Autonomic Determinants of POTS - Pilot1

  • End date
    Dec 31, 2025
  • participants needed
  • sponsor
    Vanderbilt University Medical Center
Updated on 24 March 2022
orthostatic hypotension
Accepts healthy volunteers


Postural tachycardia syndrome (POTS) is a relatively common condition affecting mostly otherwise healthy young women. It is the cause of significant disability and an impairment in quality of life. These patients have high heart rate and symptoms during standing. Many of these patients are disabled and have a poor quality of life. The sympathetic nerves are part of the nervous system that helps to maintain normal blood pressures and heart rates during activities of daily life. The purpose of this study is to determine the importance of sympathetic activation as a cause of orthostatic symptoms. The investigators will assess the effects of a blood pressure medication (Moxonidine) on the symptoms during standing. Moxonidine lowers sympathetic activity. The investigators believe patients with high resting sympathetic activity might benefit from Moxonidine. It might reduce high heart rate and improve symptoms during standing. This study should help clinicians and the growing population of patients with POTS gain a better understanding of this disorder and find more personalized treatment.


Postural tachycardia syndrome (POTS) is a relatively common condition affecting mostly otherwise healthy young women. It is the cause of significant disability and an impairment in quality of life of a magnitude comparable to patients with chronic obstructive pulmonary disease or congestive heart failure. It is characterized by sympathetic activation with an exaggerated orthostatic tachycardia that responds to low doses of beta-blockers. The underlying pathophysiology of this disorder and the nature of this sympathetic activation is not clear and is likely heterogeneous. In many patients this sympathetic activation could be an appropriate compensatory response to hypovolemia, deconditioning or partial neuropathy.

The investigators have identified a subset of patients in whom sympathetic activation appears to be a primary phenomenon. These patients are characterized by high central sympathetic outflow, as determined by muscle sympathetic nerve activity (MSNA) above the upper 95% confidence interval for the group. This "hyperadrenergic" phenotype is associated with a paradoxical increase in blood pressure on standing and exaggerated pressor response to the vasoconstrictive phase of the Valsalva maneuver, and clinical observations suggest they improve clinically when treated with central sympatholytics.

The investigators propose to test the hypothesis that there is a subset of POTS patients with a central sympathetic activation as the primary pathophysiology. In an acute double blind, placebo-controlled, randomized study, the investigators propose that administration of the central sympatholytic moxonidine will improve orthostatic symptoms and abnormalities in orthostatic hemodynamics, as well as sympathetic outflow.

Condition Postural Tachycardia Syndrome
Treatment Placebo, Moxonidine
Clinical Study IdentifierNCT04050410
SponsorVanderbilt University Medical Center
Last Modified on24 March 2022


Yes No Not Sure

Inclusion Criteria

female/male subjects, age 18-55 years
criteria for postural tachycardia syndrome (POTS)
a heart rate increase of ≥30 beats/min within 10 minutes of upright posture
lack of orthostatic hypotension (blood pressure fall ≥ 20/10 mmHg within 10 minutes of standing); and
chronic symptoms during upright posture over at least 6 months, in the absence of any other acute cause
in the follicular phase of the menstrual cycle (day 5-13 of a 28-day cycle)
POTS with primary central sympathetic activation (psPOTS) as defined as having resting muscle sympathetic nerve activity (MSNA) greater than or equal to 25 bursts/min
able and willing to provide informed consent

Exclusion Criteria

BMI>30 kg/m2
deconditioned status (if available VO2max<80% of predicted)
unable to withdraw from medications known to affect autonomic function, blood pressure or blood volume
systemic illnesses known to produce autonomic neuropathy, including but not limited to diabetes mellitus, amyloidosis, monoclonal gammopathies, and autoimmune neuropathies
Arteriosclerotic disease of carotid artery. History of neck surgery
conditions associated with inflammatory processes, such as coronary artery disease, hypertension, smoking, hypercholesterolemia (or on statin therapy), rheumatoid arthritis, diabetes
treatment with oral corticosteroids, current infections (e.g., urinary tract infection), or use of non-steroidal anti-inflammatory drugs
other factors which in the investigator's opinion would prevent the subject from completing the protocol including clinically significant abnormalities in clinical, mental or laboratory testing
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