Learning about POTS

Feb 19 2020

We saw a new referral in the Cardiology clinic for a woman who had been experiencing episodes of presyncope as well as intermittent palpitations for the past year. After reviewing and discussing her case, we considered the various possible causes for her symptoms. My staff mentioned the possibility of postural orthostatic tachycardia syndrome (POTS). I had never heard of this entity before and decided to do some further reading on the topic (1,2).

POTS is a condition characterized by insufficient blood return to the heart when moving from a lying to standing position. This orthostatic intolerance causes light-headedness and presyncope that can be eased by returning to the lying position. The hallmark of this disorder is an exaggerated heart rate increase in response to postural change - hence the name postural orthostatic tachycardia syndrome.

Epidemiology:

• It is the most prevalent form of orthostatic intolerance.
• It is commonly seen in younger patients between the ages of 15-50, and most commonly in women, with a female to male ratio of 4-5:1.

Etiology:

• The exact cause is unclear and many mechanisms have been proposed, including distal denervation, hypovolemia, changes in venous function, increased sympathetic activity, and more.

Symptoms:

• Patients report light-headedness, weakness, blurred vision, and fatigue upon standing. Other orthostatic symptoms experienced include palpitations, shakiness and anxiety.
• GI symptoms such as nausea, bloating, early satiety, constipation have also been observed.
• Syncope is less frequent but does occur in about 40% of patients.

Diagnosis:

• Diagnosis can be made by looking for an exaggerated increase in heart rate on tilt table testing or standing. Diagnostic criteria states a sustained heart rate increase of > 30 beats per minute or an increase to 120 bpm or greater within the first 10 minutes of tilt.
• There may be an increase in venous plasma norepinephrine levels at rest and with standing (>600 ng/mL), however the sensitivity and specificity of this is unknown.
• It is otherwise a diagnosis of exclusion.

Treatment:

• Goal of treatment is to improve circulatory problems that may be causing POTS, however no treatment has been systematically studied.
• In some patients, lifestyle changes such as increasing salt intake, drinking more fluids, exercising, and avoiding exacerbating factors, may improve symptoms.
• Some studies have shown benefit in using fludrocortisone (most effective when combined with increased salt and water intake). Midodrine has also been shown to be associated with improved symptoms and heart rate. 

Prognosis:

• Most patients have a good prognosis with improvement in their symptoms at the 1 year follow-up.

This patient did have several features in her history consistent with POTS. On physical exam, she had an increase in her heart rate of 20 beats upon standing, however it did not meet the cut off of a 30 bpm increase. Although we are not certain this patient has POTS and have ordered other investigations to rule out other diagnoses, it was an excellent opportunity to think critically through an interesting case and learn about a new syndrome!

-MB-

References:

1. Kaufmann H, Freeman R, Aminoff MJ (Ed.). Postural tachycardia syndrome. UpToDate. Accessed February 19, 2020 from: https://www-uptodate-com.myaccess.library.utoronto.ca/contents/postural-tachycardia-syndrome
2. Postural orthostatic tachycardia syndrome. Genetic and Rare Diseases Information Center. Accessed February 19, 2020 from: https://rarediseases.info.nih.gov/diseases/9597/postural-orthostatic-tachycardia-syndrome.