title: Diagnosis and ablation of multiform fascicular tachycardia.
abstract: BACKGROUND
  Fascicular tachycardia (FT) is an uncommon cause of monomorphic sustained ventricular tachycardia (VT). We describe 6 cases of FT with multiform QRS morphologies.
  
  
  RESULTS
  Six of 823 consecutive VT cases were retrospectively analyzed and found attributable to FT with multiform QRS patterns, with 3 cases exhibiting narrow QRS VT as well. All underwent electrophysiology study including fascicular potential mapping, entrainment pacing, and electroanatomic mapping. The first 3 cases describe similar multiform VT patterns with successful ablation in the upper mid septum. Initially, a right bundle branch block (RBBB) VT with superior axis was induced. Radiofrequency catheter ablation (RFCA) targeting the left posterior fascicle (LPF) resulted in a second VT with RBBB inferior axis. RFCA in the upper septum just apical to the LBB potential abolished VT in all cases. Cases 4 and 5 showed RBBB VT with alternating fascicular block compatible with upper septal dependent VT, resulting in bundle branch reentrant VT (BBRT) after ablation of LPF and left anterior fascicle (LAF). Finally, Cases 5 and 6 demonstrated spontaneous shift in QRS morphology during VT, implicating participation of a third fascicle. In Case 6, successful ablation was achieved over the proximal LAF, likely representing insertion of the auxiliary fascicle near the proximal LAF.
  
  
  CONCLUSIONS
  Multiform FTs show a reentrant mechanism using multiple fascicular branches. We hypothesize that retrograde conduction over the septal fascicle produces alternate fascicular patterns as well as narrow VT forms. Ablation of the respective fascicle was successful in abolishing FT but does not preclude development of BBRT unless septal fascicle is targeted and ablated.
authors.affiliation: Electrophysiology Section, Division of Cardiology, Department of Medicine, University of Colorado, Denver, Colorado 80045, USA. raphael.sung@ucdenver.edu
authors.forename: Raphael K
authors.initials: RK
authors.lastname: Sung
authors.forename: Albert M
authors.initials: AM
authors.lastname: Kim
authors.forename: Zian H
authors.initials: ZH
authors.lastname: Tseng
authors.forename: Frederick
authors.initials: F
authors.lastname: Han
authors.forename: Keiichi
authors.initials: K
authors.lastname: Inada
authors.forename: Usha B
authors.initials: UB
authors.lastname: Tedrow
authors.forename: Mohan N
authors.initials: MN
authors.lastname: Viswanathan
authors.forename: Nitish
authors.initials: N
authors.lastname: Badhwar
authors.forename: Paul D
authors.initials: PD
authors.lastname: Varosy
authors.forename: Ronn
authors.initials: R
authors.lastname: Tanel
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Olgin
authors.forename: William G
authors.initials: WG
authors.lastname: Stephenson
authors.forename: Melvin
authors.initials: M
authors.lastname: Scheinman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001900:Boston; D002036:Bundle of His / Q000503:physiopathology / Q000601:surgery*; D002037:Bundle-Branch Block / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation / Q000009:adverse effects; D002648:Child; D022062:Electrophysiologic Techniques, Cardiac; D006801:Humans; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012495:San Francisco; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome; D055815:Young Adult