Cerebral Blood Flow Dynamics in Neurogenic Orthostatic Hypotension: A Systematic Review and Meta-Analysis.

Background: Neurogenic orthostatic hypotension (nOH) causes pathological falls in standing blood pressure that may or may not be symptomatic. nOH also raises the risk of poor neurological outcomes irrespective of symptom presence, possibly reflecting subclinical cerebral hypoperfusion. Dynamic changes in cerebral blood flow velocity (CBFv) help infer how blood pressure fluctuations influence CBFv and cerebral autoregulation.

Reduced Stroke Volume and Brain Perfusion Drive Postural Hyperventilation in Postural Orthostatic Tachycardia Syndrome.

Postural hyperventilation has been implicated as a cause of postural orthostatic tachycardia syndrome (POTS), yet the precise mechanisms underlying the heightened breathing response remain unclear. This study challenges current hypotheses by revealing that exaggerated peripheral chemoreceptor activity is not the primary driver of postural hyperventilation. Instead, significant contributions from reduced stroke volume and compromised brain perfusion during orthostatic stress were identified.

Clinical Assessment of the Autonomic Nervous System.

This review explores standardized clinical assessments for evaluating autonomic nervous system function. Here, we emphasize components of the autonomic medical history as the first pivotal test of the autonomic assessment. We further focus on standard noninvasive cardiovascular autonomic tests including heart rate responses to deep breathing, Valsalva maneuvers, and orthostatic challenges, along with insights from neurochemical tests and quantitative sudomotor axon reflex testing.

Perfection is the enemy of good. A Letter to the Editor on "Orthostatic hypotension in Parkinson's disease: Sit-to-stand vs. supine-to-stand protocol and clinical correlates".

Orthostatic hypotension (OH) is prevalent in Parkinson's disease. Lim et al. report a higher OH detection rate with the supine-to-stand test compared to the sit-to-stand test.

Autonomic Manifestations of Long-COVID Syndrome.

Purpose Of Review: Long-COVID is a novel condition emerging from the COVID-19 pandemic. Long-COVID is characterized by symptoms commonly seen in autonomic disorders including fatigue, brain fog, light-headedness, and palpitations. This article will critically evaluate recent findings and studies on Long-COVID and its physiological autonomic manifestations.

Objective Hemodynamic Cardiovascular Autonomic Abnormalities in Post-Acute Sequelae of COVID-19.

Background: Many COVID-19 patients are left with symptoms several months after resolution of the acute illness; this syndrome is known as post-acute sequalae of COVID-19 (PASC). We aimed to determine the prevalence of objective hemodynamic cardiovascular autonomic abnormalities (CAA), explore sex differences, and assess the prevalence of CAA among hospitalized vs nonhospitalized patients with PASC.

Methods: Patients with PASC (n = 70; female [F] = 56; 42 years of age; 95% confidence interval [CI], 40-48) completed standard autonomic tests, including an active stand test 399 days (338, 455) after their COVID-19 infection.

Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters.

Cerebral hypoxia is a serious consequence of several cardiorespiratory illnesses. Measuring the retinal microvasculature at high altitude provides a surrogate for cerebral microvasculature, offering potential insight into cerebral hypoxia in critical illness. In addition, although sex-specific differences in cardiovascular diseases are strongly supported, few have focused on differences in ocular blood flow.

The molecular makeup of peripheral and central baroreceptors: stretching a role for Transient Receptor Potential (TRP), Epithelial Sodium Channel (ENaC), Acid Sensing Ion Channel (ASIC), and Piezo channels.

The autonomic nervous system maintains homeostasis of cardiovascular, respiratory, gastrointestinal, urinary, immune, and thermoregulatory function. Homeostasis involves a variety of feedback mechanisms involving peripheral afferents, many of which contain molecular receptors sensitive to mechanical deformation, termed mechanosensors. Here, we focus on the molecular identity of mechanosensors involved in the baroreflex control of the cardiovascular system.

Syncope and silent hypoxemia in COVID-19: Implications for the autonomic field.

