Long COVID patients may endure dizziness upon standing, research suggests.
Not everyone who overcomes the coronavirus returns to a clean bill of health, with one in 10 thought to endure lingering complications, even if they had a relatively mild bout of the infection itself.
Long COVID occurs when a former coronavirus patient develops complications like brain fog, palpitations and even organ damage despite testing negative for the infection.
With the condition a relatively new phenomenon, symptoms are increasingly emerging.
Case reports put together by Lund University in Sweden suggest postural orthostatic tachycardia syndrome (PoTS) should be added to that list; defined as an abnormal increase in heart rate after sitting up or standing, leading to dizziness and even fainting.
Watch: What is long COVID?
PoTS is a relatively common condition that usually affects females aged 15 to 50. Some have mild symptoms, while others find the syndrome affects their quality of life, but gradually improves for most.
Upon sitting up or standing, the blood vessels normally quickly narrow and the heart rate increases to maintain blood flow to the vital organs, counteracting the effect of gravity that pulls some blood to the lower body.
In PoTS, this system does not work properly, causing the blood supply to the vital organs to drop when a person becomes upright. Their heart then races to compensate for this.
PoTS does not always have an obvious cause, however, it can develop following a viral infection or traumatic event.
Writing in the journal JACC: Case Reports, the Swedish medics reported how three patients were diagnosed with PoTS more than three months after catching a suspected coronavirus infection.
All three patients developed tell-tale coronavirus symptoms in early 2020, but did not seek medical help or get tested.
In the following months, the patients endured extreme fatigue, headaches, nausea and dizziness.
They were later diagnosed with PoTS via active stand and head tilt tests.
The NHS defines PoTS as a heart rate that increases by at least 30 beats per minute usually within 10 minutes of standing, which then continues for more than 30 seconds and is accompanied by other symptoms of the syndrome, like lightheadedness or shaking.
PoTS may be diagnosed via a tilt test, when a person's heart rate and blood pressure are measured while lying on a bed that can be tilted upright.
So-called active stand tests involve the heart rate and blood pressure being recorded after lying down, immediately upon standing, and again two, five and 10 minutes later.
"As reports of COVID-19 [the disease caused by the coronavirus] patients being impacted by long-term symptoms unrelated to their original diagnosis continue to grow, it's important to raise awareness of PoTS as a possible long-term complication," said co-lead author Dr Madeleine Johansson.
"Much remains unknown about the specific mechanisms responsible for the PoTS-like symptoms in post-COVID-19 patients or how long these symptoms will last, but chronic symptoms are expected in a subset of patients based on this initial clinical experience."
Testing was not widespread at the start of the coronavirus outbreak, while those who did get swabbed may have had a false-negative. The medics therefore stressed a negative coronavirus result should not exclude long COVID.
Other causes of PoTS should also be considered, however, like dehydration, anxiety, anaemia and alternative infections, they added.
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During a PoTS episode, patients should try and counteract their drop in blood flow. This could be achieved by lying down and raising the legs.
If unable to lie down, try crossing the legs in front of each other while standing, rocking up and down on the toes, engaging the buttocks and abdominal muscles, and clenching the fists.
Symptoms may be eased by staying hydrated, gently exercising, wearing compression tights, avoiding standing for long periods of time, rising slowly, not drinking excessive amounts of caffeine or alcohol, and elevating the head end of the bed so the body is not horizontal.
Medics may also prescribe drugs that reduce the heart rate or narrow the blood vessels.