title: Polymorphic reentrant ventricular tachycardia in the isolated rabbit heart studied by high-density mapping.
abstract: BACKGROUND
  The role of dispersion of refractoriness and reentry for the genesis of polymorphic ventricular tachycardia (VT) has recently become emphasized. We investigated the mechanisms of polymorphic arrhythmias in a 2D preparation confining an area of prolonged refractoriness.
  
  
  RESULTS
  In 16 Langendorff-perfused rabbit hearts, a sheet of left ventricular epicardium was obtained by a cryoprocedure. Enhanced spatial heterogeneity in a refractory period was created by cooling a central region (diameter=12 mm). This markedly prolonged the refractory period (by 36+/-14 ms) inside but only slightly prolonged it (by 5+/-11 ms) outside the cooled area (n=6). During a control procedure, programmed stimulation with up to 3 premature stimuli induced an episode of monomorphic VT in only 1 of 10 hearts. During regional cooling, episodes of polymorphic VT with a maximum duration of 35 seconds could be induced in all hearts. High-resolution mapping (229 electrodes) of epicardial activation revealed that polymorphic VT was caused by a functional reentrant circuit located partially within the region of prolonged refractoriness. The reentrant wavefront was continuously shifting along the border of the cooled region, resulting in beat-to-beat changes in the excitation pattern. Spontaneous termination of polymorphic VT occurred either by a shift of the reentrant circuit outside the cooled region or by a block in the central common pathway during figure-of-8 reentry in the region of prolonged refractoriness.
  
  
  CONCLUSIONS
  A shifting functional reentrant circuit was the underlying mechanism of polymorphic VT in a substrate of enhanced spatial heterogeneity of refractoriness.
authors.affiliation: Physiology Department, Maastricht University, Maastricht, The Netherlands.
authors.forename: Lucas
authors.initials: L
authors.lastname: Boersma
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Zetelaki
authors.forename: Josep
authors.initials: J
authors.lastname: Brugada
authors.forename: Maurits
authors.initials: M
authors.lastname: Allessie
mesh_terms: D000818:Animals; D018780:Body Surface Potential Mapping; D003080:Cold Temperature; D004558:Electric Stimulation; D005260:Female; D006321:Heart; D007700:Kinetics; D008297:Male; D009924:Organ Culture Techniques; D011817:Rabbits; D017180:Tachycardia, Ventricular / Q000209:etiology; D016276:Ventricular Function