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Guo Y, Zhou L, Li Y, Chiang GC, Liu T, Chen H, Huang W, de Leon MJ, Wang Y, Chen F. Quantitative transport mapping of multi-delay arterial spin labeling MRI detects early blood perfusion alterations in Alzheimer's disease. Alzheimers Res Ther 2024; 16:156. [PMID: 38978146 PMCID: PMC11229285 DOI: 10.1186/s13195-024-01524-6] [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: 03/14/2024] [Accepted: 06/28/2024] [Indexed: 07/10/2024]
Abstract
BACKGROUND Quantitative transport mapping (QTM) of blood velocity, based on the transport equation has been demonstrated higher accuracy and sensitivity of perfusion quantification than the traditional Kety's method-based cerebral blood flow (CBF). This study aimed to investigate the associations between QTM velocity and cognitive function in Alzheimer's disease (AD) using multiple post-labeling delay arterial spin labeling (ASL) MRI. METHODS A total of 128 subjects (21 normal controls (NC), 80 patients with mild cognitive impairment (MCI), and 27 AD) were recruited prospectively. All participants underwent MRI examination and neuropsychological evaluation. QTM velocity and traditional CBF maps were computed from multiple delay ASL. Regional quantitative perfusion measurements were performed and compared to study group differences. We tested the hypothesis that cognition declines with reduced cerebral blood perfusion with consideration of age and gender effects. RESULTS In cortical gray matter (GM) and the hippocampus, QTM velocity and CBF showed decreased values in the AD group compared to NC and MCI groups; QTM velocity, but not CBF, showed a significant difference between MCI and NC groups. QTM velocity and CBF showed values decreasing with age; QTM velocity, but not CBF, showed a significant gender difference between male and female. QTM velocity and CBF in the hippocampus were positively correlated with cognition, including global cognition, memory, executive function, and language function. CONCLUSION This study demonstrated an increased sensitivity of QTM velocity as compared with the traditional Kety's method-based CBF. Specifically, we observed only in QTM velocity, reduced perfusion velocity in GM and the hippocampus in MCI compared with NC. Both QTM velocity and CBF demonstrated a reduction in AD vs. controls. Decreased QTM velocity and CBF in the hippocampus were correlated with poor cognitive measures. These findings suggest QTM velocity as potential biomarker for early AD blood perfusion alterations and it could provide an avenue for early intervention of AD.
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Affiliation(s)
- Yihao Guo
- Department of Radiology, Hainan General Hospital (Hainan Affiliated Hospital of Hainan Medical University), No. 19, Xiuhua St, Xiuying Dic, Haikou, Hainan, 570311, People's Republic of China
| | - Liangdong Zhou
- Department of Radiology, Brain Health Imaging Institute, Weill Cornell Medicine, 407 East 61 St ST, New York, NY, 10066, USA.
| | - Yi Li
- Department of Radiology, Brain Health Imaging Institute, Weill Cornell Medicine, 407 East 61 St ST, New York, NY, 10066, USA
| | - Gloria C Chiang
- Department of Radiology, Brain Health Imaging Institute, Weill Cornell Medicine, 407 East 61 St ST, New York, NY, 10066, USA
- Department of Radiology, Division of Neuroradiology, Weill Cornell Medicine, New York- Presbyterian Hospital, New York, NY, USA
| | - Tao Liu
- Department of Neurology, Hainan General Hospital (Hainan Affiliated Hospital of Hainan Medical University), Haikou, China
| | - Huijuan Chen
- Department of Radiology, Hainan General Hospital (Hainan Affiliated Hospital of Hainan Medical University), No. 19, Xiuhua St, Xiuying Dic, Haikou, Hainan, 570311, People's Republic of China
| | - Weiyuan Huang
- Department of Radiology, Hainan General Hospital (Hainan Affiliated Hospital of Hainan Medical University), No. 19, Xiuhua St, Xiuying Dic, Haikou, Hainan, 570311, People's Republic of China
| | - Mony J de Leon
- Department of Radiology, Brain Health Imaging Institute, Weill Cornell Medicine, 407 East 61 St ST, New York, NY, 10066, USA
| | - Yi Wang
- Department of Radiology, MRI Research Institute (MRIRI), Weill Cornell Medicine, New York, NY, USA
| | - Feng Chen
- Department of Radiology, Hainan General Hospital (Hainan Affiliated Hospital of Hainan Medical University), No. 19, Xiuhua St, Xiuying Dic, Haikou, Hainan, 570311, People's Republic of China.
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Tymko MM. Unveiling the enigma from sick to beauty: Hungry to standardize metrics for dynamic cerebral autoregulation. Exp Physiol 2024; 109:472-473. [PMID: 38402582 PMCID: PMC10988677 DOI: 10.1113/ep091781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 02/13/2024] [Indexed: 02/27/2024]
Affiliation(s)
- Michael M. Tymko
- Integrative Cerebrovascular and Environmental Physiology SB Laboratory, Department of Human Health and Nutritional Sciences, College of Biological ScienceUniversity of GuelphGuelphOntarioCanada
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Gellner AK, Frase S, Reis J, Fritsch B. Direct current stimulation increases blood flow and permeability of cortical microvasculature in vivo. Eur J Neurol 2023; 30:362-371. [PMID: 36305221 DOI: 10.1111/ene.15616] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 10/08/2022] [Accepted: 10/12/2022] [Indexed: 01/07/2023]
Abstract
BACKGROUND AND PURPOSE Transcranial direct current stimulation (DCS) structurally and functionally modulates neuronal networks and microglia dynamics. Neurovascular coupling adapts regional cerebral blood flow to neuronal activity and metabolic demands. METHODS In this study, we examined effects of anodal DCS on vessel morphology, blood flow parameters, permeability of cortical microvasculature, and perivascular microglia motility by time-lapse two-photon microscopy in anaesthetized mice. RESULTS Low-intensity DCS significantly increased vessel diameter and blood flow parameters. These effects were transient and dependent on the spontaneous vasomotion characteristics of the individual vessel. Vessel leakage increased significantly after DCS at 1.1 and was more pronounced at 2.2 A/m2 , indicating a dose-dependent increase in vascular permeability. Perivascular microglia exhibited increased soma motility post-DCS at both intensities, potentially triggered by the extravasation of intravascular substrates. CONCLUSIONS Our findings demonstrate that DCS affected only vessels with spontaneous vasomotion. This rapid vascular response may occur as an adaptation of regional blood supply to neuronal excitability altered by DCS or as a direct effect on the vessel wall. In contrast to these immediate effects during stimulation, increases in cortical vessel permeability and perivascular microglia motility appeared after the stimulation had ended.
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Affiliation(s)
- Anne-Kathrin Gellner
- Department of Psychiatry and Psychotherapy, University Hospital Bonn, Bonn, Germany
- Department of Neurology and Neuroscience, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Sibylle Frase
- Department of Neurology and Neuroscience, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Janine Reis
- Department of Neurology and Neuroscience, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Brita Fritsch
- Department of Neurology and Neuroscience, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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Semenyutin V, Antonov V, Malykhina G, Salnikov V. Investigation of Cerebral Autoregulation Using Time-Frequency Transformations. Biomedicines 2022; 10:biomedicines10123057. [PMID: 36551813 PMCID: PMC9775421 DOI: 10.3390/biomedicines10123057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 10/24/2022] [Accepted: 11/20/2022] [Indexed: 11/29/2022] Open
Abstract
The authors carried out the study of the state of systemic and cerebral hemodynamics in normal conditions and in various neurosurgical pathologies using modern signal processing methods. The results characterize the condition for the mechanisms of cerebral circulation Institute of Computer Science and Control, Higher School of Cyber-Physical Systems and Control regulation, which allows for finding a solution to fundamental and specific clinical problems for the effective treatment of patients with various pathologies. The proposed method is based on the continuous wavelet transform of systemic arterial pressure and blood flow velocity signals in the middle cerebral artery recorded by non-invasive methods of photoplethysmography and transcranial doppler ultrasonography. The study of these signals in real-time in the frequency range of Mayer waves makes it possible to determine the cerebral autoregulation state in certain diseases before and after surgical interventions. The proposed method uses a cross-wavelet spectrum, which helps obtain wavelet coherence and a phase shift between the wavelet coefficients of systemic arterial pressure signals and blood flow velocity in the Mayer wave range. The obtained results enable comparing the proposed method with that based on the short-time Fourier transform. The comparison showed that the proposed method has higher sensitivity to changes in cerebral autoregulation and better localization of changes in time and frequency.
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Affiliation(s)
- Vladimir Semenyutin
- Almazov National Medical Research Center, Ministry of Health of Russia, Polenov Neurosurgical Research Institute, 12 Mayakovsky Street, Saint-Petersburg 191014, Russia
| | - Valery Antonov
- Department of Higher Mathematics, Peter the Great St. Petersburg Polytechnic University, Saint-Petersburg 195251, Russia
| | - Galina Malykhina
- Higher School of Cyber-Physical Systems and Control, Institute of Computer Science and Control, Peter the Great St. Petersburg Polytechnic University, Saint-Petersburg 195251, Russia
- Correspondence: ; Tel.: +8-921-43-15-114
| | - Vyacheslav Salnikov
- Higher School of Cyber-Physical Systems and Control, Institute of Computer Science and Control, Peter the Great St. Petersburg Polytechnic University, Saint-Petersburg 195251, Russia
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Williams EL, Khan FM, Claydon VE. Counter pressure maneuvers for syncope prevention: A semi-systematic review and meta-analysis. Front Cardiovasc Med 2022; 9:1016420. [PMID: 36312294 PMCID: PMC9606335 DOI: 10.3389/fcvm.2022.1016420] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 09/20/2022] [Indexed: 11/24/2022] Open
Abstract
Physical counter pressure maneuvers (CPM) are movements that are recommended to delay or prevent syncope (fainting) by recruiting the skeletal muscle pump to augment cardiovascular control. However, these recommendations are largely based on theoretical benefit, with limited data evaluating the efficacy of CPM to prevent syncope in the real-world setting. We conducted a semi-systematic literature review and meta-analysis to assess CPM efficacy, identify literature gaps, and highlight future research needs. Articles were identified through a literature search (PubMed, April 2022) of peer-reviewed publications evaluating the use of counter pressure or other lower body maneuvers to prevent syncope. Two team members independently screened records for inclusion and extracted data. From 476 unique records identified by the search, 45 met inclusion criteria. Articles considered various syncopal conditions (vasovagal = 12, orthostatic hypotension = 8, postural orthostatic tachycardia syndrome = 1, familial dysautonomia = 2, spinal cord injury = 1, blood donation = 10, healthy controls = 11). Maneuvers assessed included hand gripping, leg fidgeting, stepping, tiptoeing, marching, calf raises, postural sway, tensing (upper, lower, whole body), leg crossing, squatting, “crash” position, and bending foreword. CPM were assessed in laboratory-based studies (N = 28), the community setting (N = 4), both laboratory and community settings (N = 3), and during blood donation (N = 10). CPM improved standing systolic blood pressure (+ 14.8 ± 0.6 mmHg, p < 0.001) and heart rate (+ 1.4 ± 0.5 bpm, p = 0.006), however, responses of total peripheral resistance, stroke volume, or cerebral blood flow were not widely documented. Most patients experienced symptom improvement following CPM use (laboratory: 60 ± 4%, community: 72 ± 9%). The most prominent barrier to employing CPM in daily living was the inability to recognize an impending faint. Patterns of postural sway may also recruit the skeletal muscle pump to enhance cardiovascular control, and its potential as a discrete, proactive CPM needs further evaluation. Physical CPM were successful in improving syncopal symptoms and producing cardiovascular responses that may bolster against syncope; however, practical limitations may restrict applicability for use in daily living.
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Yang L, Cho J, Chen T, Gillen KM, Li J, Zhang Q, Guo L, Wang Y. Oxygen extraction fraction (OEF) assesses cerebral oxygen metabolism of deep gray matter in patients with pre-eclampsia. Eur Radiol 2022; 32:6058-6069. [PMID: 35348866 DOI: 10.1007/s00330-022-08713-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 02/21/2022] [Accepted: 03/01/2022] [Indexed: 01/19/2023]
Abstract
OBJECTIVES The objective of this study was to compare oxygen extraction fraction (OEF) values in the deep gray matter (GM) of pre-eclampsia (PE) patients, pregnant healthy controls (PHCs), and non-pregnant healthy controls (NPHCs) to explore their brain oxygen metabolism differences in GM. METHODS Forty-seven PE patients, forty NPHCs, and twenty-one PHCs were included. Brain OEF values were computed from quantitative susceptibility mapping (QSM) plus quantitative blood oxygen level-dependent magnitude (QSM + qBOLD = QQ)-based mapping. One-way ANOVA was used to compare mean OEF values in the three groups. The area under the curve of the mean OEF value in each region of interest was estimated using a receiver operating characteristic curve analysis. RESULTS We found that the mean OEF values in the thalamus, putamen, caudate nucleus, pallidum, and substantia nigra were significantly different in these three groups (F = 5.867, p = 0.004; F = 5.142, p = 0007; F = 6.158, p = 0.003; F = 6.319, p = 0.003; F = 5.491, p = 0.005). The mean OEF values for these 5 regions were higher in PE patients than in NPHCs and in PHCs (p < 0.05). The AUC of these ROIs ranged from 0.673 to 0.692 (p < 0.01) and cutoff values varied from 35.1 to 36.6%, indicating that the OEF values could discriminate patients with and without PE. Stepwise multivariate analysis revealed that the OEF values correlated with hematocrit in pregnant women (r = 0.353, p = 0.003). CONCLUSION OEF values in the brains of pregnant women can be measured in clinical practice using QQ-based OEF mapping for noninvasive assessment of hypertensive disorders. KEY POINTS • Pre-eclampsia is a hypertensive disorder associated with abnormalities in brain oxygen extraction. • Oxygen extraction fraction (OEF) is an indicator of brain tissue viability and function. QQ-based mapping of OEF is a new MRI technique that can noninvasively quantify brain oxygen metabolism. • OEF values in the brains of pregnant women can be measured for noninvasive assessment of hypertensive disorders in clinical practice.
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Affiliation(s)
- Linfeng Yang
- Jinan Maternity and Child Care Hospital, Jinan Maternity and Child Care Hospital Affiliated to Shandong First Medical University, 2 Jian-guo Xiao Jing-san Road, Jinan, 250001, Shandong, China
| | - Junghun Cho
- Department of Radiology, Weill Cornell Medical College, New York, 407 East 61st Street, New York, NY, 10065, USA
| | - Tao Chen
- Jinan Maternity and Child Care Hospital, Jinan Maternity and Child Care Hospital Affiliated to Shandong First Medical University, 2 Jian-guo Xiao Jing-san Road, Jinan, 250001, Shandong, China
| | - Kelly M Gillen
- Department of Radiology, Weill Cornell Medical College, New York, 407 East 61st Street, New York, NY, 10065, USA
| | - Jing Li
- Department of Radiology, Beijing Friendship Hospital, Capital Medical University, 95 Yong-an Road, Xicheng District, Beijing, 100050, China
| | - Qihao Zhang
- Department of Radiology, Weill Cornell Medical College, New York, 407 East 61st Street, New York, NY, 10065, USA
| | - Lingfei Guo
- Department of Radiology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, 324 Jing-wu Road, Jinan, 250021, Shandong, China.
| | - Yi Wang
- Department of Radiology, Weill Cornell Medical College, New York, 407 East 61st Street, New York, NY, 10065, USA
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Ölmestig J, Marlet IR, Vilsbøll T, Rungby J, Rostrup E, Lambertsen KL, Kruuse C. A single dose of exenatide had no effect on blood flow velocity in the middle cerebral artery in elderly healthy volunteers: Randomized, placebo-controlled, double-blind clinical trial. Front Aging Neurosci 2022; 14:899389. [PMID: 36636739 PMCID: PMC9831269 DOI: 10.3389/fnagi.2022.899389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 07/04/2022] [Indexed: 01/26/2023] Open
Abstract
Background and aims Glucagon-like peptide 1 (GLP-1) receptor agonists (GLP-1RA) are widely used for the treatment of type 2 diabetes, and recent studies indicate that they may be cardio- and neuroprotective. The safety and effect of a single dose of exenatide, a short-acting GLP-1RA, on cerebral and peripheral arterial function remain unknown. Methods In this randomized, double-blind pilot trial, we assigned elderly healthy volunteers without diabetes and no previous history of stroke to receive a single dose of subcutaneous exenatide (5 μg) or placebo. Primary outcome was immediate changes over time in blood flow velocity of the middle cerebral arteries (VMCA) assessed by repeated transcranial Doppler measurements. Secondary outcomes were changes in peripheral arterial function with finger plethysmography, ankle-brachial index (ABI), and inflammatory- and endothelial-specific biomarkers. Results Healthy volunteers (13 women and 17 men) were included: (mean ± standard deviation) age: 62 ± 8 years; body weight: 79.6 ± 12.7 kg; VMCA: 65.3 ± 10.7 cm/s; fasting plasma glucose: 5.5 ± 0.5 mmol/L; HbA1c: 33.9 ± 4.1 mmol/mol (5.3 ± 0.38%). No differences between exenatide and placebo group were seen regarding VMCA (p = 0.058), systolic ABI (p = 0.71), plethysmography (p = 0.45), tumor necrosis factor (p = 0.33), interleukin-6 (p = 0.11), interleukin-1β (p = 0.34), vascular cell adhesion molecule 1 (p = 0.73), intercellular adhesion molecule 1 (p = 0.74), or E-selectin (p = 0.31). No severe adverse events were observed. Conclusion A single dose of exenatide did not change cerebral blood flow velocity or peripheral vessel function in elderly healthy volunteers. The medication was safe to use in persons without diabetes allowing us to investigate this drug further in search of the neuroprotective mechanisms. Clinical Trial Registration https://clinicaltrials.gov, Identifier NCT02838589.
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Affiliation(s)
- Joakim Ölmestig
- Neurovascular Research Unit, Department of Neurology, Copenhagen University Hospital – Herlev and Gentofte, Copenhagen, Denmark,Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Ida R. Marlet
- Neurovascular Research Unit, Department of Neurology, Copenhagen University Hospital – Herlev and Gentofte, Copenhagen, Denmark
| | - Tina Vilsbøll
- Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark,Steno Diabetes Center Copenhagen, Copenhagen, Denmark
| | - Jørgen Rungby
- Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark,Department of Endocrinology, Copenhagen University Hospital – Bispebjerg and Frederiksberg, Copenhagen, Denmark
| | - Egill Rostrup
- Center for Neuropsychiatric Schizophrenia Research, Copenhagen University Hospital – Mental Health Center Glostrup, Copenhagen, Denmark
| | - Kate L. Lambertsen
- Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark,Department of Neurology, Odense University Hospital, Odense, Denmark,BRIDGE – Brain Research-Inter-Disciplinary Guided Excellence, Department of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Christina Kruuse
- Neurovascular Research Unit, Department of Neurology, Copenhagen University Hospital – Herlev and Gentofte, Copenhagen, Denmark,Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark,*Correspondence: Christina Kruuse,
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Mazzucco S, Li L, McGurgan IJ, Tuna MA, Brunelli N, Binney LE, Rothwell PM. Cerebral hemodynamic effects of early blood pressure lowering after TIA and stroke in patients with carotid stenosis. Int J Stroke 2022; 17:1114-1120. [PMID: 34994271 DOI: 10.1177/17474930211068655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Effects of early blood pressure (BP) lowering on cerebral perfusion in patients with moderate/severe occlusive carotid disease after transient ischemic attack (TIA) and non-disabling stroke are uncertain. AIMS We aimed to evaluate the changes in transcranial Doppler (TCD) indices in patients undergoing blood pressure lowering soon after TIA/non-disabling stroke. METHODS Consecutive eligible patients (1 November 2011 to 30 October 2018) attending a rapid-access clinic with TIA/non-disabling stroke underwent telemetric home blood pressure monitoring (HBPM) for 1 month and middle cerebral artery velocities measurements ipsilateral to carotid stenosis on TCD ultrasound in the acute setting and at 1 month. Hypertensive patients (HBPM ⩾ 135/85) underwent intensive BP-lowering guided by HBPM unless they had bilateral severe occlusive disease (⩾ 70%). Changes in BP and TCD parameters were compared in patients with extracranial moderate/severe carotid stenosis (between 50% and occlusion) versus those with no or mild (< 50%) stenosis. RESULTS Of 764 patients with repeated TCD measures, 42 had moderate/severe extracranial carotid stenosis without bilateral severe occlusive disease. HBPM was reduced from baseline to 1 month in hypertensive patients both with versus without moderate/severe carotid stenosis (-12.44/15.99 vs -13.2/12.2 mmHg, respectively, p-difference = 0.82), and changes in TCD velocities (4.69/14.94 vs 2.69/13.86 cm/s, respectively, p-difference = 0.52 for peak systolic velocity and 0.33/7.06 vs 1.75/6.84 cm/s, p-difference = 0.34 for end-diastolic velocity) were also similar, with no evidence of greater hemodynamic compromise in patients with stenosis/occlusion. CONCLUSION There was no evidence of worsening of TCD hemodynamic indices in patients with moderate/severe occlusive carotid disease treated with BP-lowering soon after TIA/non-disabling stroke, suggesting that antihypertensive treatment in this group of patients is safe in the acute setting of TIA clinics.
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Affiliation(s)
- Sara Mazzucco
- Wolfson Centre for Prevention of Stroke and Dementia, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Linxin Li
- Wolfson Centre for Prevention of Stroke and Dementia, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Iain J McGurgan
- Wolfson Centre for Prevention of Stroke and Dementia, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Maria Assuncao Tuna
- Wolfson Centre for Prevention of Stroke and Dementia, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | | | - Lucy E Binney
- Wolfson Centre for Prevention of Stroke and Dementia, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Peter M Rothwell
- Wolfson Centre for Prevention of Stroke and Dementia, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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Klein SP, De Sloovere V, Meyfroidt G, Depreitere B. Differential Hemodynamic Response of Pial Arterioles Contributes to a Quadriphasic Cerebral Autoregulation Physiology. J Am Heart Assoc 2021; 11:e022943. [PMID: 34935426 PMCID: PMC9075199 DOI: 10.1161/jaha.121.022943] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Background Cerebrovascular autoregulation (CA) regulates cerebral vascular tone to maintain near-constant cerebral blood flow during fluctuations in cerebral perfusion pressure (CPP). Preclinical and clinical research has challenged the classic triphasic pressure-flow relationship, leaving the normal pressure-flow relationship unclear. Methods and Results We used in vivo imaging of the hemodynamic response in pial arterioles to study CA in a porcine closed cranial window model during nonpharmacological blood pressure manipulation. Red blood cell flux was determined in 52 pial arterioles during 10 hypotension and 10 hypertension experiments to describe the pressure-flow relationship. We found a quadriphasic pressure-flow relationship with 4 distinct physiological phases. Smaller arterioles demonstrated greater vasodilation during low CPP when compared with large arterioles (P<0.01), whereas vasoconstrictive capacity during high CPP was not significantly different between arterioles (P>0.9). The upper limit of CA was defined by 2 breakpoints. Increases in CPP lead to a point of maximal vasoconstriction of the smallest pial arterioles (upper limit of autoregulation [ULA] 1). Beyond ULA1, only larger arterioles maintain a limited additional vasoconstrictive capacity, extending the buffer for high CPP. Beyond ULA2, vasoconstrictive capacity is exhausted, and all pial arterioles passively dilate. There was substantial intersubject variability, with ranges of 29.2, 47.3, and 50.9 mm Hg for the lower limit, ULA1, and ULA2, respectively. Conclusions We provide new insights into the quadriphasic physiology of CA, differentiating between truly active CA and an extended capacity to buffer increased CPP with progressive failure of CA. In this experimental model, the limits of CA widely varied between subjects.
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Affiliation(s)
- Samuel P Klein
- Department of Neurosurgery University Hospitals Leuven Leuven Belgium
| | | | - Geert Meyfroidt
- Department of Intensive Care Medicine University Hospitals Leuven Leuven Belgium
| | - Bart Depreitere
- Department of Neurosurgery University Hospitals Leuven Leuven Belgium
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Gelpi F, Bari V, Cairo B, De Maria B, Tonon D, Rossato G, Faes L, Porta A. Dynamic cerebrovascular autoregulation in patients prone to postural syncope: Comparison of techniques assessing the autoregulation index from spontaneous variability series. Auton Neurosci 2021; 237:102920. [PMID: 34808528 DOI: 10.1016/j.autneu.2021.102920] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 10/20/2021] [Accepted: 11/15/2021] [Indexed: 10/19/2022]
Abstract
Three approaches to the assessment of cerebrovascular autoregulation (CA) via the computation of the autoregulation index (ARI) from spontaneous variability of mean arterial pressure (MAP) and mean cerebral blood flow velocity (MCBFV) were applied: 1) a time domain method (TDM); 2) a nonparametric method (nonPM); 3) a parametric method (PM). Performances were tested over matched and surrogate unmatched pairs. Data were analyzed at supine resting (REST) and during the early phase of 60° head-up tilt (TILT) in 13 subjects with previous history of postural syncope (SYNC, age: 28 ± 9 yrs.; 5 males) and 13 control individuals (noSYNC, age: 27 ± 8 yrs.; 5 males). Analysis was completed by computing autonomic markers from heart period (HP) and systolic arterial pressure (SAP) variability series via spectral approach. HP and SAP spectral indexes suggested that noSYNC and SYNC groups exhibited different autonomic responses to TILT. ARI analysis indicated that: i) all methods have a sufficient statistical power to separate matched from unmatched pairs with the exception of nonPM applied to impulse response; ii) ARI estimates derived from different methods might be uncorrelated and, even when correlated, might exhibit a significant bias; iii) orthostatic stressor did not induce any evident ARI change in either noSYNC or SYNC individuals; iv) this conclusion held regardless of the method. Methods for the ARI estimation from spontaneous variability provide different ARIs but none indicate that noSYNC and SYNC subjects have different dynamic component of CA.
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Affiliation(s)
- Francesca Gelpi
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy; Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Vlasta Bari
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
| | - Beatrice Cairo
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | | | - Davide Tonon
- Department of Neurology, IRCCS Sacro Cuore Don Calabria Hospital, Negrar, Verona, Italy
| | - Gianluca Rossato
- Department of Neurology, IRCCS Sacro Cuore Don Calabria Hospital, Negrar, Verona, Italy
| | - Luca Faes
- Department of Engineering, University of Palermo, Palermo, Italy
| | - Alberto Porta
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy; Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.
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Mazzucco S, Li L, McGurgan IJ, Tuna MA, Brunelli N, Binney LE, Rothwell PM. Age-specific cerebral haemodynamic effects of early blood pressure lowering after transient ischaemic attack and non-disabling stroke. Eur Stroke J 2021; 6:245-253. [PMID: 34746420 PMCID: PMC8564162 DOI: 10.1177/23969873211039716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 07/15/2021] [Indexed: 11/18/2022] Open
Abstract
INTRODUCTION There is limited knowledge of the effects of blood pressure (BP) lowering on cerebral haemodynamics after transient ischaemic attack (TIA) and non-disabling stroke, particularly at older ages. We aimed to evaluate changes in transcranial Doppler (TCD) haemodynamic indices in patients undergoing early blood pressure lowering after TIA/non-disabling stroke, irrespective of age. PATIENTS AND METHODS Among consecutive eligible patients attending a rapid-access clinic with suspected TIA/non-disabling stroke and no evidence of extra/intracranial stenosis, hypertensive ones underwent intensive BP-lowering guided by daily home telemetric blood pressure monitoring (HBPM). Clinic-based BP, HBPM, End-tidal CO2 and bilateral middle cerebral artery (MCA) velocity on TCD were compared in the acute setting versus one-month follow-up; changes were stratified by baseline hypertension (clinic-BP≥140/90) and by age (<65, 65-79 and ≥80). RESULTS In 697 patients with repeated TCD measures, mean/SD baseline systolic-BP (145.0/21.3 mmHg) was reduced by an average of 11.3/19.9 mmHg (p < 0.0001) at one-month (133.7/17.4 mmHg), driven by patients hypertensive at baseline (systolic-BP change = -19.0/19.2 mmHg, p < 0.001; vs -0.5/15.4, p = 0.62 in normotensives). Compared with baseline, a significant change was observed at one-month only in mean/SD MCA end diastolic velocity (EDV) (0.77/7.26 cm/s, p = 0.005) and in resistance index (RI) (-0.005/0.051, p = 0.016), driven by hypertensive patients (mean/SD EDV change: 1.145/6.96 cm/s p = 0.001, RI change -0.007/0.06, p = 0.014). Findings were similar at all ages (EDV change - ptrend=0.357; RI change - ptrend=0.225), including 117 patients aged ≥80. EDV and RI changes were largest in 100 patients with clinic systolic-BP decrease ≥30 mmHg (mean/SD EDV change = 2.49/7.47 cm/s, p = 0.001; RI change -0.024/0.063, p < 0.0001). CONCLUSION There was no evidence of worsening of TCD haemodynamic indices associated with BP-lowering soon after TIA/non-disabling stroke, irrespective of age and degree of BP reduction. In fact, EDV increase and RI decrease observed after treatment of hypertensive patients suggest a decrease in distal vascular resistance.
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Affiliation(s)
- Sara Mazzucco
- Nuffield Department of Clinical
Neurosciences, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford
| | - Linxin Li
- Nuffield Department of Clinical
Neurosciences, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford
| | - Iain J McGurgan
- Nuffield Department of Clinical
Neurosciences, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford
| | - Maria A Tuna
- Nuffield Department of Clinical
Neurosciences, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford
| | - Nicoletta Brunelli
- institution-id-type="Ringgold" />Campus Bio-Medico University of
Rome, Rome, Italy
| | - Lucy E Binney
- Nuffield Department of Clinical
Neurosciences, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford
| | - Peter M Rothwell
- Nuffield Department of Clinical
Neurosciences, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford
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12
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Physiology of the cerebrovascular adaptation to pregnancy. HANDBOOK OF CLINICAL NEUROLOGY 2021. [PMID: 32736760 DOI: 10.1016/b978-0-444-64239-4.00004-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
The adaptation of the cerebral circulation to pregnancy is unique compared with other organs and circulatory systems, because the brain requires relatively constant blood flow and water and solute composition to maintain homeostasis. Thus, a major adaptation of the maternal cerebrovasculature to pregnancy is to maintain normalcy in the face of expanded plasma volume, increased cardiac output, and high levels of permeability factors. In this chapter, the effect of pregnancy on critical functions of the cerebral circulation is discussed, including changes occurring at the endothelium and blood-brain barrier (BBB), which protect the maternal brain from changes in BBB permeability. Further, pregnancy-induced changes in the structure and function of cerebral arteries, arterioles, and veins will be discussed as they relate to cerebral vascular resistance, hemodynamics, and cerebral blood flow autoregulation.
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13
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Sobczyk O, Fierstra J, Venkatraghavan L, Poublanc J, Duffin J, Fisher JA, Mikulis DJ. Measuring Cerebrovascular Reactivity: Sixteen Avoidable Pitfalls. Front Physiol 2021; 12:665049. [PMID: 34305634 PMCID: PMC8294324 DOI: 10.3389/fphys.2021.665049] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Accepted: 06/07/2021] [Indexed: 12/04/2022] Open
Abstract
An increase in arterial PCO2 is the most common stressor used to increase cerebral blood flow for assessing cerebral vascular reactivity (CVR). That CO2 is readily obtained, inexpensive, easy to administer, and safe to inhale belies the difficulties in extracting scientifically and clinically relevant information from the resulting flow responses. Over the past two decades, we have studied more than 2,000 individuals, most with cervical and cerebral vascular pathology using CO2 as the vasoactive agent and blood oxygen-level-dependent magnetic resonance imaging signal as the flow surrogate. The ability to deliver different forms of precise hypercapnic stimuli enabled systematic exploration of the blood flow-related signal changes. We learned the effect on CVR of particular aspects of the stimulus such as the arterial partial pressure of oxygen, the baseline PCO2, and the magnitude, rate, and pattern of its change. Similarly, we learned to interpret aspects of the flow response such as its magnitude, and the speed and direction of change. Finally, we were able to test whether the response falls into a normal range. Here, we present a review of our accumulated insight as 16 “lessons learned.” We hope many of these insights are sufficiently general to apply to a range of types of CO2-based vasoactive stimuli and perfusion metrics used for CVR.
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Affiliation(s)
- Olivia Sobczyk
- Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, ON, Canada.,Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, ON, Canada
| | - Jorn Fierstra
- Department of Neurosurgery, University Hospital Zurich, Zürich, Switzerland
| | - Lakshmikumar Venkatraghavan
- Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, ON, Canada
| | - Julien Poublanc
- Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, ON, Canada
| | - James Duffin
- Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Joseph A Fisher
- Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - David J Mikulis
- Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
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14
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Bari V, Fantinato A, Vaini E, Gelpi F, Cairo B, De Maria B, Pistuddi V, Ranucci M, Porta A. Impact of propofol general anesthesia on cardiovascular and cerebrovascular closed loop variability interactions. Biomed Signal Process Control 2021. [DOI: 10.1016/j.bspc.2021.102735] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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15
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Amemiya S, Takao H, Abe O. Origin of the Time Lag Phenomenon and the Global Signal in Resting-State fMRI. Front Neurosci 2020; 14:596084. [PMID: 33250709 PMCID: PMC7673396 DOI: 10.3389/fnins.2020.596084] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 10/12/2020] [Indexed: 11/13/2022] Open
Abstract
The global mean signal of resting-state fMRI (rs-fMRI) shows a characteristic spatiotemporal pattern that is closely related to the pattern of vascular perfusion. Although being increasingly adopted in the mapping of the flow of neural activity, the mechanism that gives rise to the BOLD signal time lag remains controversial. In the present study, we compared the time lag of the global mean signal with those of the local network components obtained by applying temporal independent component analysis to the resting-state fMRI data, as well as by using simultaneous wide-field visual stimulation, and demonstrated that the time lag patterns are highly similar across all types of data. These results suggest that the time lag of the rs-fMRI signal reflects the local variance of the hemodynamic responses rather than the arrival or transit time of the stimulus, whether the trigger is neuronal or non-neuronal in origin as long as it is mediated by local hemodynamic responses. Examinations of the internal carotid artery signal further confirmed that the arterial signal is tightly inversely coupled with the global mean signal in accordance with previous studies, presumably reflecting the blood flow or blood pressure changes that are occurring almost simultaneously in the internal carotid artery and the cerebral pial/capillary arteries, within the low-frequency component in human rs-fMRI.
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Affiliation(s)
- Shiori Amemiya
- Department of Radiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hidemasa Takao
- Department of Radiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Osamu Abe
- Department of Radiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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16
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Jung KO, Lee SJ, Lee TK. A Breath-Holding Index Applied to the Internal Carotid Artery Siphon in Transcranial Doppler Studies. J Neuroimaging 2020; 30:862-866. [PMID: 32937001 DOI: 10.1111/jon.12752] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 06/05/2020] [Accepted: 06/22/2020] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND AND PURPOSE The breath-holding index (BHI) is a useful method to assess cerebrovascular reactivity. It is calculated based on the mean flow velocities of the middle cerebral artery (MCA) using transcranial Doppler (BHIMCA ). Therefore, it is not feasible in patients with poor temporal windows. This study tested the feasibility of a BHI using the internal carotid artery (ICA) siphon flow velocity (BHIICA ). METHODS Twenty-four patients (aged 38-79 years) with unilateral or bilateral stenosis of the cervical ICAs were prospectively recruited. The 48 examined bilateral ICAs were divided into three groups according to the stenosis degree: <50%, 50-99%, and occlusion. We investigated the reproducibility of both BHI methods (BHIMCA and BHIICA ), the correlation between the two BHI methods, and the tendency for the BHIs to decrease with increasing degree of cervical ICA stenosis. RESULTS For the BHIMCA , we found a good reproducibility (intraclass correlation coefficient, rI > .9) and a significantly decreased BHI with increasing stenosis of the ICA (P = .001). For the BHIICA , good reproducibility was demonstrated (rI > or ≒ .9), but there was no significant decrease in the BHI related to the increasing degree of ICA stenosis (P = .952). Furthermore, the correlation between the two BHI methods was not robust (kappa coefficient, right .259; left .619). CONCLUSIONS Our study suggests that the BHIICA is not a feasible alternative method to the BHIMCA.
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Affiliation(s)
- Kyu-On Jung
- All authors are from Department of Neurology, Soonchunhyang University Bucheon Hospital, Bucheon, South Korea
| | - Seung-Jae Lee
- All authors are from Department of Neurology, Soonchunhyang University Bucheon Hospital, Bucheon, South Korea
| | - Tae-Kyeong Lee
- All authors are from Department of Neurology, Soonchunhyang University Bucheon Hospital, Bucheon, South Korea
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17
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Wu T, Shen J, Li Z, Zou T, Xin W, Xing F, Zhang F, Man Z, Fu S. Graphene-based ultrasensitive optical microfluidic sensor for the real-time and label-free monitoring of simulated arterial blood flow. OPTICS EXPRESS 2020; 28:16594-16604. [PMID: 32549478 DOI: 10.1364/oe.392993] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 05/11/2020] [Indexed: 06/11/2023]
Abstract
Highly sensitive, real-time and label-free sensing of liquid flow in microfluidic environments remains challenging. Here, by growing high-quality graphene directly on a glass substrate, we designed a microfluidic-integrated graphene-based flow sensor (GFS) capable of detecting complex, weak, and transient flow velocity and pressure signals in a microfluidic environment. This device was used to study weak and transient liquid flows, especially blood flow, which is closely related to heart and artery functions. By simulating cardiac peristalsis and arterial flow using peristaltic pumps and microfluidic systems, we monitored simulated arterial blood flow. This ultrasensitive graphene-based flow sensor accurately detected a flow velocity limit as low as 0.7 mm/s, a pumping frequency range of 0.04 Hz to 2.5 Hz, and a pressure range from 0.6 kPa to 14 kPa. By measuring the blood flow velocities and pressures, pathological blood flow signals were distinguished and captured by the corresponding flow velocities or pressures, which can reflect vascular occlusion and heart functions. This sensor may be used for the real-time and label-free monitoring of patients' basic vital signs using their blood flow and provide a possible new method for the care of critically ill patients.
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18
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Cardiovascular disease risk is associated with middle cerebral artery blood flow velocity in older adults. Cardiopulm Phys Ther J 2020; 31:38-46. [PMID: 33100924 PMCID: PMC7580865 DOI: 10.1097/cpt.0000000000000110] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Purpose The aim of this study was to evaluate the relationship of cardiovascular disease (CVD) on middle cerebral blood flow velocity (MCAv) at rest and during exercise. A secondary aim was to explore the relationship between MCAv and 1) the presence of white matter lesions and 2) cognitive function. Methods We recruited individuals who were cognitively normal older adults. CVD risk was assessed by the Pooled Cohort atherosclerotic cardiovascular disease (ASCVD) risk score. Transcranial Doppler ultrasound measured middle cerebral artery at rest and during a bout of moderate intensity exercise. We quantified white matter lesions from MRI and cognitive function outcomes included executive function, language, processing speed, and attention. Results Seventy-two participants 70.1 ± 4.7 years of age completed the study protocol. ASCVD risk score was significantly associated with resting and exercise MCAv (p<0.01) but not associated with white matter lesions (p>0.468). We observed a significant association between resting and exercise MCAv and language processing (p=0.010) but not other cognitive domains. Conclusion In cognitively normal older adults, higher ASCVD risk score was associated with blunted resting and exercise MCAv and with lower language processing performance. These results highlight the need for CVD risk management to maintain optimal brain health.
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19
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Gibbons TD, Zuj KA, Prince CN, Kingston DC, Peterson SD, Hughson RL. Haemodynamic and cerebrovascular effects of intermittent lower-leg compression as countermeasure to orthostatic stress. Exp Physiol 2019; 104:1790-1800. [PMID: 31578774 DOI: 10.1113/ep088077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 09/30/2019] [Indexed: 02/04/2023]
Abstract
NEW FINDINGS What is the central question of this study? Does smartly timed intermittent compression of the lower legs alter cerebral blood velocity and oxygenation during acute orthostatic challenges? What is the main finding and its importance? Intermittent compression timed to the local diastolic phase increased the blood flux through the legs and heart after two different orthostatic stress tests. Cerebral blood velocity improved during the first minute of recovery, and indices of cerebral tissue oxygenation remained elevated for 2 min. These results provide promise for the use of lower-leg active compression as a therapeutic tool for individuals vulnerable to initial orthostatic hypotension and orthostatic stress. ABSTRACT Intermittent compression of the lower legs provides the possibility of improving orthostatic tolerance by actively promoting venous return and improving central haemodynamics. We tested the hypothesis that intermittent compression of 65 mmHg timed to occur only within the local diastolic phase of each cardiac cycle would attenuate the decrease in blood pressure and improve cerebral haemodynamics during the first minute of recovery from two different orthostatic stress tests. Fourteen subjects (seven female) performed four squat-to-stand transitions and four repeats of standing bilateral thigh-cuff occlusion and release (TCR), with intermittent compression of the lower legs applied in half of the trials. Blood flow in the superficial femoral artery, mean arterial pressure, Doppler ultrasound cardiac output, total peripheral resistance, middle cerebral artery blood velocity (MCAv) and cerebral tissue saturation index (TSI%) were monitored. With both orthostatic stress tests, there was a significant compression × time interaction for superficial femoral artery flow (P < 0.001). The hypotensive state was attenuated with intermittent compression despite decreased total peripheral resistance (squat-to-stand, compression × time interaction, P < 0.001; TCR, compression × time interaction, P = 0.002) as a consequence of elevated cardiac output in both tests (P < 0.001). Intermittent compression also increased MCAv (P = 0.001) and TSI% (P < 0.001) during the squat-to-stand transition and during TCR (MCAv and TSI%, compression × time interaction, P < 0.001). Intermittent compression of the lower legs during quiet standing after an active orthostatic challenge augmented local, central and cerebral haemodynamics, providing potential as a therapeutic tool for individuals vulnerable to orthostatic stress.
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Affiliation(s)
- Travis D Gibbons
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Kathryn A Zuj
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Chekema N Prince
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
| | - David C Kingston
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Sean D Peterson
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
| | - Richard L Hughson
- Schlegel-University of Waterloo Research Institute for Aging, Faculty of Applied Health Sciences, Waterloo, ON, Canada
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20
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Klein SP, De Sloovere V, Meyfroidt G, Depreitere B. Autoregulation assessment by direct visualisation of pial arterial blood flow in the piglet brain. Sci Rep 2019; 9:13333. [PMID: 31527671 PMCID: PMC6746693 DOI: 10.1038/s41598-019-50046-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 09/04/2019] [Indexed: 12/22/2022] Open
Abstract
Impairment of cerebrovascular autoregulation (CAR) is common after brain injury, although the pathophysiology remains elusive. The mechanisms of vascular dysregulation, their impact on brain function, and potential therapeutic implications are still incompletely understood. Clinical assessment of CAR remains challenging. Observational studies suggest that CAR impairment is associated with worse outcomes, and that optimization of cerebral blood flow (CBF) by individual arterial blood pressure (ABP) targets could potentially improve outcome. We present a porcine closed cranial window model that measures the hemodynamic response of pial arterioles, the main site of CBF control, based on changes in their diameter and red blood cell velocity. This quantitative direct CAR assessment is compared to laser Doppler flow (LDF). CAR breakpoints are determined by segmented regression analysis and validated using LDF and brain tissue oxygen pressure. Using a standardized cortical impact, CAR impairment in traumatic brain injury can be studied using our method of combining pial arteriolar diameter and RBC velocity to quantify RBC flux in a large animal model. The model has numerous potential applications to investigate CAR physiology and pathophysiology of CAR impairment after brain injury, the impact of therapeutic interventions, drugs, and other confounders, or to develop personalized ABP management strategies.
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Affiliation(s)
- S P Klein
- Department of Neurosurgery, University Hospitals Leuven, Leuven, Belgium.
| | - V De Sloovere
- Department of Anesthesiology, University Hospitals Leuven, Leuven, Belgium
| | - G Meyfroidt
- Department of Intensive Care Medicine, University Hospitals Leuven, Leuven, Belgium
| | - B Depreitere
- Department of Neurosurgery, University Hospitals Leuven, Leuven, Belgium
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21
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Iyer PC, Rosenberg A, Baynard T, Madhavan S. Influence of neurovascular mechanisms on response to tDCS: an exploratory study. Exp Brain Res 2019; 237:2829-2840. [PMID: 31455998 DOI: 10.1007/s00221-019-05626-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 08/08/2019] [Indexed: 10/26/2022]
Abstract
The beneficial effects of transcranial direct current stimulation (tDCS) for stroke rehabilitation are limited by the variability in changes in corticomotor excitability (CME) after tDCS. Neuronal activity is closely related to cerebral blood flow; however, the cerebral hemodynamics of neuromodulation in relation to neural effects have been less explored. In this study, we examined the effects of tDCS on cerebral blood velocity (CBv) in chronic stroke survivors using transcranial Doppler (TCD) ultrasound in relation to changes in CME and described the neurovascular characteristics of tDCS responders. Middle cerebral artery (MCA) CBv, cerebrovascular resistance (CVRi) and other cerebral hemodynamics-related variables were continuously measured before and after 15 min of 1 mA anodal tDCS to the lesioned lower limb M1. tDCS did not modulate CBv in the whole group and upon TMS-based stratification of responders and non-responders. However, at baseline, responders demonstrated lower CME levels, lower CBv and higher CVRi as compared to non-responders. These results indicate a possible difference in baseline CME and CBv in tDCS responders that may influence their response to neuromodulation. Future trials with a large sample size and repeated baseline measurements may help validate these findings and establish a relationship between neuromodulation and neurovascular mechanisms in stroke.
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Affiliation(s)
- Pooja C Iyer
- Graduate Program in Rehabilitation Science, College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Alexander Rosenberg
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA.,Integrative Physiology Laboratory, College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Tracy Baynard
- Integrative Physiology Laboratory, College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Sangeetha Madhavan
- Brain Plasticity Laboratory, Department of Physical Therapy, College of Applied Health Sciences, University of Illinois at Chicago, 1919 West Taylor Street, Chicago, IL, 60612, USA.
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22
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Perdomo SJ, Balzer JR, Jakicic JM, Kline CE, Gibbs BB. Acute effects of aerobic exercise duration on blood pressure, pulse wave velocity and cerebral blood flow velocity in middle-aged adults. SPORT SCIENCES FOR HEALTH 2019. [DOI: 10.1007/s11332-019-00566-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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23
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Burlakoti A, Kumaratilake J, Taylor J, Henneberg M. Asymmetries of total arterial supply of cerebral hemispheres do not exist. Heliyon 2019; 5:e01086. [PMID: 30671556 PMCID: PMC6328356 DOI: 10.1016/j.heliyon.2018.e01086] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 11/19/2018] [Accepted: 12/19/2018] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Total blood supply to an organ, or its part, is proportional to its function. The aim of this project was to investigate whether there is a lateralisation of total functions of cerebral hemispheres by determining differences in the arterial blood supply to left and right cerebral hemispheres. METHODS Diameters of right and left anterior, middle and posterior cerebral arteries were measured at specific sites and cross-sectional areas calculated in 203 adult brains (51 donated and dissected brain specimens and 152 cerebral arterial Computed Tomography Angiography and Magnetic Resonance Angiography images). FINDINGS The sample size was large enough to provide a power of detecting as significant differences of 4%, but neither of the average cross-sectional areas of right anterior, middle and posterior cerebral arteries were significantly different from those of the anterior, middle and posterior cerebral arteries of the left side. Furthermore, combined areas of the three right cerebral arteries were not significantly different from combined areas of the left three arteries. This clearly indicates that the blood supply into the right cerebral hemisphere is not different from that of the left cerebral hemisphere. Therefore, there is no total functional lateralisation between the two cerebral hemispheres. CONCLUSION Brain lateralisation, frequently discussed in the literature, does not deferentially influence the total activity levels of cerebral hemispheres.
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Affiliation(s)
- Arjun Burlakoti
- School of Health Sciences, University of South Australia, Australia
- Adelaide Medical School, Biological and Anthropology and Comparative Anatomy Research Unit, The University of Adelaide, Australia
| | - Jaliya Kumaratilake
- Adelaide Medical School, Biological and Anthropology and Comparative Anatomy Research Unit, The University of Adelaide, Australia
| | - Jamie Taylor
- Magnetic Resonance Imaging Centre, Royal Adelaide Hospital, Australia
| | - Maciej Henneberg
- Adelaide Medical School, Biological and Anthropology and Comparative Anatomy Research Unit, The University of Adelaide, Australia
- Institute of Evolutionary Medicine, University of Zurich, Switzerland
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The relative effects of dexmedetomidine and propofol on cerebral blood flow velocity and regional brain oxygenation: A randomised noninferiority trial. Eur J Anaesthesiol 2018; 34:732-739. [PMID: 28891839 DOI: 10.1097/eja.0000000000000662] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Dexmedetomidine constricts cerebral blood vessels without a concomitant reduction in cerebral metabolic oxygen consumption. Its safety as a sedative in patients with neurological diseases thus remains uncertain. OBJECTIVE Our primary objective was to test the hypothesis that dexmedetomidine is noninferior to propofol as regards cerebral blood flow (CBF) velocity and brain oxygenation. DESIGN Unblinded randomised trial. SETTING Cleveland Clinic Hospital, Cleveland, from November 2010 to July 2013. PATIENTS Forty-four patients scheduled for insertion of a deep-brain stimulating electrodes. INTERVENTIONS Patients were randomised to receive either dexmedetomidine or propofol sedation during deep-brain stimulating electrode insertion. MAIN OUTCOME MEASURES Intraoperative CBF velocity was measured with transcranial Doppler, and brain oxygenation was assessed with near-infrared spectroscopy. Noninferiority of dexmedetomidine to propofol was defined as a less than 20% difference in means. RESULTS Twenty-three patients were given dexmedetomidine and 21 propofol. Baseline characteristics and operative management were similar in each group. Dexmedetomidine was noninferior to propofol on both CBF and brain oxygenation, confirming our primary hypothesis. For cerebral flood flow, the estimated ratio of means (dexmedetomidine/propofol) was 0.94 [90% CI: 0.84 to 1.05], P = 0.011 for noninferiority. For brain oxygenation, the estimated ratio of means was 0.99 [90% CI: 0.96 to 1.02], P < 0.001 for noninferiority. Superiority was not found for either primary outcome. Dexmedetomidine provided deeper sedation than propofol, with a difference of medians of 1 [90% CI: 0 to 2], P < 0.001 on the Observer's Assessment of Alertness/Sedation scale. No significant differences were observed in pulsatility index, cerebral perfusion pressure, number of hypertensive or apnoeic episodes. CONCLUSION Regional brain oxygenation and CBF velocity are comparably preserved during dexmedetomidine and propofol sedation. Thus, the use of dexmedetomidine in patients with movement disorders appears reasonable. TRIAL REGISTRATION The trial was registered at ClinicalTrials.gov (NCT 01200433).
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Rey B, Rodríguez A, Lloréns-Bufort E, Tembl J, Muñoz MÁ, Montoya P, Herrero-Bosch V, Monzo JM. Design and Validation of an FPGA-Based Configurable Transcranial Doppler Neurofeedback System for Chronic Pain Patients. SENSORS 2018; 18:s18072278. [PMID: 30011900 PMCID: PMC6069097 DOI: 10.3390/s18072278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 07/09/2018] [Accepted: 07/12/2018] [Indexed: 11/23/2022]
Abstract
Neurofeedback is a self-regulation technique that can be applied to learn to voluntarily control cerebral activity in specific brain regions. In this work, a Transcranial Doppler-based configurable neurofeedback system is proposed and described. The hardware configuration is based on the Red Pitaya board, which gives great flexibility and processing power to the system. The parameter to be trained can be selected between several temporal, spectral, or complexity features from the cerebral blood flow velocity signal in different vessels. As previous studies have found alterations in these parameters in chronic pain patients, the system could be applied to help them to voluntarily control these parameters. Two protocols based on different temporal lengths of the training periods have been proposed and tested with six healthy subjects that were randomly assigned to one of the protocols at the beginning of the procedure. For the purposes of the testing, the trained parameter was the mean cerebral blood flow velocity in the aggregated data from the two anterior cerebral arteries. Results show that, using the proposed neurofeedback system, the two groups of healthy volunteers can learn to self-regulate a parameter from their brain activity in a reduced number of training sessions.
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Affiliation(s)
- Beatriz Rey
- Departamento de Ingeniería Gráfica, Universitat Politècnica de València, Camino Vera s/n, 46022 Valencia, Spain.
| | - Alejandro Rodríguez
- Departamento de Ingeniería Gráfica, Universitat Politècnica de València, Camino Vera s/n, 46022 Valencia, Spain.
| | - Enrique Lloréns-Bufort
- Instituto de Instrumentación para Imagen Molecular (I3M), Centro Mixto CSIC-Universitat Politècnica de València-CIEMAT, Camino de Vera s/n, 46022 Valencia, Spain.
| | - José Tembl
- Departamento de Neurología, Hospital Universitari i Politècnic La Fe, 46026 Valencia, Spain.
| | - Miguel Ángel Muñoz
- Departamento de Personalidad, Evaluación y Tratamiento Psicológico, Universidad de Granada, 18071 Granada, Spain.
| | - Pedro Montoya
- Instituto Universitario de Investigación en Ciencias de la Salud, Universitat Illes Balears, 07122 Palma, Spain.
| | - Vicente Herrero-Bosch
- Instituto de Instrumentación para Imagen Molecular (I3M), Centro Mixto CSIC-Universitat Politècnica de València-CIEMAT, Camino de Vera s/n, 46022 Valencia, Spain.
| | - Jose M Monzo
- Instituto de Instrumentación para Imagen Molecular (I3M), Centro Mixto CSIC-Universitat Politècnica de València-CIEMAT, Camino de Vera s/n, 46022 Valencia, Spain.
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Nelander M, Hannsberger D, Sundström-Poromaa I, Bergman L, Weis J, Åkerud H, Wikström J, Wikström AK. Assessment of cerebral perfusion and edema in preeclampsia with intravoxel incoherent motion MRI. Acta Obstet Gynecol Scand 2018; 97:1212-1218. [PMID: 29786833 DOI: 10.1111/aogs.13383] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Accepted: 05/15/2018] [Indexed: 11/30/2022]
Abstract
INTRODUCTION Cerebral complications are the main reasons for morbidity and mortality in preeclampsia and eclampsia. As yet, we do not know whether the pathophysiology entails hypo- or hyperperfusion of the brain, or how and when edema emerges, due to the difficulty of examining the cerebral circulation. MATERIAL AND METHODS We have used a non-invasive diffusion weighted-magnetic resonance imaging technique, intravoxel incoherent motion, to study cerebral perfusion on the capillary level and cerebral edema in women with preeclampsia (n = 30), normal pregnancy (n = 32), and non-pregnant women (n = 16). Estimates of cerebral blood volume, blood flow, and edema were measured in 5 different regions. These points were chosen to represent blood supply areas of both the carotid and vertebrobasilar arteries, and to include both white and gray matter. RESULTS Except for the caudate nucleus, we did not detect any differences in cerebral perfusion measures on a group level. In the caudate nucleus, we found lower cerebral blood volume and lower blood flow in preeclampsia than in either normal pregnancy (P = .01 and P = .03, respectively) or non-pregnant women (both P = .02). No differences in edema were detected between study groups. CONCLUSION The cerebral perfusion measures were comparable between the study groups, except for a portion of the basal ganglia where hypoperfusion was detected in preeclampsia but not in normal pregnancy or non-pregnant women.
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Affiliation(s)
- Maria Nelander
- Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden
| | | | | | - Lina Bergman
- Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden.,Center for Clinical Research Dalarna, Falun, Sweden
| | - Jan Weis
- Department of Radiology, Uppsala University, Uppsala, Sweden.,Department of Medical Physics, Uppsala University Hospital, Uppsala, Sweden
| | - Helena Åkerud
- Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden.,Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Johan Wikström
- Department of Radiology, Uppsala University, Uppsala, Sweden
| | - Anna-Karin Wikström
- Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden
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Affiliation(s)
- Y C Tzeng
- Wellington Medical Technology Group, Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - R B Panerai
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
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De Bortoli M, Maillet A, Skopinski S, Sassoust G, Constans J, Boulon C. [Cerebral vasoreactivity: Concordance of breath holding test and acetazolamide injection in current practice: 20 cases of asymptomatic carotid artery stenosis]. JOURNAL DE MEDECINE VASCULAIRE 2017; 42:272-281. [PMID: 28964386 DOI: 10.1016/j.jdmv.2017.06.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 05/30/2017] [Indexed: 11/30/2022]
Abstract
INTRODUCTION Cerebral vasoreactivity (CVR) is the ability of the brain's vascular system to keep cerebral blood inflow stable. Impaired CVR is a risk marker of stroke in patients with asymptomatic carotid stenosis. The gold standard to assess CVR with transcranial ultrasound is acetazolamide (ACTZ) injection. The breath holding test (BHT) might be easier to perform. CVR proved to be efficient in laboratory conditions but not in routine practice. OBJECTIVES To study the validity of BHT versus ACTZ in routine practice in a vascular exploration unit in patients with asymptomatic carotid stenosis. METHODS Study of concordance of BHT and ACTZ, to assess CVR in patients consecutively explored on the same day. RESULTS Eighteen patients with 20 carotid stenosis were included. The temporal window was missing in 20% of cases. Only 11 out of the 20 procedures were analyzed. Concordance was low between BHT and ACTZ to assess CVR (k=0.3714). CONCLUSION BHT cannot replace ACTZ injection. It might be a first-step test so that ACTZ injection might be avoided if CVR is normal. Our present results must be confirmed by further study enrolling many more patients.
