Postural Orthostatic Tachycardia Syndrome | Dietary Salt in Postural Tachycardia Syndrome
Postural Orthostatic Tachycardia Syndrome research study
What is the primary objective of this study?
Patients with 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 DA, may be impaired in POTS and may respond inappropriately to changes in dietary sodium.The purpose of this study is to determine (1) whether a high dietary sodium level appropriately expands plasma volume in POTS; (2) whether plasma renin activity and aldosterone are modified appropriately by changes in dietary sodium in POTS; and (3) 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: - 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 - Age between 18-50 years old - Non-smokers - Premenopausal patients with POTS and healthy volunteers - 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 - Pregnant (positive pregnancy test) or breastfeeding - Hypertension defined as supine resting BP>145/95 mmHg off medications 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:Blood Volumewe will measure the amount of hemoglobin and myoglobin in the body by a procedure called carbon monoxide (CO) rebreathing. One teaspoon of blood is taken before and after a small amount of CO has been absorbed into the bloodstream.
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 Sodium LevelPOTS and healthy controls will be randomly assigned the order of dietary sodium levels. All procedures are performed at both levels.
Low Sodium Dietary Level
Active, not recruiting
Start Date: March 2012
Completed Date: December 2018
Primary Outcome: blood volume
Secondary Outcome: Magnitude of suppression of aldosterone (from low sodium to high sodium diets) and a reduction in orthostatic tachycardia and orthostatic symptoms in POTS patients with the high-sodium diet.
Study sponsors, principal investigator, and references
Principal Investigator: Satish R Raj, MD MSCI
Lead Sponsor: Vanderbilt University
Collaborator: National Institutes of Health (NIH)