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Thompson N, Ravagli E, Mastitskaya S, Challita R, Hadaya J, Iacoviello F, Idil AS, Shearing PR, Ajijola OA, Ardell JL, Shivkumar K, Holder D, Aristovich K. Towards spatially selective efferent neuromodulation: anatomical and functional organization of cardiac fibres in the porcine cervical vagus nerve. J Physiol 2024. [PMID: 39183636 DOI: 10.1113/jp286494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 08/09/2024] [Indexed: 08/27/2024] Open
Abstract
Spatially selective vagus nerve stimulation (sVNS) offers a promising approach for addressing heart disease with enhanced precision. Despite its therapeutic potential, VNS is limited by off-target effects and the need for time-consuming titration. Our research aimed to determine the spatial organization of cardiac afferent and efferent fibres within the vagus nerve of pigs to achieve targeted neuromodulation. Using trial-and-error sVNS in vivo and ex vivo micro-computed tomography fascicle tracing, we found significant spatial separation between cardiac afferent and cardiac efferent fibres at the mid-cervical level and they were localized on average on opposite sides of the nerve cross-section. This was consistent between both in vivo and ex vivo methods. Specifically, cardiac afferent fibres were located near pulmonary fibres, consistent with findings of cardiopulmonary convergent circuits and, notably, cardiac efferent fascicles were exclusive. These cardiac efferent regions were located in close proximity to the recurrent laryngeal regions. This is consistent with the roughly equitable spread across the nerve of the afferent and efferent fibres. Our study demonstrated that targeted neuromodulation via sVNS could achieve scalable heart rate decreases without eliciting cardiac afferent-related reflexes; this is desirable for reducing sympathetic overactivation associated with heart disease. These findings indicate that understanding the spatial organization of cardiac-related fibres within the vagus nerve can lead to more precise and effective VNS therapy, minimizing off-target effects and potentially mitigating the need for titration. KEY POINTS: Spatially selective vagus nerve stimulation (sVNS) presents a promising approach for addressing chronic heart disease with enhanced precision. Our study reveals significant spatial separation between cardiac afferent and efferent fibres in the vagus nerve, particularly at the mid-cervical level. Utilizing trial-and-error sVNS in vivo and micro-computed tomography fascicle tracing, we demonstrate the potential for targeted neuromodulation, achieving therapeutic effects such as scalable heart rate decrease without stimulating cardiac afferent-related reflexes. This spatial understanding opens avenues for more effective VNS therapy, minimizing off-target effects and potentially eliminating the need for titration, thereby expediting therapeutic outcomes in myocardial infarction and related conditions.
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Affiliation(s)
- Nicole Thompson
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - Enrico Ravagli
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - Svetlana Mastitskaya
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - Ronald Challita
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Joseph Hadaya
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Francesco Iacoviello
- Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London, UK
| | - Ahmad Shah Idil
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - Paul R Shearing
- Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London, UK
| | - Olujimi A Ajijola
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Jeffrey L Ardell
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Kalyanam Shivkumar
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - David Holder
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - Kirill Aristovich
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, UK
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Thompson N, Ravagli E, Mastitskaya S, Challita R, Hadaya J, Iacoviello F, Shah Idil A, Shearing PR, Ajijola OA, Ardell JL, Shivkumar K, Holder D, Aristovich K. Anatomical and functional organization of cardiac fibers in the porcine cervical vagus nerve allows spatially selective efferent neuromodulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.09.574861. [PMID: 38260584 PMCID: PMC10802425 DOI: 10.1101/2024.01.09.574861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Cardiac disease progression reflects the dynamic interaction between adversely remodeled neurohumoral control systems and an abnormal cardiac substrate. Vagal nerve stimulation (VNS) is an attractive neuromodulatory option to dampen this dynamic interaction; however, it is limited by off-target effects. Spatially-selective VNS (sVNS) offers a promising solution to induce cardioprotection while mitigating off-target effects by specifically targeting pre-ganglionic parasympathetic efferent cardiac fibers. This approach also has the potential to enhance therapeutic outcomes by eliminating time-consuming titration required for optimal VNS. Recent studies have demonstrated the independent modulation of breathing rate, heart rate, and laryngeal contraction through sVNS. However, the spatial organization of afferent and efferent cardiac-related fibers within the vagus nerve remains unexplored. By using trial-and-error sVNS in vivo in combination with ex vivo micro-computed tomography fascicle tracing, we show the significant spatial separation of cardiac afferent and efferent fibers (179±55° SD microCT, p<0.05 and 200±137° SD, p<0.05 sVNS - degrees of separation across a cross-section of nerve) at the mid-cervical level. We also show that cardiac afferent fibers are located in proximity to pulmonary fibers consistent with recent findings of cardiopulmonary convergent neurons and circuits. We demonstrate the ability of sVNS to selectively elicit desired scalable heart rate decrease without stimulating afferent-related reflexes. By elucidating the spatial organization of cardiac-related fibers within the vagus nerve, our findings pave the way for more targeted neuromodulation, thereby reducing off-target effects and eliminating the need for titration. This, in turn, will enhance the precision and efficacy of VNS therapy in treating cardiac pathology, allowing for improved therapeutic efficacy.
