How Long Covid causes POTS - A Theory
Spoiler Alert: it's NOT the autonomic nervous system...
Over the past several months, we’ve looked at the molecular mechanisms underlying Long Covid - including microclots and platelet hyperactivation - as well as an experimental pharmaceutical treatment (Triple Anticoagulant Therapy) and potential natural remedies.
Now I want to shift gears and start examining the molecular mechanisms that cause some of the worst symptoms of Long Covid.
Today we are going to start with a truly debilitating symptom for Long Covid sufferers: POTS.
Let’s look at some basic questions.
What is POTS?
POTS stands for “postural orthostatic tachycardia syndrome”. This is the technical medical term for an increase in heart rate, dizziness, and fatigue that occur when a person moves from laying or sitting down to standing up. This type of tachycardia typically results in a heart rate over 100 beats per minute. The dizziness is caused by a lack of blood flow (and oxygen) to the brain.
Why Does POTS Happen?
When a person stands up, gravity causes 10%-15% of the volume of your blood to settle into your abdomen, legs, and arms (“the extremities”).
The pooling of the blood leads to a drop in blood pressure unless the body responds.
The body has two things that it can control to try to maintain a stable blood pressure: heart rate and the contraction or dilation of the peripheral blood vessels (known as peripheral resistance) by the autonomic nervous system (the involuntary nervous system responsible for breathing, heart beat, blood flow).
Here’s how they are all related:
So to maintain a stable blood pressure when standing up: peripheral resistance has to increase (⬆️), heart rate has to increase (⬆️), or some combination of those two.
When a normal healthy person stands up, the autonomic nervous system responds and attempts to maintain a stable blood pressure by increasing peripheral resistance. This is accomplished by releasing epinephrine or norepinephrine, which causes constriction of the blood vessels and helps pump the blood out of the extremities and circulate it around the body. This allows the heart rate to stay normal and is why normal healthy people don’t get tachycardia when they stand up. Here’s what that looks like:
POTS occurs when there is dysfunction in the ability of the body to regulate peripheral resistance. If the body can’t increase peripheral resistance in order to increase blood pressure, then there is only one other option…
So when a person with POTS stands up, the heart rate increases in an attempt to maintain a stable blood pressure. This leads to the tachycardia that people experience. Here’s what that looks like:
And since it’s harder for heart rate to maintain a stable blood pressure, POTS patients also experience dizziness caused by lack of oxygen and blood flow to the brain and fatigue.
What Causes POTS in Long Covid? - A Theory
In the discussion section of the preprint article of the use of Triple Anticoagulant Therapy to treat Long Covid patients (reference & link below), Pretorius and Kell lay out a theory of how POTS is caused in Long Covid.
They suggest that the inability to increase peripheral resistance in Long Covid patients is NOT due to failure of the autonomic nervous system.
Instead, they suggest that the lack of increase in peripheral resistance is due to endotheliitis - inflammation of the lining of the blood vessels - or other damage to the endothelial layer of the blood vessels due to Long Covid.
This inflammation makes the endothelium unresponsive to the epinephrine & norepinephrine signaling that attempts to increase peripheral resistance to raise the blood pressure upon standing up. Which leaves increasing the heart rate as the only physiological response available to increase blood pressure.
They conclude this section by suggesting that POTS caused by endothelial inflammation may be what’s happening at the early stages of Long Covid, but that autonomic dysfunction could be potentially responsible long term.
Molecular Mechanisms of Endothelial Inflammation?
Thinking of POTS in Long Covid as being caused by inflammation - as opposed to autonomic nervous system dysfunction - opens a whole new line of questions to ask and answer about what the underlying molecular mechanism(s) could be.
What could the Covid virus or the Spike protein be doing to the endothelium that would make the cells unresponsive epinephrine & norepinephrine?
That’s the question I’m going to be working on next…
Stay tuned for that information and much, much more.
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Reference
Treatment of Long COVID symptoms with triple anticoagulant therapy. Research Square Preprint 2023, rs-2697680/v1. https://doi.org/10.21203/rs.3.rs-2697680/v1