title: Electrophysiologic delineation of the tachycardia circuit in the slow-slow form of atrioventricular nodal reentrant tachycardia.
abstract: BACKGROUND
  Little is known about the exact boundaries of the reentrant circuit in the slow-slow form of atrioventricular nodal reentrant tachycardia (AVNRT).
  
  
  OBJECTIVE
  The purpose of this study was to examine the tachycardia circuit in the slow-slow form of AVNRT.
  
  
  METHODS
  Single extrastimuli were delivered during the slow-slow form of AVNRT at 10 sites along the right interatrial septum: superior portion of the His-bundle (HB) site, the HB site, three equidistantly divided sites of the AV junction between HB site and coronary sinus ostium (CSOS; sites S, M, and I), and inferior, superior, posterior, posteroinferior, and internal portions of the CSOS in 13 patients. The longest coupling interval of a single extrastimulus that reset the tachycardia and the following return cycle were measured.
  
  
  RESULTS
  The tachycardia cycle length was 409 +/- 50 ms. The earliest atrial electrogram during tachycardia was observed at site I in all patients. The longest coupling intervals at superior-HB, HB site, sites S, M, and I, and inferior-CSOS, superior-CSOS, posterior-CSOS, posteroinferior-CSOS, and internal-CSOS were 340 +/- 52, 355 +/- 50, 367 +/- 50, 378 +/- 51, 398 +/- 49, 398 +/- 52, 355 +/- 60, 351 +/- 50, 371 +/- 48, and 363 +/- 54 ms, respectively. The following return cycles were 468 +/- 52, 453 +/- 52, 442 +/- 52, 431 +/- 50, 411 +/- 52, 410 +/- 49, 454 +/- 45, 457 +/- 57, 438 +/- 54, and 445 +/- 53 ms, respectively. The longest coupling intervals at site I and inferior-CSOS were significantly longer than those at the other sites (P <.0001). The return cycles at site I and inferior-CSOS did not differ from the tachycardia cycle length, whereas those at the other sites were significantly longer than the tachycardia cycle length (P <.0001).
  
  
  CONCLUSIONS
  Site I and inferior-CSOS are involved in the slow-slow form of AVNRT circuit, and the atrial tissue between those sites form an integral limb of the reentrant circuit.
authors.affiliation: Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan. yamabe_hi@ybb.ne.jp
authors.forename: Hiroshige
authors.initials: H
authors.lastname: Yamabe
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Kenji
authors.initials: K
authors.lastname: Morihisa
authors.forename: Takashi
authors.initials: T
authors.lastname: Uemura
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kawano
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Nagayoshi
authors.forename: Sunao
authors.initials: S
authors.lastname: Kojima
authors.forename: Hisao
authors.initials: H
authors.lastname: Ogawa
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001283:Atrioventricular Node / Q000503:physiopathology*; D002036:Bundle of His / Q000503:physiopathology*; D017115:Catheter Ablation; D003331:Coronary Vessels / Q000503:physiopathology*; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology* / Q000628:therapy