title: Electroanatomic mapping of postpacing intervals clarifies the complete active circuit and variants in atrial flutter.
abstract: BACKGROUND
  Typical atrial flutter is characterized by cavotricuspid isthmus dependence and activation sequentially around the tricuspid annulus (TA), usually counterclockwise. However, analysis of the upper portion of the annulus by postpacing interval after entrainment sometimes suggests it is outside the circuit. Details on the true active circuit are limited, particularly in the upper portions.
  
  
  OBJECTIVE
  The purpose of this study was to define the full active circuit in atrial flutter.
  
  
  METHODS
  In 26 patients with isthmus-dependent atrial flutter, we created detailed electroanatomic maps of postpacing intervals throughout the entire right atrium. Postpacing intervals within 20 ms of the flutter cycle length were defined as within the circuit.
  
  
  RESULTS
  Creating postpacing interval maps allowed characterization of the full active circuit in all patients, and revealed significant variations despite similar counterclockwise or clockwise patterns with activation mapping. In 8, the active circuit was solely around the TA. In 14, an oblique course between the anterior and posterior borders was found, with the upper circuit off the annulus, posterior to the right atrial appendage base. Of these, 8 coursed anterior to the SVC, 5 behind the SVC and 1 bifurcated the SVC. In 4 others, bifurcation of the upper circuit was seen around the right atrial appendage (n = 3), or around the combined right atrial appendage-superior vena cava (n = 1).
  
  
  CONCLUSIONS
  Despite similar activation around the TA, creating electroanatomic postpacing interval maps distinguishes the active flutter circuit from passively activated myocardium. Significant variability exists in the active circuit, with only a minority around the TA. Most commonly, the circuit courses not around a single barrier but obliquely between anterior and posterior borders.
authors.affiliation: Division of Cardiology, Loyola University, Maywood, Illinois, USA. psantucci@lumc.edu
authors.forename: Peter A
authors.initials: PA
authors.lastname: Santucci
authors.forename: Niraj
authors.initials: N
authors.lastname: Varma
authors.forename: Joseph
authors.initials: J
authors.lastname: Cytron
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Akar
authors.forename: David J
authors.initials: DJ
authors.lastname: Wilber
authors.forename: M Obadah
authors.initials: MO
authors.lastname: Al Chekakie
authors.forename: Neil
authors.initials: N
authors.lastname: Brysiewicz
mesh_terms: D000328:Adult; D000368:Aged; D001282:Atrial Flutter / Q000175:diagnosis* / Q000628:therapy*; D018780:Body Surface Potential Mapping; D002304:Cardiac Pacing, Artificial; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial