title: Right and left inferior extensions of the atrioventricular node may represent the anatomic substrate of the slow pathway in humans.
abstract: OBJECTIVE
  The purpose of this study was to investigate the electrophysiologic characteristics of the inferior extensions of the human atrioventricular (AV) node and their possible relationship to slow pathway conduction.
  
  
  BACKGROUND
  The human heart contains right and left inferior extensions of the AV node that relate to right and left atrial inputs.
  
  
  METHODS
  Fourteen patients admitted for catheter ablation of left-sided accessory pathways were studied. Atrial pacing was performed from multiple sites in both atria, and simultaneous His-bundle recordings from right and left sides of the septum were made.
  
  
  RESULTS
  Significant differences of A-H and stimulus to His (St-H) intervals with pacing at various sites were found. St-H intervals were similar during constant pacing from the low right atrium or the left inferoparaseptal area (112 +/- 28 ms vs 112 +/- 26 ms, P = .8, for right His recordings and 114 +/- 23 ms vs 111 +/- 25 ms, P = .9, for left His recordings). At maximum decrement, there were significantly shorter St-H intervals during left inferoparaseptal pacing compared to low right atrial pacing (201 +/- 24 ms vs 218 +/- 44 ms, P = .02, for right His recordings, and 200 +/- 24 ms vs 219 +/- 41 ms, P = .009, for left His recordings). Differences on right His recordings between St-H intervals at maximum decrement and at constant pacing from the low right atrium were significantly higher than corresponding differences on left His recordings during pacing from the left inferoparaseptal area (P = .035).
  
  
  CONCLUSIONS
  Our findings support the concept that the right and left inferior extensions of the human AV node may represent the anatomic substrate of the slow pathway as defined electrophysiologically.
authors.affiliation: Department of Cardiology, Athens Euroclinic, Greece. dkatrits@otenet.gr
authors.forename: Demosthenes G
authors.initials: DG
authors.lastname: Katritsis
authors.forename: Anton E
authors.initials: AE
authors.lastname: Becker
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Ellenbogen
authors.forename: Ilias
authors.initials: I
authors.lastname: Karabinos
authors.forename: Eleftherios
authors.initials: E
authors.lastname: Giazitzoglou
authors.forename: Socrates
authors.initials: S
authors.lastname: Korovesis
authors.forename: A John
authors.initials: AJ
authors.lastname: Camm
mesh_terms: D000328:Adult; D001146:Arrhythmia, Sinus / Q000503:physiopathology / Q000601:surgery; D001283:Atrioventricular Node / Q000502:physiology*; D002036:Bundle of His / Q000502:physiology; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged