title: Atypical atrioventricular nodal reentrant tachycardia: prevalence, electrophysiologic characteristics, and tachycardia circuit.
abstract: OBJECTIVE
  This study aimed at assessing the prevalence, electrophysiologic characteristics, and mechanism of atypical atrioventricular nodal reentrant tachycardia (AVNRT).
  
  
  RESULTS
  We studied 925 consecutive patients with AVNRT. Atrial-His (AH) and His-atrial (HA) intervals were measured during atypical AVNRT (HA > 70 ms), and compared with measurements in 34 patients with typical (slow-fast) AVNRT. Assuming that conduction velocity over the fast pathway is similar in the anterograde and retrograde directions, the AH interval during the fast-slow form should be smaller than the HA during slow-fast. Atypical AVNRT was diagnosed in 59 patients (6.4%), median age 50 years (range 19-79 years), and 37 (59.7%) of them female. Fast-slow AVNRT was diagnosed in 44 patients (74.5%), and slow-slow AVNRT in 9 patients (15.2%). The remaining six patients (10.2%) could not be reliably classified due to inconsistent AH, and HA/AH patterns or variable intervals. Tachycardia induction with anterograde conduction jumps was seen in two patients with the fast-slow, and in three patients with slow-slow or intermediate forms. Atrial-His in the fast-slow group was significantly longer than HA in the slow-fast group, 99.7 ± 40.5 ms vs. 45.8 ± 7.7 ms, P < 0.001. Tachycardia cycle length was longer in fast-slow compared with slow-fast, 379.1 ± 68.5 ms vs. 317.1 ± 42.8 ms, P < 0.001.
  
  
  CONCLUSIONS
  Of AVNRT cases, 6.4% are atypical and may display patterns that do not necessarily correspond to the fast-slow or slow-slow conventional types. Atypical fast-slow and typical AVNRT do not appear to utilize the same limb for fast conduction.
authors: Athens Euroclinic, Athens, Greece dgkatr@otenet.gr dkatritsis@euroclinic.gr.
authors: Demosthenes G
authors: DG
authors: Katritsis
authors: The Heart Hospital, London, UK.
authors: Ali
authors: A
authors: Sepahpour
authors: Johns Hopkins Hospital, Baltimore, MD, USA.
authors: Joseph E
authors: JE
authors: Marine
authors: The Oxford University Clinical Academic Graduate School, Oxford, UK.
authors: George D
authors: GD
authors: Katritsis
authors: Johns Hopkins Hospital, Baltimore, MD, USA.
authors: Tanyanan
authors: T
authors: Tanawuttiwat
authors: Johns Hopkins Hospital, Baltimore, MD, USA.
authors: Hugh
authors: H
authors: Calkins
authors: The Heart Hospital, London, UK.
authors: Edward
authors: E
authors: Rowland
authors: Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors: Mark E
authors: ME
authors: Josephson
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D004562:Electrocardiography / Q000706:statistics & numerical data*; D005260:Female; D006115:Greece / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D018570:Risk Assessment; D017678:Sex Distribution; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000175:diagnosis* / Q000453:epidemiology*; D006113:United Kingdom / Q000453:epidemiology; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: Atypical atrioventricular nodal tachycardia; Fast-slow tachycardia; Nodal extensions; Slow–slow tachycardia