POTS and autonomic dysfunction Postural orthostatic tachycardia syndrome and related disorders of the autonomic nervous system

What POTS is

POTS stands for postural orthostatic tachycardia syndrome. In plain terms: when you stand up, your heart rate climbs much higher than it should, and it stays there.

Normally your body adjusts automatically when you go from lying or sitting to standing. Blood vessels tighten, and your heart rate rises slightly to keep blood flowing to your brain. In POTS, that adjustment doesn’t work properly. Blood pools in your legs and abdomen, and your heart compensates by beating much faster.

The result is a set of symptoms that can be genuinely disabling, and that are often mistaken for anxiety, dehydration, or simply being out of shape.

POTS is one form of dysautonomia, a problem with the autonomic nervous system.

Autonomic dysfunction (dysautonomia)

The autonomic nervous system runs everything your body does without you thinking about it: heart rate, blood pressure, breathing, digestion, sweating, temperature control, bladder function, and pupil size.

It works through two branches that balance each other: the sympathetic branch, the accelerator, active in stress and standing, and the parasympathetic branch, the brake, active in rest and digestion.

Dysautonomia is the general term for that system not working properly. POTS is one specific pattern within it. Because the autonomic nervous system reaches nearly every organ, symptoms often extend well beyond the heart, and this is why people with POTS frequently have complaints that seem unrelated to each other.

They are not unrelated.

When you stand, roughly 500 to 800 mL of blood shifts downward into your legs and abdomen within seconds. Sensors in your neck and chest detect the drop in returning blood, and the autonomic system responds instantly: blood vessels constrict, the heart rate rises modestly, and blood pressure holds steady.

If any part of that reflex is impaired, whether the sensing, the signalling, the vessel response, or the circulating blood volume itself, you develop orthostatic intolerance: symptoms that appear on standing and settle on lying down.

What the system controls, and what happens when that control is impaired:

• Heart and circulation

  Rapid or pounding heartbeat on standing, lightheadedness, presyncope or fainting, chest discomfort, blood pressure swings, exercise intolerance, cold or purple-blue hands and feet.

• Digestive tract

  Nausea, early fullness, bloating, constipation or diarrhoea, delayed stomach emptying, worsening of symptoms after meals.

• Temperature and sweating

  Heat intolerance, excessive sweating or unusually little sweating, flushing, feeling feverish without a fever.

• Brain and cognition

  Brain fog, poor concentration, word-finding difficulty, headaches, non-restorative sleep, fatigue that rest doesn’t fix.

• Bladder and pupils

  Urinary urgency or frequency, light sensitivity, blurred vision on standing.

Other forms of autonomic dysfunction

POTS is not the only pattern, and distinguishing between these matters because the treatments differ.

• Vasovagal (neurocardiogenic) syncope

  A sudden reflex drop in heart rate and blood pressure causing fainting, often with a warning of nausea, sweating, and greying vision. The commonest cause of fainting, and generally benign.

• Orthostatic hypotension

  Blood pressure falls on standing rather than heart rate rising. A sustained drop of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes. Treated differently from POTS.

• Inappropriate sinus tachycardia

  A persistently fast resting heart rate that is not specifically triggered by posture.

• Orthostatic intolerance without tachycardia

  The full symptom picture without the 30 bpm heart rate criterion being met.

• Autonomic neuropathy

  Nerve damage from diabetes, amyloidosis, autoimmune disease, chemotherapy, or vitamin B12 deficiency.

• Neurodegenerative autonomic failure

  Uncommon, and typically with additional neurological findings.

Screening for these is part of a thorough assessment, because treating them improves the autonomic symptoms.

Symptoms of POTS

The hallmark is that symptoms come on or get worse when you’re upright, and improve when you lie down.

Many people with POTS have been unwell for months or years before getting a diagnosis, and many have been told at some point that their symptoms are due to anxiety. Anxiety and POTS can look similar from the outside, a racing heart and a feeling of being unwell, but they are different problems, and POTS is measurable.

Who gets POTS

POTS is most often diagnosed in people between roughly 15 and 50, and it affects women considerably more often than men.

It frequently starts after a specific trigger:

• Viral illness

  Including COVID-19. POTS is now recognized as one presentation of long COVID.

• Pregnancy

  Onset during or after pregnancy.

• Surgery or injury

  A significant injury or an operation.

• Prolonged bed rest

  Any extended period of immobility.

It also occurs more commonly in people with hypermobile Ehlers-Danlos syndrome or generalized joint hypermobility, and in people with certain autoimmune conditions. Sometimes there’s no identifiable trigger at all. That doesn’t make the diagnosis any less real.

How autonomic function is assessed

• Active stand test

  Heart rate and blood pressure lying down, then at intervals over ten minutes standing. Simple, and the single most informative test.

• Tilt table test

  The same principle on a motorized table, used when the diagnosis is unclear or fainting is the main problem.

• Holter monitor

  24 to 48 hours of continuous rhythm recording during ordinary activity, to link your symptoms to what your heart is actually doing. Holter monitoring is launching soon at this clinic.

• 24-hour ambulatory blood pressure monitoring

  Captures day-night blood pressure patterns and postural swings.