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Affiliation(s)
- M De Bortoli
- Service de médecine vasculaire, hôpital St-André, 1, rue Jean-Burguet, 33075 Bordeaux, France.
| | - A Maillet
- Service de médecine vasculaire, hôpital St-André, 1, rue Jean-Burguet, 33075 Bordeaux, France
| | - S Skopinski
- Service de médecine vasculaire, hôpital St-André, 1, rue Jean-Burguet, 33075 Bordeaux, France
| | - G Sassoust
- Service de chirurgie vasculaire, hôpital Pellegrin, place Amélie-Raba-Léon, 33000 Bordeaux, France
| | - J Constans
- Service de médecine vasculaire, hôpital St-André, 1, rue Jean-Burguet, 33075 Bordeaux, France
| | - C Boulon
- Service de médecine vasculaire, hôpital St-André, 1, rue Jean-Burguet, 33075 Bordeaux, France
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Kane SC, Brennecke SP, da Silva Costa F. Ophthalmic artery Doppler analysis: a window into the cerebrovasculature of women with pre-eclampsia. ULTRASOUND IN OBSTETRICS & GYNECOLOGY : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY OF ULTRASOUND IN OBSTETRICS AND GYNECOLOGY 2017; 49:15-21. [PMID: 27485824 DOI: 10.1002/uog.17209] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 07/22/2016] [Indexed: 05/27/2023]
Affiliation(s)
- S C Kane
- University of Melbourne, Department of Obstetrics and Gynaecology, The Royal Women's Hospital, Parkville, Victoria, Australia
- Pregnancy Research Centre, Department of Maternal Fetal Medicine, The Royal Women's Hospital, Parkville, Victoria, Australia
| | - S P Brennecke
- University of Melbourne, Department of Obstetrics and Gynaecology, The Royal Women's Hospital, Parkville, Victoria, Australia
- Pregnancy Research Centre, Department of Maternal Fetal Medicine, The Royal Women's Hospital, Parkville, Victoria, Australia
| | - F da Silva Costa
- University of Melbourne, Department of Obstetrics and Gynaecology, The Royal Women's Hospital, Parkville, Victoria, Australia
- Perinatal Services, Monash Health, Clayton, Victoria, Australia
- Monash Ultrasound for Women, Clayton, Victoria, Australia
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30
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Hoiland RL, Ainslie PN. CrossTalk proposal: The middle cerebral artery diameter does change during alterations in arterial blood gases and blood pressure. J Physiol 2016; 594:4073-5. [PMID: 27010010 DOI: 10.1113/jp271981] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 02/12/2016] [Indexed: 11/08/2022] Open
Affiliation(s)
- Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, British Columbia, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, British Columbia, Canada
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Bleton H, Perera S, Sejdić E. Cognitive tasks and cerebral blood flow through anterior cerebral arteries: a study via functional transcranial Doppler ultrasound recordings. BMC Med Imaging 2016; 16:22. [PMID: 26969112 PMCID: PMC4788871 DOI: 10.1186/s12880-016-0125-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 02/29/2016] [Indexed: 01/12/2023] Open
Abstract
Background Functional transcanial Doppler ultrasound (fTCD) is a convenient approach to examine cerebral blood flow velocity (CBFV) in major cerebral arteries. Methods In this study, the anterior cerebral artery (ACA) was insonated on both sides, that is, right ACA (R-ACA) and left ACA (L-ACA). The envelope signals (the maximum velocity) and the raw signals were analyzed during cognitive processes, i.e. word-generation tasks, geometric tasks and resting state periods separating each task. Data which were collected from 20 healthy participants were used to investigate the changes and the hemispheric functioning while performing cognitive tasks. Signal characteristics were analyzed in time domain, frequency domain and time-frequency domain. Results Significant results have been obtained through the use of both classic/modern methods (i.e. envelope/raw, time and frequency/information-theoretic and time-frequency domains). The frequency features extracted from the raw signals highlighted sex effects on cerebral blood flow which revealed distinct brain response during each process and during resting periods. In the time-frequency analysis, the distribution of wavelet energies on the envelope signals moved around the low frequencies during mental processes and did not experience any lateralization during cognitive tasks. Conclusions Even if no lateralization effects were noticed during resting-state, verbal and geometric tasks, understanding CBFV in ACA during cognitive tasks could complement information extracted from cerebral blood flow in middle cerebral arteries during similar cognitive tasks (i.e. sex effects).
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Affiliation(s)
- Héloïse Bleton
- Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Subashan Perera
- Division of Geriatric Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ervin Sejdić
- Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, PA, USA.
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Arulvelan A, Manikandan S, Easwer HV, Krishnakumar K. Cerebral vascular effects of loading dose of dexmedetomidine: A Transcranial Color Doppler study. Indian J Crit Care Med 2016; 20:9-13. [PMID: 26955211 PMCID: PMC4760000 DOI: 10.4103/0972-5229.173680] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Background: Dexmedetomidine has been widely used in critical care settings because of its property of maintaining stable hemodynamics and inducing conscious sedation. The use of dexmedetomidine is in increasing trend particularly in patients with neurological disorders. Very few studies have focused on the cerebral hemodynamic effects of dexmedetomidine. This study is aimed to address this issue. Methods: Thirty patients without any intracranial pathology were included in this study. Middle cerebral artery flow velocity obtained from transcranial color Doppler was used to assess the cerebral hemodynamic indices. Mean flow velocity (mFV), pulsatility index (PI), cerebral vascular resistant index (CVRi), estimated cerebral perfusion pressure (eCPP), and zero flow pressure (ZFP) were calculated bilaterally at baseline and after infusion of injection Dexmedetomidine 1 mcg/Kg over 10 min. Results: Twenty-six patients completed the study protocol. After administration of loading dose of dexmedetomidine, mFV and eCPP values were significantly decreased in both hemispheres (P < 0.05); PI, CVRi, and ZFP values showed significant increase (P < 0.05) after dexmedetomidine infusion. Conclusion: Increase in PI, CVRi, and ZFP suggests that there is a possibility of an increase in distal cerebral vascular resistance (CVR) with loading dose of dexmedetomidine. Decrease in mFV and eCPP along with an increase in CVR may lead to a decrease in cerebral perfusion. This effect can be exaggerated in patients with preexisting neurological illness. Further studies are needed to evaluate the effect of dexmedetomidine on various other pathological conditions involving brain like traumatic brain injury and vascular malformations.
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Affiliation(s)
- Appavoo Arulvelan
- Department of Anesthesiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Ulloor, Trivandrum, Kerala, India
| | - Sethuraman Manikandan
- Department of Anesthesiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Ulloor, Trivandrum, Kerala, India
| | - Hari Venkat Easwer
- Department of Anesthesiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Ulloor, Trivandrum, Kerala, India
| | - Kesavapisharady Krishnakumar
- Department of Anesthesiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Ulloor, Trivandrum, Kerala, India
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33
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Sitzer M, Diehl RR, Hennerici M. Visually Evoked Cerebral Blood Flow Responses. J Neuroimaging 2016. [DOI: 10.1111/jon19922265] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Abnormal transcranial Doppler cerebral blood flow velocity and blood pressure profiles in children with syndromic craniosynostosis and papilledema. J Craniomaxillofac Surg 2016; 44:465-70. [PMID: 26857754 DOI: 10.1016/j.jcms.2016.01.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 12/09/2015] [Accepted: 01/04/2016] [Indexed: 11/22/2022] Open
Abstract
OBJECTIVE Children with syndromic craniosynostosis are at risk of intracranial hypertension. This study aims to examine patient profiles of transcranial Doppler (TCD) cerebral blood flow velocity (CBFv) and systemic blood pressure (BP) in subjects with and without papilledema at the time of surgery, and subsequent effect of cranial vault expansion. METHODS Prospective study of patients treated at a national referral center. Patients underwent TCD of the middle cerebral artery 1 day before and 3 weeks after surgery. Measurements included mean CBFv, peak systolic velocity, and end diastolic velocity; age-corrected resistive index (RI) was calculated. Systemic BP was recorded. Papilledema was used to indicate intracranial hypertension. RESULTS Twelve patients (mean age 3.1 years, range 0.4-9.5) underwent TCD; 6 subjects had papilledema. Pre-operatively, patients with papilledema, in comparison to those without, had higher TCD values, RI, and BP (all p = 0.04); post-operatively, the distinction regarding BP remained (p = 0.04). There is a significant effect of time following vault surgery with a decrease in RI (p < 0.01). CONCLUSION Patients with syndromic craniosynostosis who have papilledema have a different TCD profile with raised BP. Vault surgery results in increased CBFv and decrease in RI, however the associated systemic BP response to intracranial hypertension remained at short-term follow-up.
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Schmidt B, Lezaic V, Weinhold M, Plontke R, Schwarze J, Klingelhöfer J. Is Impaired Autoregulation Associated with Mortality in Patients with Severe Cerebral Diseases? ACTA NEUROCHIRURGICA. SUPPLEMENT 2016; 122:181-185. [PMID: 27165903 DOI: 10.1007/978-3-319-22533-3_37] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
BACKGROUND Cerebral autoregulation (CA) is a mechanism that compensates for variations in cerebral perfusion pressure (CPP) by changes in cerebral blood flow resistance to keep the cerebral blood flow constant. In this study, the relationship between lethal outcome during hospitalisation and the autoregulation-related indices PRx and Mx was investigated. MATERIALS AND METHODS Thirty patients (aged 18-77 years, mean 53 ± 16 years) with severe cerebral diseases were studied. Cerebral blood flow velocity (CBFV), arterial blood pressure (ABP) and intracranial pressure (ICP) were repeatedly recorded. CA indices were calculated as the averaged correlation between CBFV and CPP (Mx) and between ABP and ICP (PRx). Positive index values indicated impairment of CA. RESULTS Six patients died in hospital. In this group both PRx and Mx were significantly higher than in the group of survivors (PRx: 0.41 ± 0.33 vs 0.09 ± 0.25; Mx: 0.28 ± 0.40 vs 0.03 ± 0.21; p = 0.01 and 0.04, respectively). PRx and Mx correlated significantly with Glasgow Outcome Scale (GOS) score (PRx: R = -0.40, p < 0.05; Mx: R = -0.54, p < 0.005). PRx was the only significant risk factor for mortality (p < 0.05, logistic regression). CONCLUSION Increased PRx and Mx were associated with risk of death in patients with severe cerebral diseases. The relationship with mortality was more pronounced in PRx, whereas Mx showed a better correlation with GOS score.
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MESH Headings
- Adolescent
- Adult
- Aged
- Brain Diseases/mortality
- Brain Diseases/physiopathology
- Brain Injuries, Traumatic/mortality
- Brain Injuries, Traumatic/physiopathology
- Cerebral Hemorrhage/mortality
- Cerebral Hemorrhage/physiopathology
- Cerebrovascular Circulation/physiology
- Encephalitis/mortality
- Encephalitis/physiopathology
- Female
- Homeostasis
- Humans
- Hypoxia, Brain/mortality
- Hypoxia, Brain/physiopathology
- Infarction, Middle Cerebral Artery/mortality
- Infarction, Middle Cerebral Artery/physiopathology
- Intracranial Hemorrhages/mortality
- Intracranial Hemorrhages/physiopathology
- Intracranial Pressure/physiology
- Male
- Middle Aged
- Middle Cerebral Artery/diagnostic imaging
- Middle Cerebral Artery/physiopathology
- Monitoring, Physiologic
- Prognosis
- Retrospective Studies
- Sinus Thrombosis, Intracranial/mortality
- Sinus Thrombosis, Intracranial/physiopathology
- Subarachnoid Hemorrhage/mortality
- Subarachnoid Hemorrhage/physiopathology
- Subarachnoid Hemorrhage, Traumatic/mortality
- Subarachnoid Hemorrhage, Traumatic/physiopathology
- Ultrasonography, Doppler, Transcranial
- Young Adult
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Affiliation(s)
- Bernhard Schmidt
- Department of Neurology, Chemnitz Medical Center, Dresdner Strasse 178, Chemnitz, 09131, Germany.
| | - Vesna Lezaic
- Department of Neurology, Chemnitz Medical Center, Dresdner Strasse 178, Chemnitz, 09131, Germany
| | - Marco Weinhold
- Department of Neurology, Chemnitz Medical Center, Dresdner Strasse 178, Chemnitz, 09131, Germany
| | - Ronny Plontke
- Department of Neurology, Chemnitz Medical Center, Dresdner Strasse 178, Chemnitz, 09131, Germany
| | - Jens Schwarze
- Department of Neurology, Chemnitz Medical Center, Dresdner Strasse 178, Chemnitz, 09131, Germany
| | - Jürgen Klingelhöfer
- Department of Neurology, Chemnitz Medical Center, Dresdner Strasse 178, Chemnitz, 09131, Germany
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Kasprowicz M, Czosnyka M, Poplawska K, Reinhard M. Cerebral Arterial Time Constant Recorded from the MCA and PICA in Normal Subjects. ACTA NEUROCHIRURGICA. SUPPLEMENT 2016; 122:211-4. [PMID: 27165908 DOI: 10.1007/978-3-319-22533-3_42] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cerebral arterial time constant (τ) estimates how quickly the cerebral arterial bed distal to the point of insonation is filled with arterial blood following a cardiac contraction. It is not known how τ behaves in different vascular territories in the brain. We therefore investigated the differences in τ of two cerebral arteries: the posterior inferior cerebellar artery (PICA) and the middle cerebral artery (MCA).Transcranial Doppler cerebral blood flow velocity (CBFV) in the PICA and left MCA along with Finapres arterial blood pressure (ABP) were simultaneously recorded in 35 young healthy volunteers. τ was estimated using mathematical transformations of pulse waveforms of ABP and the CBFV of the MCA and the PICA. Since τ is independent from the vessel radius, its comparison in different cerebral arteries was feasible. Mean ABP was 76.1 ± 9.6 mmHg. The CBFV of the MCA was higher than that of the PICA (59.7 ± 7.7 vs. 41.0 ± 4.5 cm/s; p < 0.000001). τ of the PICA was shorter than that of the MCA (0.15 ± 0.03 vs. 0.18 ± 0.03 s; p < 0.000001). The MCA-supplied vascular bed has a longer distal average length, measured from the place of insonation up to the small arterioles, than the PICA-supplied vascular bed. Therefore, a longer time is needed to fill it with arterial blood volume. This study thus confirms the physiological validity of the τ concept.
