Exactly what causes Postural Orthostatic Tachycardia Syndrome, or POTS, is unclear. But researchers believe the condition likely has multiple underlying mechanisms that vary from person to person. POTS may arise from problems with the autonomic nervous system or immune system. It may result when blood volume is reduced, or blood flow gets disrupted throughout the body when a person goes from lying down to an upright position. Or it could occur because of a combination of these factors.
Genetic factors may also play a role. And some people report having a preceding health event or disruption, such as a viral infection, concussion, surgery, pregnancy, or the start of puberty, before experiencing POTS symptoms. Many others cannot pinpoint any specific event that could have triggered the onset of POTS. Because the signs and symptoms of POTS tend to vary, doctors still do not know whether it is best defined as a single syndrome or as a syndrome with several subtypes that have distinct underlying causes.
Some believe POTS can be categorized as primary or secondary. “Primary POTS” results from a disruption in the autonomic and circulatory systems that cannot be explained by other conditions. Those with an existing or identified underlying condition – such as heart failure, a thyroid condition, or another condition in which there is a loss of blood volume – may experience “secondary POTS” as a consequence of their primary condition. We are still unsure if these secondary cases can truly be considered POTS. Just because we think someone has POTS, does not mean we should stop looking for another underlying disease.
Other research shows the key to defining POTS is to focus on the “S” for syndrome. From a patient point of view, POTS is a cluster of symptoms, but we need better ways of defining and understanding it. We need good biomarkers. Ultimately, we want to tease out the different mechanisms associated with it.
Limits to treatment
Until there is a cure, people who suspect they have POTS are working to feel as well as they can with treatments focused on controlling symptoms. Many patients, for example, benefit by making sure they get enough salt in their diets and by staying well hydrated. Their doctors may prescribe medications that help them maintain normal blood pressure, expand their blood volume, and lower their heart rate. Many see improvement from exercise training, with a focus on aerobic reconditioning.
To manage her own condition, one patient takes fludrocortisone, a steroid and frequent treatment choice for POTS patients. “It helps a lot, and it’s manageable – I was able to get my stamina back,” she said. She must be mindful, however. “When I exercise, I have to make sure my heart rate stays in a healthy range,” she noted. She also drinks plenty of liquids and makes sure she does not stand in one place for too long without moving around. And because she is sensitive to heat, she needs to keep cool.
A Future for POTS Research
As a person living with POTS, the aforementioned patient wants to see researchers focus more on why POTS happens. “I feel like current treatments aren’t really getting to the root problem, and I also worry about the effects of taking steroids long term,” she said. “I’d like to see possibly better treatments that get to the reason for the condition.” We still have an incomplete picture of the underlying mechanisms of POTS. If we understand the mechanisms better, we can come up with better targeted treatments. We also need objective tests that clearly differentiate POTS from other distinct syndromes like chronic fatigue, myalgic encephalomyelitis, and fibromyalgia.
Long COVID – lingering symptoms experienced by many survivors of COVID-19 – can sometimes look like POTS. But while researchers cannot yet say what, if any, mechanisms the two conditions have in common, strategies being developed to treat POTS could potentially be used to treat Long COVID patients, and vice versa.
Better treatments are needed. Because there are no FDA-approved treatments specifically for POTS, doctors prescribe medications off-label to treat its symptoms, and that can sometimes result in problems with insurance coverage and patient access.
Some doctors would also like to see more epidemiological research on POTS. The WHO’s ICD-10, which is currently in use in the United States, does not include a POTS designation, referring to the World Health Organization’s coding system for diseases used both domestically and internationally, which limits doctors’ ability to diagnose the syndrome officially for tracking purposes. This means that our estimates of prevalence are inexact, and the data are not uniformly collected. It also can result in insurance coverage challenges. The WHO’s ICD-11 does include a code for POTS.
In addition to better understanding the fundamental aspects of POTS, doctors are interested in why POTS seems to impact girls and women almost exclusively. Indeed, POTS primarily affects women of child-bearing age, with most studies reporting around 80-90 percent female predominance. It is thought to be related to estrogen and other female hormones, but a close link has not been shown. Some have found that POTS may cycle along with the menstrual cycle, but some have found the exact opposite. We are exploring the potential association between POTS and iron deficiency often seen in menstruating women.
Recognizing the gap in the understanding and treatment of POTS, the NHLBI and the National Institute of Neurological Disorders and Stroke have issued a Notice of Special Interest to encourage researchers to submit proposals designed to answer fundamental questions about POTS. Initial applications are due June 5, 2021.