What is POTS?
Postural Orthostatic Tachycardia Syndrome, or POTS, is a disorder of the autonomic nervous system, the nervous system that helps control blood flow and heart rate.
Sufferers describe feeling lightheaded, dizzy and with a racing heart rate when they stand up and it is relieved when they sit or lie back down.
Normally, when we stand up from sitting, gravity lowers our blood pressure and the heart has to beat a little faster to compensate. In POTS, the system overshoots and the heart rate goes too high too quickly, over 30 beats more than before, whilst blood pressure stays the same.
POTS predominantly affects women younger than 50 years of age. Often, there are additional symptoms such as fatigue, headaches, palpitations, sleep disturbances, nausea, bloating, among others.
What causes POTS?
POTS is a dysregulation of the autonomic nervous system, that is a problem coordinating the nerve signals that increase heart rate and blood pressure and those that calm it down.
What is the Autonomic Nervous System?
The Autonomic Nervous System, or ANS, runs constantly in the background to maintain blood pressure. It comprises:
The sympathetic nervous system, the fight or flight pathway involving adrenalin, which increases the heart rate, constricts blood vessel diameter and thus boosts blood pressure.
The parasympathetic nervous system; which generally counteracts the sympathetic nervous system .
Reference: https://franklincardiovascular.com/overactive-sympathetic-nervous-system/
This is not the same as orthostatic hypotension, a condition whereby the blood pressure drops when standing. This is another entity and needs to be investigated differently.
In POTS, the general problem is that the cardiovascular system can not effectively coordinate itself. It has multiple causative factors:
Increased sympathetic activity and noradrenalin: This may cause palpitations, tremors, hypertension, anxiety, and tachycardia in the background.
Volume dysregulation: blood may not be staying in the vessels but leaking into the tissues
Cardiovascular deconditioning, the pump and vessels are not coordinating well.
Autoimmune dysfunction; which affects nerves and blood vessels.
Nerve dysfunction; Typically along long nerves to the lower limb whereby the return of blood to the heart is not as efficient and blood pools in the legs.
Patients thus may describe a range of problems such as agitation, depression, going to the bathroom a lot to pass urine, gut disturbances, clammy hands to name a few.
The real underlying cause is multifactorial; bad gut bacteria, environmental chemicals and an imbalance in how your body cleans up damage and thrives.
How is POTS diagnosed?
The first place to start is to take a history looking for autonomic dysfunction, such as the problems listed above. If dizziness is suspected, a comprehensive body check including heart investigations such as an echocardiogram (Ultrasound to check the structure of the heart) and ECG (to check the electrical activity) are recommended.
The gold standard test for POTS is to stand somebody up and measure their heart rate and blood pressure. POTS is diagnosed if the heart rate increases more than 30 beats per minute in the first ten minutes after standing up.
Commonly, a tilt table test is used to detect POTS. This involves the patient being in a table that is tilted upwards to simulate standing, whilst heart rate and blood pressure are measured.
An alternative is the active stand test, which involves the patient lying horizontal for 10 minutes with measurement of baseline blood pressure and heart rate; the patient then stands and with re-measurement of BP and HR at timed intervals (1, 3, 5, and 10 minutes).
All patients should fast from midnight, except small sips of water, prior to these tests.
How is POTS treated?
The first place to start is to reverse or treat any underlying issues: Encourage exercise to condition the heart and blood vessels.
Reduce any source of inflammation which may impact the autonomic nervous system
Increase salt intake.
Reduce medications which impact blood volume, encourage sympathetic tone.
Medications; fludrocortisone, pyridostigmine, midodrine, or a beta blocker may.
Compression stockings
Lifestyle: reduce alcohol or caffeine at night and elevated the bed. This may reduce urine formation.
References
Benarroch EE. Postural tachycardia syndrome: a heterogeneous and multifactorial disorder. Mayo Clin Proc. 2012;87(12):1214-1225.
doi:10.1016/j.mayocp.2012.08.013
Zhao S, Tran VH. Postural Orthostatic Tachycardia Syndrome. [Updated 2021 Aug 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-.
