View clinical trials related to Postural Tachycardia Syndrome.
Filter by:The purpose of this study is to see if people with Postural Tachycardia Syndrome (POTS) have different levels of certain chemicals in their blood than people who don't have POTS. This study will test whether the blood vessels of people with POTS will react differently to certain tests than people without POTS. The hypothesis of the study is: Patients with POTS will have vascular endothelial dysfunction compared with control subjects.
The investigators study will determine how often blood flow regulation abnormalities and abnormalities of sympathetic regulation produced by nitric oxide, angiotensin-II, and oxidative stress occur in POTS and the mechanism(s) of POTS in individual patients. Specific causes for POTS may vary from patient to patient. Patients will be compared to healthy control subjects. There is a treatment arm with a medication (losartan) that reduces the binding of angiotensin and increases NO. If the investigators know the specific biochemical mechanism the investigators may be able to offer further specific treatments to specific patients.
The main limitation patients with orthostatic intolerance (OI, or postural tachycardia syndrome, POTS) have to exercise is related to their increase in heart rate when standing. Main pharmacological treatment today is aimed at reducing heart rate with the use of betablockers (propanolol), this theoretically could also improve their exercise capacity; if their heart rate do not increase as much with the medication, they could exercise more. In addition, it has been suggested that in healthy volunteers subjected to head down tilt for 2 weeks (situation that produces a "simulated" transient POTS-like state) a single bout of intense exercise can improve orthostatic tolerance the day after exercising. The mechanisms involved in such response are not that clear but could be an increase in plasma volume already diminished in POTS patients. It seems likely that the same could be true for POTS patients. The purpose of the present study are to pharmacologically improve the amount of exercise POTS patients can perform by reducing their baseline heart rate (specific aim 1) and to evaluate next day heart responses to an acute bout of intense exercise. Therefore, the specific aims of this study are: 1. To test the hypothesis that lowering heart rate response with propanolol will result in an increase in exercise capacity. 2. To test the hypothesis that a single bout of exercise will result in an improvement in orthostatic tolerance the day after exercising.
The purpose of the proposed research is to determine how changes in kidney dopamine (DA) activity influence urinary sodium excretion. We will decrease DA activity in the kidney by inhibiting DA synthesis via carbidopa administration. We want to compare findings in normal volunteers and in patients with postural tachycardia syndrome (POTS). We will test the null hypothesis (Ho) that the effects of oral carbidopa administration on urinary sodium excretion will not differ between patients with POTS and healthy volunteers.
We wish to study sleep architecture in patients with chronic orthostatic intolerance. We will test the null hypothesis that there is no difference in time during the various phases of sleep between patients and healthy control subjects.
The investigators propose to test the hypothesis that the sympathetic nervous system contributes to the cardiovascular and inflammatory abnormalities present in the chronic fatigue syndrome (CFS) and, in particular in the subset of patients characterized by postural tachycardia syndrome (POTS). CFS and POTS are seen mostly in otherwise normal young women, and are the cause of significant disability. A substantial proportion of patients referred for evaluation of POTS met diagnostic criteria for CFS and, conversely, a subset of patients referred for treatment for CFS have POTS. The investigators hypothesize that sympathetic activation underlies the pathophysiology of patients in whom CFS and POTS overlap (CFS-P).
This study will investigate the relationship between susceptibility to hypnosis and regulation of the autonomic nervous system (nerves that control involuntary body functions, such as heart rate and sweating). Hypnosis is a state of mind in which the individual is highly focused, relatively unaware of his or her surroundings, and possibly more able to accept and use therapeutic suggestions. People vary in their responsiveness, or susceptibility, while in hypnosis. People with certain conditions, such as chronic fatigue syndrome (CFS), chronic pain, posttraumatic stress disorder (PTSD), and generalized anxiety disorder (GAD) have altered hypnotic susceptibility. Patients with chronic orthostatic intolerance (COI) often have symptoms similar to those of individuals with CFS, chronic pain, PTSD, and GAD, and this study will examine how patients with COI respond to hypnosis as compared with healthy normal volunteers. COI is a group of disorders characterized by intolerance to prolonged standing. Among them are neurocardiogenic syncope (NCS), in which patients have recurrent episodes of sudden loss of consciousness, and postural tachycardia syndrome (POTS), in which patients have a sustained increase in heart rate after standing. In addition to the comparison of COI and normal volunteer responses to hypnosis, the study will examine how hypnotic susceptibility is related to the ability to control autonomic functions such as blood pressure, heart rate, and sweating. The autonomic nervous system is activated when the body is stressed, not only from physical stimuli such as cold temperature, but also from mental stimuli, such as seeing a rattlesnake up close. Hypnosis may, therefore, be a useful tool to understand how the mind controls the autonomic nervous system. Healthy normal volunteers and patients with NCS or POTS who are 18 years of age or older may be eligible for this two-part study. In part 1, participants complete a questionnaire and are then tested for hypnotic susceptibility. For this test, a professionally trained physician guides the subject through a procedure to achieve a hypnotic state. The subject is asked to perform several simple tasks and is then guided back to a normal state of being. In part 2, the subject undergoes hypnosis again, during which the physician offers various suggestions while monitoring activity of the subject's autonomic nervous system. The subject is connected to various sensors that continuously monitor blood pressure, heart rate, blood flow, sweat response, skin electrical conduction, and brain wave activity. An intravenous catheter is inserted into an arm vein to collect blood samples. At the end, the subject is guided back to a normal state of being. The hypnosis session in part 1 is videotaped in order to: 1) permit review by a scientist who is unaware of the subject's condition and whose judgment will not, therefore, be biased; and 2) have a record of the experimental data. Only qualified investigators will view the videotape.