title: Left atrial flutter accelerates during ablation of atrial fibrillation: a paradoxical effect of electrical remodelling.
abstract: OBJECTIVE
  Atrial fibrillation (AF)-induced electrical remodelling causes shortening of refractory period and slowing of conduction velocity. During the course of catheter ablation of AF, there are often transitions from AF to left atrial flutter (AFL) and from faster to slower AFL. The purpose of this study was to characterize the time course of change in AFL rate during AF ablation.
  
  
  RESULTS
  Fourier transformation was performed on 16 s segments of coronary sinus and ablation catheter bipolar electrograms. Ablation-induced AF-to-AFL and AFL-to-AFL transitions were defined as a sudden drop in the dominant frequency (DF) of at least 10 bpm, followed by a regular rhythm. Forty-five transitions were detected in 24 ablation procedures. The mean DF in AF was 5.31 ± 0.79 Hz, which was significantly faster than AFL, 4.52 ± 0.62 Hz (P< 0.05). The mean ΔDF at transitions was -51 ± 16 bpm in AF and -40 ± 14 bpm in AFL. Dominant frequency slope was positive (rate increased) after all the transitions during AF (P< 0.0001) and in 11 of 14 transitions in AFL (P= 0.033). The time constant of the DF recovery curve was 161 ± 105 s.
  
  
  CONCLUSIONS
  After ablation-induced transition from AF to AFL, or faster to slower AFL, there is a progressive increase in AFL rate over time. The mechanism of this acceleration is uncertain, but the time constant of this rate increase is consistent with the recovery of the slow/ultraslow sodium current in the setting of established electrical remodelling.
authors.affiliation: Division of Cardiology, Emory University, Atlanta, GA, USA. shahriar.x.iravanian@kp.org
authors.forename: Shahriar
authors.initials: S
authors.lastname: Iravanian
authors.forename: Michael S
authors.initials: MS
authors.lastname: Lloyd
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Langberg
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D001282:Atrial Flutter / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery*; D017115:Catheter Ablation; D004562:Electrocardiography / Q000379:methods; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods; D005260:Female; D005583:Fourier Analysis; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular