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Ovsenik A, Podbregar M, Lakič N, Brešar M, Boškoski P, Verdenik I, Fabjan A. Neurovascular coupling in severe aortic valve stenosis. Brain Behav 2023; 13:e3155. [PMID: 37475651 PMCID: PMC10454277 DOI: 10.1002/brb3.3155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 05/18/2023] [Accepted: 07/06/2023] [Indexed: 07/22/2023] Open
Abstract
OBJECTIVES Aortic stenosis (AS) is characterized by obstruction of blood outflow from the left ventricle, which can impair target organ perfusion such as the brain. We hypothesized that hemodynamic changes in AS may lead to dysfunction of cerebral blood flow regulatory mechanisms. The aim of our study was to evaluate neurovascular coupling in patients with AS by Transcranial Doppler ultrasonography. METHODS Neurovascular coupling was assessed using visually evoked cerebral blood flow velocity responses (VEFR) calculated as relative blood flow velocity changes in the posterior cerebral artery upon visual stimulation. We analyzed peak systolic, mean and end diastolic VEFR in 54 patients with severe AS and 43 controls in 10 consecutive cycles of visual stimulation. Repeated-measures ANOVA test was used to compare cerebral hemodynamic data by group. RESULTS Patients with AS had significantly higher peak systolic (12.9% ± 5.6% and 10.5% ± 4.5%; p = .009) and mean VEFR (14.4% ± 5.8% and 12.2% ± 4.9%; p = .021) compared to controls, whereas only a tendency for higher end diastolic VEFR was observed (16.7% ± 6.9% and 14.4% ± 6.2%; p = .061). CONCLUSION We have shown for the first time that patients with severe AS exhibit higher VEFR than controls indicating dysregulation of neurovascular coupling, which can be one of the factors contributing to development of cognitive decline.
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Affiliation(s)
- Ana Ovsenik
- Faculty of Medicine, Department of BiomedicineUniversity of LjubljanaLjubljanaSlovenia
- Department of CardiologyUniversity Medical Centre LjubljanaLjubljanaSlovenia
| | - Matej Podbregar
- Faculty of Medicine, Department of Internal MedicineUniversity of LjubljanaLjubljanaSlovenia
- Department of Intensive CareGeneral Hospital CeljeCeljeSlovenia
| | - Nikola Lakič
- Department of Cardiovascular SurgeryUniversity Medical Centre LjubljanaLjubljanaSlovenia
| | - Martin Brešar
- Jožef Stefan International Postgraduate SchoolLjubljanaSlovenia
- Department of Systems and ControlJožef Stefan InstituteLjubljanaSlovenia
| | - Pavle Boškoski
- Department of Systems and ControlJožef Stefan InstituteLjubljanaSlovenia
| | - Ivan Verdenik
- Department of Obstetrics and Gynaecology, Division for ResearchUniversity Medical Centre LjubljanaLjubljanaSlovenia
| | - Andrej Fabjan
- Faculty of Medicine, Institute for PhysiologyUniversity of LjubljanaLjubljanaSlovenia
- Department of Vascular Neurology and Neurological Intensive CareUniversity Medical Centre LjubljanaLjubljanaSlovenia
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Samora M, Vianna LC, Carmo JC, Macedo V, Dawes M, Phillips AA, Paton JFR, Fisher JP. Neurovascular coupling is not influenced by lower body negative pressure in humans. Am J Physiol Heart Circ Physiol 2020; 319:H22-H31. [PMID: 32442032 DOI: 10.1152/ajpheart.00076.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cerebral blood flow is tightly coupled with local neuronal activation and metabolism, i.e., neurovascular coupling (NVC). Studies suggest a role of sympathetic nervous system in the regulation of cerebral blood flow. However, this is controversial, and the sympathetic regulation of NVC in humans remains unclear. Since impaired NVC has been identified in several chronic diseases associated with a heightened sympathetic activity, we aimed to determine whether reflex-mediated sympathetic activation via lower body negative pressure (LBNP) attenuates NVC in humans. NVC was assessed using a visual stimulation protocol (5 cycles of 30 s eyes closed and 30 s of reading) in 11 healthy participants (aged 24 ± 3 yr). NVC assessments were made under control conditions and during LBNP at -20 and -40 mmHg. Posterior (PCA) and middle (MCA) cerebral artery mean blood velocity (Vmean) and vertebral artery blood flow (VAflow) were simultaneously determined with cardiorespiratory variables. Under control conditions, the visual stimulation evoked a robust increase in PCAVmean (∆18.0 ± 4.5%), a moderate rise in VAflow (∆9.6 ± 4.3%), and a modest increase in MCAVmean (∆3.0 ± 1.9%). The magnitude of NVC response was not affected by mild-to-moderate LBNP (all P > 0.05 for repeated-measures ANOVA). Given the small change that occurred in partial pressure of end-tidal CO2 during LBNP, this hypocapnia condition was matched via voluntary hyperventilation in absence of LBNP in a subgroup of participants (n = 8). The mild hypocapnia during LBNP did not exert a confounding influence on the NVC response. These findings indicate that the NVC is not influenced by LBNP or mild hypocapnia in humans.NEW & NOTEWORTHY Visual stimulation evoked a robust increase in posterior cerebral artery velocity and a modest increase in vertebral artery blood flow, i.e., neurovascular coupling (NVC), which was unaffected by lower body negative pressure (LBNP) in humans. In addition, although LBNP induced a mild hypocapnia, this degree of hypocapnia in the absence of LBNP failed to modify the NVC response.
