Active clinical trials for "Orthostatic Intolerance"

The investigators are interested in whether discrete counterpressure maneuvers, or muscle movements in the lower body, will boost blood pressure and cardiovascular control in children who faint. We will record cardiovascular responses to maneuvers of exaggerated sway, leg crossing, crouching, and gluteal muscle tensing in children who faint (N=20), as well as their height, weight, muscularity, and pubertal (Tanner) stage. Autonomic cardiovascular control will be measured using a Valsalva manoeuvre (expiration against a closed airway for 20 seconds) and a supine-stand test. The primary outcomes are noninvasive measures of cardiovascular responses to the maneuvers (blood pressure, cerebral blood flow, and stroke volume (volume of blood pumped per heartbeat). Comparisons will be made across levels of sex, diagnosis, Tanner stage, muscularity, height, and degree of autonomic control.

The investigators will assess the efficacy of clinically recommended counterpressure maneuvers (CPM) in preventing syncope for paediatric patients. Participants presenting to the emergency department (ED) will first provide written informed consent. In stage I, they will be asked to complete a brief survey documenting the presentation of their syncopal episode, and any prodromal symptoms they experienced. Participants that consent to the second stage of the study will either receive usual care (control arm) or training in counter pressure maneuvers alongside usual care (intervention arm; leg crossing, bending, arm tensing). These patients will be followed for one years time, and will be asked to complete monthly surveys detailing their syncopal and presyncopal recurrence. Medical records will be accessed over the duration of the study to identify any changes in medical diagnosis.

The mechanism behind postural orthostatic tachycardia syndrome (POTS) involves many causes including a sympathetic nervous system problem. Blood gases, like carbon dioxide (CO2), have an important effect on sympathetic activation. The purpose of this research study is to determine if higher CO2 levels have any effect in lowering heart rate and reducing POTS symptoms when upright/standing. The investigators are also searching for the ideal CO2 concentration to achieve the most effective response

This study is aimed primarily at providing a simple and effective form of treatment to reduce the symptoms of Initial Orthostatic Hypotension (IOH) and prevent syncope. We will first characterize the physiology of IOH, and then we will study four sit-to-stand maneuvers, each with a different stress tests to identify the role of sympathetic activity vs. simple muscle contraction in IOH. Then we will complete an additional two sit-to-stands with interventions designed to decrease the blood pressure drop (and hopefully symptoms) with initial stand. These consist of physical counter maneuvers, which may be a possible treatment that can be used to mitigate the drop in blood pressure (BP) seen in IOH during a stand and relieve presyncope symptoms.

This trial is designed to study the effects of various mechanistically unique medications in controlling excessive increases in heart rate with standing and in improving the symptoms of orthostatic intolerance in patients with this disorder.

The investigators will test whether an intravenous infusion of saline (salt water) will improve the exercise capacity in patients with postural tachycardia syndrome (POTS).

The purpose of this study is to describe the mechanism of orthostatic intolerance, relying on cardiovascular physiological studies. The syndrome is of undetermined etiology, but the syndrome causes impairment of a number of young adults, females more than males, with symptoms of tachycardia, fatigue, lightheadedness, palpitations, blurred vision, chest discomfort, difficulty concentrating, and dizziness with the upright posture. It is believed that many different pathophysiological processes can give rise to this disorder.

The purpose of this study is to see if some people with postural tachycardia syndrome (POTS) have higher levels of immune proteins (autoantibodies) directed against receptors of the autonomic nervous system, and if these autoantibodies make a difference in their POTS symptoms. The investigators also want to see if the levels of these autoantibodies stay the same over time.

Rationale: Systolic hypertension represents the leading risk for burden of disease among older adults (age >70 years), with an increasing prevalence due to the increase in lifespan. Antihypertensive drug treatment (AHT) is beneficial in fit (non-frail) older adults, with substantial (≈40 %) risk reductions for cardiovascular events and mortality. Scarce evidence exists on the risks of adverse effects related to AHT. It has been suggested in medical literature that AHT in frail elderly might cause cerebral hypoperfusion and/or orthostatic hypotension. Therefore, current guidelines advise clinicians to be more cautious regarding treatment targets in this population. However, the evidence for these adverse effects is limited to observational and cross-sectional data and opinion pieces. In contrast to the suggestion of potential adverse effects of AHT in elderly, recent experimental data and secondary analyses of clinical trials do not provide support for this statement. However, evidence in frail older patients remains scarce. Studies that directly examine the safety of AHT with regard to cerebral hemodynamics and orthostatic tolerance in frail elderly are needed to inform potential changes in current treatment guidelines and prevent undertreatment of hypertension in frail older patients. Objective: To examine the impact of medication induced systolic BP (SBP) reductions ≥10 mmHg, while reaching a treatment target of ≤140 mmHg, on cerebral blood flow (CBF) in frail elderly with untreated or uncontrolled systolic hypertension at baseline. We hypothesise that these blood pressure lowering targets (which are consistent with clinical guidelines for non-frail older patients) are not accompanied by detrimental reductions in CBF (i.e. >10% from baseline). Study design: An explorative observational study will be performed to examine the effects of medication induced SBP reductions ≥10 mmHg to office SBP ≤140 mmHg on CBF in frail elderly with untreated or uncontrolled hypertension. Participants will be treated as in usual patient care for older adults with hypertension. Participants will undergo one baseline assessment before exposure to (additional) AHT, followed by in duplo follow-up assessments 6-10 weeks after the start of AHT. The in duplo follow-up evaluations will be performed on separate days within 2 weeks while continuing treatment. Study population: Twelve frail (Clinical Frailty Scale 4-7) elderly (age ≥70 years) with untreated or uncontrolled systolic hypertension (office SBP ≥150 mmHg) that will be subjected to (additional) AHT as part of regular care. Main study parameters/endpoints: The change in resting CBF from baseline to follow-up (i.e. the average of the in duplo follow-up assessments). Secondary outcomes relate to cerebrovascular autoregulation (CA) and orthostatic tolerance. Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Subjects will be subjected to AHT, essentially identical to what is considered 'guideline care', while their wellbeing will be monitored closely. Since all study procedures and used measurement techniques are non-invasive, the nature and extent of burden and risks associated with participation and measurements are negligible.

The goal of this clinical trial (pilot study) is to learn about the microcirculatory regulation of the lower extremity under orthostatic stress with and without RIC - Remote Ischemic Preconditioning in healthy participants. The main question it aims to answer are: Do the beneficial effects of RIC withstand orthostatic stress? / Does RIC benefit lower extremity microcirculation in ortho-statically stressed subjects? Is there a relationship/correlation between the variables of microcirculation and hemodynamics in the context of RIC and orthostatic loading?