Coronavirus-19 (COVID-19), the infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, has wreaked havoc across the globe since its emergence in December 2019. Reports of patients presenting with syncope and pre-syncope, as well as hypoxemia without symptoms of dyspnea ("silent hypoxemia"), have led researchers to speculate whether SARS-CoV-2 can alter autonomic nervous system function. As viral infections are commonly reported triggers of altered autonomic control, we must consider whether SARS-CoV-2 can also interfere with autonomic activity, at least in some patients.

Evidence of Impaired Cerebellar Connectivity at Rest and During Autonomic Maneuvers in Patients with Autonomic Failure.

The objective of the current study was to investigate whether patients with neurogenic orthostatic hypotension (NOH) secondary to autonomic failure have impaired functional connectivity between the cerebellum and central autonomic structures during autonomic challenges. Fifteen healthy controls (61 ± 14 years) and 15 NOH patients (67 ± 6 years; p = 0.12) completed the following tasks during a functional brain MRI: (1) 5 min of rest, (2) 5 min of lower-body negative pressure (LBNP) performed at - 35 mmHg, and (3) Three, 15-s Valsalva maneuvers (VM) at 40 mmHg.

Reduced brainstem functional connectivity in patients with peripheral autonomic failure.

Autonomic homeostasis is dependent upon several brainstem nuclei, as well as several cortical and subcortical structures. Together, these sites make up, in part, the central autonomic network. Neurogenic orthostatic hypotension (NOH) is a cardinal feature of autonomic failure that occurs due to a failure to increase sympathetic efferent activity in response to postural changes.

The Orthostatic Discriminant and Severity Scale (ODSS): an assessment of orthostatic intolerance.

Purpose: To assess the ability of the Orthostatic Discriminant and Severity Scale (ODSS) to distinguish symptoms of orthostatic intolerance from non-orthostatic symptoms.

Methods: Clinical evaluations and questionnaire responses were collected in 73 healthy controls and 132 patients referred to the Autonomic Disorders Clinic from September 1, 2016, through April 30, 2018, for queries regarding autonomic dysfunction. A receiver operating characteristic (ROC) curve analysis was used to interpret sensitivity and specificity and to determine cutoff scores for symptom assessment.

Cerebellar impairment during an orthostatic challenge in patients with neurogenic orthostatic hypotension.

Objective: Compare activation patterns within the cortical autonomic network in patients with neurogenic orthostatic hypotension (NOH) versus healthy age-matched controls during an orthostatic challenge.

Methods: Fifteen health controls and 15 NOH patients performed 3 Valsalva maneuvers, and 5-min of lower-body negative pressure (LBNP) during a functional brain MRI.

Results: Compared to controls, NOH patients had significantly less activation within the cerebellum during both LBNP and VM.

An updated normative data set from the autonomic reflex screen representative of Southwestern Ontario.

In evaluating autonomic dysfunction, the autonomic reflex screen (ARS) is an established set of standardized tests to evaluate the presence and severity of autonomic dysfunction. Our laboratory previously reported normative data on 121 healthy individuals; however, the sample size in older individuals was reduced compared with other age groups. Therefore, the objective of the current study was to provide updated normative values representative of young, middle-aged, and older individuals from Southwestern Ontario.

Impaired cortical autonomic responses during sympathetic activation in neurogenic orthostatic hypotension characterized by postganglionic autonomic dysfunction.

Neurogenic orthostatic hypotension (NOH) is a cardinal feature of autonomic dysfunction. The cortical autonomic network (CAN) is a network of brain regions associated with autonomic function. Therefore, our objective was to investigate whether impairment of CAN structures is involved in the pathophysiology of NOH.

Role of melatonin in blood pressure regulation: An adjunct anti-hypertensive agent.

Cardiovascular diseases account for approximately one-third of all deaths each year. Of this, hypertension accounts for approximately 9.4 million deaths.

Initial validation of symptom scores derived from the orthostatic discriminant and severity scale.

Objective: To develop a scale to quantify and discriminate orthostatic from non-orthostatic symptoms. In the current study, we present validation and reliability of orthostatic and non-orthostatic symptom scores taken from the orthostatic discriminate and severity scale (ODSS).

Methods: Validity and reliability were assessed in participants with and without orthostatic intolerance.