title: Electrophysiological measurements that can explain and guide temporary accelerated pacing to avert (re)occurrence of torsade de pointes arrhythmias in the canine chronic atrioventricular block model.
abstract: Pacing at higher rates is known to suppress torsade de pointes (TdP) arrhythmias. Nevertheless, exact application and mechanism need further clarification. In the anesthetized canine chronic atrioventricular block model, ventricular remodeling is responsible for a high and reproducible incidence of TdP upon a challenge with dofetilide.
  
  
  
  We used this model to investigate by what mechanism accelerated pacing averts TdP and what repolarization parameter could be used to guide temporary accelerated pacing (TAP).
  
  
  
  Ten dogs with repetitive TdP after administration of dofetilide when paced at 60 beats/min were selected. In a serial experiment, TAP was initiated at 100 beats/min after the first ectopic beat. Electrocardiogram and right and left ventricular (LV) monophasic action potential durations (MAPDs) were recorded. In a subset, vertical dispersion was determined with a duodecapolar catheter. Temporal dispersion was quantified as short-term variability (STV). Arrhythmias were quantified with the arrhythmia score.
  
  
  
  The increase in repolarization parameters observed after administration of dofetilide was counteracted by TAP (eg, LV MAPD from 381 ± 94 ms back to 310 ± 17 ms; P < .05). Temporal dispersion (STVLVMAPD) increased from 0.69 ± 0.37 to 2.59 ± 0.96 ms (P < .05) after administration of dofetilide and back to 1.15 ± 0.54 ms (P < .05) with TAP. This was accompanied by suppression of recurrent TdP in 7 of 10 dogs (P < .05) and a trend toward reduction in vertical (spatial) dispersion from 56 ± 25 to 31 ± 4 ms (P = .06). In those dogs, seconds after capture of TAP, almost all ectopy disappeared, causing a decrease in arrhythmia score from 21 ± 12 to 4 ± 3 (P < .05).
  
  
  
  TAP is effective in averting TdP by decreasing spatial and temporal measures of repolarization. Increase in temporal dispersion (STV) can guide TAP.
authors.affiliation: Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Sofieke C
authors.initials: SC
authors.lastname: Wijers
authors.affiliation: Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Bossu
authors.affiliation: Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Albert
authors.initials: A
authors.lastname: Dunnink
authors.affiliation: Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Jet D M
authors.initials: JDM
authors.lastname: Beekman
authors.affiliation: Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Rosanne
authors.initials: R
authors.lastname: Varkevisser
authors.affiliation: Medtronic Bakken Research Center, Maastricht, The Netherlands.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Aranda Hernández
authors.affiliation: Department of Cardiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Mathias
authors.initials: M
authors.lastname: Meine
authors.affiliation: Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands. Electronic address: m.a.vos@umcutrecht.nl.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Vos
mesh_terms: D000818:Animals; D054537:Atrioventricular Block / Q000150:complications / Q000503:physiopathology* / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D002908:Chronic Disease; D004195:Disease Models, Animal; D004285:Dogs; D022062:Electrophysiologic Techniques, Cardiac; D055724:Electrophysiological Phenomena; D006339:Heart Rate / Q000502:physiology; D012008:Recurrence; D016171:Torsades de Pointes / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control*; D020257:Ventricular Remodeling / Q000502:physiology
keywords: Dispersion; Pacing; Prevention; Short-term variability; Torsade de pointes