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Affiliation(s)
- Magdalena Kasprowicz
- Department of Biomedical Engineering, Wroclaw University of Technology, Wroclaw, Poland.
| | - Marek Czosnyka
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Karolina Poplawska
- Department of Biomedical Engineering, Wroclaw University of Technology, Wroclaw, Poland
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Johnson AC, Cipolla MJ. The cerebral circulation during pregnancy: adapting to preserve normalcy. Physiology (Bethesda) 2015; 30:139-47. [PMID: 25729059 DOI: 10.1152/physiol.00048.2014] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The adaptation of the brain and cerebral circulation to pregnancy are unique compared with other organs and circulatory systems, ultimately functioning to maintain brain homeostasis. In this review, the effect of pregnancy on critical functions of the cerebral circulation is discussed, including changes occurring at the endothelium and blood-brain barrier, and changes in the structure and function of cerebral arteries and arterioles, hemodynamics, and cerebral blood flow autoregulation.
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Affiliation(s)
- Abbie C Johnson
- Department of Neurological Sciences, University of Vermont College of Medicine, Burlington, Vermont
| | - Marilyn J Cipolla
- Department of Neurological Sciences, University of Vermont College of Medicine, Burlington, Vermont
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Abstract
Doppler ultrasonography plays an ever-increasing role in obstetric imaging. Although commonly purported to assess blood flow, most studies in this area report purely on velocimetric parameters, rather than true volumetric flow. This review article highlights the physiological importance of this distinction, and reports on a literature review of uterine artery Doppler interrogation in the context of pre-eclampsia, which identified only four original research papers that attempted to assess blood flow. Attention is needed for true volumetric flow assessment in pre-eclampsia research, which may permit a more complete conceptualisation of the pathogenesis and haemodynamic consequences of this condition.
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Affiliation(s)
- Stefan C Kane
- a Department of Perinatal Medicine , The Royal Women's Hospital , Parkville , Victoria , Australia .,b Department of Obstetrics and Gynaecology , The University of Melbourne , Melbourne , Victoria , Australia
| | - Alicia T Dennis
- b Department of Obstetrics and Gynaecology , The University of Melbourne , Melbourne , Victoria , Australia .,c Department of Anaesthesia , The Royal Women's Hospital , Parkville , Victoria , Australia , and.,d Department of Pharmacology , The University of Melbourne , Melbourne , Victoria , Australia
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Boban M, Črnac P, Junaković A, Malojčić B. Hemodynamic monitoring of middle cerebral arteries during cognitive tasks performance. Psychiatry Clin Neurosci 2014; 68:795-803. [PMID: 24735174 DOI: 10.1111/pcn.12191] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2013] [Revised: 02/25/2014] [Accepted: 04/11/2014] [Indexed: 01/03/2023]
Abstract
AIM The aim of this study was to obtain temporal pattern and hemispheric dominance of blood flow velocity (BFV) changes and to assess suitability of different cognitive tasks for monitoring of BFV changes in the middle cerebral arteries (MCA). METHODS BFV were recorded simultaneously in MCA during performance of phonemic verbal fluency test (pVFT), Trail Making Tests A and B (TMTA and TMTB) and Stroop tests in 14 healthy, right-handed volunteers aged 20-26 years. RESULTS A significant increase of BFV in both MCA was obtained during performance of all cognitive tasks. Statistically significant lateralization was found during performance of Stroop test with incongruent stimuli, while TMTB was found to have the best activation potential for MCA. CONCLUSION Our findings specify TMTB as the most suitable cognitive test for monitoring of BFV in MCA.
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Affiliation(s)
- Marina Boban
- Department of Neurology, University Hospital Centre, Zagreb, Croatia; School of Medicine, University of Zagreb, Zagreb, Croatia
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Wallace S, Logallo N, Faiz KW, Lund C, Brucher R, Russell D. Relative blood flow changes measured using calibrated frequency-weighted Doppler power at different hematocrit levels. ULTRASOUND IN MEDICINE & BIOLOGY 2014; 40:828-836. [PMID: 24462159 DOI: 10.1016/j.ultrasmedbio.2013.04.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Revised: 04/14/2013] [Accepted: 04/21/2013] [Indexed: 06/03/2023]
Abstract
In theory, the power of a trans-cranial Doppler signal may be used to measure changes in blood flow and vessel diameter in addition to velocity. In this study, a flow index (FI) of relative changes in blood flow was derived from frequency-weighted Doppler power signals. The FI, plotted against velocity, was calibrated to the zero intercept with absent flow to reduce the effects of non-uniform vessel insonation. An area index was also calculated. FIs were compared with actual flow in four silicone tubes of different diameter at increasing flow rates and increasing hematocrit (Hct) in a closed-loop phantom model. FI values were strongly correlated with actual flow, at constant Hct, but varied substantially with changes in Hct. Percentage changes in area indexes, relative to the 4-mm tube, were strongly correlated with tube cross-sectional area. The implications of these results for in vivo use are discussed.
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Affiliation(s)
- Sean Wallace
- Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.
| | - Nicola Logallo
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
| | - Kashif W Faiz
- Department of Neurology, Akershus University Hospital, Oslo, Norway
| | - Christian Lund
- Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Rainer Brucher
- Department of Medical Engineering, University of Applied Sciences, Ulm, Germany
| | - David Russell
- Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
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Cross TJ, Kavanagh JJ, Breskovic T, Johnson BD, Dujic Z. Dynamic cerebral autoregulation is acutely impaired during maximal apnoea in trained divers. PLoS One 2014; 9:e87598. [PMID: 24498340 PMCID: PMC3911978 DOI: 10.1371/journal.pone.0087598] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 12/21/2013] [Indexed: 11/22/2022] Open
Abstract
Aims To examine whether dynamic cerebral autoregulation is acutely impaired during maximal voluntary apnoea in trained divers. Methods Mean arterial pressure (MAP), cerebral blood flow-velocity (CBFV) and end-tidal partial pressures of O2 and CO2 (PETO2 and PETCO2) were measured in eleven trained, male apnoea divers (28±2 yr; 182±2 cm, 76±7 kg) during maximal “dry” breath holding. Dynamic cerebral autoregulation was assessed by determining the strength of phase synchronisation between MAP and CBFV during maximal apnoea. Results The strength of phase synchronisation between MAP and CBFV increased from rest until the end of maximal voluntary apnoea (P<0.05), suggesting that dynamic cerebral autoregulation had weakened by the apnoea breakpoint. The magnitude of impairment in dynamic cerebral autoregulation was strongly, and positively related to the rise in PETCO2 observed during maximal breath holding (R2 = 0.67, P<0.05). Interestingly, the impairment in dynamic cerebral autoregulation was not related to the fall in PETO2 induced by apnoea (R2 = 0.01, P = 0.75). Conclusions This study is the first to report that dynamic cerebral autoregulation is acutely impaired in trained divers performing maximal voluntary apnoea. Furthermore, our data suggest that the impaired autoregulatory response is related to the change in PETCO2, but not PETO2, during maximal apnoea in trained divers.
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Affiliation(s)
- Troy J. Cross
- Griffith Health Institute and Heart Foundation Research Centre, Griffith University, Gold Coast Campus, Queensland, Australia
- Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America
- * E-mail:
| | - Justin J. Kavanagh
- Griffith Health Institute and Heart Foundation Research Centre, Griffith University, Gold Coast Campus, Queensland, Australia
| | - Toni Breskovic
- Department of Physiology, University of Split School of Medicine, Split, Croatia
| | - Bruce D. Johnson
- Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Zeljko Dujic
- Department of Physiology, University of Split School of Medicine, Split, Croatia
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Boban M, Crnac P, Junaković A, Garami Z, Malojčić B. Blood flow velocity changes in anterior cerebral arteries during cognitive tasks performance. Brain Cogn 2013; 84:26-33. [PMID: 24270848 DOI: 10.1016/j.bandc.2013.10.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 10/25/2013] [Accepted: 10/26/2013] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Transcranial Doppler sonography (TCD) enables monitoring of blood flow velocities (BFVs) in basal cerebral arteries during different cognitive tasks performance with great temporal resolution. So far, BFVs changes during mental activity were monitored primarily in middle cerebral arteries (MCAs) and little is known about these changes in anterior cerebral arteries (ACAs). AIM To determine the effect of different cognitive tasks performance on BFV changes and hemispheric dominance in ACAs and to assess the most suitable activation test for monitoring of BFV changes in ACAs. METHODS Fourteen right-handed, healthy subjects aged 20-26 were included in the study. BFVs in both ACAs were recorded simultaneously during performance of cognitive tasks designed to activate frontal lobes: phonemic verbal fluency test (pVFT), Stroop tests and Trail Making Tests (TMTs). RESULTS A statistically significant BFV increase was recorded in both ACAs during performance of all cognitive tasks. Statistically significant right ACA dominance was found during performance of pVFT and TMTB. The most significant BFV increase was obtained during performance of TMTB. CONCLUSION Our result addressed cognitive tests with great activation potential for monitoring of ACAs that might be used in distinguishing of healthy individuals and patients with neurovascular or neurodegenerative diseases.
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Affiliation(s)
- Marina Boban
- School of Medicine, University of Zagreb, Šalata 2, Zagreb, Croatia; Department of Neurology, University Hospital Centre Zagreb, Kišpatićeva 12, Zagreb, Croatia.
| | - Petra Crnac
- School of Medicine, University of Zagreb, Šalata 2, Zagreb, Croatia
| | - Anamari Junaković
- Department of Neurology, University Hospital Centre Zagreb, Kišpatićeva 12, Zagreb, Croatia
| | - Zsolt Garami
- Department of Cardiovascular Surgery, Methodist DeBakey Heart and Vascular Center, The Methodist Hospital, 5656 Fannin Street, Houston, TX, USA
| | - Branko Malojčić
- School of Medicine, University of Zagreb, Šalata 2, Zagreb, Croatia; Department of Neurology, University Hospital Centre Zagreb, Kišpatićeva 12, Zagreb, Croatia
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Liu J, Zhu YS, Hill C, Armstrong K, Tarumi T, Hodics T, Hynan LS, Zhang R. Cerebral autoregulation of blood velocity and volumetric flow during steady-state changes in arterial pressure. Hypertension 2013; 62:973-9. [PMID: 24041946 DOI: 10.1161/hypertensionaha.113.01867] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The validity of using transcranial Doppler measurement of cerebral blood flow velocity (CBFV) to assess cerebral autoregulation (CA) still is a concern. This study measured CBFV in the middle cerebral artery using transcranial Doppler and volumetric cerebral blood flow (CBF) in the internal carotid artery (ICA) using color-coded duplex ultrasonography to assess CA during steady-state changes in mean arterial pressure (MAP). Twenty-one healthy adults participated. MAP was changed stepwise by intravenous infusion of sodium nitroprusside and phenylephrine. Changes in CBFV, CBF, cerebrovascular resistance (CVR=MAP/CBF), or cerebrovascular resistance index (CVRi=MAP/CBFV) were measured to assess CA by linear regression analysis. The relationship between changes in ICA diameter and MAP was assessed. All values were normalized as percentage changes from baseline. Drug-induced changes in MAP were from -26% to 31%. Changes in CBFV and CVRi in response to MAP were linear, and the regression slopes were similar between middle cerebral artery and ICA. However, CBF in ICA remained unchanged despite large changes in MAP. Consistently, a steeper slope of changes in CVR relative to CVRi was observed (0.991 versus 0.804; P<0.05). The ICA diameter changed inversely in response to MAP (r=-0.418; P<0.05). These findings indicate that CA can be assessed with transcranial Doppler measurements of CBFV and CVRi in middle cerebral artery. However, it is likely to be underestimated when compared with the measurements of CBF and CVR in ICA. The inverse relationship between changes in ICA diameter and MAP suggests that large cerebral arteries are involved in CA.
