Phenotyping of Postural Orthostatic Tachycardia Syndrome (POTS)

Inclusion Criteria:

POTS Patients

• Age ≥ 14 years, able to provide informed consent (assent with parental consent forage < 18) and comply with procedures

• Meets consensus criteria for POTS: (1) sustained increase in heart rate ≥ 30 bpmabove supine baseline within 10 min of quiet standing or upright tilt (≥ 40 bpm inindividuals 12 to 19 years of age) OR sustained upright HR (heart rate) >120 bpm, (2) absence of orthostatic hypotension, (3) symptoms with standing that improve withsitting or lying down, (4) resting supine heart rate < 100 bpm, (5) orthostaticsymptoms present for at least 6 months

• Stable oral medication regimen for at least 14 days

Non-POTS Control Patients

• Healthy women, age 18 - 30 years, able to provide informed consent and comply withstudy procedures

• Does NOT meet consensus criteria for postural tachycardia syndrome

• No symptoms of orthostatic intolerance or dysautonomia. No history of other majormedical disorder

• Resting supine heart rate < 100 bpm

Exclusion Criteria:

None of the following exclusion criteria:

• Use of amphetamine-type stimulants, diuretics, selective norepinephrine reuptakeinhibitor, anticholinergic medications (including tricyclic antidepressantmedications), fludrocortisone, desmopressin in past 14 days

• Use of other autonomic drugs (adrenergic agents, pyridostigmine, droxidopa,triptans, ivabradine) in past 48 hours

• Currently receiving IVIG (Intravenous immunoglobulin), subcutaneous IgG (Immunoglobulin G), or any investigational medication (in past year)

• Infusion of iv fluids in past 7 days

• History or evidence of another condition explaining symptoms or orthostatictachycardia (e.g. structural heart disease, CSF (Cerebrospinal fluid) hypovolemia,or severe traumatic brain injury)