title: Characterization of transient atrial rhythm occurring between typical atrial flutter and its termination with class III drugs.
abstract: BACKGROUND
  The transient atrial rhythm intervened between atrial flutter (AFL) and its termination during class III antiarrhythmic drug therapy for AFL has not been characterized well.
  
  
  METHODS
  Eighteen patients with typical AFL were included in this study. The transient atrial rhythms converted from AFL with different class III antiarrhythmic drugs, ibutilide (group 1, N = 8) and nifekalant (group 2, N = 10), were determined.
  
  
  RESULTS
  AFL terminated, without any intervened transient atrial rhythms, due to conduction block within the isthmus in three patients in each group. The transient atrial rhythm could be characterized into the following types of rhythm based on the initiating mechanisms. (1) The lower-loop reentry or atrial fibrillation that was triggered by a premature excitation in the lateral right atrium caused by breakdown of a functional barrier predisposed AFL to the termination in three patients in each group. (2) The return excitation that repetitively emerged within the isthmus collided with the antegrade excitation, resulting in the termination in two group 1 patients and in one group 2 patient. In the patients who developed these atrial rhythms, the cycle length (CL) oscillation coincidently increased with emergence of such rhythms and became significantly greater than that in the patients who did not develop such transient rhythms (P < 0.05).
  
  
  CONCLUSIONS
  The transient atrial rhythms that emerged with class III drugs are associated with the disruption of the stable AFL reentry that may be triggered by similar electrophysiologic mechanisms with different class III drugs. The increased flutter CL oscillation developing after such drugs might signal the AFL termination.
authors.affiliation: Division of Cardiology, Department of Medicine, Nippon Medical School, Tokyo, Japan. morita@nms.ac.jp
authors.forename: Norishige
authors.initials: N
authors.lastname: Morita
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Yu-Ki
authors.initials: YK
authors.lastname: Iwasaki
authors.forename: Meiso
authors.initials: M
authors.lastname: Hayashi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Miyauchi
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Atarashi
authors.forename: Keiji
authors.initials: K
authors.lastname: Tanaka
authors.forename: Takao
authors.initials: T
authors.lastname: Katoh
authors.forename: Kyoichi
authors.initials: K
authors.lastname: Mizuno
mesh_terms: D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage*; D001282:Atrial Flutter / Q000175:diagnosis* / Q000188:drug therapy*; D004562:Electrocardiography / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome
chemical_list: D000889:Anti-Arrhythmia Agents