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OpenTrials
Active, Not Recruiting

NCT Number: NCT00608725

Pathophysiology of Orthostatic Intolerance

The purpose of this study is to describe the mechanism of orthostatic intolerance, relying on cardiovascular physiological studies. The syndrome is of undetermined etiology, but the syndrome causes impairment of a number of young adults, females more than males, with symptoms of tachycardia, fatigue, lightheadedness, palpitations, blurred vision, chest discomfort, difficulty concentrating, and dizziness with the upright posture. It is believed that many different pathophysiological processes can give rise to this disorder.

Active, Not Recruiting

This study is active but is not currently recruiting participants.

Key information

Conditions

Tachycardia Arrhythmias, Cardiac Autonomic Nervous System Diseases Cardiac Conduction System Disease Cardiovascular Diseases Heart Diseases Nervous System Diseases Neurologic Manifestations Orthostatic Intolerance Pathologic Processes Pathological Conditions, Signs and Symptoms Postural Orthostatic Tachycardia Syndrome Primary Dysautonomias Signs and Symptoms

Age range

18 year–80 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Vanderbilt University

Nashville, Tennessee, 37232, United States

About this study

The purpose of this study is to describe the mechanism of orthostatic intolerance, relying on cardiovascular physiological studies. The syndrome is of undetermined etiology, but the syndrome causes impairment of a number of young adults, females more than males, with symptoms of tachycardia, fatigue, lightheadedness, palpitations, blurred vision, chest discomfort, difficulty concentrating, and dizziness with the upright posture. It is believed that many different pathophysiological processes can give rise to this disorder.

This is not a clinical trial in the classical sense, but an omnibus protocol to allow for disntinct and personalized pathophysiological testing.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Orthostatic intolerance

Exclusion criteria

  • Inability or unwillingness to give informed consent

Treatment and study plan

DAXOR

Radiation

131-I-Human Serum Albumin Blood Volume Assessment Kit

Other names: Volumex

QSweat

Procedure

Quantitative Sweat Testing

Other names: QSART, Quantitative Axonal Sudomotor Reflex Testing

Intrinsic Heart Rate

Drug

Atropine 0.04 mg/kg IV in divided doses Propranolol 0.2 mg/kg IV in divided doses

Other names: Inderal, IHR

Primary outcomes

  1. Physiological abnormalities in orthostatic intolerance

    Time frame: 1 day

    varied metrics used here

Secondary outcomes

  1. blood volume

    Time frame: 1 day

    Blood volume as measured by DAXOR technique

  2. intrinsic heart rate

    Time frame: 1 hour

    Heart rate after IV propranolol and IV atropine

  3. quantitative sweat testing

    Time frame: 2 hours

    sweat volumes after a QSweat test

  4. residual sympathetic function after pharmacological autonomic blockade

    Time frame: 3 hours

    changes in BP after trimethaphan infusions

  5. norepinephrine spillover

    Time frame: 3 hours

    tritiated norepunephrine spillover data

Sponsors and collaborators

Lead sponsor

Satish R. Raj

Other

Registry information

Important dates

Study start
1996
Primary completion
2029
Study completion
2029
First posted
Feb 6, 2008
Registry last updated
Oct 8, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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