title: Variation of P-QRS relation during atrioventricular node reentry tachycardia.
abstract: OBJECTIVE
  The main objective of this study was to characterize the phenomenon of variation in the P-QRS relation during atrioventricular node reentry tachycardia.
  
  
  BACKGROUND
  Variation of P-QRS relation during tachycardia has been observed occasionally in atrioventricular node reentry tachycardia. However, the incidence, the characteristics and the mechanisms of this phenomenon have not been investigated previously.
  
  
  METHODS
  Retrospective analysis was performed in 311 consecutive patients with slow-fast form and 108 patients with atypical or multiple form of atrioventricular node reentry tachycardia to examine whether variation of P-QRS relation with changes in AH, HA and AH/HA (A = atria; H = His bundle) ratio occurred during tachycardia.
  
  
  RESULTS
  A total of 28 patients, 8 with slow-fast and 20 with atypical or multiple tachycardias, were found to manifest this phenomenon. There were 6 males and 22 females, with an average age of 38+/-16 years. In 10 patients, this phenomenon occurred transiently following electrical induction of the tachycardia. In 15 patients, changes in AH, HA and AH/HA ratio were associated with the occurrence of Wenckebach or 2:1 block proximal to the His bundle (H) recording site without interruption of the tachycardia. In nine patients, three with nonsustained tachycardia and six after administration of adenosine triphosphate, this phenomenon was observed at the termination of the tachycardia. This phenomenon was usually accompanied by a mild lengthening of the tachycardia cycle length.
  
  
  CONCLUSIONS
  Variation of P-QRS relation with or without block may occur during atrioventricular node reentry tachycardia, especially in atypical or multiple-form tachycardias. It was postulated that decremental conduction in the distal common pathway, which exists between the distal link of the reentry circuit and the H, is primarily responsible for this phenomenon.
authors.affiliation: Department of Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taipei, Taiwan.
authors.forename: Y
authors.initials: Y
authors.lastname: Taniguchi
authors.forename: S J
authors.initials: SJ
authors.lastname: Yeh
authors.forename: M S
authors.initials: MS
authors.lastname: Wen
authors.forename: C C
authors.initials: CC
authors.lastname: Wang
authors.forename: F C
authors.initials: FC
authors.lastname: Lin
authors.forename: D
authors.initials: D
authors.lastname: Wu
mesh_terms: D000255:Adenosine Triphosphate / Q000008:administration & dosage / Q000627:therapeutic use; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001283:Atrioventricular Node / Q000503:physiopathology; D002036:Bundle of His / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial; D002648:Child; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology* / Q000628:therapy