title: Detection of a local slow potential preceding the surface QRS complex during non-preexcited impulse propagation--a phenomenon reflecting anterograde concealed conduction through the accessory pathway?
abstract: A case of Wolff-Parkinson-White (WPW) syndrome with several interesting electrophysiologic findings is presented. Although manifest preexcitation had not been documented in clinical routine check-ups for the 2 years before the ablation session, an intermittent preexcitation emerged after an initial unsuccessful radiofrequency current delivery directed at the subvalvular mitral annulus 1 cm distal from the subsequent successful ablation site. During intermittent manifestation of preexcitation, the following observations were made: (1) during manifest preexcitation, a possible Kent potential was recorded at the successful ablation site; (2) during non-preexcited impulse propagation, a local slow potential preceding the QRS complex (pre-QRS potential) was clearly observed at the same site; (3) the pre-QRS potential disappeared during orthodromic atrioventricular reciprocating tachycardia, spontaneous atrial premature contraction and after the subsequent successful ablation; and (4) when the pre-QRS potential was obvious, a small change in QRS morphology of the body-surface ECG was appreciable, compared with that during beats of negative pre-QRS potential. A comparable preceding component was also detected in a signal-averaged ECG. It is considered that the pre-QRS potential might be related to the anterograde concealed conduction through the accessory pathway.
authors.affiliation: First Department of Internal Medicine, Nippon Medical School, Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Y
authors.initials: Y
authors.lastname: Miyauchi
authors.forename: N
authors.initials: N
authors.lastname: Kawaguchi
authors.forename: K
authors.initials: K
authors.lastname: Ohmura
authors.forename: H
authors.initials: H
authors.lastname: Saitoh
authors.forename: T
authors.initials: T
authors.lastname: Ino
authors.forename: H
authors.initials: H
authors.lastname: Atarashi
authors.forename: T
authors.initials: T
authors.lastname: Katoh
authors.forename: H
authors.initials: H
authors.lastname: Kishida
authors.forename: H
authors.initials: H
authors.lastname: Hayakawa
mesh_terms: D004594:Electrophysiology; D006321:Heart / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011226:Pre-Excitation Syndromes / Q000503:physiopathology; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology*