title: Left posteroseptal Mahaim fiber associated with marked longitudinal dissociation.
abstract: We report a patient who underwent radiofrequency catheter ablation of a left posteroseptal atrioventricular (AV) Mahaim fiber with a marked longitudinal dissociation. During atrial pacing, Wenckebach-type atrioventricular block over the accessory pathway was observed with progressive preexcitation and no change in polarity of the delta waves. The AV conduction curve was discontinuous, with a distinct "jump-up" in local AV conduction time of 84 ms. The earliest ventricular activation was recorded from the posteroseptal portion of the mitral annulus, and the unipolar electrogram from a distal electrode had a high, steep deflection with uniphasic QS-like activity with 62 ms of local AV conduction time.
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tada
authors.forename: A
authors.initials: A
authors.lastname: Nogami
authors.forename: S
authors.initials: S
authors.lastname: Naito
authors.forename: S
authors.initials: S
authors.lastname: Oshima
authors.forename: K
authors.initials: K
authors.lastname: Taniguchi
authors.forename: Y
authors.initials: Y
authors.lastname: Kutsumi
mesh_terms: D000328:Adult; D002036:Bundle of His / Q000503:physiopathology / Q000601:surgery; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation; D004562:Electrocardiography; D006325:Heart Atria / Q000503:physiopathology; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male; D011227:Pre-Excitation, Mahaim-Type / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery