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Chest Jan 2017Hypoxic pulmonary vasoconstriction (HPV) is a homeostatic mechanism that is intrinsic to the pulmonary vasculature. Intrapulmonary arteries constrict in response to... (Review)
Review
Hypoxic pulmonary vasoconstriction (HPV) is a homeostatic mechanism that is intrinsic to the pulmonary vasculature. Intrapulmonary arteries constrict in response to alveolar hypoxia, diverting blood to better-oxygenated lung segments, thereby optimizing ventilation/perfusion matching and systemic oxygen delivery. In response to alveolar hypoxia, a mitochondrial sensor dynamically changes reactive oxygen species and redox couples in pulmonary artery smooth muscle cells (PASMC). This inhibits potassium channels, depolarizes PASMC, activates voltage-gated calcium channels, and increases cytosolic calcium, causing vasoconstriction. Sustained hypoxia activates rho kinase, reinforcing vasoconstriction, and hypoxia-inducible factor (HIF)-1α, leading to adverse pulmonary vascular remodeling and pulmonary hypertension (PH). In the nonventilated fetal lung, HPV diverts blood to the systemic vasculature. After birth, HPV commonly occurs as a localized homeostatic response to focal pneumonia or atelectasis, which optimizes systemic Po without altering pulmonary artery pressure (PAP). In single-lung anesthesia, HPV reduces blood flow to the nonventilated lung, thereby facilitating thoracic surgery. At altitude, global hypoxia causes diffuse HPV, increases PAP, and initiates PH. Exaggerated or heterogeneous HPV contributes to high-altitude pulmonary edema. Conversely, impaired HPV, whether due to disease (eg, COPD, sepsis) or vasodilator drugs, promotes systemic hypoxemia. Genetic and epigenetic abnormalities of this oxygen-sensing pathway can trigger normoxic activation of HIF-1α and can promote abnormal metabolism and cell proliferation. The resulting pseudohypoxic state underlies the Warburg metabolic shift and contributes to the neoplasia-like phenotype of PH. HPV and oxygen sensing are important in human health and disease.
Topics: Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Oxygen Consumption; Pulmonary Circulation; Pulmonary Gas Exchange; Vasoconstriction
PubMed: 27645688
DOI: 10.1016/j.chest.2016.09.001 -
Arteriosclerosis, Thrombosis, and... Sep 2019While the opioid epidemic has garnered significant attention, the use of methamphetamines is growing worldwide independent of wealth or region. Following overdose and... (Review)
Review
While the opioid epidemic has garnered significant attention, the use of methamphetamines is growing worldwide independent of wealth or region. Following overdose and accidents, the leading cause of death in methamphetamine users is cardiovascular disease, because of significant effects of methamphetamine on vasoconstriction, pulmonary hypertension, atherosclerotic plaque formation, cardiac arrhythmias, and cardiomyopathy. In this review, we examine the current literature on methamphetamine-induced changes in cardiovascular health, discuss the potential mechanisms regulating these varied effects, and highlight our deficiencies in understanding how to treat methamphetamine-associated cardiovascular dysfunction.
Topics: Arrhythmias, Cardiac; Atherosclerosis; Cardiomyopathies; Cardiovascular Diseases; Humans; Hypertension, Pulmonary; Methamphetamine; Vasoconstriction
PubMed: 31433698
DOI: 10.1161/ATVBAHA.119.312461 -
Journal of Biomedical Science Sep 2022Reversible cerebral vasoconstriction syndrome (RCVS) is a complex neurovascular disorder being recognized during the past two decades. It is characterized by multiple... (Review)
Review
Reversible cerebral vasoconstriction syndrome (RCVS) is a complex neurovascular disorder being recognized during the past two decades. It is characterized by multiple abrupt severe headaches and widespread cerebral vasoconstrictions, with potential complications such as ischemic stroke, convexity subarachnoid hemorrhage, intracerebral hemorrhage and posterior reversible encephalopathy syndrome. The clinical features, imaging findings, and dynamic disease course have been delineated. However, the pathophysiology of RCVS remains elusive. Recent studies have had substantial progress in elucidating its pathogenesis. It is now believed that dysfunction of cerebral vascular tone and impairment of blood-brain barrier may play key roles in the pathophysiology of RCVS, which explains some of the clinical and radiological manifestations of RCVS. Some other potentially important elements include genetic predisposition, sympathetic overactivity, endothelial dysfunction, and oxidative stress, although the detailed molecular mechanisms are yet to be identified. In this review, we will summarize what have been revealed in the literature and elaborate how these factors could contribute to the pathophysiology of RCVS.
Topics: Brain; Cerebral Hemorrhage; Humans; Posterior Leukoencephalopathy Syndrome; Vasoconstriction; Vasospasm, Intracranial
PubMed: 36127720
DOI: 10.1186/s12929-022-00857-4 -
La Radiologia Medica Sep 2022Reversible cerebral vasoconstriction syndrome (RCVS) is a group of disorders characterized by segmental narrowing and dilatation of medium-to-large cerebral arteries,... (Review)
Review
Reversible cerebral vasoconstriction syndrome (RCVS) is a group of disorders characterized by segmental narrowing and dilatation of medium-to-large cerebral arteries, clinically presenting with recurrent episodes of sudden-onset thunderclap headaches, with or without focal neurological deficits. Cerebral vasoconstriction is typically reversible, with spontaneous resolution within 3 months. Although the syndrome has generally a benign course, patients with neurological deficits may experience worse outcome. The main imaging finding is segmental constriction of intracranial arteries, which can be associated with subarachnoid hemorrhage and/or ischemic foci. Other possible findings are intracranial hemorrhage, subdural bleeding and cerebral edema. The latter may have a pattern which can resemble that of posterior reversible encephalopathy syndrome, a condition that can overlap with RCVS. New imaging techniques, such as vessel wall imaging and arterial spin labeling, are proving useful in RCVS and are giving new insights into the pathophysiology of this condition. In this paper, we aim to review neuroimaging findings of RCVS.
Topics: Cerebrovascular Disorders; Headache Disorders, Primary; Humans; Neuroimaging; Posterior Leukoencephalopathy Syndrome; Vasoconstriction; Vasospasm, Intracranial
PubMed: 35932443
DOI: 10.1007/s11547-022-01532-2 -
Critical Care (London, England) 2015This article presents a personal viewpoint of the shortcoming of conventional hemodynamic resuscitation procedures in achieving organ perfusion and tissue oxygenation...
This article presents a personal viewpoint of the shortcoming of conventional hemodynamic resuscitation procedures in achieving organ perfusion and tissue oxygenation following conditions of shock and cardiovascular compromise, and why it is important to monitor the microcirculation in such conditions. The article emphasizes that if resuscitation procedures are based on the correction of systemic variables, there must be coherence between the macrocirculation and microcirculation if systemic hemodynamic-driven resuscitation procedures are to be effective in correcting organ perfusion and oxygenation. However, in conditions of inflammation and infection, which often accompany states of shock, vascular regulation and compensatory mechanisms needed to sustain hemodynamic coherence are lost, and the regional circulation and microcirculation remain in shock. We identify four types of microcirculatory alterations underlying the loss of hemodynamic coherence: type 1, heterogeneous microcirculatory flow; type 2, reduced capillary density induced by hemodilution and anemia; type 3, microcirculatory flow reduction caused by vasoconstriction or tamponade; and type 4, tissue edema. These microcirculatory alterations can be observed at the bedside using direct visualization of the sublingual microcirculation with hand-held vital microscopes. Each of these alterations results in oxygen delivery limitation to the tissue cells despite the presence of normalized systemic hemodynamic variables. Based on these concepts, we propose how to optimize the volume of fluid to maximize the oxygen-carrying capacity of the microcirculation to transport oxygen to the tissues.
Topics: Capillaries; Hemodynamics; Humans; Microcirculation; Resuscitation; Shock; Vasoconstriction
PubMed: 26729241
DOI: 10.1186/cc14726 -
Clinical Orthopaedics and Related... Mar 2020Blood flow restriction (BFR) is a process of using inflatable cuffs to create vascular occlusion within a limb during exercise. The technique can stimulate muscle...
BACKGROUND
Blood flow restriction (BFR) is a process of using inflatable cuffs to create vascular occlusion within a limb during exercise. The technique can stimulate muscle hypertrophy and improve physical function; however, most of these studies have enrolled healthy, young men with a focus on athletic performance. Furthermore, much of the information on BFR comes from studies with small samples sizes, limited follow-up time, and varied research designs resulting in greater design, selection, and sampling bias. Despite these limitations, BFR's popularity is increasing as a clinical rehabilitation tool for aging patients. It is important for practitioners to have a clear understanding of the reported effects of BFR specifically in older adults while simultaneously critically evaluating the available literature before deciding to employ the technique.
QUESTIONS/PURPOSES
(1) Does BFR induce skeletal muscle hypertrophy in adults older than 50 years of age? (2) Does BFR improve muscle strength and/or physical function in adults older than 50 years?
METHODS
Using PubMed, Google Scholar, Web of Science, and Science Direct, we conducted a systematic review of articles using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to assess the reported effects of BFR on skeletal muscle in older adults. Included articles enrolled participants 50 years of age or older and used BFR in conjunction with exercise to study the effects of BFR on musculoskeletal outcomes and functionality. The following search terms were used: "blood flow restriction" OR "KAATSU" OR "ischemic training" AND "clinical" AND "elderly." After duplicates were removed, 1574 articles were reviewed for eligibility, and 30 articles were retained with interventions duration ranging from cross-sectional to 16 weeks. Sample sizes ranged from 6 to 56 participants, and exercise tasks included passive mobilization or electrical stimulation; walking; resistance training using machines, free weights, body weight, or elastic bands; and water-based activities. Furthermore, healthy participants and those with cardiovascular disease, osteoarthritis, osteoporosis, sporadic inclusion body myositis, spinal cord injuries, and current coma patients were studied. Lastly, retained articles were assigned a risk of bias score using aspects of the Risk of Bias in Nonrandomized Studies of Interventions and the Cochrane Collaboration's tool for assessing the risk of bias in randomized trials.
