title: Comparison of atrial-His intervals during tachycardia and atrial pacing in patients with long RP tachycardia.
abstract: BACKGROUND
  The purpose of this study is to describe a simple and reliable diagnostic maneuver that allows for the rapid differentiation of atypical AV nodal reentrant tachycardia (AVNRT) from other causes of long RP tachycardia. Long RP tachycardias may be caused by atypical AVNRT, orthodromic reciprocating tachycardia (ORT) involving a slowly conducting retrograde accessory pathway, or atrial tachycardia. The differentiation of atypical AVNRT from ORT or atrial tachycardia may be difficult, especially when the differential diagnosis includes a posteroseptal accessory pathway or an atrial tachycardia arising in the posteroseptal right atrium.
  
  
  RESULTS
  Twelve patients with atypical AVNRT, 21 with ORT, and 12 with an atrial tachycardia diagnosed using conventional criteria were enrolled in this study. The atrial-His (AH) interval was measured at the His-bundle position during the tachycardia and during atrial pacing from the high right atrium at the tachycardia cycle length in the setting of sinus rhythm. In patients with atypical AVNRT, the mean AH interval was 69 69 msec +/- 50 msec (+/- SD) longer during high right atrial pacing than during the tachycardia (P < 0.001). In 10 of 12 patients with atypical AVNRT, the AH interval during atrial pacing was more than 40 msec longer than the AH interval measured during the tachycardia. In contrast, in patients with ORT or atrial tachycardia, the differences in AH interval between atrial pacing and tachycardia were never more than 20 and 10 msec, respectively.
  
  
  CONCLUSIONS
  The difference in the AH interval between atrial pacing and the tachycardia allows a simple and rapid means of differentiating atypical AVNRT from other types of long RP tachycardias.
authors.affiliation: Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0022, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Man
authors.forename: M
authors.initials: M
authors.lastname: Niebauer
authors.forename: E
authors.initials: E
authors.lastname: Daoud
authors.forename: S A
authors.initials: SA
authors.lastname: Strickberger
authors.forename: W
authors.initials: W
authors.lastname: Kou
authors.forename: B D
authors.initials: BD
authors.lastname: Williamson
authors.forename: F
authors.initials: F
authors.lastname: Morady
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002036:Bundle of His / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D003937:Diagnosis, Differential; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D013612:Tachycardia, Ectopic Atrial / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy