title: Atrial tachyarrhythmias and repolarization changes induced by discrete activation of dorsal mediastinal cardiac nerves in canines.
abstract: BACKGROUND
  Chronotropic "vagal responses" elicited by high-frequency stimulation have been used to identify atrial targets for ablative treatment of atrial tachyarrhythmias (AT), whereas an anatomic approach consisting of extensive ablation of the ganglionated plexus areas has been proposed as an alternative. Therefore, there is a need for precise delineation of juxtacardiac nerves involved in AT initiation and clarification of their regional influences throughout the atria in relation to AT sites of origin, beyond chronotropic effects related to sinus node modulation.
  
  
  RESULTS
  Unipolar electrograms were recorded from 191 biatrial epicardial sites in 13 anesthetized canines, with concomitant left atrial endocardial recording from 63 sites in 5 of 13 animals. When electric stimuli were delivered to dorsal mediastinal nerves during the atrial refractory period, atrial premature depolarizations initiating AT were elicited in all animals, most frequently without prior sinus cycle length modification. Among 63 episodes, the sites of origin of early AT beats were localized to (1) the posterolateral left atrial wall in the pulmonary vein region (33%), (2) superior left atrial loci along the Bachmann bundle (55%), and (3) the region of Bachmann bundle insertion into the superior right atrial wall (11%). Moreover, the AT sites of origin were spatially concordant with regional waveform changes during the repolarization phase of unipolar recordings. AT induction and repolarization changes were abolished after atropine administration.
  
  
  CONCLUSIONS
  Activation of individual dorsal mediastinal nerves induces AT arising from distinct sites of origin which are spatially concordant with regional atrial repolarization changes.
authors.affiliation: Department of Pharmacology and Surgery, Université de Montréal, Montréal, Québec, Canada. rene.cardinal@umontreal.ca
authors.forename: René
authors.initials: R
authors.lastname: Cardinal
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Armour
authors.forename: Caroline
authors.initials: C
authors.lastname: Bouchard
authors.forename: Michel
authors.initials: M
authors.lastname: Vermeulen
authors.forename: Alain
authors.initials: A
authors.lastname: Vinet
authors.forename: Réginald
authors.initials: R
authors.lastname: Nadeau
authors.forename: Pierre
authors.initials: P
authors.lastname: Pagé
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004285:Dogs; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006339:Heart Rate; D008297:Male; D008482:Mediastinum / Q000294:innervation*; D013612:Tachycardia, Ectopic Atrial / Q000209:etiology* / Q000503:physiopathology; D055536:Vagus Nerve Stimulation / Q000009:adverse effects*