Dietary Salt in Postural Tachycardia Syndrome

Postural Orthostatic Tachycardia Syndrome Clinical Trial

Official title: Dietary Salt in Postural Tachycardia Syndrome

Status Completed

Clinical Trial Summary

Patients with POTS may not adequately expand their plasma volume in response to a high-sodium (Na+) diet. Mechanisms involved in the regulation of plasma volume, such as the renin-angiotensin-aldosterone system and renal dopamine, 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.

Clinical Trial Description

Study Day 1

• Start 150 milliequivalents (mEq) Na+/day diet (POTS patients as inpatients; healthy control subjects with clinical research center (CRC)- provided outpatient diet)

• Start a 24h urine collection (for Na+, K+, Cr, fractionated catecholamines)

• Blood work

• Blood volume - carbon monoxide rebreathing

Study Day 2

• Complete 24h urine

• Start STUDY DIET (10 mEq Na+/day or 300 mEq Na+/day in a random order) after 3 meals of 150 mEq Na+/day are complete; water ad lib

Study Day 3 - 5

• Continue STUDY DIET; water ad lib

• On Day 5, a 24 hr holter combined ECG monitor will be placed on the subjects.

Study Day 6

• Continue STUDY DIET; water ad lib

• Remove 24h Holter combined ECG monitor and BP monitor from subject

• Start a 24h urine collection (for Na+, K+, Cr, fractionated catecholamines)

• Complete questionnaires

• Nothing by mouth (NPO) after midnight for study next day

Study Day 7 (BIG DAY)

• Awaken early (~6am) to void (still collecting 24h urine)

• Patient returns to bed, IV catheter inserted

• Posture Study (in morning; between 7-8am ideally)

• Blood pressure and heart rate will be measured while supine and then while standing for up to 30 minutes

• We will draw 3 tablespoons of blood in each body position to measure hormones that regulate blood pressure and blood volume

• Hormones to verify the subject's phase of menstrual cycle

• Serum/plasma aliquots for future analysis

• Subjects will rate symptoms during supine period and at end of stand using Vanderbilt Orthostatic Symptoms Score (VOSS)

• Total Blood Volume (DAXOR)- using injection of iodinated I-131 tagged human serum albumin nominally 25 micro-Ci of radiation blood samples drawn through IV catheter before injection and for ~30 minutes post-injection (total - 25 ml)

• This will be done after supine assessment, but before standing the subject up

• Autonomic Function Test with Cardiac Output and Brief Tilt

• The subject will be tilted up to 60-75 degrees head-up tilt for up to 10 minutes to measure the changes in heart rate and blood pressure and symptoms with upright challenge.

• Blood volume - carbon monoxide rebreathing

• Exercise Capacity Test (in the afternoon) Will estimate maximal oxygen consumption (VO2 max) This test will be conducted on a stationary bicycle. Effort will be gradually increase while expired air is measured during exhaustive physical work.

All procedures are repeated at least a month later with the 2nd level of dietary salt. (Randomized to high or low salt to the first phase, the second phase is the remaining level) ;

Related Conditions & MeSH terms

• Postural Orthostatic Tachycardia Syndrome
• Syndrome
• Tachycardia

• NCT number: NCT01547117
• Study type: Interventional
• Source: Vanderbilt University Medical Center
• Status: Completed
• Phase: N/A
• Start date: March 2012
• Completion date: December 2021