title: Slow pathway ablation decreases vulnerability to pacing-induced atrial fibrillation: Possible role of vagal denervation.
abstract: BACKGROUND
  Studies indicate that success of radiofrequency (RF) ablation of atrial fibrillation (AF) may be in part due to vagal denervation. RFAof supraventricular tachycardia (SVT) has been associated with vagal denervation. The effects of slow pathway (SP) ablation on AF inducibility have not been studied.
  
  
  OBJECTIVE
  To test the hypothesis that SP ablation renders AF less inducible.
  
  
  METHODS
  Consecutive patients referred for SVT were studied. After atrioventricular nodal reentrant tachycardia (AVNRT) was confirmed they underwent induction of AF. After SP ablation AF induction was reattempted. Vulnerability to AF was reassessed.
  
  
  RESULTS
  Twenty-four patients were enrolled; eight were not inducible for AF in the preablative state. Mean CLof the AVNRT was 340 +/- 16 ms. The average RF ablation time was 131 +/- 42 seconds. Presence of junctional rhythm was required. Of the 16 with inducible AF two patients had AF induced during routine invasive electrophysiology study. None of these had inducible AF after SP ablation. Fourteen of 16 patients required specific AF induction. Ten of these were noninducible after SP ablation; two were inducible after SP ablation but with a more aggressive pacing protocol (P < 0.03 compared to preablation) and two had no change in AF vulnerability. Seven of the eight noninducible patients remained noninducible for AF post SP ablation. In the 12 patients who were inducible prior but noninducible after ablation the mean atrial effective refractory period (AERP) increased for both BCL at 400 and 600 ms (400/216 +/- 8 ms preablation vs 400/248 +/- 12 ms postablation, P < 0.03; 600/228 +/- 8 ms preablation vs 600/259 +/- 6 ms postablation, P < 0.04). There were no significant changes in AERP of patients who remained inducible or who were noninducible before ablation. The average ablation time for patients who became noninducible after ablation was significantly higher than those who had no change in inducibility or remained inducible but at a more aggressive pacing threshold (157 +/- 24 seconds vs 35 +/- 5 seconds; P < 0.005).
  
  
  CONCLUSIONS
  SP ablation acutely decreases vulnerability to pacing-induced AF in patients with AVNRT. This may reflect the effect of ablation on atrial vagal tone.
authors.affiliation: Texas Heart Institute/St. Luke's Episcopal Hospital, Houston, Texas 77030, USA. mehdirazavi@mailsnare.net
authors.forename: Mehdi
authors.initials: M
authors.lastname: Razavi
authors.forename: Jie
authors.initials: J
authors.lastname: Cheng
authors.forename: Abdi
authors.initials: A
authors.lastname: Rasekh
authors.forename: Donghui
authors.initials: D
authors.lastname: Yang
authors.forename: Scott
authors.initials: S
authors.lastname: Delapasse
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Ai
authors.forename: Thomas
authors.initials: T
authors.lastname: Meade
authors.forename: Alan
authors.initials: A
authors.lastname: Donsky
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Goodman
authors.forename: Ali
authors.initials: A
authors.lastname: Massumi
mesh_terms: D001281:Atrial Fibrillation / Q000209:etiology / Q000517:prevention & control*; D017763:Autonomic Denervation / Q000379:methods*; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D017115:Catheter Ablation / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000601:surgery*; D016896:Treatment Outcome; D014630:Vagus Nerve / Q000601:surgery*