title: Electrophysiologic characteristics and radiofrequency catheter ablation in atrioventricular node reentrant tachycardia with second-degree atrioventricular block.
abstract: BACKGROUND
  Detailed electrophysiologic study of AV nodal reentrant tachycardia (AVNRT) with 2:1 AV block has been limited.
  
  
  RESULTS
  Six hundred nine consecutive patients with AVNRT underwent electrophysiologic study and radiofrequency catheter ablation of the slow pathway. Twenty-six patients with 2:1 AV block during AVNRT were designated as group I, and those without this particular finding were designated as group II. The major findings of the present study were: (1) group I patients had better anterograde and retrograde AV nodal function, shorter tachycardia cycle length (during tachycardia with 1:1 conduction) (307 +/- 30 vs 360 +/- 58 msec, P < 0.001), and higher incidence of transient bundle branch block during tachycardia (18/26 vs 43/609, P < 0.001) than group II patients; (2) 21 (80.8%) group I patients had alternans of AA intervals during AVNRT with 2:1 AV block. Longer AH intervals (264 +/- 26 vs 253 +/- 27 msec, P = 0.031) were associated with the blocked beats. However, similar HA intervals (51 +/- 12 vs 50 +/- 12 msec, P = 0.363) and similar HV intervals (53 +/- 11 vs 52 +/- 12, P = 0.834) were found in the blocked and conducted beats; (3) ventricular extrastimulation before or during the His-bundle refractory period bundle could convert 2:1 AV block to 1:1 AV conduction.
  
  
  CONCLUSIONS
  Fast reentrant circuit, rather than underlying impaired conduction of the distal AV node or infranodal area, might account for second-degree AV block during AVNRT. Slow pathway ablation is safe and effective in patients who have AVNRT with 2:1 AV block.
authors.affiliation: Department of Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China.
authors.forename: S H
authors.initials: SH
authors.lastname: Lee
authors.forename: S A
authors.initials: SA
authors.lastname: Chen
authors.forename: C T
authors.initials: CT
authors.lastname: Tai
authors.forename: C E
authors.initials: CE
authors.lastname: Chiang
authors.forename: Z C
authors.initials: ZC
authors.lastname: Wen
authors.forename: K C
authors.initials: KC
authors.lastname: Ueng
authors.forename: C W
authors.initials: CW
authors.lastname: Chiou
authors.forename: Y J
authors.initials: YJ
authors.lastname: Chen
authors.forename: W C
authors.initials: WC
authors.lastname: Yu
authors.forename: J L
authors.initials: JL
authors.lastname: Huang
authors.forename: J J
authors.initials: JJ
authors.lastname: Cheng
authors.forename: M S
authors.initials: MS
authors.lastname: Chang
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation / Q000009:adverse effects; D004594:Electrophysiology; D005260:Female; D006327:Heart Block / Q000150:complications / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000150:complications / Q000503:physiopathology* / Q000601:surgery*