title: Identification of unusual reentry circuit sites of nonischemic ventricular outflow tract tachycardia.
abstract: BACKGROUND
  Reentrant ventricular outflow tract (OT) tachycardia is rare in patients with nonischemic heart disease. The mechanism of ventricular tachycardia (VT) arising from the region of the aortic sinus of Valsalva (ASOV) is usually focal, rather than reentrant. Consequently, less is known about reentrant circuits in the OT and the aortic sinuses. The purpose of this study was to evaluate existence of reentry circuits in these areas using entrainment mapping techniques.
  
  
  METHODS
  We performed electrophysiological study in 51 consecutive patients with idiopathic or nonischemic symptomatic VT arising from the OT. Six of these patients were found to have VT of reentrant mechanism with 8 VT morphologies. Entrainment mapping, electroanatomical mapping (in 2 patients), and radiofrequency catheter ablation were performed.
  
  
  RESULTS
  Pacing entrained the VT at 93 sites, 52 of which were determined to be in the reentry circuit based on matching of the postpacing interval and VT cycle length. Of the reentry circuit sites, 6 were in the aortic sinus, 43 were below the aortic valve, and 3 were in the right OT below the pulmonary valve. Classification of reentry circuit sites identified 7 as exit, 1 as central-proximal, 19 as inner loop, and 25 as outer loop sites. Catheter ablation terminated VT at 4 of the 6 aortic sinus sites and 4 of the 46 OT sites (P = 0.0006).
  
  
  CONCLUSIONS
  We definitively demonstrated involvement of the ASOV in OT reentrant tachycardia using entrainment mapping. It may be useful for successful VT ablation to identify reentry circuit localization.
authors.affiliation: Cardiovascular Division, Kawasaki Municipal Tama Hospital, Kawasaki, Kanagawa, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Nakano
authors.forename: Tomoo
authors.initials: T
authors.lastname: Harada
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Aonuma
authors.forename: Kyoko
authors.initials: K
authors.lastname: Soejima
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Wakimoto
authors.forename: Naoki
authors.initials: N
authors.lastname: Matsumoto
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Miyake
mesh_terms: D000368:Aged; D017115:Catheter Ablation / Q000379:methods; D004562:Electrocardiography / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012850:Sinus of Valsalva / Q000503:physiopathology*; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D014694:Ventricular Outflow Obstruction / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery