title: Entrainment mapping of dual-loop macroreentry in common atrial flutter: new insights into the atrial flutter circuit.
abstract: BACKGROUND
  The aim of this study was to determine using entrainment mapping whether the reentrant circuit of common type atrial flutter (AFL) is single loop or dual loop.
  
  
  RESULTS
  In 12 consecutive patients with counterclockwise (CCW) AFL, entrainment mapping was performed with evaluation of atrial electrograms from the tricuspid annulus (TA) and the posterior right atrial (RA) area. We hypothesized that a dual-loop reentry could be surmised from "paradoxical delayed capture" of the proximal part of the circuit having a longer interval from the stimulus to the captured beat compared with the distal part of the circuit. In 6 of 12 patients with CCW AFL, during entrainment from the septal side of the posterior blocking line, the interval from the stimulus to the last captured beat was longer at the RA free wall than at the isthmus position. In these six patients with paradoxical delayed capture, flutter cycle length (FCL) was 227 +/- 12 ms and postpacing interval minus FCL was significantly shorter at the posterior blocking line than at the RA free wall (20 +/- 11 ms vs 48 +/- 33 ms, P < 0.05). In two of these patients, early breakthrough occurred at the lateral TA. A posterior block line was confirmed in all six patients in the sinus venosa area by intracardiac echocardiography.
  
  
  CONCLUSIONS
  Half of the patients with common type AFL had a dual-loop macroreentrant circuit consisting of an anterior loop (circuit around the TA) and a posterior loop (circuit around the inferior vena cava and the posterior blocking line).
authors.affiliation: Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Toyama, Japan. fujiki@ms.toyama-mpu.ac.jp
authors.forename: Akira
authors.initials: A
authors.lastname: Fujiki
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Nishida
authors.forename: Masao
authors.initials: M
authors.lastname: Sakabe
authors.forename: Masataka
authors.initials: M
authors.lastname: Sugao
authors.forename: Takayuki
authors.initials: T
authors.lastname: Tsuneda
authors.forename: Koichi
authors.initials: K
authors.lastname: Mizumaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Inoue
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001282:Atrial Flutter / Q000175:diagnosis* / Q000601:surgery; D018780:Body Surface Potential Mapping; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation; D004452:Echocardiography; D004567:Electrodes, Implanted; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006325:Heart Atria / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D006329:Heart Conduction System / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D006346:Heart Septum / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D014261:Tricuspid Valve / Q000601:surgery; D014682:Vena Cava, Inferior / Q000601:surgery