Assessment of Vascular Endothelial Function in Postural Tachycardia Syndrome

Assessment of Vascular Endothelial Function in Postural Tachycardia Syndrome (POTS)

The purpose of this study is to see if people with Postural Tachycardia Syndrome (POTS) have different levels of certain chemicals in their blood than people who don't have POTS. This study will test whether the blood vessels of people with POTS will react differently to certain tests than people without POTS.

The hypothesis of the study is:

Patients with POTS will have vascular endothelial dysfunction compared with control subjects.

Inclusion Criteria:

ALL:

• Ages between 18-60 years old
• Male and female subjects are eligible
• Able and willing to give informed consent

Additional criteria for POTS:

• Diagnosed with postural tachycardia syndrome by the Vanderbilt Autonomic - Dysfunction Center (1. increase in heart rate >/= 30 beats/minute with position change from supine to standing for 10 minutes and/or 2. Chronic symptoms consistent with POTS that are worse when upright and get better with recumbence.

Additional criteria for Control subjects:

• Healthy, non-obese, non-smokers without orthostatic tachycardia
• Selected to match profiles of POTS patients (gender, age)
• Not using vasoactive medications

Exclusion Criteria:

• Overt cause for postural tachycardia (such as acute dehydration)
• Inability to give, or withdraw informed consent
• Pregnancy
• Other factors in the investigator's opinion would prevent the subject from completing the study