title: Improvement of defibrillation efficacy with preshock synchronized pacing.
abstract: BACKGROUND
  We previously demonstrated that wavefront synchronization by spatiotemporal excitable gap pacing (Sync P) is effective at facilitating spontaneous termination of ventricular fibrillation (VF). Therefore, we hypothesized that a spatiotemporally controlled defibrillation (STCD) strategy using defibrillation shocks preceded by Sync P can improve defibrillation efficacy.
  
  
  RESULTS
  We explored the STCD effects in 13 isolated rabbit hearts. During VF, a low-voltage gradient (LVG) area was synchronized by Sync P for 0.92 second. For Sync P, optical action potentials (OAPs) adjacent to four pacing electrodes (10 mm apart) were monitored. When one of the electrodes was in the excitable gap, a 5-mA current was administered from all electrodes. A shock was delivered 23 ms after the excitable gap when the LVG area was unexcitable. The effects of STCD was compared to random shocks (C) by evaluating the defibrillation threshold 50% (DFT(50); n = 35 for each) and preshock coupling intervals (n = 208 for STCD, n = 172 for C). Results were as follows. (1) Sync P caused wavefront synchronization as indicated by a decreased number of phase singularity points (P < 0.0001) and reduced spatial dispersion of VF cycle length (P < 0.01). (2) STCD decreased DFT(50) by 10.3% (P < 0.05). (3) The successful shocks showed shorter preshock coupling intervals (CI; P < 0.05) and a higher proportion of unexcitable shock at the LVG area (P < 0.001) than failed shocks. STCD showed shorter CIs (P < 0.05) and a higher unexcitable shock rate at LVG area (P < 0.05) than C.
  
  
  CONCLUSIONS
  STCD improves defibrillation efficacy by synchronizing VF activations and increasing probability of shock delivery to the unexcitable LVG area.
authors.affiliation: Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center and David Geffen School of Medicine, UCLA, 90048, USA.
authors.forename: Hui-Nam
authors.initials: HN
authors.lastname: Pak
authors.forename: Yuji
authors.initials: Y
authors.lastname: Okuyama
authors.forename: Yong-Seog
authors.initials: YS
authors.lastname: Oh
authors.forename: Hideki
authors.initials: H
authors.lastname: Hayashi
authors.forename: Yen-Bin
authors.initials: YB
authors.lastname: Liu
authors.forename: Peng-Sheng
authors.initials: PS
authors.lastname: Chen
authors.forename: Shien-Fong
authors.initials: SF
authors.lastname: Lin
mesh_terms: D000818:Animals; D004554:Electric Countershock / Q000379:methods*; D006329:Heart Conduction System / Q000503:physiopathology*; D066298:In Vitro Techniques; D011817:Rabbits; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy*