title: Idiopathic focal ventricular arrhythmias originating from the anterior papillary muscle in the left ventricle.
abstract: BACKGROUND
  Focal ventricular arrhythmias (VAs) have been reported to arise from the posterior papillary muscle in the left ventricle (LV). We report a distinct subgroup of idiopathic VAs arising from the anterior papillary muscle (APM) in the LV.
  
  
  RESULTS
  We studied 432 consecutive patients undergoing catheter ablation for VAs based on a focal mechanism. Six patients were identified with ventricular tachycardia (VT, n = 1) or premature ventricular contractions (PVCs, n = 5) with the earliest site of ventricular activation localized to the base (n = 3) or middle portion (n = 3) of the LV APM. No Purkinje potentials were recorded at the ablation site during sinus rhythm or the VAs. All patients had a normal baseline electrocardiogram and normal LV systolic function. The VAs exhibited a right bundle branch block (RBBB) and right inferior axis (RIA) QRS morphology in all patients. Oral verapamil and/or Na(+) channel blockers failed to control the VAs in 4 patients. VT was not inducible by programmed electrical stimulation in any of the patients. In 4 patients, radiofrequency current with an irrigated or conventional 8-mm-tip ablation catheter was required to achieve a lasting success. Two patients had recurrent PVCs after a conventional radiofrequency ablation with a 4-mm-tip ablation catheter had initially suppressed the arrhythmia.
  
  
  CONCLUSIONS
  VAs may arise from the base or middle portion of the APM and are characterized by an RBBB and RIA QRS morphology and focal mechanism. Catheter ablation of APM VAs is typically challenging, and creation of a deep radiofrequency lesion may be necessary for long-term success.
authors.affiliation: Division of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama 35294-0019, USA. takumi-y@fb4.so-net.ne.jp
authors.forename: Takumi
authors.initials: T
authors.lastname: Yamada
authors.forename: H Thomas
authors.initials: HT
authors.lastname: McElderry
authors.forename: Taro
authors.initials: T
authors.lastname: Okada
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Murakami
authors.forename: Harish
authors.initials: H
authors.lastname: Doppalapudi
authors.forename: Naoki
authors.initials: N
authors.lastname: Yoshida
authors.forename: James D
authors.initials: JD
authors.lastname: Allred
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Murohara
authors.forename: G Neal
authors.initials: GN
authors.lastname: Kay
mesh_terms: D000328:Adult; D000368:Aged; D017115:Catheter Ablation / Q000379:methods; D005260:Female; D006352:Heart Ventricles / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D010210:Papillary Muscles / Q000503:physiopathology* / Q000601:surgery; D017180:Tachycardia, Ventricular / Q000503:physiopathology* / Q000601:surgery