title: Right ventricular pacing to assess transisthmus conduction in patients undergoing isthmus-dependent atrial flutter ablation: a new useful technique?
abstract: BACKGROUND
  Successful radiofrequency (RF) ablation of typical, isthmus-dependent atrial flutter requires establishment and confirmation of bidirectional conduction block across the cavotricuspid isthmus. Low atrial pacing usually is performed from the bipoles of the 20-pole Halo catheter, septal and lateral to the cavotricuspid isthmus ablation line. However, occasionally this is difficult because of high pacing thresholds and/or saturation of the atrial electrograms recorded near the pacing catheter.
  
  
  OBJECTIVE
  The purpose of this study was to assess if right ventricular (RV) pacing and resulting retrograde atrial activation can be used to assess conduction block from the septum to the lateral wall in a clockwise direction.
  
  
  METHODS
  Thirty-five consecutive male patients (mean age 64 +/- 10 years; mean ejection fraction 42 +/- 13%; mean left atrial dimension 44 +/- 6 mm) with typical isthmus-dependent atrial flutter were studied. The following electrophysiology catheters were used: 20-pole catheter along the tricuspid annulus, quadripolar catheters at the His and/or RV apex, and 8-mm ablation catheter. Following RF ablation of the cavotricuspid isthmus, bidirectional conduction block was confirmed in all 35 patients by pacing at a cycle length of 600 ms from bipoles septal and lateral to the cavotricuspid isthmus ablation line. Conduction times from pacing artifact to adjacent bipolar atrial electrograms and reversal of atrial activation pattern were analyzed. RV pacing was performed and retrograde atrial activation pattern assessed. If retrograde AV nodal conduction was absent, isoproterenol was infused intravenously at 2 microg/min, and RV pacing was repeated. The conduction time between the double potentials across the cavotricuspid isthmus ablation line was measured.
  
  
  RESULTS
  Mean conduction times across the isthmus during septal (S), lateral (L), and RV pacing were 145 +/- 21 ms, 144 +/- 24 ms, and 129 +/- 20 ms, respectively. Retrograde AV nodal conduction was present in 34 of 35 patients (isoproterenol 8 patients). Evidence of conduction block by a clear change in activation pattern across the isthmus was seen during RV pacing in 33 of 35 patients with bidirectional conduction block.
  
  
  CONCLUSIONS
  RV pacing is a simple and easy maneuver that can be performed to assess isthmus conduction in most patients.
authors.affiliation: Division of Cardiac Electrophysiology, Geisinger Wyoming Valley Medical Center, MC 36-10, 1000 E. Mountain Boulevard, Wilkes-Barre, PA 18711, USA. pvijayaraman1@geisinger.edu
authors.forename: Pugazhendhi
authors.initials: P
authors.lastname: Vijayaraman
authors.forename: Lai Chow
authors.initials: LC
authors.lastname: Kok
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wood
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Ellenbogen
mesh_terms: D001282:Atrial Flutter / Q000503:physiopathology / Q000601:surgery*; D018780:Body Surface Potential Mapping; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation / Q000379:methods*; D004562:Electrocardiography; D004594:Electrophysiology; D006329:Heart Conduction System / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome