Origin and pharmacological response of atrial tachyarrhythmias induced by activation of mediastinal nerves in canines

• Published in: Autonomic neuroscience Vol. 118; no. 1; pp. 68 - 78
• Main Authors: Armour, J. Andrew, Richer, Louis-Philippe, Pagé, Pierre, Vinet, Alain, Kus, Teresa, Vermeulen, Michel, Nadeau, Réginald, Cardinal, René
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 31.03.2005; Elsevier
• Subjects: Adrenergic efferent neuron; Animals; Atrial tachyarrhythmias; Atropine; Autonomic Nerve Block - methods; Autonomic Nervous System - anatomy & histology; Autonomic Nervous System - physiology; Biological and medical sciences; Body Surface Potential Mapping; Cholinergic efferent neuron; Dogs; Electric Stimulation - methods; Electroencephalography - methods; Epicardial and endocardial atrial mapping; Female; Functional Laterality; Fundamental and applied biological sciences. Psychology; Heart Atria - drug effects; Heart Atria - physiopathology; Heart Conduction System - cytology; Heart Conduction System - physiology; Hexamethonium; Intrinsic cardiac ganglionated plexus; Male; Peripheral nervous system. Autonomic nervous system. Neuromuscular transmission. Ganglionic transmission. Electric organ; Reaction Time - physiology; Reaction Time - radiation effects; Tachycardia - chemically induced; Tachycardia - physiopathology; Time Factors; Timolol; Vagotomy - methods; Vertebrates: nervous system and sense organs; Atrial tachyarrhythmias; Intrinsic cardiac ganglionated plexus; Adrenergic efferent neuron; Cholinergic efferent neuron; Epicardial and endocardial atrial mapping; Fissipedia; Cholinergic neuron; Carnivora; Vertebrata; Tachycardia; Mammalia; Autonomic nervous system; Adrenergic neuron; Dog
• ISSN: 1566-0702; 1872-7484
• DOI: 10.1016/j.autneu.2005.01.006

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.