title: Ridge-related reentry: a variant of perimitral atrial tachycardia.
abstract: BACKGROUND
  The ridge between the left pulmonary veins (PV) and the left atrial appendage composes part of the lateral mitral isthmus (LMI). Following circumferential PV isolation and LMI linear ablation for the treatment of atrial fibrillation (AF), a critical pathway might develop over the ridge leading to a ridge-related reentry (RRR).
  
  
  RESULTS
  Out of 61 patients who underwent circumferential PV isolation appended by LMI ablation, 5 patients developed RRR. The diagnosis of RRR was based on (1) macro-reentrant atrial tachycardia involving the septum, anterior and inferior wall of the left atrium; (2) slow conduction along the ridge; (3) wide-split double potentials in the ventricular aspect of the LMI were identified with the coronary sinus (CS) electrodes. RRR was investigated with electroanatomical mapping and entrainment mapping and catheter ablation was carried out in all patients. The mean cycle length (CL) of RRR was 312 ± 82 milliseconds and the PPIs at the left atrial septum, inferior and anterior wall during RRR were 10 ± 6, 12 ± 8, 9 ± 5 milliseconds longer than the RRR CL. The interval of the double potentials recorded in the CS electrodes crossing the LMI was 164 ± 38 milliseconds during RRR and the PPI on the LMI near the mitral annulus was 57 ± 10 milliseconds longer than the RRR CL. Catheter ablation was performed anatomically by targeting the ridge and successfully terminated RRR.
  
  
  CONCLUSIONS
  After circumferential PV isolation and ablation for LMI in patients with AF, RRR can develop by utilizing the surviving myocardial tissue of the ridge as a critical pathway.
authors.affiliation: Department of Cardiology, Keio University Hospital, Tokyo, Japan. seiji.takatsuki@gmail.com
authors.forename: Seiji
authors.initials: S
authors.lastname: Takatsuki
authors.forename: Kotaro
authors.initials: K
authors.lastname: Fukumoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Igawa
authors.forename: Takehiro
authors.initials: T
authors.lastname: Kimura
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Nishiyama
authors.forename: Yoshiyasu
authors.initials: Y
authors.lastname: Aizawa
authors.forename: Yoko
authors.initials: Y
authors.lastname: Tanimoto
authors.forename: Kojiro
authors.initials: K
authors.lastname: Tanimoto
authors.forename: Shunichiro
authors.initials: S
authors.lastname: Miyoshi
authors.forename: Keiichi
authors.initials: K
authors.lastname: Fukuda
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology / Q000601:surgery*; D017115:Catheter Ablation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve; D013610:Tachycardia / Q000503:physiopathology / Q000601:surgery*
keywords: atrial fibrillation; catheter ablation; left atrial flutter; left atrial tachycardia; pulmonary vein isolation