RESULTS
BFR, in combination with a variety of exercises, was found to result in muscle hypertrophy as measured by muscle cross-sectional area, thickness, volume, mass, or circumference. Effect sizes for BFR's ability to induce muscle hypertrophy were calculated for 16 of the 30 papers and averaged 0.75. BFR was also shown to improve muscle strength and functional performance. Effect sizes were calculated for 21 of the 30 papers averaging 1.15.
CONCLUSIONS
Available evidence suggests BFR may demonstrate utility in aiding rehabilitation efforts in adults older than 50 years of age, especially for inducing muscle hypertrophy, combating muscle atrophy, increasing muscle strength, and improving muscle function. However, most studies in this systematic review were at moderate or high risk of bias; that being so, the findings in this systematic review should be confirmed, ideally using greater sample sizes, randomization of participants, and extended follow-up durations.
LEVEL OF EVIDENCE
Level II, systematic review.
Topics: Aged; Exercise Therapy; Female; Humans; Hypertrophy; Male; Middle Aged; Muscle Strength; Muscle, Skeletal; Orthopedic Procedures; Regional Blood Flow; Vasoconstriction
PubMed: 31860546
DOI: 10.1097/CORR.0000000000001090 -
Arteriosclerosis, Thrombosis, and... Nov 2019Perivascular adipocytes residing in the vascular adventitia are recognized as distinct endocrine cells capable of responding to inflammatory stimuli and communicating... (Review)
Review
Perivascular adipocytes residing in the vascular adventitia are recognized as distinct endocrine cells capable of responding to inflammatory stimuli and communicating with the sympathetic nervous system and adjacent blood vessel cells, thereby releasing adipocytokines and other signaling mediators to maintain vascular homeostasis. Perivascular adipocytes exhibit phenotypic heterogeneity (both white and brown adipocytes) and become dysfunctional in conditions, such as diet-induced obesity, thus promoting vascular inflammation, vasoconstriction, and smooth muscle cell proliferation to potentially contribute to the development of vascular diseases, such as atherosclerosis, hypertension, and aortic aneurysms. Although accumulating data have advanced our understanding of the role of perivascular adipocytes in modulating vascular function, their impact on vascular disease, particularly in humans, remains to be fully defined. This brief review will discuss the mechanisms whereby perivascular adipocytes regulate vascular disease, with a particular emphasis on recent findings and current limitations in the field of research.
Topics: Adipocytes; Adipokines; Animals; Computed Tomography Angiography; Endothelium, Vascular; Humans; Obesity; Phenotype; Signal Transduction; Vascular Diseases; Vasoconstriction; Vasodilation
PubMed: 31510794
DOI: 10.1161/ATVBAHA.119.312304 -
Journal of Neurology Feb 2023Reversible cerebral vasoconstriction syndrome may be underdiagnosed. It can be accompanied by various complications, mainly intracerebral hemorrhage and ischemic stroke.... (Review)
Review
BACKGROUND/OBJECTIVE
Reversible cerebral vasoconstriction syndrome may be underdiagnosed. It can be accompanied by various complications, mainly intracerebral hemorrhage and ischemic stroke. The clinical presentation of this condition varies according to its localization. The aims of this review are to raise awareness of the disease, especially in the presence of corresponding risk factors; to connect its precipitating factors, pathophysiology, and complications; and to compare various differential diagnoses of vasoconstriction.
METHODS
A review of the literature in PubMed/MEDLINE and Google Scholar was conducted from May 1997 until May 2022.
RESULTS
Reversible cerebral vasoconstriction syndrome, which is a clinical-radiological syndrome, is mainly characterized by the occurrence of thunderclap headache and widespread vasoconstriction. The most common precipitating factors are the use of vasoactive substances and postpartum status. The pathophysiology is currently assumed to include two mechanisms: sympathetic overactivity and endothelial dysfunction. From these mechanisms, it is possible to derive potential complications as well as the most important differential diagnoses: posterior reversible encephalopathy syndrome, convexity subarachnoid hemorrhage, ischemic and hemorrhagic stroke, and primary angiitis of the central nervous system.
CONCLUSION
In general, the outcome of reversible cerebral vasoconstriction syndrome is very good. Vasospasm as well as thunderclap headache attacks can be fully reversible, and > 90% of patients are functionally independent at discharge.
Topics: Female; Humans; Vasospasm, Intracranial; Posterior Leukoencephalopathy Syndrome; Cerebrovascular Disorders; Headache Disorders, Primary; Vasoconstriction
PubMed: 36305970
DOI: 10.1007/s00415-022-11425-z -
British Journal of Anaesthesia Aug 2019
Topics: Anesthesia; Hemodynamics; Humans; Perioperative Care; Regional Blood Flow; Vasoconstriction; Vasoconstrictor Agents
PubMed: 31153629
DOI: 10.1016/j.bja.2019.04.052 -
CMAJ : Canadian Medical Association... Jan 2021
Topics: Cerebrum; Computed Tomography Angiography; Defecation; Female; Headache Disorders, Primary; Humans; Middle Aged; Vasoconstriction
PubMed: 33667187
DOI: 10.1503/cmaj.201234-f