Postural Orthostatic Tachycardia Syndrome | Dietary Sodium's Effect on Urinary Sodium and Dopamine Excretion in Patients With Postural Tachycardia Syndrome
Postural Orthostatic Tachycardia Syndrome research study
What is the primary objective of this study?
Patients with Postural Tachycardia Syndrome (POTS) may not adequately expand their plasma volume in response to a high sodium diet. Mechanisms involved in the regulation of plasma volume, such as the renin-angiotensin-aldosterone system and renal dopamine (DA), may be impaired in POTS and may respond inappropriately to changes in dietary sodium. The investigators propose that the changes in urinary sodium and dopamine excretion caused by consuming low-sodium and high-sodium diets will be different between patients with POTS and healthy volunteers. The purpose of this study is to determine (1) whether changes in dietary sodium level appropriately influence sodium excretion in POTS; (2) whether changes in dietary sodium level appropriately influence DA excretion in POTS; (3) whether a high dietary sodium level appropriately expands plasma volume in POTS; and (4) whether patients with POTS have improvements in their orthostatic tachycardia and symptoms as a result of a high dietary sodium level.
Who is eligible to participate?
Inclusion Criteria: - Premenopausal patients with POTS and healthy volunteers, 18-50 years old, who are non-smokers and free of medications with the potential to influence blood pressure - Patients diagnosed with postural tachycardia syndrome by the Vanderbilt Autonomic Dysfunction Center - Increase in heart rate ≥30 beats/min with position change from supine to standing (10 minutes) - Chronic symptoms consistent with POTS that are worse when upright and get better with recumbence - Only female participants are eligible. Since 80-90% of POTS patients are female, and there can be differences in measures with the menstrual cycle, including a small number of males might introduce a significant amount of noise. - Able and willing to provide informed consent Exclusion Criteria: - Smokers - Overt cause for postural tachycardia, i.e., acute dehydration - Significant cardiovascular, pulmonary, hepatic, or hematological disease by history or screening results - Positive pregnancy test or breastfeeding - Hypertension defined as BP>145/95 off medications when supine or needing antihypertensive medication - Other factors which in the investigator's opinion would prevent the participant from completing the protocol, including poor compliance during previous studies or an unpredictable schedule - Unable to give informed consent
Which medical condition, disease, disorder, syndrome, illness, or injury is researched?
Postural Orthostatic Tachycardia Syndrome
Interventions can include giving participants drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available or noninvasive approaches such as surveys, education, and interviews.
Radiation:Total Blood VolumeUsing injection of iodinated I-131 tagged human serum albumin nominally 25 micro-Ci of radiation, blood samples are drawn before and 30 minutes after injection.
Procedure:Exercise Capacity Test - Bicyclesubjects breath room air through a mouthpiece and exhale the air into a tube that connects to a machine (metabolic cart) that analyzes carbon dioxide and oxygen content, which allows the investigator to calculate the amount of oxygen they are using under resting and exercise conditions.
Procedure:Posture StudyBlood pressure and heart rate will be measured while supine and then while standing for up to 30 minutes. Blood will be drawn in each position to measure hormones that regulate blood pressure and blood volume.
Research studies and clinical trials typically have two or more research arms. An arm is a group of people who receive the same treatment in the study.
High Salt DietPOTS and healthy controls will be randomly assigned the order of dietary sodium levels. All procedures are performed at both levels.
Low Salt Diet
Active, not recruiting
Start Date: March 2012
Completed Date: March 2018
Primary Outcome: Urinary sodium
Secondary Outcome: Blood Volume
Study sponsors, principal investigator, and references
Principal Investigator: Emily M Garland, PhD, MSCI
Lead Sponsor: Vanderbilt University
Collaborator: National Heart, Lung, and Blood Institute (NHLBI)