TachycardiaNCT00608725
Pathophysiology of Orthostatic Intolerance
A study testing DAXOR, QSweat and Intrinsic Heart Rate in people with Tachycardia and Postural Orthostatic Tachycardia Syndrome, run by Satish R. Raj at 1 site in United States.
Trial summary
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… Read more about this study
- Who is it for?
- Ages 18 to 80 yearsHealthy volunteers can take part
- Conditions the study is for
- Tachycardia, Postural Orthostatic Tachycardia Syndrome
- What is being tested?
- DAXOR, QSweat and Intrinsic Heart Rate
- Type of treatment
- Injection or infusion, Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 260 participants
- Where
- 1 siteUnited States
- Study dates
- Dec 1996to Dec 2029
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 80 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Orthostatic intolerance
Who cannot join
- Inability or unwillingness to give informed consent
Trial locations and contacts
1 site in 1 country.
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.
Read the detailed description
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.
- Being tested
- DAXOR, QSweat, Intrinsic Heart Rate
- Keywords
- heart rate, blood pressure, blood volume, sympathetic nervous system, orthostatic tachycardia, orthostatic intolerance, POTS
- Medical subject headings
- Tachycardia, Postural Orthostatic Tachycardia Syndrome, Orthostatic Intolerance
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
DAXORRadiation
Also called Volumex
131-I-Human Serum Albumin Blood Volume Assessment Kit
QSweatProcedure or surgery
Also called QSART, Quantitative Axonal Sudomotor Reflex Testing
Quantitative Sweat Testing
Intrinsic Heart RateDrug
Also called Inderal, IHR
Atropine 0.04 mg/kg IV in divided doses Propranolol 0.2 mg/kg IV in divided doses
| Study group | Role | What they receive |
|---|---|---|
| Patients | Other | Patients with orthostatic intolerance Receives: Radiation: DAXOR; Procedure: QSweat; Drug: Intrinsic Heart Rate |
| Healthy Control Subjects | Other | Healthy subjects to determine "normal" response Receives: Radiation: DAXOR; Procedure: QSweat; Drug: Intrinsic Heart Rate |
What is being measured
The primary outcome is the main question the study is designed to answer.
Physiological abnormalities in orthostatic intolerance
varied metrics used here
Measured: 1 day
Secondary outcomes (5)
blood volume
Blood volume as measured by DAXOR technique
Measured: 1 day
intrinsic heart rate
Heart rate after IV propranolol and IV atropine
Measured: 1 hour
quantitative sweat testing
sweat volumes after a QSweat test
Measured: 2 hours
residual sympathetic function after pharmacological autonomic blockade
changes in BP after trimethaphan infusions
Measured: 3 hours
norepinephrine spillover
tritiated norepunephrine spillover data
Measured: 3 hours
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted6 Feb 2008 (estimated)
- Study startDec 1996
- Primary completionDec 2029 (estimated)
- Study completionDec 2029 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for TachycardiaStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Diagnosis
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 260 participants (actual)
Sponsor and investigators
- Lead sponsor
- Satish R. Raj
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor-investigator, Satish R. Raj, Vanderbilt University Medical Center
- Investigators
- David Robertson, MD, Principal investigator, Vanderbilt University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT00608725
- Sponsor's protocol ID
- 8398
- Status last verified
- Oct 2026
- First submitted
- 22 Jan 2008
- Last updated
- 13 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
Publications
Mustafa HI, Garland EM, Biaggioni I, Black BK, Dupont WD, Robertson D, Raj SR. Abnormalities of angiotensin regulation in postural tachycardia syndrome. Heart Rhythm. 2011 Mar;8(3):422-8. doi: 10.1016/j.hrthm.2010.11.009. Epub 2011 Jan 22.
PubMed 21266211
Study at a glance
From the registry record, last updated by the sponsor on 13 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Pathophysiology of Orthostatic Intolerance
- ClinicalTrials.gov ID
- NCT00608725
- Acronym / sponsor ID
- 8398
- Keywords
- heart rate, blood pressure, blood volume, sympathetic nervous system, orthostatic tachycardia, orthostatic intolerance, POTS
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 260 participants (actual)
- Lead sponsor
- Satish R. RajUniversity, hospital or other
- Study start
- Dec 1996
- Primary completion
- Dec 2029 (estimated)
- Study completion
- Dec 2029 (estimated)
- First posted
- 6 Feb 2008 (estimated)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
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.
Study design
- Primary purpose
- Diagnosis
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Patients | Other | Radiation: DAXOR, Procedure: QSweat, Drug: Intrinsic Heart RatePatients with orthostatic intolerance |
| Healthy Control Subjects | Other | Radiation: DAXOR, Procedure: QSweat, Drug: Intrinsic Heart RateHealthy subjects to determine "normal" response |
Who may qualify
- Ages
- 18 to 80 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- Orthostatic intolerance
Key exclusion criteria (1 listed)
- Inability or unwillingness to give informed consent
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| DAXORAlso: Volumex131-I-Human Serum Albumin Blood Volume Assessment Kit | Radiation | Healthy Control Subjects, Patients |
| QSweatAlso: QSART, Quantitative Axonal Sudomotor Reflex TestingQuantitative Sweat Testing | Procedure or surgery | Healthy Control Subjects, Patients |
| Intrinsic Heart RateAlso: Inderal, IHRAtropine 0.04 mg/kg IV in divided doses Propranolol 0.2 mg/kg IV in divided doses | Drug | Healthy Control Subjects, Patients |
Primary outcome
Physiological abnormalities in orthostatic intolerance
Time frame: 1 day
varied metrics used here
5 secondary outcomes
blood volume
Time frame: 1 day
intrinsic heart rate
Time frame: 1 hour
quantitative sweat testing
Time frame: 2 hours
residual sympathetic function after pharmacological autonomic blockade
Time frame: 3 hours
norepinephrine spillover
Time frame: 3 hours
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 13 Oct 2026.
- Derived from this study: PubMed 21266211Mustafa HI, Garland EM, Biaggioni I, Black BK, Dupont WD, Robertson D, Raj SR. Abnormalities of angiotensin regulation in postural tachycardia syndrome. Heart Rhythm. 2011 Mar;8(3):422-8. doi: 10.1016/j.hrthm.2010.11.009. Epub 2011 Jan 22.
- Website of the Vanderbilt Autonomic Dysfunction CenterLink provided by the sponsor.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
David Robertson, MD principal investigator
Vanderbilt University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing DAXOR, QSweat and Intrinsic Heart Rate in people with Tachycardia and Postural Orthostatic Tachycardia Syndrome, run by Satish R. Raj at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 1 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 13 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Physiological abnormalities in orthostatic intolerance (time frame: 1 day). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT00608725, which also lists 1 linked publication.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 13 Oct 2026.