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Affiliation(s)
- Milena Samora
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.,NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Lauro C Vianna
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Jake C Carmo
- Biomechanics and Biological Signal Processing Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Victor Macedo
- Biomechanics and Biological Signal Processing Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Matthew Dawes
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Aaron A Phillips
- Departments of Physiology, Pharmacology, and Clinical Neurosciences, Libin Cardiovascular Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Alberta, Canada
| | - Julian F R Paton
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - James P Fisher
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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Exhaustive exercise attenuates the neurovascular coupling by blunting the pressor response to visual stimulation. BIOMED RESEARCH INTERNATIONAL 2015; 2015:671063. [PMID: 25866801 PMCID: PMC4383341 DOI: 10.1155/2015/671063] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Revised: 10/18/2014] [Accepted: 11/01/2014] [Indexed: 11/17/2022]
Abstract
Neurovascular coupling (NVC) is assessed as an increase response to visual stimulation, and is monitored by blood flow of the posterior cerebral artery (PCA). To investigate whether exhaustive exercise modifies NVC, and more specifically, the relative contributions of vasodilatation in the downstream of PCA and the pressor response on NVC, we measured blood flow velocity in the PCA (PCAv) in 13 males using transcranial Doppler ultrasound flowmetry during a leg-cycle exercise at 75% of maximal heart rate until exhaustion. NVC was estimated as the relative change in PCAv from the mean value obtained during 20-s with the eyes closed to the peak value obtained during 40-s of visual stimulation involving looking at a reversed checkerboard. Conductance index (CI) was calculated by dividing PCAv by mean arterial pressure (MAP) to evaluate the vasodilatation. At exhaustion, PCAv was significantly decreased relative to baseline measurements, and the PCAv response to visual stimulation significantly decreased. Compared to baseline, exhaustive exercise significantly suppressed the increase in MAP to visual stimulation, while the CI response did not significantly change by the exercise. These results suggest that exhaustive exercise attenuates the magnitude of NVC by blunting the pressor response to visual stimulation.
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Effects of vasodilatation and pressor response on neurovascular coupling during dynamic exercise. Eur J Appl Physiol 2014; 115:619-25. [PMID: 25399314 DOI: 10.1007/s00421-014-3049-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 11/07/2014] [Indexed: 10/24/2022]
Abstract
PURPOSE Visual stimulation increases the blood flow in the posterior cerebral artery (PCA), which supplies blood to the visual cortex by neurovascular coupling (NVC). Relative contributions of vasodilatation and pressor response on NVC during dynamic exercise are still unknown. METHODS We measured the blood flow velocity in the PCA (PCAv) by transcranial Doppler ultrasound flowmetry during rest and exercise in 14 healthy males while they performed 12-min submaximal leg-cycle exercises at mild-, moderate-, and high-intensity, which corresponded to heart rates of 120, 140, and 160 bpm, respectively. NVC was estimated as the relative change in PCAv from 20 s eye-closing to the peak response during 40 s looking at a reversed checkerboard. Conductance index was calculated for evaluating vasodilatation as pressure divided by blood flow. RESULTS In response to visual stimulation, a magnitude of vasodilatation was significantly decreased under the moderate-intensity, while pressor response was significantly suppressed under the high-intensity exercises, compared with the control condition. Conversely, peak response to visual stimulation in PCAv was not affected by exercise intensity though relative and absolute responses were significantly lower in the moderate- and high-intensity exercises than the control. CONCLUSION It is suggested that the contributions of pressor response and vasodilatation were modified by exercise intensity, partly playing a role for stabilizing the peak response of PCAv with visual stimulation during dynamic exercise.
