Effect of Dietary Sodium Intake on Vascular Endothelium

Not Applicable

Completed

Conditions: Postural Tachycardia Syndrome (POTS)

Interventions: Procedure: Pulsitile Arterial Tonometry (PAT) Protocol
Device: Calf Blood Flow in Reactive Hyperemia (CBF-RH)
Device: Evaluation of Forearm-Mediated Dilation

Registration Number: NCT01550315

Lead Sponsor: Vanderbilt University Medical Center

Brief Summary: The investigators will test the hypothesis that markers of vascular endothelial dysfunction will be exaggerated acutely with an extreme high sodium diet compared to an extreme low-sodium diet. The investigators will compare patients with postural orthostatic tachycardia (POTS) to healthy control subjects.

Detailed Description: The study will involve a crossover design in which each subject will be assessed (as below) while on a very low-sodium (10 mEq/day) diet compared with a very high-sodium diet. These acute dietary interventions will be part of the parent study ("Dietary Salt in Postural Tachcyardia Syndrome" funded by R01 HL102387) for 4-5 days at the time of the study. Dietary success will be assessed using a 24h urine for sodium and creatinine as a part of the parent study.

Blood will be drawn and collected in a fasting state for future assay and analysis of the following tests:

* Glucose, Insulin (glucose impairment, insulin resistance)

* Fasting lipid profile

* C-Reactive Protein (hsCRP) (inflammatory state)

* Inflammatory cytokines (inflammatory state)

* aliquots (future analysis)

Pulsitile Arterial Tonometry (PAT) Protocol Calf Blood Flow in Reactive Hyperemia (CBF-RH) - venous occlusion plethysmography Evaluation of Forearm-Mediated Dilation

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 27

Inclusion Criteria

Subjects will be enrolled in the parent study "Dietary Salt in Postural Tachcyardia Syndrome" funded by R01 HL102387 Postural Tachycardia Syndrome
Diagnosed with postural tachycardia syndrome by the Vanderbilt Autonomic Dysfunction Center
Subjects will be enrolled in the parent study "Dietary Salt in Postural Tachcyardia Syndrome" funded by R01 HL102387
Postural Tachycardia Syndrome
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 Control Subjects
Healthy, non-obese, non-smokers without orthostatic tachycardia
Selected to match profiles of POTS patients (gender, age)
Not using vasoactive medication
Age between 18-60 years
Male and female subjects are eligible.
Able and willing to provide informed consent

Exclusion Criteria

Overt cause for postural tachycardia (such as acute dehydration)
Inability to give, or withdrawal of, informed consent
Pregnant
Other factors which in the investigator's opinion would prevent the subject from completing the protocol.

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Low Sodium Diet (POTS & Controls)	Pulsitile Arterial Tonometry (PAT) Protocol	Participants will consume a very low sodium diet (10 mEq/day) for 4-5 days prior to study day. Procedures include: blood work, urine collection, Pulsitile Arterial Tonometry (PAT), PAT analysis, Calf Blood Flow in Reactive Hyperemia (CBF-RH), \& evaluation of forearm-mediated dilation.
High Sodium - POTS & Controls	Pulsitile Arterial Tonometry (PAT) Protocol	Subjects will receive a high sodium diet for 4-5 days prior to study day. Procedures include: blood work, urine collection, Pulsitile Arterial Tonometry (PAT), PAT analysis, Calf Blood Flow in Reactive Hyperemia (CBF-RH), \& evaluation of forearm-mediated dilation.
High Sodium - POTS & Controls	Calf Blood Flow in Reactive Hyperemia (CBF-RH)	Subjects will receive a high sodium diet for 4-5 days prior to study day. Procedures include: blood work, urine collection, Pulsitile Arterial Tonometry (PAT), PAT analysis, Calf Blood Flow in Reactive Hyperemia (CBF-RH), \& evaluation of forearm-mediated dilation.
High Sodium - POTS & Controls	Evaluation of Forearm-Mediated Dilation	Subjects will receive a high sodium diet for 4-5 days prior to study day. Procedures include: blood work, urine collection, Pulsitile Arterial Tonometry (PAT), PAT analysis, Calf Blood Flow in Reactive Hyperemia (CBF-RH), \& evaluation of forearm-mediated dilation.
Low Sodium Diet (POTS & Controls)	Calf Blood Flow in Reactive Hyperemia (CBF-RH)	Participants will consume a very low sodium diet (10 mEq/day) for 4-5 days prior to study day. Procedures include: blood work, urine collection, Pulsitile Arterial Tonometry (PAT), PAT analysis, Calf Blood Flow in Reactive Hyperemia (CBF-RH), \& evaluation of forearm-mediated dilation.
Low Sodium Diet (POTS & Controls)	Evaluation of Forearm-Mediated Dilation	Participants will consume a very low sodium diet (10 mEq/day) for 4-5 days prior to study day. Procedures include: blood work, urine collection, Pulsitile Arterial Tonometry (PAT), PAT analysis, Calf Blood Flow in Reactive Hyperemia (CBF-RH), \& evaluation of forearm-mediated dilation.

Primary Outcome Measures

Name	Time	Method
FMD (% Change)	FMD was assessed on the morning of day 7, after 6 days of being on either a high salt diet or a low salt diet.	The primary analysis will involve a non-parametric, paired, Signed Rank test of flow mediated dilation (FMD) between all subjects (POTS \& control subjects) on the high sodium diet vs low sodium diet

Secondary Outcome Measures