title: Utility of tachycardia cycle length variability in discriminating atrial tachycardia from ventricular tachycardia.
abstract: BACKGROUND
  Inappropriate implantable cardioverter-defibrillator (ICD) therapy of atrial tachycardia (AT) with 1:1 atrioventricular (AV) conduction is common because it is difficult to discriminate from ventricular tachycardia (VT) with 1:1 retrograde conduction. Tachycardia cycle length (CL) variability and the relationship between atrial and ventricular CLs may be useful in discriminating AT from VT with 1:1 retrograde conduction.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the usefulness of the relationship between the atrial and ventricular CLs in differentiating AT with 1:1 conduction from VT with 1:1 retrograde conduction.
  
  
  METHODS
  We studied 71 patients who had a tachycardia with a 1:1 AV relationship and significant CL variability. Thirty-nine patients had AT (21 inducible and 18 simulated), and 32 patients had VT (11 inducible and 21 simulated). The relationship between atrial and ventricular CLs was examined.
  
  
  RESULTS
  A change in atrial CL predicted the change in subsequent ventricular CL in 37 (95%) of 39 patients with AT and in none of the patients with VT. A change in preceding ventricular CL predicted the change in atrial CL in 31 (97%) of 32 patients with VT and in only one (3%) of 39 patients with AT. The sensitivity, specificity, and positive and negative predictive values of a change in atrial CL predicting the change in ventricular CL for AT with significant CL variability were 95%, 100%, 100%, and 94%, respectively. The corresponding values for the change in preceding ventricular CL predicting the change in atrial CL for AT with significant CL variability were 97%.
  
  
  CONCLUSIONS
  The relationship between atrial and ventricular CL is useful in differentiating AT from VT with retrograde conduction. A change in atrial CL that predicts the change in subsequent ventricular CL rules in AT and excludes VT.
authors.affiliation: Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI, USA. kritj@med.umich.edu
authors.forename: Krit
authors.initials: K
authors.lastname: Jongnarangsin
authors.forename: Satchana
authors.initials: S
authors.lastname: Pumprueg
authors.forename: Narawudt
authors.initials: N
authors.lastname: Prasertwitayakij
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Crawford
authors.forename: Siddharth
authors.initials: S
authors.lastname: Mukerji
authors.forename: Rita
authors.initials: R
authors.lastname: McLemore-McGregor
authors.forename: Carol
authors.initials: C
authors.lastname: Chen-Scarabelli
authors.forename: Matthew
authors.initials: M
authors.lastname: Ebinger
authors.forename: Eric
authors.initials: E
authors.lastname: Good
authors.forename: Aman
authors.initials: A
authors.lastname: Chugh
authors.forename: Frank
authors.initials: F
authors.lastname: Bogun
authors.forename: Frank
authors.initials: F
authors.lastname: Pelosi
authors.forename: Hakan
authors.initials: H
authors.lastname: Oral
authors.forename: Fred
authors.initials: F
authors.lastname: Morady
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D016009:Chi-Square Distribution; D017147:Defibrillators, Implantable; D003937:Diagnosis, Differential; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013617:Tachycardia, Supraventricular / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy