POTS (Postural Orthostatic Tachycardia Syndrome)

When a healthy person stands up, there is an immediate drop of about ½ liter of blood from the chest to the lower abdomen, buttocks and legs.  About ¼ of the plasma in the blood vessels moves out of the vessels and into tissues.  This means that less fluid is returning to the heart, which effectively decreases blood pressure.  To compensate for this, the body increases heart rate and makes its blood vessels less permeable to retain more fluid.  Standing results in a 10-20 bpm increase in heart rate and a very small increase in blood pressure.  If the body cannot regulate these changes correctly, it can cause either orthostatic tachycardia or orthostatic hypotension, a decrease in blood pressure by at least 20 mmHg.

Postural orthostatic tachycardia syndrome (POTS) is a kind of dysautonomia, a malfunction of the autonomic nervous system.  The ANS regulates such functions as heart rate, blood pressure, digestion, and sweating.  In patients with this diagnosis, there is a heart rate increase of at least 30 bpm within 5-30 minutes when going from resting to standing; symptoms worsen with standing; symptoms last at least 6 months; standing plasma norepinephrine is at least 600 pg/ml; and there is no other obvious cause of orthostatic symptoms or tachycardia, such as active bleeding.  In POTS, blood pressure is usually maintained or may increase on standing.  This syndrome has been known for at least 150 years and has gone by many names during that time, including mitral valve prolapse syndrome, neurocirculatory asthenia and orthostatic intolerance.

Patients experience rapid heartbeat, inability to exercise, lightheadedness, extreme fatigue, headache, brain fog, chest discomfort, nausea, tremulousness, and blurred/tunnel vision.  Pre-syncope (lightheadedness before fainting) is very common, but only about 30% actually pass out.  POTS is often highly disabling, even in people without other chronic conditions.  Daily living activities, such as cleaning and bathing, can hugely exacerbate symptoms.  It primarily affects women of child-bearing age, with 4 times as many women affected as men.

POTS is usually seen in the presence of other health issues, such as IBS and autoimmune diseases.  There is a known association between POTS and joint hypermobility.  Many patients also have bowel disorders.  Despite having chest pain, POTS patients almost never have coronary artery involvement.  Their rhythm is a sinus tachycardia, a normal rhythm with a rapid heart rate.  Symptoms often start after episodes of obvious physical stress such as pregnancy or major surgery, but not always.  About 80% of female patients report worse symptoms during the premenstrual phase of their cycle. 

In about 40-50% of patients, there is a clear physical sign called acryocyanosis.  The lower legs, from feet to as high as above the knees show dark red/blue discoloration and are cold to the touch.  The reason for this is unclear but is thought to be due to decreased blood flow to skin.

POTS patients are sometimes diagnosed with anxiety disorders, but these symptoms can be caused by the hyperadrenergic state in POTS.  Much of the anxiety attributed to POTS patients might be due to misinterpretation of their physical symptoms.  However, they do often have diminished attention and concentration.

Historically, a tilt table test has been used to diagnose POTS.  In recent years, this has fallen out of favor as being tilted into a standing position does not accurately simulate active standing.  Additionally, tilt table testing can sometimes cause a diagnosis of POTS in healthy patients.  A standing test is three times more accurate.   (I was diagnosed with a standing test.)

In many cases of POTS, hyperadrenergic state is caused by dysautonomia or low blood volume.  However, in some cases, the primary problem is that the body releases too much epinephrine and norepinephrine.  This causes extremely high levels of upright norepinephrine with large blood pressure increases on standing.  This type of POTS is called HyperPOTS, or hyperadrenergic POTS. 

Patients should avoid triggers such as dehydration and extreme heat.  They should drink 8-10 cups of water daily, and can rapidly drink 16 fl oz of water to lower their heart rate.  They should also increase salt intake up to 200 mEq/day.  Salt tablets can be taken to supplement this effort.  Support hose can minimize pooling of blood in the legs.  Exercise is encouraged and can be beneficial, but vigorous exercise can acutely worsen symptoms and prolong fatigue. 

Acute blood volume expansion is effective at controlling heart rate and reducing symptoms.  1L of saline infused over 1 hour decreased orthostatic tachycardia by over 50%.  There are recent reports of patients having regular saline infusions, typically 1L of NS every other day or every day.  This has resulted in considerable symptom reduction for many of them.  (I infuse 2L three nights a week.  It has helped to stabilize my blood pressure and has reduced other symptoms.) 

There are no medications approved by the FDA for the treatment of POTS, so all medications used are off label.  For this reason, there are no long-term clinical trials.  If low blood volume is known or suspected, fludrocortisone or DDAVP is often used.  Rarely, erythropoietin is useful if other therapies have failed, but this is cost prohibitive and more likely to cause complications. Midodrine can also be used in patients with low blood pressure.  For HyperPOTS, clonidine and methyldopa can be used.  Beta blockers can be helpful at low doses. (WARNING: USE OF BETA BLOCKERS CAN PREVENT PROPER ACTION OF EPINEPHRINE.  MAST CELL PATIENTS ON BETA BLOCKERS SHOULD HAVE A GLUCAGON AUTOINJECTOR TO BE USED PRIOR TO USING AN EPIPEN DURING ANAPHYLAXIS.)

POTS commonly occurs in the presence of mast cell disease.  The most common presentation is MCAS with POTS, sometimes also in the presence of Ehlers Danlos Syndrome (EDS.)