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Affiliation(s)
- Nicole Thompson
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Enrico Ravagli
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Svetlana Mastitskaya
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Ronald Challita
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Joseph Hadaya
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Francesco Iacoviello
- Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London, United Kingdom
| | - Ahmad Shah Idil
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Paul R. Shearing
- Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London, United Kingdom
| | - Olujimi A. Ajijola
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Jeffrey L. Ardell
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Kalyanam Shivkumar
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - David Holder
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Kirill Aristovich
- EIT and Neurophysiology Research Group, Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
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Tarotin I, Mastitskaya S, Ravagli E, Perkins JD, Holder D, Aristovich K. Overcoming temporal dispersion for measurement of activity-related impedance changes in unmyelinated nerves. J Neural Eng 2022; 19. [PMID: 35413701 DOI: 10.1088/1741-2552/ac669a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Accepted: 04/11/2022] [Indexed: 11/11/2022]
Abstract
Objective.Fast neural electrical impedance tomography is an imaging technique that has been successful in visualising electrically evoked activity of myelinated fibres in peripheral nerves by measurement of the impedance changes (dZ) accompanying excitation. However, imaging of unmyelinated fibres is challenging due to temporal dispersion (TP) which occurs due to variability in conduction velocities of the fibres and leads to a decrease of the signal below the noise with distance from the stimulus. To overcome TP and allow electrical impedance tomography imaging in unmyelinated nerves, a new experimental and signal processing paradigm is required allowing dZ measurement further from the site of stimulation than compound neural activity is visible. The development of such a paradigm was the main objective of this study.Approach.A finite element-based statistical model of TP in porcine subdiaphragmatic nerve was developed and experimentally validatedex-vivo. Two paradigms for nerve stimulation and processing of the resulting data-continuous stimulation and trains of stimuli, were implemented; the optimal paradigm for recording dispersed dZ in unmyelinated nerves was determined.Main results.While continuous stimulation and coherent spikes averaging led to higher signal-to-noise ratios (SNRs) at close distances from the stimulus, stimulation by trains was more consistent across distances and allowed dZ measurement at up to 15 cm from the stimulus (SNR = 1.8 ± 0.8) if averaged for 30 min.Significance.The study develops a method that for the first time allows measurement of dZ in unmyelinated nerves in simulation and experiment, at the distances where compound action potentials are fully dispersed.
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Affiliation(s)
- Ilya Tarotin
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Svetlana Mastitskaya
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Enrico Ravagli
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Justin D Perkins
- Clinical Science and Services, Royal Veterinary College, Hawkshead Lane, Hatfield, United Kingdom
| | - David Holder
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Kirill Aristovich
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
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Ravagli E, Mastitskaya S, Thompson N, Iacoviello F, Shearing PR, Perkins J, Gourine AV, Aristovich K, Holder D. Imaging fascicular organization of rat sciatic nerves with fast neural electrical impedance tomography. Nat Commun 2020; 11:6241. [PMID: 33288760 PMCID: PMC7721735 DOI: 10.1038/s41467-020-20127-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 11/13/2020] [Indexed: 02/06/2023] Open
Abstract
Imaging compound action potentials (CAPs) in peripheral nerves could help avoid side effects in neuromodulation by selective stimulation of identified fascicles. Existing methods have low resolution, limited imaging depth, or are invasive. Fast neural electrical impedance tomography (EIT) allows fascicular CAP imaging with a resolution of <200 µm, <1 ms using a non-penetrating flexible nerve cuff electrode array. Here, we validate EIT imaging in rat sciatic nerve by comparison to micro-computed tomography (microCT) and histology with fluorescent dextran tracers. With EIT, there are reproducible localized changes in tissue impedance in response to stimulation of individual fascicles (tibial, peroneal and sural). The reconstructed EIT images correspond to microCT scans and histology, with significant separation between the fascicles (p < 0.01). The mean fascicle position is identified with an accuracy of 6% of nerve diameter. This suggests fast neural EIT can reliably image the functional fascicular anatomy of the nerves and so aid selective neuromodulation.
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Affiliation(s)
- Enrico Ravagli
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - Svetlana Mastitskaya
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK.
| | - Nicole Thompson
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - Francesco Iacoviello
- Electrochemical Innovation Laboratory, Department of Chemical Engineering, University College London, London, UK
| | - Paul R Shearing
- Electrochemical Innovation Laboratory, Department of Chemical Engineering, University College London, London, UK
| | - Justin Perkins
- Clinical Science and Services, Royal Veterinary College, Hawkshead Lane, Hatfield, UK
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Kirill Aristovich
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - David Holder
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK
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Interfacing with the Peripheral Nervous System. J Neurosci Methods 2020; 340:108745. [DOI: 10.1016/j.jneumeth.2020.108745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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