​                     Professor Francisco Leyva-León

Postural Orthostatic Tachycardia Syndrome (POTS)

POTS is characterised by an abnormally fast heart rate and various other symptoms when you move from a sitting or lying down position to standing. It is a disorder of the autonomic nervous system (ANS), which controls involuntary bodily functions like heart rate, blood pressure, digestion, and sweating. In people with POTS, the ANS doesn't regulate these functions properly when standing, leading to a variety of symptoms, including:

• Dizziness or lightheadedness, especially when standing or after prolonged standing.

• Fainting or near-fainting.

• Noticeable heart palpitations (feeling like your heart is pounding or skipping a beat).

• Fatigue or extreme tiredness.

• Brain fog: difficulty thinking, concentrating, or remembering.

• Shortness of breath.

• Chest pain.

• Headaches.

• Nausea and other digestive issues (e.g., bloating, diarrhoea, constipation).

• Shakiness and excessive sweating.

• Weakness or heaviness in the legs.

• Blurred vision or tunnel vision.

• Hands and feet looking purple or discoloured (due to blood pooling).

Symptoms often worsen with heat, dehydration, prolonged standing, exercise, alcohol, and sometimes after eating.

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Causes

The exact cause of POTS is not fully understood and can vary from person to person. It can develop suddenly or gradually. It's sometimes triggered by:

• Viral or bacterial infections (including COVID-19).

• Pregnancy.

• Major surgery or trauma.

• Puberty.

POTS is more common in women, particularly between the ages of 15 and 50. It can also be associated with other conditions like Ehlers-Danlos syndrome, chronic fatigue syndrome (ME/CFS), and autoimmune disorders.

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Diagnosis

The diagnosis typically involves a medical history, physical exam, and specific tests. A key diagnostic criterion is the significant increase in heart rate upon standing without a significant drop in blood pressure. It is essential to rule out heart rhythm abnormalities that can mimick POTS. ECG monitoring, echocardiography and other investigations will be necessary. A tilt table test may be used to confirm the diagnosis, where heart rate and blood pressure are monitored as a person is tilted from a lying to an upright position.

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Treatment

There is currently no cure, but symptoms can often be managed with a combination of lifestyle changes and, in some cases, medication.

 

Lifestyle modifications include:

• Increasing fluid and salt intake.

• Wearing compression stockings.

• Elevating the head of the bed.

• Avoiding triggers like prolonged standing, heat, and alcohol.

• Gradual exercise programs.

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Medications to increase blood volume:

• Fludrocortisone: This is a mineralocorticoid (a type of steroid) that helps the kidneys retain sodium and water, thereby increasing blood volume. This can be particularly helpful for patients with lower blood volume.

• Desmopressin (DDAVP): This synthetic hormone helps the body retain water and reduce urine production, which can increase blood volume and potentially decrease heart rate. It's often taken at bedtime.

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Medications to control heart rate:

• Beta-blockers (e.g., Propranolol, Bisoprolol, Metoprolol): These medications block the effects of adrenaline on the heart, helping to slow down a fast heart rate and reduce palpitations. Low doses are often preferred, as higher doses can sometimes worsen fatigue or hypotension. Non-selective beta-blockers like propranolol are often recommended.

• Ivabradine: This medication specifically slows the heart rate by targeting the "funny current" in the heart's natural pacemaker. It can be a good option for those who don't tolerate beta-blockers or when beta-blockers are not effective enough.

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Medications to improve vasoconstriction (narrowing of blood vessels):

• Midodrine: This is an alpha-1 adrenergic agonist that causes blood vessels to constrict, particularly in the legs and abdomen. This helps to reduce blood pooling when standing, improving blood pressure and reducing orthostatic symptoms. It's often taken multiple times a day due to its short-acting nature, and patients are usually advised not to lie flat for several hours after taking it.

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Medications to Modulate the Autonomic Nervous System:

• Pyridostigmine: This acetylcholinesterase inhibitor can help improve nerve signals within the autonomic nervous system, potentially reducing tachycardia and improving symptoms, particularly in cases with autonomic dysfunction.

• Clonidine or Methyldopa: These centrally acting sympatholytic drugs reduce sympathetic nervous system activity, which can lower heart rate and blood pressure. They are sometimes used in patients with "hyperadrenergic" POTS, where there's an overactive sympathetic response.

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Other Medications for Specific Symptoms:

• Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs): While not directly treating the orthostatic symptoms, these medications (like bupropion, venlafaxine, duloxetine) can sometimes improve nerve communication and help with co-existing conditions like anxiety, depression, or chronic fatigue often seen in POTS patients. However, some SNRIs may worsen tachycardia.

• Modafinil: A stimulant sometimes used to improve alertness and reduce "brain fog" or fatigue.

• Octreotide: This medication can tighten blood vessels in the abdominal cavity, useful for some patients, but it requires injections and can have side effects.