View clinical trials related to Orthostatic Intolerance.
Filter by:Incidence and pathophysiologic hemodynamics of postoperative orthostatic intolerance and orthostatic hypotension in patients receiving antihypertensives
Postural Orthostatic Tachycardia Syndrome (POTS) is characterized by symptoms of chronic orthostatic intolerance such as fatigue, lightheadedness, dizziness, palpitations and by pronounced tachycardia upon standing. The aims of the present research study are to test whether a daily transcutaneous vagal nerve stimulation (tVNS) performed for 14 consecutive days may improve heart rate response and reduce disabling symptoms while standing.
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
Incidence and pathophysiologic hemodynamics of orthostatic intolerance and orthostatic hypotension in patients undergoing UKA
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.
More than 78 million adults in the U.S. are obese. Bariatric surgery is the only modality that results in sustained weight loss along with reversal of diabetes mellitus, and a decrease in cardiovascular events. Obesity is associated with increased sympathetic nervous system (SNS) activity that contributes to blood pressure regulation; sympathetic vasoconstrictor activity is maximally activated upon standing and is fundamental for the maintenance of orthostatic tolerance. After bariatric surgery, there is a significant and sustained reduction in SNS activity at three and six months after the procedure, which is related to weight loss. Recently, multiple retrospective studies have reported an orthostatic intolerance (OI) syndrome after bariatric surgery characterized by chronic pre-syncopal symptoms, syncope and orthostatic hypotension. In the Vanderbilt University Medical Center bariatric surgical center, 741 post-bariatric surgery patients reported OI symptoms, 98 (13.2%) of these patients, progressed to chronic OI and in17 cases, the OI was so disabling that patients initiated treatment with pressor agents. More than 50% of OI cases in the cohort developed the condition during a weight-stable period. Hence, investigators propose the novel hypothesis that after bariatric surgery, the persistent reduction in SNS activity contributes to impaired orthostatic tolerance, which is independent of weight loss.
Incidence and pathophysiologic hemodynamics of orthostatic intolerance and orthostatic hypotension in patients undergoing unilateral THA
Incidence of Postoperative Orthostatic Intolerance and Postoperative Orthostatic Hypotension in Patients Undergoing Unilateral Total Knee Arthroplasty
Postural tachycardia syndrome (POTS), is the chronic form of orthostatic intolerance associated with excessive upright tachycardia, and occurs predominantly in young females (>85%). Among its most troubling symptoms are lightheadedness, fatigue, and decreased memory often called "brain fog" by patients. Task-related neurovascular coupling (NVC) links neural activity to an increase in CBF known as "functional hyperemia". Although memory task performance and NVC deteriorated with angle of tilt in POTS but not healthy controls, cerebral blood flow (CBF) remained similar to control. Instead, the investigators observed extensive narrow band low frequency (0.07-0.13 Hz) oscillations in BP (OBP) that entrained and amplified oscillations in CBF (OCBF). OBP and OCBF increased with tilt angle and caused impaired working memory and reduced functional hyperemia. The cardiovagal baroreflex couples BP to HR to buffer BP changes. The investigators hypothesize that the cardiovagal baroreflex becomes progressively impaired with orthostasis in POTS, but not in healthy volunteers, and accounts for OBP, OCBF, and loss of NVC; further, improving the baroreflex reduces OBP, OCBF and Brain Fog in POTS.
The purpose of this study is to test the hypothesis that patients with non-neuropathic POTS will have different responsiveness than patients with neuropathic POTS to direct alpha-1 adrenoreceptor agonist therapy (droxidopa) and to non-selective beta-adrenoreceptor antagonist therapy (atenolol). The specific goal of this protocol is to investigate the effect of atenolol and droxidopa on cardiovascular autonomic functions such as cardiovagal control, sympathetic nerve activity, and sympathetic vascular transduction, systemic hemodynamic response to orthostatic stress and on the quality of life in neuropathic and non-neuropathic patients with postural tachycardia syndrome (POTS). Standardized tests are used to assess cardiovagal control function, sympathetic nerve activity, sympathetic vascular transduction, systemic hemodynamic response to head-up tilt test and standardized questionnaires to assess the quality of life in patients with POTS. The cardiovagal, sympathetic and hemodynamic measurements are performed after and during drug administration. To control the effect of medications placebo is used on separate testing visits. The order of drugs and placebo is randomized.