Clinical Trial: Evaluation of Chronic Orthostatic Intolerance

Study Status: Completed
Recruit Status: Completed
Study Type: Observational

Official Title: Clinical Laboratory Evaluation of Chronic Orthostatic Intolerance

Brief Summary:

This study will conduct tests with patients with primary chronic orthostatic intolerance (COI) to learn more about this disorder of the autonomic nervous system.

Healthy normal volunteers and patients 18 years of age and older with COI may be eligible for this study. Participants undergo one or more of the following tests and procedures:

• Blood studies, including arterial catheter insertion to measure blood pressure and collect arterial blood samples, blood flow studies using sensors applied to the skin and a pressure cuff around a limb, blood volume studies using injection of radioactively labeled human serum albumin and gene studies to look for genetic abnormalities associated with certain proteins.
• Imaging studies, including CT scan of the adrenal glands, heart ultrasound, and PET scanning.
• Electrocardiogram
• Microdialysis to measures levels of chemicals in the body fluid of certain tissues. A thin tube is inserted into the skin and a solution is passed through it. Chemicals in the body tissues enter the solution in the tube. The solution is collected and the chemical levels are measured.
• Neck suction. Neck suction is applied to test a reflex the brain uses to regulate blood pressure.
• Perometry. Limb volume is measured using an infrared light that moves up the limb.
• Quantitative sudomotor axon reflex test to evaluate an aspect of autonomic nervous system function. A small amount of a brain chemical (acetylcholine) is applied to the skin with a tiny amount of electricity, and the sweat in a nearby patch of skin is measured.
• Skin electrical conduction
  

  Detailed Summary: This protocol is to identify and characterize distinct types of chronic orthostatic intolerance (COI). COI can be a manifestation of primary chronic autonomic failure, which is covered under a separate protocol. The present protocol concerns patients with COI who under resting conditions have intact sympathetic neurocirculatory function. COI can reflect different pathophysiologic mechanisms; until now, few studies have attempted to distinguish these mechanisms in individual patients. We hypothesize that results of clinical assessment and physiologic, chemical, pharmacologic, and imaging tests will reveal internally consistent patterns that distinguish particular forms of COI. We wish to determine the relative frequencies of these forms in a referral population. The first phase of testing is to identify sympathetic neurocirculatory failure, baroreflex failure, and secondary causes of COI (hypovolemia, excessive orthostatic venous pooling, or excessive orthostatic extravasation). In a subsequent inpatient phase, tilt table testing is done, with concurrent hemodynamic and chemical measurements, to confirm subtypes of postural tachycardia syndrome and neurocardiogenic syncope. The results of these evaluations will be used for stratification of specific, pathophysiologically defined diagnostic groups for therapeutic protocols. In an off-site study, we will evaluate members of a large family where COI seems to be transmitted as an autosomal dominant trait.
  Sponsor: National Institute of Neurological Disorders and Stroke (NINDS)
  

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  Information By: National Institutes of Health Clinical Center (CC)
  

  Dates:
  Date Received: September 29, 2003
  Date Started: September 26, 2003
  Date Completion: August 5, 2008
  Last Updated: January 24, 2017
  Last Verified: August 5, 2008