Pathophysiology of Orthostatic Intolerance

Study Overview
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Brief Summary
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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.

Official Title
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Pathophysiology of Orthostatic Intolerance

Conditions
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Tachycardia, Postural Orthostatic Tachycardia Syndrome

Intervention / Treatment
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* Radiation: DAXOR
* Procedure: QSweat
* Drug: Intrinsic Heart Rate


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Orthostatic intolerance Exclusion Criteria: Inability or unwillingness to give informed consent

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Patients<br>Patients with orthostatic intolerance | Radiation: DAXOR<br>* 131-I-Human Serum Albumin Blood Volume Assessment Kit<br>* Other names: Volumex;Procedure: QSweat<br>* Quantitative Sweat Testing<br>* Other names: Quantitative Axonal Sudomotor Reflex Testing;Drug: Intrinsic Heart Rate<br>* Atropine 0.04 mg/kg IV in divided doses Propranolol 0.2 mg/kg IV in divided doses<br>* Other names: IHR;|
| Other: Healthy Control Subjects<br>Healthy subjects to determine normal response | Radiation: DAXOR<br>* 131-I-Human Serum Albumin Blood Volume Assessment Kit<br>* Other names: Volumex;Procedure: QSweat<br>* Quantitative Sweat Testing<br>* Other names: Quantitative Axonal Sudomotor Reflex Testing;Drug: Intrinsic Heart Rate<br>* Atropine 0.04 mg/kg IV in divided doses Propranolol 0.2 mg/kg IV in divided doses<br>* Other names: IHR;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Physiological abnormalities in orthostatic intolerance |  | 1 day | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| blood volume |  | 1 day | 
| intrinsic heart rate |  | 1 hour | 
| quantitative sweat testing |  | 2 hours | 
| residual sympathetic function after pharmacological autonomic blockade |  | 3 hours | 
| norepinephrine spillover |  | 3 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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heart rate, blood pressure, blood volume, sympathetic nervous system, orthostatic tachycardia, orthostatic intolerance, POTS