title: Radiofrequency ablation of a concealed nodoventricular Mahaim fiber guided by a discrete potential.
abstract: BACKGROUND
  We present the case of a 17-year-old woman who underwent an electrophysiological study and radiofrequency (RF) ablation of supraventricular tachycardia refractory to medical treatment. Two right-sided, concealed, nondecremental atrioventricular accessory pathways (AV-APs) involved in orthodromic circus movement tachycardias were identified. After RF ablation of both AV-APs, evidence of bidirectional dual AV nodal conduction was demonstrated and regular narrow complex tachycardia was induced.
  
  
  RESULTS
  During the tachycardia, retrograde slow and fast AV nodal pathway conduction with second-degree ventriculoatrial (VA) block and VA dissociation were observed. During the tachycardia with second-degree VA block, ventricular extrastimuli elicited during His-bundle refractoriness advanced the next His potential or terminated the tachycardia. Mapping the right atrial mid-septal region, a distinct high-frequency activation P potential was recorded in a discrete area, two thirds of the way from the His bundle toward the os of the coronary sinus. Detailed electrophysiologic testing with the recordable P potential demonstrated that the tachycardia utilized a concealed nodoventricular AP arising from the proximal slow AV nodal pathway.
  
  
  CONCLUSIONS
  The tachycardia with slow 1:1 VA conduction could be reset by ventricular extrastimuli elicited during His-bundle refractoriness advancing the subsequent activation P potential and atrial activation. RF ablation guided by recording of the activation P potential resulted in elimination of both the slow AV nodal pathway and the nodoventricular connection with preservation of the normal AV conduction system.
authors.affiliation: Department of Cardiology and Angiology, Elisabeth Hospital, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Hluchy
authors.forename: P
authors.initials: P
authors.lastname: Schlegelmilch
authors.forename: S
authors.initials: S
authors.lastname: Schickel
authors.forename: U
authors.initials: U
authors.lastname: Jörger
authors.forename: O
authors.initials: O
authors.lastname: Jurkovicova
authors.forename: G V
authors.initials: GV
authors.lastname: Sabin
mesh_terms: D000293:Adolescent; D002036:Bundle of His / Q000503:physiopathology / Q000601:surgery*; D017115:Catheter Ablation; D004562:Electrocardiography; D005260:Female; D006801:Humans; D013617:Tachycardia, Supraventricular / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D014927:Wolff-Parkinson-White Syndrome / Q000150:complications / Q000503:physiopathology / Q000601:surgery*