implant testing may be preferred with RICDs.
  
  
  BACKGROUND
  NCT00873691.
authors.affiliation: J2-2 Cardiology, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
authors.forename: Niraj
authors.initials: N
authors.lastname: Varma
authors.affiliation: Providence St. Joseph, Burbank, CA, USA.
authors.forename: Raymond
authors.initials: R
authors.lastname: Schaerf
authors.affiliation: The Ohio State University Medical Center, Columbus, OH, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Kalbfleisch
authors.affiliation: Mid-America Cardiology Associates, Kansas City, KS, USA.
authors.forename: Rhea
authors.initials: R
authors.lastname: Pimentel
authors.affiliation: University of Minnesota, Minneapolis, MN, USA.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Kroll
authors.affiliation: St. Jude Medical, Sylmar, CA, USA.
authors.forename: Ashish
authors.initials: A
authors.lastname: Oza
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D058406:Cardiac Resynchronization Therapy / Q000009:adverse effects / Q000379:methods; D058409:Cardiac Resynchronization Therapy Devices; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010369:Pectoralis Muscles; D011446:Prospective Studies; D011474:Prosthesis Design; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States; D016277:Ventricular Function, Left
keywords: Defibrillation threshold; Impedance; Implantable cardioverter-defibrillator; Phase duration; Right sided; Shock waveform