title: Vagal nerve stimulation activates vagal afferent fibers that reduce cardiac efferent parasympathetic effects.
abstract: Vagal nerve stimulation (VNS) has been shown to have antiarrhythmic effects, but many of these benefits were demonstrated in the setting of vagal nerve decentralization. The purpose of this study was to evaluate the role of afferent fiber activation during VNS on efferent control of cardiac hemodynamic and electrophysiological parameters. In 37 pigs a 56-electrode sock was placed over the ventricles to record local activation recovery intervals (ARIs), a surrogate of action potential duration. In 12 of 37 animals atropine was given systemically. Right and left VNS were performed under six conditions: both vagal trunks intact (n = 25), ipsilateral right (n = 11), ipsilateral left (n = 14), contralateral right (n = 7), contralateral left (n = 10), and bilateral (n = 25) vagal nerve transection (VNTx). Unilateral VNTx significantly affected heart rate, PR interval, Tau, and global ARIs. Right VNS after ipsilateral VNTx had augmented effects on hemodynamic parameters and increase in ARI, while subsequent bilateral VNTx did not significantly modify this effect (%change in ARI in intact condition 2.2 ± 0.9% vs. ipsilateral VNTx 5.3 ± 1.7% and bilateral VNTx 5.3 ± 0.8%, P < 0.05). Left VNS after left VNTx tended to increase its effects on hemodynamics and ARI response (P = 0.07), but only after bilateral VNTx did these changes reach significance (intact 1.1 ± 0.5% vs. ipsilateral VNTx 3.6 ± 0.7% and bilateral VNTx 6.6 ± 1.6%, P < 0.05 vs. intact). Contralateral VNTx did not modify VNS response. The effect of atropine on ventricular ARI was similar to bilateral VNTx. We found that VNS activates afferent fibers in the ipsilateral vagal nerve, which reflexively inhibit cardiac parasympathetic efferent electrophysiological and hemodynamic effects.
authors.affiliation: University of California Los Angeles Neurocardiology Research Center of Excellence, Los Angeles, California; and Department of Anesthesiology, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Yamakawa
authors.affiliation: University of California Los Angeles Cardiac Arrhythmia Center, Los Angeles, California; University of California Los Angeles Neurocardiology Research Center of Excellence, Los Angeles, California; and.
authors.forename: Pradeep S
authors.initials: PS
authors.lastname: Rajendran
authors.affiliation: University of California Los Angeles Neurocardiology Research Center of Excellence, Los Angeles, California; and Department of Anesthesiology, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Takamiya
authors.affiliation: University of California Los Angeles Cardiac Arrhythmia Center, Los Angeles, California; University of California Los Angeles Neurocardiology Research Center of Excellence, Los Angeles, California; and.
authors.forename: Daigo
authors.initials: D
authors.lastname: Yagishita
authors.affiliation: University of California Los Angeles Cardiac Arrhythmia Center, Los Angeles, California; University of California Los Angeles Neurocardiology Research Center of Excellence, Los Angeles, California; and.
authors.forename: Eileen L
authors.initials: EL
authors.lastname: So
authors.affiliation: University of California Los Angeles Cardiac Arrhythmia Center, Los Angeles, California; University of California Los Angeles Neurocardiology Research Center of Excellence, Los Angeles, California; and Department of Anesthesiology, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California.
authors.forename: Aman
authors.initials: A
authors.lastname: Mahajan
authors.affiliation: University of California Los Angeles Cardiac Arrhythmia Center, Los Angeles, California; University of California Los Angeles Neurocardiology Research Center of Excellence, Los Angeles, California; and.
authors.forename: Kalyanam
authors.initials: K
authors.lastname: Shivkumar
authors.affiliation: University of California Los Angeles Cardiac Arrhythmia Center, Los Angeles, California; University of California Los Angeles Neurocardiology Research Center of Excellence, Los Angeles, California; and mvaseghi@mednet.ucla.edu.
authors.forename: Marmar
authors.initials: M
authors.lastname: Vaseghi
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004525:Efferent Pathways / Q000502:physiology*; D005260:Female; D006321:Heart / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006352:Heart Ventricles / Q000187:drug effects / Q000294:innervation*; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D008297:Male; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D010276:Parasympatholytics / Q000494:pharmacology; D034421:Sus scrofa; D013552:Swine; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology* / Q000601:surgery; D055536:Vagus Nerve Stimulation; D016276:Ventricular Function / Q000187:drug effects / Q000502:physiology*
chemical_list: D010276:Parasympatholytics; D001285:Atropine
keywords: afferent cardiac neurotransmission; electrophysiology; parasympathetic; vagotomy