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Regulation of cerebral blood flow in humans: physiology and clinical implications of autoregulation.Physiological Reviews Oct 2021Brain function critically depends on a close matching between metabolic demands, appropriate delivery of oxygen and nutrients, and removal of cellular waste. This... (Review)
Review
Brain function critically depends on a close matching between metabolic demands, appropriate delivery of oxygen and nutrients, and removal of cellular waste. This matching requires continuous regulation of cerebral blood flow (CBF), which can be categorized into four broad topics: ) autoregulation, which describes the response of the cerebrovasculature to changes in perfusion pressure; ) vascular reactivity to vasoactive stimuli [including carbon dioxide (CO)]; ) neurovascular coupling (NVC), i.e., the CBF response to local changes in neural activity (often standardized cognitive stimuli in humans); and ) endothelium-dependent responses. This review focuses primarily on autoregulation and its clinical implications. To place autoregulation in a more precise context, and to better understand integrated approaches in the cerebral circulation, we also briefly address reactivity to CO and NVC. In addition to our focus on effects of perfusion pressure (or blood pressure), we describe the impact of select stimuli on regulation of CBF (i.e., arterial blood gases, cerebral metabolism, neural mechanisms, and specific vascular cells), the interrelationships between these stimuli, and implications for regulation of CBF at the level of large arteries and the microcirculation. We review clinical implications of autoregulation in aging, hypertension, stroke, mild cognitive impairment, anesthesia, and dementias. Finally, we discuss autoregulation in the context of common daily physiological challenges, including changes in posture (e.g., orthostatic hypotension, syncope) and physical activity.
Topics: Animals; Cerebrovascular Circulation; Cerebrovascular Disorders; Homeostasis; Humans; Nervous System Diseases; Neurovascular Coupling
PubMed: 33769101
DOI: 10.1152/physrev.00022.2020 -
Nature Neuroscience Sep 2021The brain is supplied by an elaborate vascular network that originates extracranially and reaches deep into the brain. The concept of the neurovascular unit provides a... (Review)
Review
The brain is supplied by an elaborate vascular network that originates extracranially and reaches deep into the brain. The concept of the neurovascular unit provides a useful framework to investigate how neuronal signals regulate nearby microvessels to support the metabolic needs of the brain, but it does not consider the role of larger cerebral arteries and systemic vasoactive signals. Furthermore, the recently emerged molecular heterogeneity of cerebrovascular cells indicates that there is no prototypical neurovascular unit replicated at all levels of the vascular network. Here, we examine the cellular and molecular diversity of the cerebrovascular tree and the relative contribution of systemic and brain-intrinsic factors to neurovascular function. Evidence supports the concept of a 'neurovascular complex' composed of segmentally diverse functional modules that implement coordinated vascular responses to central and peripheral signals to maintain homeostasis of the brain. This concept has major implications for neurovascular regulation in health and disease and for brain imaging.
Topics: Animals; Brain; Cerebrovascular Circulation; Homeostasis; Humans; Neurovascular Coupling
PubMed: 34354283
DOI: 10.1038/s41593-021-00904-7 -
Circulation Journal : Official Journal... Aug 2022Ischemic heart disease (IHD) is commonly recognized as the consequence of coronary atherosclerosis and obstructive coronary artery disease (CAD). However, a significant...
Ischemic heart disease (IHD) is commonly recognized as the consequence of coronary atherosclerosis and obstructive coronary artery disease (CAD). However, a significant number of patients may present angina or myocardial infarction even in the absence of any significant coronary artery stenosis and impairment of the coronary microcirculation has been increasingly implicated as a relevant cause of IHD. The term "coronary microvascular dysfunction" (CMD) encompasses several pathogenic mechanisms resulting in functional and/or structural changes in the coronary microcirculation and determining angina and myocardial ischemia in patients with angina without obstructive CAD ("primary" microvascular angina), as well as in several other conditions, including obstructive CAD, cardiomyopathies, Takotsubo syndrome and heart failure, especially the phenotype with preserved ejection fraction. The pathogenesis of CMD is complex and involves the combination of functional and structural alterations leading to impaired coronary blood flow and resulting in myocardial ischemia. In the absence of therapies specifically targeting CMD, attention has been focused on the role of modifiable risk factors. Here, we provide updated evidence regarding the pathophysiological mechanisms underlying CMD, with a particular focus on the role of cardiovascular risk factors and comorbidities. Moreover, we discuss the specific pathogenic mechanisms of CMD across the different cardiovascular diseases, aiming to pave the way for further research and the development of novel strategies for a precision medicine approach.
Topics: Coronary Artery Disease; Coronary Circulation; Coronary Vessels; Humans; Microcirculation; Microvascular Angina; Myocardial Ischemia
PubMed: 34759123
DOI: 10.1253/circj.CJ-21-0848 -
Trends in Endocrinology and Metabolism:... Feb 2021Blood flow restriction resistance training (BFRT) employs partial vascular occlusion of exercising muscles via inflation cuffs. Compared with high-load resistance... (Review)
Review
Blood flow restriction resistance training (BFRT) employs partial vascular occlusion of exercising muscles via inflation cuffs. Compared with high-load resistance training, mechanical load is markedly reduced with BFRT, but induces similar gains in muscle mass and strength. BFRT is thus an effective training strategy for people with physical limitations. Recent research indicates that BFRT has beneficial effects on glucose and mitochondrial metabolism. BFRT may therefore qualify as a valuable exercise alternative for individuals with type 2 diabetes (T2D), a disorder characterized by impaired glucose metabolism, musculoskeletal decline, and exacerbated progression of sarcopenia. This review covers the effects of BFRT in healthy populations and in persons with impaired physical fitness, the mechanisms of action of this novel training modality, and possible applications for individuals with T2D.
Topics: Blood Circulation; Diabetes Mellitus, Type 2; Humans; Muscle Strength; Muscle, Skeletal; Resistance Training
PubMed: 33358931
DOI: 10.1016/j.tem.2020.11.010 -
Neurology India 2021Various studies highlight the significance of alterations in cerebrospinal fluid (CSF) and cerebral blood flow (CBF) dynamics in the pathogenesis of hydrocephalus and... (Review)
Review
BACKGROUND
Various studies highlight the significance of alterations in cerebrospinal fluid (CSF) and cerebral blood flow (CBF) dynamics in the pathogenesis of hydrocephalus and suggest the role of mathematical modeling in studying these complex interactions.
OBJECTIVE
This narrative review discusses mathematical models of CSF and CBF dynamics, including Marmarou's compartmental model of CSF spaces and a model of cardiac changes in cerebral arterial blood volume. The diagnostic utility of CSF compensatory parameters is described along with current information on secondary model-based indices of cerebral hemodynamics in hydrocephalus.
CONCLUSIONS
Compensatory parameters derived from the model of CSF circulation have long been used in the diagnosis and management of hydrocephalus patients. However, recent studies using mathematical models of cerebral circulation also show alterations in CBF dynamics, and model-based indices of cerebral hemodynamics, which can be calculated non-invasively using transracranial Doppler ultrasonography, can be used as a complementary source of information about the state of the cerebrospinal space.
Topics: Cerebrovascular Circulation; Hemodynamics; Humans; Hydrocephalus; Models, Theoretical
PubMed: 35102977
DOI: 10.4103/0028-3886.332259 -
Biomedical Journal Jun 2020Neurocritical monitoring is important in caring for patients in the neurological intensive care unit. Although clinical neurologic examination is standard for... (Review)
Review
Neurocritical monitoring is important in caring for patients in the neurological intensive care unit. Although clinical neurologic examination is standard for neurocritical monitoring, changes found during the examination are often late signs and insufficient to detect and prevent secondary brain injury. Therefore, various neuromonitoring tools have been developed to monitor different physiologic parameters, such as cerebral oxygenation, cerebral blood flow, cerebral pressure, cerebral autoregulation, cerebral electric activity, and cerebral metabolism. In this review, we have discussed current commonly used neurocritical monitoring tools. No single monitor is sufficient and perfect for neurocritical monitoring. Multimodal neurocritical monitoring is the current trend. However, the lack of common formatting standards and uncertainty of improvement in patients' outcomes warrant further studies of multimodal neurocritical monitoring. Nevertheless, multimodal neurocritical monitoring considers individual pathophysiological variations in patients or their injuries and allows clinicians to tailor individualized management decisions.
Topics: Brain Injuries; Cerebrovascular Circulation; Critical Care; Humans; Intracranial Pressure; Monitoring, Physiologic
PubMed: 32651135
DOI: 10.1016/j.bj.2020.05.005 -
Turk Kardiyoloji Dernegi Arsivi : Turk... Jun 2022
Topics: Blood Flow Velocity; Coronary Angiography; Coronary Circulation; Coronary Vessels; Humans
PubMed: 35695358
DOI: 10.5543/tkda.2022.22485 -
Journal of Neurochemistry Jan 2022Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating cerebrovascular disease with high mortality and morbidity. In recent years, a large number of studies have... (Review)
Review
Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating cerebrovascular disease with high mortality and morbidity. In recent years, a large number of studies have focused on the mechanism of early brain injury (EBI) and delayed cerebral ischemia (DCI), including vasospasm, neurotoxicity of hematoma and neuroinflammatory storm, after aSAH. Despite considerable efforts, no novel drugs have significantly improved the prognosis of patients in phase III clinical trials, indicating the need to further re-examine the multifactorial pathophysiological process that occurs after aSAH. The complex pathogenesis is reflected by the destruction of the dynamic balance of the energy metabolism in the nervous system after aSAH, which prevents the maintenance of normal neural function. This review focuses on the fluid metabolic pathways of the central nervous system (CNS), starting with ruptured aneurysms, and discusses the dysfunction of blood circulation, cerebrospinal fluid (CSF) circulation and the glymphatic system during disease progression. It also proposes a hypothesis on the metabolic disorder mechanism and potential therapeutic targets for aSAH patients. Cover Image for this issue: https://doi.org/10.1111/jnc.15384.
Topics: Animals; Brain; Cerebrovascular Circulation; Glymphatic System; Humans; Metabolic Networks and Pathways; Subarachnoid Hemorrhage
PubMed: 34160835
DOI: 10.1111/jnc.15458 -
International Journal of Molecular... Dec 2021Vascular occlusive diseases such myocardial infarction, peripheral artery disease of the lower extremities, or stroke still represent a substantial health burden...
Vascular occlusive diseases such myocardial infarction, peripheral artery disease of the lower extremities, or stroke still represent a substantial health burden worldwide [...].
Topics: Angiogenesis Inducing Agents; Arterial Occlusive Diseases; Blood Circulation; Early Diagnosis; Humans; Neovascularization, Pathologic; Neovascularization, Physiologic
PubMed: 34948041
DOI: 10.3390/ijms222413244 -
Frontiers in Immunology 2022Depressive disorder is the most prevalent affective disorder today. Depressive disorder has been linked to changes in the white matter. White matter changes in... (Review)
Review
Depressive disorder is the most prevalent affective disorder today. Depressive disorder has been linked to changes in the white matter. White matter changes in depressive disorder could be a result of impaired cerebral blood flow (CBF) and CBF self-regulation, impaired blood-brain barrier function, inflammatory factors, genes and environmental factors. Additionally, white matter changes in patients with depression are associated with clinical variables such as differential diagnosis, severity, treatment effect, and efficacy assessment. This review discusses the characteristics, possible mechanisms, clinical relevance, and potential treatment of white matter alterations caused by depressive disorders.
Topics: Cerebrovascular Circulation; Depressive Disorder; Humans; White Matter
PubMed: 35634314
DOI: 10.3389/fimmu.2022.826812