• Echocardiogram

  An ultrasound of the heart that confirms the structure, valves, and pumping function are normal, and looks for the small number of cardiac conditions that can mimic POTS.

• Exercise treadmill test (ETT)

  A monitored walk on a treadmill that shows how your heart rate and blood pressure behave under a controlled workload, whether your exercise capacity is genuinely reduced, and whether any rhythm disturbance appears with exertion.

• Heart rate variability, deep breathing, and Valsalva responses

  Measure how well each branch of the autonomic system responds.

• Blood work

  Thyroid function, hemoglobin, ferritin, electrolytes, cortisol where indicated, and B12. These exclude conditions that mimic dysautonomia.

Autonomic symptoms are real and measurable, even when routine tests such as the ECG and echocardiogram come back normal. A normal heart structure does not rule out dysautonomia. In POTS the heart is usually structurally normal, and that is expected.

How POTS is diagnosed

Diagnosis rests on measuring what your heart rate actually does when you stand, and on ruling out other causes.

1. 01

   Assessing your heart rate response to standing

   This may be an active stand test, where your heart rate and blood pressure are measured lying down and then at intervals after standing, or a tilt table test. In adults, POTS is diagnosed when heart rate rises by at least 30 beats per minute within ten minutes of standing, without a significant drop in blood pressure, alongside symptoms that have been present for at least three months.

   The absence of a blood pressure drop matters. It is what distinguishes POTS from orthostatic hypotension, which is a different condition with different treatment.

2. 02

   Ruling out other explanations

   Several conditions produce similar symptoms and need to be excluded before POTS is diagnosed. These include thyroid problems, anemia, adrenal conditions, dehydration, and side effects of medications you may already be taking. Blood work is a routine part of the assessment.

3. 03

   Looking at your heart itself

   An ECG records your heart’s electrical activity. An echocardiogram, an ultrasound of the heart, checks that its structure and pumping function are normal. A Holter monitor, worn for 24 to 48 hours, records your heart rhythm during ordinary daily activity and can capture what happens during your symptoms.

   None of these tests are painful, and none involve needles beyond the blood work.

4. 04

   Testing you under exertion

   An exercise treadmill test (ETT) records your ECG, heart rate, and blood pressure while you walk on a treadmill that gets gradually faster and steeper. In POTS it serves three purposes: it measures how much your exercise capacity is actually reduced, it shows whether your heart rate rise is out of proportion to the workload, and it checks that an abnormal rhythm or reduced blood flow to the heart muscle is not the explanation for your symptoms.

   It also gives a starting point for your reconditioning program. You’ll be asked to wear comfortable shoes, avoid caffeine beforehand, and you can stop the test at any time.

How POTS is treated

POTS is manageable. Most people improve substantially with treatment, and some recover completely, particularly when it followed a viral illness. Treatment is built in layers, and the non-drug measures do most of the work.

1. 01

   Fluid and salt

   Increasing fluid intake, often to two to three litres a day, and increasing dietary salt raises blood volume and reduces symptoms. Your specialist will give you specific targets. This needs to be individualized, and it isn’t appropriate for everyone, particularly if you have high blood pressure or kidney problems.

2. 02

   Compression garments

   Waist-high compression stockings or abdominal binders reduce blood pooling in the legs and abdomen. These are more effective than knee-high stockings for POTS.

3. 03

   Graded exercise reconditioning

   This is the single most effective long-term treatment, and it’s also the hardest, because exercise initially makes symptoms worse. The approach is to start with recumbent exercise, a recumbent bike, rowing machine, or swimming, where you’re not fighting gravity, and build gradually over months before moving to upright activity. Structured programs exist for exactly this, and going too fast is the most common reason people give up.

4. 04

   Practical adjustments

   Raising the head of your bed, standing up slowly, avoiding long periods of standing still, being careful in hot weather and hot showers, and eating smaller and more frequent meals all help.

   Counter-pressure manoeuvres, such as crossing your legs, clenching your buttocks, or squeezing a ball, can abort symptoms when you feel them coming on.

5. 05

   Treating the associated problems

   Digestive symptoms, migraine, poor sleep, iron deficiency, and mast cell symptoms each have their own treatment, and addressing them usually improves the autonomic picture as a whole.

6. 06

   Medication

   When the measures above aren’t enough, several medications can help. These include beta blockers or ivabradine to slow heart rate, midodrine to tighten blood vessels, fludrocortisone to increase blood volume, and pyridostigmine. Which one suits you depends on your particular pattern of symptoms, and finding the right fit sometimes takes some adjustment.

What to expect at your appointment

Your first visit is a consultation with a cardiologist. Expect it to take about an hour.

• How to do a home standing test

  If you have a blood pressure cuff, lie flat and rest for five minutes, then record heart rate and blood pressure. Stand up and record again at one, three, five, and ten minutes, noting any symptoms alongside each reading. Repeat over several days, ideally including a morning reading. This gives your cardiologist real data to work with and often shortens the path to a diagnosis.

Depending on what’s found, testing may happen on the same day or be booked shortly afterward. A letter goes back to your referring doctor, usually within 1 to 7 days.