Editor’s word: First in a two-part collection on postural orthostatic tachycardia syndrome (POTS). Click on right here for half two.
This previous February, a 57-year-old firefighter got here to my cardiology clinic after experiencing a wierd set of signs. A number of weeks earlier, he had gotten COVID-19. Predictably, he misplaced his sense of odor, developed a low-grade fever, and skilled muscle aches. Inside every week his COVID-19 signs have been gone, however he continued to really feel off. And the brand new signs he described — sudden lightheadedness when standing up and an unusually quick heartbeat — made me suspect a situation known as postural orthostatic tachycardia syndrome, or POTS.
Under I’ll clarify what’s identified to date concerning the triggers and hallmark signs of POTS. In a later publish, I’ll focus on prognosis and therapy.
POTS is a syndrome, which suggests it’s a set of signs and medical findings that always cluster collectively. The hallmark of POTS is bothersome signs that happen when standing upright. The medical time period for these signs is orthostatic intolerance.
Mostly, individuals report
- lightheadedness or dizziness with standing (fainting might happen in additional extreme circumstances)
- problem concentrating (additionally known as mind fog)
- palpitations (a way of speedy, pounding, or irregular heartbeat).
Individuals who have POTS additionally usually expertise complications, digestive issues like bloating and constipation, insomnia, warmth intolerance, and problem exercising because of shortness of breath and fatigue.
Who will get POTS?
POTS most frequently impacts ladies between the ages of 15 and 50. Nonetheless, it has just lately been recognized in different teams of individuals following an infection with COVID-19. Individuals who have lengthy COVID (typically known as lengthy haulers) might develop a number of several types of signs affecting varied organs together with the mind, lungs, and kidneys. One subtype of lengthy COVID is POTS.
What is thought about restoration?
Analysis suggests about half of individuals recognized with POTS will recuperate or enhance over a interval of some years.
Nonetheless, for others, a vicious cycle can develop if POTS goes untreated. The cycle begins as a result of individuals begin to spend extra time in mattress, avoiding actions that provoke signs. As individuals develop into far much less lively, muscle mass within the legs is misplaced, coronary heart capability shrinks, and the quantity of circulating blood is decreased. These modifications make standing upright much more uncomfortable, resulting in but extra time spent in mattress.
Over time, some individuals caught on this cycle can develop into disabled. They’re unable to carry out every day family duties with out changing into dizzy and exhausted. Many take time without work from college or work.
What causes POTS?
The underlying reason behind POTS just isn’t but identified. It usually follows a interval of bedrest after an harm corresponding to a concussion, surgical procedure, or a viral sickness like mononucleosis or the flu. Extra just lately, POTS has been recognized in some individuals who have had COVID-19. Even after the acute an infection resolves, these individuals might have lingering fatigue, lightheadedness, and a speedy coronary heart price when upright.
Many researchers suspect that POTS could also be an autoimmune dysfunction, brought on by the physique’s immune system changing into overzealous. When this occurs, the immune system accurately targets the intruding virus however mistakenly targets the physique’s personal wholesome tissues, inflicting undesirable injury. Within the case of POTS, this injury is believed to have an effect on the liner of the blood vessels, which lose their means to tighten, or constrict, in response to standing upright.
Three clues: Lightheadedness, modifications in coronary heart price, and the results of gravity
Earlier than our firefighter, whom I’ll name David, grew to become sick, he saved observe of his coronary heart price on his smartwatch. It was usually about 60 to 70 beats per minute (bpm) at relaxation. Now, nevertheless, his resting coronary heart price was within the 80s and spiked into the 130s after one flight of stairs. Merely standing up precipitated lightheadedness and a racing heartbeat. He may not get by way of his common spin class. He stopped taking scorching showers as a result of they made him really feel dizzy.
Whereas most of us take without any consideration the easy act of standing upright, an individual with POTS might discover it extraordinarily uncomfortable. Why does POTS trigger orthostatic intolerance? It helps to first perceive the conventional response to standing:
- Gravity causes about one-third of blood quantity to immediately pool under the waist.
- Much less blood returns to the center, so much less blood is then pumped out to the physique.
- This results in a drop in blood stress to the mind (have you ever ever skilled a short-lived sense of lightheadedness or “seeing stars” when leaping up rapidly after sitting for an extended time period?).
- The drop in blood stress is detected by sensors within the coronary heart.
- These sensors activate the sympathetic nervous system (SNS), instructing the adrenal glands to launch an adrenaline-like substance known as norepinephrine into the bloodstream to assist remedy the issue.
How norepinephrine impacts the physique
Norepinephrine alerts the center to beat extra quickly and forcefully, restoring regular blood circulation to the mind. It additionally alerts the blood vessels to tighten, which drives blood to return to the center as a substitute of pooling within the decrease half of the physique. Inside a number of seconds of standing, blood stress is restored to regular.
Nonetheless, for causes not totally understood, this sign is ineffective in POTS, and the blood vessels don’t tighten in response to norepinephrine. Extra blood stays within the decrease physique, in order that much less returns to the center, and subsequently much less is pumped out to important tissues and organs. To keep up regular blood stress, the center beats quicker to compensate for the decrease quantity of blood pumped with every contraction of the center.
An overactive flight-or-fight response?
Hundreds of years in the past, evolution favored those that responded to the stress of bodily hazard by producing excessive ranges of norepinephrine, permitting them to battle off an assault or run from hurt. By releasing norepinephrine into the bloodstream, the nervous system primes just about each organ for bodily exercise and potential harm. The pupils dilate; digestion slows; the center beats rapidly. This has been dubbed the fight-or-flight response.
Norepinephrine ranges measured within the blood of people that have POTS are considerably greater than in those that don’t, resulting in an excessively quick coronary heart price and infrequently a powerful, pounding heartbeat. Along with these results on the center, elevated norepinephrine ranges can goal different organs together with the digestive system, inflicting belly bloating and constipation.
In the event you usually expertise the signs described on this publish, it’s possible you’ll wish to ask your physician to examine you for POTS. A later publish will focus on prognosis, therapy, and residing with POTS.
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