title: Regional cooling facilitates termination of spiral-wave reentry through unpinning of rotors in rabbit hearts.
abstract: BACKGROUND
  Moderate global cooling of myocardial tissue was shown to destabilize 2-dimensional (2-D) reentry and facilitate its termination.
  
  
  OBJECTIVE
  This study sought to test the hypothesis that regional cooling destabilizes rotors and facilitates termination of spontaneous and DC shock-induced subepicardial reentry in isolated, endocardially ablated rabbit hearts.
  
  
  METHODS
  Fluorescent action potential signals were recorded from 2-D subepicardial ventricular myocardium of Langendorff-perfused rabbit hearts. Regional cooling (by 5.9°C ± 1.3°C) was applied to the left ventricular anterior wall using a transparent cooling device (10 mm in diameter).
  
  
  RESULTS
  Regional cooling during constant stimulation (2.5 Hz) prolonged the action potential duration (by 36% ± 9%) and slightly reduced conduction velocity (by 4% ± 4%) in the cooled region. Ventricular tachycardias (VTs) induced during regional cooling terminated earlier than those without cooling (control): VTs lasting >30 seconds were reduced from 17 of 39 to 1 of 61. When regional cooling was applied during sustained VTs (>120 seconds), 16 of 33 (48%) sustained VTs self-terminated in 12.5 ± 5.1 seconds. VT termination was the result of rotor destabilization, which was characterized by unpinning, drift toward the periphery of the cooled region, and subsequent collision with boundaries. The DC shock intensity required for cardioversion of the sustained VTs decreased significantly by regional cooling (22.8 ± 4.1 V, n = 16, vs 40.5 ± 17.6 V, n = 21). The major mode of reentry termination by DC shocks was phase resetting in the absence of cooling, whereas it was unpinning in the presence of cooling.
  
  
  CONCLUSIONS
  Regional cooling facilitates termination of 2-D reentry through unpinning of rotors.
authors.affiliation: Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Chikusa-ku, Nagoya, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Yamazaki
authors.forename: Haruo
authors.initials: H
authors.lastname: Honjo
authors.forename: Takashi
authors.initials: T
authors.lastname: Ashihara
authors.forename: Masahide
authors.initials: M
authors.lastname: Harada
authors.forename: Ichiro
authors.initials: I
authors.lastname: Sakuma
authors.forename: Kazuo
authors.initials: K
authors.lastname: Nakazawa
authors.forename: Natalia
authors.initials: N
authors.lastname: Trayanova
authors.forename: Minoru
authors.initials: M
authors.lastname: Horie
authors.forename: Jérôme
authors.initials: J
authors.lastname: Kalifa
authors.forename: José
authors.initials: J
authors.lastname: Jalife
authors.forename: Kaichiro
authors.initials: K
authors.lastname: Kamiya
authors.forename: Itsuo
authors.initials: I
authors.lastname: Kodama
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D003080:Cold Temperature; D006321:Heart / Q000502:physiology*; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D011817:Rabbits; D017180:Tachycardia, Ventricular / Q000503:physiopathology*; D056969:Voltage-Sensitive Dye Imaging