title: Participation of a concealed atriohisian tract in the reentrant circuit of the slow-fast type of atrioventricular nodal reentrant tachycardia.
abstract: BACKGROUND
  The retrograde fast pathway in typical atrioventricular nodal reentrant tachycardia (AVNRT) exhibits marked variation in its electrophysiologic properties.
  
  
  OBJECTIVE
  The purpose of this study was to characterize the retrograde fast pathway and localize the lower turnaround site of the reentrant circuit in typical AVNRT.
  
  
  METHODS
  Seventy-four patients with typical AVNRT were divided into two groups according to the response of the retrograde fast pathway to intravenous administration of adenosine triphosphate (ATP) during ventricular pacing: ATP-S [n = 47 (63.5%)] with and ATP-R without [n = 27 (36.5%)] His-atrial (H-A) block. H-A intervals were measured from the most proximal His-bundle electrogram to the earliest atrial activation during the tachycardia (HAt) and entrainment pacing from the parahisian right ventricular region (HAe). It was postulated that the HAt was the difference in conduction time between the lower common pathway (x) and retrograde fast pathway (y) (HAt = y - x), whereas HAe was the sum of the two (HAe = y + x). Hence, x = (HAe-HAt)/2. x >0 suggested the presence of a lower common pathway, whereas x <0 suggested the absence of a lower common pathway and lower turnaround site within the His bundle.
  
  
  RESULTS
  x was significantly smaller in ATP-R than ATP-S (-6 +/- 5 vs 4 +/- 4 ms, P <.05) and was <0 in 23 (85%) of 27 ATP-R patients. The maximal increment in H-A interval during ventricular pacing was significantly longer in ATP-S than ATP-R (35 +/- 33 vs 2 +/- 2 ms, P <.05).
  
  
  CONCLUSIONS
  A concealed atriohisian tract totally bypassing the atrioventricular node constituted the retrograde fast pathway in one third of all typical AVNRT cases.
authors.affiliation: Division of Cardiology, National Cardiovascular Center, Suita, Japan. k-otomo@fj8.so-net.ne.jp
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Otomo
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Suyama
authors.forename: Hideo
authors.initials: H
authors.lastname: Okamura
authors.forename: Takashi
authors.initials: T
authors.lastname: Noda
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Satomi
authors.forename: Wataru
authors.initials: W
authors.lastname: Shimizu
authors.forename: Takashi
authors.initials: T
authors.lastname: Kurita
authors.forename: Naohiko
authors.initials: N
authors.lastname: Aihara
authors.forename: Shiro
authors.initials: S
authors.lastname: Kamakura
mesh_terms: D001283:Atrioventricular Node / Q000503:physiopathology*; D002036:Bundle of His / Q000503:physiopathology*; D017115:Catheter Ablation; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology* / Q000628:therapy