title: The mechanisms of spontaneous termination of reentrant supraventricular tachycardias.
abstract: BACKGROUND
  Atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT) often terminate spontaneously, presumably due to changes in the electrophysiological properties of the reentrant circuit. However, the mechanism of spontaneous termination of these arrhythmias is incompletely understood.
  
  
  METHODS
  We included 70 consecutive patients with reentrant supraventricular tachycardias (35 AVNRT, 35 AVRT) in whom the arrhythmia ended spontaneously during the electrophysiologic study. We determined in each patient the duration of the induced arrhythmia, site of block, beat-to-beat oscillations in tachycardia cycle-length (CL), A-H, H-V, H-A and V-A intervals.
  
  
  RESULTS
  In 21/34 (62%) patients with AVNRT and 19/30 (63%) with orthodromic AVRT, tachycardia termination was preceded by progressive increase in tachycardia CL due to prolongation of the A-H interval (Mobitz type-I pattern). In 13/34 patients with AVNRT (38%) and 11/30 with orthodromic AVRT (37%), termination occurred suddenly without a preceding change in CL, with block ensuing retrogradely either in the fast AV nodal pathway or the accessory pathway (Mobitz type-II pattern). In 4/5 patients with antidromic AVRT the tachycardia ended at the retrograde limb with previous prolongation of the VA interval.
  
  
  CONCLUSIONS
  Spontaneous termination of AVNRT and AVRT is a time-related phenomenon. Despite different pathways being involved in these two reentrant tachycardias, termination can follow antegrade or retrograde block in similar ratio (60% antegradely and 40% retrogradely). Antegrade block is preceded by prolongation of the AH interval (Mobitz type-I), whereas retrograde block occurs unexpectedly in the retrograde limb (Mobitz type-II). Fatigue of conduction appears to be involved in this phenomenon.
authors.affiliation: School of Medicine, Argentine Catholic University "Santa María de los Buenos Aires", Buenos Aires, Argentina.
authors.forename: Pablo A
authors.initials: PA
authors.lastname: Chiale
authors.affiliation: Cardiac Electrophysiology and Pacing Laboratory, Kingston General Hospital, Ontario, Canada.
authors.forename: Adrián
authors.initials: A
authors.lastname: Baranchuk
authors.affiliation: Clinical Electrophysiology, Hershey Medical Center, Penn State University, PA, USA. Electronic address: mgonzalez@hmc.psu.edu.
authors.forename: Mario D
authors.initials: MD
authors.lastname: González
authors.affiliation: Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, Cardiology Division-J.M. Ramos Mejía Hospital, Buenos Aires, Argentina.
authors.forename: Rubén A
authors.initials: RA
authors.lastname: Sánchez
authors.affiliation: School of Medicine, Argentine Catholic University "Santa María de los Buenos Aires", Buenos Aires, Argentina; Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, Cardiology Division-J.M. Ramos Mejía Hospital, Buenos Aires, Argentina.
authors.forename: Hugo A
authors.initials: HA
authors.lastname: Garro
authors.affiliation: Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, Cardiology Division-J.M. Ramos Mejía Hospital, Buenos Aires, Argentina.
authors.forename: Pablo A
authors.initials: PA
authors.lastname: Fernández
authors.affiliation: Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, Cardiology Division-J.M. Ramos Mejía Hospital, Buenos Aires, Argentina.
authors.forename: Carlos Quiroga
authors.initials: CQ
authors.lastname: Avalos
authors.affiliation: Cardiac Electrophysiology and Pacing Laboratory, Kingston General Hospital, Ontario, Canada.
authors.forename: Andres
authors.initials: A
authors.lastname: Enriquez
authors.affiliation: National Academy of Medicine, Buenos Aires, Argentina.
authors.forename: Marcelo V
authors.initials: MV
authors.lastname: Elizari
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001283:Atrioventricular Node / Q000503:physiopathology*; D002036:Bundle of His / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012075:Remission, Spontaneous; D012189:Retrospective Studies; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology*; D013614:Tachycardia, Paroxysmal / Q000503:physiopathology*; D055815:Young Adult
keywords: AV node reentrant tachycardia; AV reentrant tachycardia; Wenckebach