title: Differential effect of adenosine on anterograde and retrograde fast pathway conduction in patients with atrioventricular nodal reentrant tachycardia.
abstract: BACKGROUND
  Several studies have shown that the fast pathway is more responsive to adenosine than the slow pathway in patients with AV nodal reentrant tachycardia. Little information is available regarding the effect of adenosine on anterograde and retrograde fast pathway conduction.
  
  
  RESULTS
  The effects of adenosine on anterograde and retrograde fast pathway conduction were evaluated in 116 patients (mean age 47 +/- 16 years) with typical AV nodal reentrant tachycardia. Each patient received 12 mg of adenosine during ventricular pacing at a cycle length 20 msec longer than the fast pathway VA block cycle length and during sinus rhythm or atrial pacing at 20 msec longer than the fast pathway AV block cycle length. Anterograde block occurred in 98% of patients compared with retrograde fast pathway block in 62% of patients (P < 0.001). Unresponsiveness of the retrograde fast pathway to adenosine was associated with a shorter AV block cycle length (374 +/- 78 vs 333 +/- 74 msec, P < 0.01), a shorter VA block cycle length (383 +/- 121 vs 307 +/- 49 msec, P < 0.001), and a shorter VA interval during tachycardia (53 +/- 23 vs 41 +/- 17 msec, P < 0.01).
  
  
  CONCLUSIONS
  Although anterograde fast pathway conduction is almost always blocked by 12 mg of adenosine, retrograde fast pathway conduction is not blocked by adenosine in 38% of patients with typical AV nodal reentrant tachycardia. This indicates that the anterograde and retrograde fast pathways may be anatomically and/or functionally distinct. Unresponsiveness of VA conduction to adenosine is not a reliable indicator of an accessory pathway.
authors.affiliation: University of Michigan Medical Center, Ann Arbor 48109-0022, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Souza
authors.forename: A
authors.initials: A
authors.lastname: Zivin
authors.forename: M
authors.initials: M
authors.lastname: Flemming
authors.forename: F
authors.initials: F
authors.lastname: Pelosi
authors.forename: H
authors.initials: H
authors.lastname: Oral
authors.forename: B P
authors.initials: BP
authors.lastname: Knight
authors.forename: R
authors.initials: R
authors.lastname: Goyal
authors.forename: K C
authors.initials: KC
authors.lastname: Man
authors.forename: S A
authors.initials: SA
authors.lastname: Strickberger
authors.forename: F
authors.initials: F
authors.lastname: Morady
mesh_terms: D000241:Adenosine; D000328:Adult; D000889:Anti-Arrhythmia Agents; D002316:Cardiotonic Agents; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects* / Q000503:physiopathology; D006801:Humans; D007545:Isoproterenol; D008297:Male; D008875:Middle Aged; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000175:diagnosis* / Q000503:physiopathology
chemical_list: D000889:Anti-Arrhythmia Agents; D002316:Cardiotonic Agents; D000241:Adenosine; D007545:Isoproterenol