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Affiliation(s)
- Jie Liu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Ave, Dallas, TX 75231.
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Cross TJ, Kavanagh JJ, Breskovic T, Zubin Maslov P, Lojpur M, Johnson BD, Dujic Z. The Effects of Involuntary Respiratory Contractions on Cerebral Blood Flow during Maximal Apnoea in Trained Divers. PLoS One 2013; 8:e66950. [PMID: 23840561 PMCID: PMC3694127 DOI: 10.1371/journal.pone.0066950] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 05/14/2013] [Indexed: 11/26/2022] Open
Abstract
The effects of involuntary respiratory contractions on the cerebral blood flow response to maximal apnoea is presently unclear. We hypothesised that while respiratory contractions may augment left ventricular stroke volume, cardiac output and ultimately cerebral blood flow during the struggle phase, these contractions would simultaneously cause marked ‘respiratory’ variability in blood flow to the brain. Respiratory, cardiovascular and cerebrovascular parameters were measured in ten trained, male apnoea divers during maximal ‘dry’ breath holding. Intrathoracic pressure was estimated via oesophageal pressure. Left ventricular stroke volume, cardiac output and mean arterial pressure were monitored using finger photoplethysmography, and cerebral blood flow velocity was obtained using transcranial ultrasound. The increasingly negative inspiratory intrathoracic pressure swings of the struggle phase significantly influenced the rise in left ventricular stroke volume (R2 = 0.63, P<0.05), thereby contributing to the increase in cerebral blood flow velocity throughout this phase of apnoea. However, these contractions also caused marked respiratory variability in left ventricular stroke volume, cardiac output, mean arterial pressure and cerebral blood flow velocity during the struggle phase (R2 = 0.99, P<0.05). Interestingly, the magnitude of respiratory variability in cerebral blood flow velocity was inversely correlated with struggle phase duration (R2 = 0.71, P<0.05). This study confirms the hypothesis that, on the one hand, involuntary respiratory contractions facilitate cerebral haemodynamics during the struggle phase while, on the other, these contractions produce marked respiratory variability in blood flow to the brain. In addition, our findings indicate that such variability in cerebral blood flow negatively impacts on struggle phase duration, and thus impairs breath holding performance.
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Affiliation(s)
- Troy J. Cross
- Griffith Health Institute and Heart Foundation Research Centre, Griffith University, Gold Coast Campus, Queensland, Australia
- Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America
- * E-mail:
| | - Justin J. Kavanagh
- Griffith Health Institute and Heart Foundation Research Centre, Griffith University, Gold Coast Campus, Queensland, Australia
| | - Toni Breskovic
- Department of Physiology, University of Split School of Medicine, Split, Croatia
| | - Petra Zubin Maslov
- Department of Physiology, University of Split School of Medicine, Split, Croatia
| | - Mihajlo Lojpur
- Department of Anaesthesiology, Clinical Hospital Center Split, Split, Croatia
| | - Bruce D. Johnson
- Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Zeljko Dujic
- Department of Physiology, University of Split School of Medicine, Split, Croatia
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Blood pressure regulation IX: cerebral autoregulation under blood pressure challenges. Eur J Appl Physiol 2013. [PMID: 23737006 DOI: 10.1007/s00421‐013‐2667‐y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Cerebral autoregulation (CA) is integral to the delicate process of maintaining stable cerebral perfusion and brain tissue oxygenation against changes in arterial blood pressure. The last four decades has seen dramatic advances in understanding CA physiology, and the role that CA might play in the causation and progression of disease processes that affect the cerebral circulation such as stroke. However, the translation of these basic scientific advances into clinical practice has been limited by the maintenance of old constructs and because there are persistent gaps in our understanding of how this vital vascular mechanism should be quantified. In this review, we re-evaluate relevant studies that challenge established paradigms about how the cerebral perfusion pressure and blood flow are related. In the context of blood pressure being a major haemodynamic challenge to the cerebral circulation, we conclude that: (1) the physiological properties of CA remain inconclusive, (2) many extant methods for CA characterisation are based on simplistic assumptions that can give rise to misleading interpretations, and (3) robust evaluation of CA requires thorough consideration not only of active vasomotor function, but also the unique properties of the intracranial environment.
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Tzeng YC, Ainslie PN. Blood pressure regulation IX: cerebral autoregulation under blood pressure challenges. Eur J Appl Physiol 2013; 114:545-59. [PMID: 23737006 PMCID: PMC3929776 DOI: 10.1007/s00421-013-2667-y] [Citation(s) in RCA: 153] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 05/21/2013] [Indexed: 12/11/2022]
Abstract
Cerebral autoregulation (CA) is integral to the delicate process of maintaining stable cerebral perfusion and brain tissue oxygenation against changes in arterial blood pressure. The last four decades has seen dramatic advances in understanding CA physiology, and the role that CA might play in the causation and progression of disease processes that affect the cerebral circulation such as stroke. However, the translation of these basic scientific advances into clinical practice has been limited by the maintenance of old constructs and because there are persistent gaps in our understanding of how this vital vascular mechanism should be quantified. In this review, we re-evaluate relevant studies that challenge established paradigms about how the cerebral perfusion pressure and blood flow are related. In the context of blood pressure being a major haemodynamic challenge to the cerebral circulation, we conclude that: (1) the physiological properties of CA remain inconclusive, (2) many extant methods for CA characterisation are based on simplistic assumptions that can give rise to misleading interpretations, and (3) robust evaluation of CA requires thorough consideration not only of active vasomotor function, but also the unique properties of the intracranial environment.
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Affiliation(s)
- Yu-Chieh Tzeng
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, 23A Mein Street, PO Box 7343, Wellington South, New Zealand,
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Cipolla MJ. The adaptation of the cerebral circulation to pregnancy: mechanisms and consequences. J Cereb Blood Flow Metab 2013; 33:465-78. [PMID: 23321787 PMCID: PMC3618397 DOI: 10.1038/jcbfm.2012.210] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 12/02/2012] [Accepted: 12/08/2012] [Indexed: 12/21/2022]
Abstract
The adaptation of the cerebral circulation to pregnancy is unique from other vascular beds. Most notably, the growth and vasodilatory response to high levels of circulating growth factors and cytokines that promote substantial hemodynamic changes in other vascular beds is limited in the cerebral circulation. This is accomplished through several mechanisms, including downregulation of key receptors and transcription factors, and production of circulating factors that counteract the vasodilatory effects of vascular endothelial growth factor (VEGF) and placental growth factor. Pregnancy both prevents and reverses hypertensive inward remodeling of cerebral arteries, possibly through downregulation of the angiotensin type 1 receptor. The blood-brain barrier (BBB) importantly adapts to pregnancy by preventing the passage of seizure provoking serum into the brain and limiting the permeability effects of VEGF that is more highly expressed in cerebral vasculature during pregnancy. While the adaptation of the cerebral circulation to pregnancy provides for relatively normal cerebral blood flow and BBB properties in the face of substantial cardiovascular changes and high levels of circulating factors, under pathologic conditions, these adaptations appear to promote greater brain injury, including edema formation during acute hypertension, and greater sensitivity to bacterial endotoxin.
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Affiliation(s)
- Marilyn J Cipolla
- Departments of Neurological Sciences, Obstetrics, Gynecology and Reproductive Sciences, Pharmacology, University of Vermont College of Medicine, Burlington, VT, USA.
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Hajjar I, Hart M, Chen YL, Mack W, Novak V, C Chui H, Lipsitz L. Antihypertensive therapy and cerebral hemodynamics in executive mild cognitive impairment: results of a pilot randomized clinical trial. J Am Geriatr Soc 2013; 61:194-201. [PMID: 23350899 DOI: 10.1111/jgs.12100] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To compare the effects of three antihypertensive medications on cerebral hemodynamic and cognitive function in hypertensive individuals with executive dysfunction. DESIGN Double-blind randomized clinical trial. SETTING Community. PARTICIPANTS Fifty-three individuals aged 60 and older with hypertension and executive dysfunction. INTERVENTION Lisinopril, candesartan, or hydrochlorothiazide for 1 year. MEASUREMENTS Cerebral blood flow velocity (BFV; transcranial Doppler ultrasonography during rest, sitting, standing, hypercapnia, and hypocapnia), cognition, and blood pressure were measured at baseline and after 6 and 12 months. Linear mixed models were used to compare the three groups. RESULTS Of the 53 participants, 47 had successful insonation (mean age 72; 70% white; 57% women). There was a tendency toward an increase in BFV in the candesartan group and a decrease in the lisinopril and hydrochlorothiazide groups (between-group P = .57) that was significant in those with low BFV at baseline (<median 27.6 cm/s, between-group P = .03). The candesartan group also had the greatest improvement in executive function (Trail Making Test Part B improved by 17.1 seconds, vs hydrochlorothiazide improved by 4.2 seconds and lisinopril worsened by 14.4 seconds, P = .008). Carbon dioxide vasoreactivity and vasomotor range declined significantly in the lisinopril (within-group P = .001 for vasoreactivity and .02 for vasomotor range) and hydrochlorothiazide groups (within-group P = .10 and .009, respectively) but not in the candesartan group (within-group P = .25 and .38, respectively; between-group P = .30 and .46, respectively). CONCLUSION Angiotensin receptor blockers may preferentially preserve cerebral hemodynamics and executive function in individuals with executive dysfunction. These findings warrant further investigation in a larger trial.
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Affiliation(s)
- Ihab Hajjar
- Division of Geriatric, Hospital, and General Internal Medicine, Department of Medicine, University of Southern California, Los Angeles, CA 90033, USA. ihajjar@usc
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de Riva N, Budohoski KP, Smielewski P, Kasprowicz M, Zweifel C, Steiner LA, Reinhard M, Fábregas N, Pickard JD, Czosnyka M. Transcranial Doppler pulsatility index: what it is and what it isn't. Neurocrit Care 2012; 17:58-66. [PMID: 22311229 DOI: 10.1007/s12028-012-9672-6] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Transcranial Doppler (TCD) pulsatility index (PI) has traditionally been interpreted as a descriptor of distal cerebrovascular resistance (CVR). We sought to evaluate the relationship between PI and CVR in situations, where CVR increases (mild hypocapnia) and decreases (plateau waves of intracranial pressure-ICP). METHODS Recordings from patients with head-injury undergoing monitoring of arterial blood pressure (ABP), ICP, cerebral perfusion pressure (CPP), and TCD assessed cerebral blood flow velocities (FV) were analyzed. The Gosling pulsatility index (PI) was compared between baseline and ICP plateau waves (n = 20 patients) or short term (30-60 min) hypocapnia (n = 31). In addition, a modeling study was conducted with the "spectral" PI (calculated using fundamental harmonic of FV) resulting in a theoretical formula expressing the dependence of PI on balance of cerebrovascular impedances. RESULTS PI increased significantly (p < 0.001) while CVR decreased (p < 0.001) during plateau waves. During hypocapnia PI and CVR increased (p < 0.001). The modeling formula explained more than 65% of the variability of Gosling PI and 90% of the variability of the "spectral" PI (R = 0.81 and R = 0.95, respectively). CONCLUSION TCD pulsatility index can be easily and quickly assessed but is usually misinterpreted as a descriptor of CVR. The mathematical model presents a complex relationship between PI and multiple haemodynamic variables.
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Affiliation(s)
- Nicolás de Riva
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Hills Road, Box 167, Cambridge, CB2 0QQ, UK
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