title: Origin and pharmacological response of atrial tachyarrhythmias induced by activation of mediastinal nerves in canines.
abstract: We sought to determine the sites of origin of atrial tachyarrhythmias induced by activating mediastinal nerves, as well as the response of such arrhythmias to autonomic modulation. Under general anaesthesia, atrioventricular block was induced after thoracotomy in 19 canines. Brief trains of 5 electrical stimuli were delivered to right-sided mediastinal nerves during the atrial refractory period. Unipolar electrograms were recorded from 191 right and left atrial epicardial sites under several conditions, i.e. (i) with intact nervous systems and following (ii) acute decentralization of the intrathoracic nervous system or administration of (iii) atropine, (iv) timolol, (v) hexamethonium. Concomitant right atrial endocardial mapping was performed in 7 of these dogs. Mediastinal nerve stimulation consistently initiated bradycardia followed by atrial tachyarrhythmias. In the initial tachyarrhythmia beats, early epicardial breakthroughs were identified in the right atrial free wall (28/50 episodes) or Bachmann bundle region (22/50), which corresponded to endocardial sites of origin associated with the right atrial subsidiary pacemaker complex, i.e. the crista terminalis and dorsal locations including the right atrial aspect of the interatrial septum. Neuronally induced responses were eliminated by atropine, modified by timolol and unaffected by acute neuronal decentralization. After hexamethonium, responses to extra-pericardial but not intra-pericardial nerve stimulation were eliminated. It is concluded that concomitant activation of cholinergic and adrenergic efferent intrinsic cardiac neurons induced by right-sided efferent neuronal stimulation initiates atrial tachyarrhythmias that originate from foci anatomically related to the right atrial pacemaker complex and tissues underlying major atrial ganglionated plexuses.
authors.affiliation: Centre de recherche, Hôpital du Sacré-Coeur de Montréal, Montréal, Canada H4J 1C5.
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Armour
authors.forename: Louis-Philippe
authors.initials: LP
authors.lastname: Richer
authors.forename: Pierre
authors.initials: P
authors.lastname: Pagé
authors.forename: Alain
authors.initials: A
authors.lastname: Vinet
authors.forename: Teresa
authors.initials: T
authors.lastname: Kus
authors.forename: Michel
authors.initials: M
authors.lastname: Vermeulen
authors.forename: Réginald
authors.initials: R
authors.lastname: Nadeau
authors.forename: René
authors.initials: R
authors.lastname: Cardinal
mesh_terms: D000818:Animals; D001285:Atropine; D001340:Autonomic Nerve Block / Q000379:methods; D001341:Autonomic Nervous System / Q000033:anatomy & histology / Q000502:physiology*; D018780:Body Surface Potential Mapping; D004285:Dogs; D004558:Electric Stimulation / Q000379:methods; D004569:Electroencephalography / Q000379:methods; D005260:Female; D007839:Functional Laterality; D006325:Heart Atria / Q000187:drug effects* / Q000503:physiopathology*; D006329:Heart Conduction System / Q000166:cytology / Q000502:physiology*; D018738:Hexamethonium; D008297:Male; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D013610:Tachycardia / Q000139:chemically induced / Q000503:physiopathology*; D013997:Time Factors; D013999:Timolol; D014628:Vagotomy / Q000379:methods
chemical_list: D018738:Hexamethonium; D001285:Atropine; D013999:Timolol