title: Mechanisms of destabilization and early termination of spiral wave reentry in the ventricle by a class III antiarrhythmic agent, nifekalant.
abstract: Nifekalant (NF) is a novel class III antiarrhythmic agent that is effective in preventing life-threatening ventricular tachycardia/fibrillation (VT/VF). We investigated mechanisms of destabilization and early termination of spiral-type reentrant VT by NF in a two-dimensional subepicardial myocardial layer of Langendorff-perfused rabbit hearts (n = 21) using a high-resolution optical action potential mapping system. During basic stimulation, NF (0.1 microM) caused uniform prolongation of action potential duration (APD) without affecting conduction velocity and an increase of APD restitution slope. VTs induced by direct current stimulation in the presence of NF were of shorter duration (VTs > 30 s: 2/54 NF vs. 19/93 control). During VTs in control (with visible rotors), the wave front chased its own tail with a certain distance (repolarized zone), and they seldom met each other. The average number of phase singularity (PS) points was 1.31 +/- 0.14 per 665 ms (n = 7). In the presence of NF, the wave front frequently encountered its own tail, causing a transient breakup of the spiral wave or sudden movement of the rotation center (spatial jump of PS). The average number of PS was increased to 1.63 +/- 0.22 per 665 ms (n = 7, P < 0.05) after NF. The mode of spontaneous termination of rotors in control was in most cases (9/10, 90.0%) the result of mutual annihilation of counterrotating wave fronts. With NF, rotors frequently terminated by wave front collision with the atrioventricular groove (12/19, 63.2%) or by trapping the spiral tip in a refractory zone (7/19, 36.8%). Destabilization and early termination of spiral wave reentry induced by NF are the result of a limited proportion of excitable tissue after modulation of repolarization.
authors.affiliation: Dept. of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya Univ., Chikusa-ku, Nagoya 464-8601, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Yamazaki
authors.forename: Haruo
authors.initials: H
authors.lastname: Honjo
authors.forename: Harumichi
authors.initials: H
authors.lastname: Nakagawa
authors.forename: Yuko S
authors.initials: YS
authors.lastname: Ishiguro
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Okuno
authors.forename: Mari
authors.initials: M
authors.lastname: Amino
authors.forename: Ichiro
authors.initials: I
authors.lastname: Sakuma
authors.forename: Kaichiro
authors.initials: K
authors.lastname: Kamiya
authors.forename: Itsuo
authors.initials: I
authors.lastname: Kodama
mesh_terms: D000200:Action Potentials; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects / Q000503:physiopathology*; D006352:Heart Ventricles / Q000187:drug effects / Q000503:physiopathology*; D008297:Male; D011744:Pyrimidinones / Q000008:administration & dosage*; D011817:Rabbits; D017180:Tachycardia, Ventricular / Q000188:drug therapy* / Q000503:physiopathology*; D016896:Treatment Outcome
chemical_list: D000889:Anti-Arrhythmia Agents; D011744:Pyrimidinones; C076259:nifekalant