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Static autoregulation in humans: a review and reanalysis. Med Eng Phys 2014; 36:1487-95. [DOI: 10.1016/j.medengphy.2014.08.001] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 06/07/2014] [Accepted: 08/03/2014] [Indexed: 01/12/2023]
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Fabjan A, Bajrović FF, Musizza B, Vidmar J, Štrucl M, Zaletel M. Study of neurovascular coupling during cold pressor test in patients with migraine. Cephalalgia 2014; 35:692-701. [PMID: 25330769 DOI: 10.1177/0333102414554661] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 09/13/2014] [Indexed: 11/15/2022]
Abstract
BACKGROUND Altered neurovascular coupling in migraineurs could be a consequence of impaired function of modulatory brainstem nuclei. The cold pressor test (CPT) should activate brainstem structures. We measured visually evoked cerebral blood flow velocity response (VEFR) to CPT in migraine. METHODS Twenty-three healthy volunteers and 29 migraineurs participated in the study. We measured arterial blood pressure, end-tidal CO2, heart rate and cerebral blood flow velocity in posterior and middle cerebral artery using transcranial Doppler. VEFR was calculated as cerebrovascular reactivity to photic stimulation before, during and after CPT. RESULTS In healthy individuals, there was a significant decrease in peak systolic VEFR from CPT phase to recovery phase (p < 0.05). There was an increase in mean VEFR from basal to CPT phase and a decrease from CPT to recovery phase, both significant (p < 0.05). End-diastolic VEFR increased from basal to CPT phase and decreased in recovery phase below the basal phase values, all changes significant (p < 0.05). In migraine, no statistically significant changes in peak systolic, mean or end-diastolic VEFRs were observed between phases (p > 0.05). The differences in phases in mean and end-diastolic VEFRs between the basal phase and the CPT phase and between the CPT phase and the recovery phase were significantly higher in healthy individuals (p < 0.05). CONCLUSIONS The absence of the effect of CPT on VEFR in migraine is likely to be a consequence of impaired subcortical modulation of neurovascular coupling.
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Affiliation(s)
- Andrej Fabjan
- Institute of Physiology, Medical Faculty, University of Ljubljana, Slovenia
| | - Fajko F Bajrović
- Institute of Pathophysiology, Medical Faculty, University of Ljubljana, Slovenia University Medical Centre of Ljubljana, Department of Vascular Neurology, Slovenia
| | | | - Jernej Vidmar
- Institute of Physiology, Medical Faculty, University of Ljubljana, Slovenia
| | - Martin Štrucl
- Institute of Physiology, Medical Faculty, University of Ljubljana, Slovenia
| | - Marjan Zaletel
- University Medical Centre of Ljubljana, Department of Vascular Neurology, Slovenia
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Yamaguchi Y, Kashima H, Fukuba Y, Hayashi N. Cerebral blood flow and neurovascular coupling during static exercise. J Physiol Sci 2014; 64:195-201. [PMID: 24682807 PMCID: PMC10717924 DOI: 10.1007/s12576-014-0311-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 03/13/2014] [Indexed: 12/30/2022]
Abstract
The effect of static exercise on neurovascular coupling (NVC) was investigated by measuring the blood flow velocity in the posterior cerebral artery (PCAv) during 2-min static handgrip exercises (HG) at 30 % of the maximum voluntary contraction in 17 healthy males. NVC was estimated as the relative change in PCAv from eye closing to a peak response to looking at a reversed checkerboard. The conductance index (CI) was calculated by dividing PCAv by the mean arterial pressure (MAP). HG significantly increased PCAv from the resting baseline, with an increase in MAP and a reduction in CI, whereas NVC did not differ significantly between the resting and HG. Compared to the resting baseline, HG significantly increased the pressor response to visual stimulation by 5.6 ± 1.1 (mean ± SE) mmHg, while the CI response was significantly inhibited by -7.0 ± 1.5 %. These results indicate that NVC was maintained during HG via contributions from both the pressor response and vasodilatation.
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Affiliation(s)
- Yuji Yamaguchi
- Graduate School of Human-Environment Studies, Kyushu University, Kasuga, Fukuoka 816-8580 Japan
| | - Hideaki Kashima
- Department of Exercise Science and Physiology, School of Health and Nutritional Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558 Japan
| | - Yoshiyuki Fukuba
- Department of Exercise Science and Physiology, School of Health and Nutritional Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558 Japan
| | - Naoyuki Hayashi
- Graduate School of Decision Science and Technology, Tokyo Insitute of Technology, Meguro, Tokyo, 152-8852 Japan
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Fabjan A, Vidmar J, Musizza B, Bajrović FF, Zaletel M, Štrucl M. The effect of the cold pressor test on a visually evoked cerebral blood flow velocity response in patients with migraine. J Headache Pain 2013. [PMCID: PMC3620005 DOI: 10.1186/1129-2377-14-s1-p120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Fabjan A, Vidmar J, Musizza B, Bajrović FF, Zaletel M, Štrucl M. The effect of the cold pressor test on a visually evoked cerebral blood flow velocity response in patients with migraine. J Headache Pain 2013. [DOI: 10.1186/1129-2377-1-s1-p120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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