title: Short atrioventricular Mahaim fibers: observations on their clinical, electrocardiographic, and electrophysiologic profile.
abstract: Short A-V manheim fiber.
  
  
  BACKGROUND
  A short atrioventricular decrementally conducting accessory pathway is an uncommon variant of preexcitation. Available data from small series suggest that their decremental properties might not be caused by A-V nodal-like tissue.
  
  
  METHODS
  We compared clinical, electrocardiographic and electrophysiologic parameters in two groups of patients: 8 patients with a short A-V Mahaim pathway (Group A), and 33 patients with atriofascicular pathways (Group B). Radiofrequency catheter ablation was carried out guided by activation mapping at the annulus in Group A patients and targeting the "M" potential in Group B patients.
  
  
  RESULTS
  After ablation of all associated rapidly conducting bypass tracts, 7 of the 8 Group A patients showed clear preexcitation. In only 1 of 8 patients the short A-V Mahaim fiber was actively engaged in a reentrant tachycardia circuit. During radiofrequency catheter ablation an automatic rhythm occurred in 4 of 8 patients. Intravenous adenosine caused conduction a block in the Mahaim fiber in 3 of the 5 patients tested. In group B, no patient showed clear preexcitation (P<00001) while 72% had a minimal preexcitation pattern. Twenty-nine of the 33 patients had a circus movement tachycardia with AV conduction over the atriofascicular fiber. During radiofrequency catheter ablation 30 of 33 patients showed accessory pathway automaticity. Adenosine caused transient block at the atriofascicular pathway in 11 (92%) of the 12 patients tested.
  
  
  CONCLUSIONS
  While short decrementally conducting right-sided accessory pathways show a typical ECG pattern different from atriofascicular pathways, their electrophysiologic properties do not seem to be uniform. Those pathways can be successfully interrupted by catheter ablation.
authors.affiliation: Biocor Instituto, Nova Lima, Brazil. eduardosternick@aol.com
authors.forename: Eduardo Back
authors.initials: EB
authors.lastname: Sternick
authors.forename: Márcio L
authors.initials: ML
authors.lastname: Fagundes
authors.forename: Fernando E S
authors.initials: FE
authors.lastname: Cruz
authors.forename: Carl
authors.initials: C
authors.lastname: Timmermans
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Sosa
authors.forename: Luz-Maria
authors.initials: LM
authors.lastname: Rodriguez
authors.forename: Luiz M
authors.initials: LM
authors.lastname: Gerken
authors.forename: Maurício I
authors.initials: MI
authors.lastname: Scanavacca
authors.forename: Hein J J
authors.initials: HJ
authors.lastname: Wellens
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000293:Adolescent; D000328:Adult; D001283:Atrioventricular Node / Q000502:physiology; D017115:Catheter Ablation; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D013610:Tachycardia / Q000503:physiopathology / Q000601:surgery
chemical_list: D000255:Adenosine Triphosphate