title: Method for differentiating left superior pulmonary vein exit conduction from pseudo-exit conduction.
abstract: BACKGROUND
  Electrical isolation of pulmonary vein (PV) conduction from the left atrium (LA) is the cornerstone of successful atrial fibrillation (AF) ablation. Exit block is confirmed by the absence of LA capture during pacing from a circular mapping catheter positioned in the PV; however, far-field capture of the left atrial appendage (LAA) (pseudo-pulmonary vein exit conduction) can occur. In this study, we evaluated a methodology for identifying pseudo-exit conduction.
  
  
  RESULTS
  A total of 135 consecutive AF patients undergoing PV isolation were studied. After circumferential ablation established PV entrance block, circumferential pacing (10 mA at 2.0 msec) was performed to assess exit block. In 16 (11.9%) patients, pacing the anterior poles of the left superior PV (LSPV) captured the LA. To differentiate true PV exit conduction from pseudo-exit conduction, the ablation catheter was positioned within the LAA during PV pacing. LAA activation preceding PV capture was consistent with far-field capture and this was confirmed by demonstrating local capture and exit block with decreasing pacing output. Using this approach, 14 patients (10.4%) were identified with pseudo-exit conduction.
  
  
  CONCLUSIONS
  Due to the close proximity between the LSPV and LAA, pseudo-exit conduction is not uncommon and may lead to the erroneous conclusion that the LSPV is not isolated. Using this method to differentiate pseudo-exit conduction from true exit conduction should prevent unnecessary ablation after achievement of complete PV isolation.
authors: Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, NY 10021, USA.
authors: James E
authors: JE
authors: Ip
authors: Steven M
authors: SM
authors: Markowitz
authors: Jim W
authors: JW
authors: Cheung
authors: Christopher F
authors: CF
authors: Liu
authors: George
authors: G
authors: Thomas
authors: Seth J
authors: SJ
authors: Lessner
authors: Joseph M
authors: JM
authors: Lee
authors: Bruce B
authors: BB
authors: Lerman
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000601:surgery*; D002320:Cardiovascular Physiological Phenomena; D017115:Catheter Ablation; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011667:Pulmonary Veins / Q000503:physiopathology*