title: Demonstration of a posterior atrial input to the atrioventricular node during sustained anterograde slow pathway conduction.
abstract: OBJECTIVE
  This study sought to demonstrate electrophysiologic evidence for the existence of different anatomic atrial input sites of fast and slow conduction pathways in patients with dual atrioventricular (AV) node physiology.
  
  
  BACKGROUND
  Although a separate posterior exit site exists for a retrograde slow AV node pathway, it remains unresolved whether a separate atrial input site into the AV node actually exists in patients with dual anterograde AV node pathway physiology.
  
  
  METHODS
  In 10 patients with dual AV node pathway physiology, atrial pacing at three chosen drive cycle lengths (DCL1, DCL2 and DCL3) was performed at an anterior site (A) just above the His bundle recording site and at a posterior atrial site (P) just below the coronary sinus ostium. DCL3 was chosen as the one cycle length that resulted in a long AH interval consistent with slow pathway conduction. The stimulus to His bundle conduction times (SH) at both sites (SH(P) and SH(A), respectively) and their differences (deltaSH = SH(P) - SH(A)) at each of the three drive cycle lengths were analyzed.
  
  
  RESULTS
  The mean +/- SD deltaSH values for DCL1 and DCL2 measured 9 +/- 16 and 8 +/- 18 ms, respectively, and the mean deltaSH value at DCL3 measured -34 +/- 24 ms, which was significantly different from the mean deltaSH values at DCL1 and DCL2 (both p < 0.05).
  
  
  CONCLUSIONS
  The significant change in the deltaSH (SH(P) - SH(A)) value during slow pathway conduction could be accounted for by a corresponding shift of anterograde input from an anterior to a posterior entry site to the AV node. These findings support the notion that a separate anterograde entry site of the slow pathway does exist in patients with dual AV node pathway physiology.
authors.affiliation: Cardiac Electrophysiology Laboratories, Kaiser Foundation Hospital-Santa Teresa, San Jose, California, USA. charlie.young@ncal.kaiser.org
authors.forename: C
authors.initials: C
authors.lastname: Young
authors.forename: M R
authors.initials: MR
authors.lastname: Lauer
authors.forename: L B
authors.initials: LB
authors.lastname: Liem
authors.forename: H
authors.initials: H
authors.lastname: Chun
authors.forename: R J
authors.initials: RJ
authors.lastname: Sung
mesh_terms: D001283:Atrioventricular Node / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004594:Electrophysiology; D006801:Humans; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology* / Q000628:therapy