Postural orthostatic tachycardia (POTS) is characterized by abnormalities in the autonomic nervous system in the body. The autonomic nervous system controls and regulates body functions such as heart rate, breathing, digestion, and more.

The investigator has shown that patients with POTS have higher cardiovascular and adrenergic activating autoantibodies (AAb), which likely changes the normal make-up of POTS. There are autoantibodies that have been suggested by a few reports of their presence in POTS, but their role different aspects of POTS is unknown. The study will look at the body's responses in patients with POTS. The crossover study design is to have half of the patients will start with sham followed by active stimulation and half will start by active followed by sham stimulation. It is anticipated that results will provide a potential therapeutic approach based on the understanding of POTS.

Inclusion Criteria:

-Female or male participants age 18-80

Group 1 (20 participants):

• A physician-based diagnosis of POTS
• Participants that have a postural pulse rise of >35 for adolescents and >30 for adults with a Blood Pressure (BP) that does not drop >10/5 mmHg will be qualified. These participants may be on salt and fluid loading.

Group 2 (10 participants):

• Previously diagnosed with POTS
• Patients is on Intravenous immunoglobulin (IVIG) infusion but who have an incomplete symptomatic response

Exclusion Criteria:

• Age < 18 years
• Sick sinus syndrome, 2nd or 3rd degree Atrioventricular (AV) block, bifascicular block or prolonged 1st degree AV block (PR>300ms).
• Currently pregnant women or women planning on becoming pregnant ≤ 6 months
• History of hypotension due to autonomic dysfunction
• Have a secondary causes of tachycardia (acute anemia or blood loss, drugs, significant cardiomyopathy, diabetes mellitus)
• Patients with active implants (such as a cardiac pacemaker, or a cochlear implant).