title: Atrial premature beats during decrementally conducting antidromic tachycardia.
abstract: BACKGROUND
  Advancement of ventricular activation by an atrial premature beat (APB) given during His bundle refractoriness followed by resetting of an antidromic tachycardia (AT) in patients with decrementally conducting accessory pathway (DAP) is a helpful maneuver to prove pathway existence and participation in the circuit. We aim to assess in a large cohort the role of APB during AT in patients with a DAP.
  
  
  RESULTS
  Thirty-three patients with a DAP having 34 AT were included in the study: 29 patients had an atriofascicular pathway, 1 had a long atrioventricular DAP, and 4 had a short atrioventricular fiber. APBs were delivered initially from the lateral right atrium, scanning diastole with a 10-ms decrement until AT termination or refractoriness. We observed 4 patterns of response after APB during AT: advancement of activation (29 cases), delay (2), advancement followed by delay (3), and termination (7). Eight patients required an earlier APB to advance or delay ventricular activation. These 8 patients had a shorter AT cycle length (median of 273 versus 315 ms; P=0.003) and had a shorter resetting zone (median coupling interval of 30 versus 50 ms; P=0.01).
  
  
  CONCLUSIONS
  APB delivered during AT in patients with a DAP advanced and/or delayed ventricular activation in all patients. In 1 of 5 of cases the AT was terminated by a single APB. In approximately a quarter of the patients an earlier coupled APB was needed to reset AT. The high RA was an adequate stimulation site in all right-sided DAP.
authors: Arrhythmia and Electrophysiology Unit, Biocor Instituto, Nova Lima, Brazil. eduardosternick@terra.com.br
authors: Eduardo Back
authors: EB
authors: Sternick
authors: Yash
authors: Y
authors: Lokhandwala
authors: Carl
authors: C
authors: Timmermans
authors: Luiz
authors: L
authors: Gerken
authors: Frederico
authors: F
authors: Soares
authors: Liana
authors: L
authors: Dias
authors: Yan
authors: Y
authors: Huo
authors: Gerhard
authors: G
authors: Hindricks
authors: Hein J J
authors: HJ
authors: Wellens
mesh_terms: D000328:Adult; D018880:Atrial Premature Complexes / Q000209:etiology* / Q000503:physiopathology; D001283:Atrioventricular Node / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006325:Heart Atria / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D011446:Prospective Studies; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000150:complications* / Q000503:physiopathology