I am especially blown away by how many Long Covid & MECFS patients have autonomic nervous dysfunction or POTS.
In fact, it is so striking I rarely see anyone with post-exertional malaise without POTS. Always test for POTS.
(post-exertional malaise is worsening of symptoms with activity, physical or cognitive, and by activity, I mean even *speaking* for some people)
It is pretty specific to post viral illnesses. Around half of long Covid patients have PEM. Its why exercise can make them sick.
The Vagus nerve is a giant nerve known as ‘the wandering nerve’. It ‘wanders’ from the brain into the organs in the neck, chest, and abdomen. A highway from the brain to the body and back. It’s the longest nerve in the body. And neglected in medicine.
Fun fact-a branch of the Vagus nerve in giraffes is 15 feet long (recurrent laryngeal nerve). 7.5feet up and down due to how they evolved. They have to have a huge blood pressure to get blood up 7 feet to the head. Adapted blood vessels to stop them exploding…
Highly elastic blood vessels stop blood pooling in their legs. Like compression stockings in humans. All because the left recurrent laryngeal nerve took a massive detour. But pretty cool they don’t have POTS.
Anyway-in humans the Vagus nerve has many functions as part of the autonomic (‘automatic’) nervous system (ANS). Thankfully, we don’t have to consciously think about our heartbeat, breathing, digestion, sweating and swallowing. It just does its thing.
Like anything else in the body, it can become diseased and dysfunction. The most common condition is called postural orthostatic tachycardia syndrome (POTS). In POTS, the blood pools in the feet due to the leg blood vessels not tightening on standing.
In an effort to get blood to the brain, the heart speeds up to pump faster. The body will always prioritise blood to the brain. So, the heart is going faster appropriately but it’s not that efficient. Eventually people can feel dizzy or rarely, faint. They usually sit down.
The symptoms of POTS are legion and can be very unpleasant, I've used the below list from - https://notjustbendy.com/blog/postural-orthostatic-tachycardia-syndrome/
What I tend to see is people who have brain fog, intolerance to exercise, purple feet on standing and fatigue. Often people do not get dizzy or notice their heart rate is very high on standing.
Doctors get a bit obsessed with numbers- officially POTS is when heart rate increases by 30bpm on a 10-minute stand test with no drop in blood pressure. I’ve seen people refused a diagnosis as the rise was *only* 29bpm.
However, if someone has symptoms on being upright (sitting or standing) and the pulse goes up significantly I call it POTS. And treat it. Yes, indeed it can be treated. Which makes me wonder why we hardly test for it.
Another type of autonomic issue is ‘inappropriate sinus tachycardia’. This is a normal heart rate but- fast. Inappropriately fast for activity. Usually, >100bpm at rest. Again, unpleasant. Again, there is treatment.
Why am I telling you this? Well in the context of the Covid pandemic we now have a LOT of people with POTS/ autonomic dysfunction. 50-80% of those with long Covid. Added to the existing POTS from ME/CFS and autoimmune POTS.
WHY do we have an epidemic of POTS? It is now becoming clear that viruses are responsible for most cases of POTS. Not only can viruses INFLAME the Vagus nerve, they can directly INFECT it.
Studies this year showed thickening of the Vagus nerve in 20% of long Covid patients. The thickening is inflammation. There was also flattening of the diaphragm- a pretty important muscle for breathing!
Post mortem study of Vagus nerve showed that both of the binding sites for the Covid viral spike proteins, ACE2 and NRP1, are widely expressed in the nerve bundles, in myelin sheaths as well as axons. Vascular walls also contain these entry sites.
Multiple mechanisms are proposed for how Covid infects the Vagus nerve- from entry up the nose into the brain to direct spread from lungs to the brain stem. Doesn’t sound great- infection of the biggest automatic nerve of the body.
Which leads me to the ‘enteric nervous system’. Even more neglected. - The enteric nervous system (ENS) is a division of the autonomic nervous system that extends throughout the gut, regulating gastrointestinal function.
It is a neuronal network arranged in two major plexuses- Referred to as “the second brain,” the ENS has more than 500 million neurons and a wide diversity of transmitters. -this is involved in gut inflammation, blood flow control, & interacts with the immune system.
Many viruses that affect GI tract are also known to affect the ENS. Varicella zoster virus can infect & be latent in enteric neurons, while VZV, cytomegalovirus &Epstein–Barr virus (EBV) have been found in the mesenteric ganglia with inflammation.
Disorders caused by human coronaviruses (HCoVs) include GI symptoms in up to 57% of the cases. GI symptoms are an important feature of COVID-19 since they occur in a range that can reach 79% of patients.
SARS-CoV-2 can infect the GI Tract
The intestinal epithelial barrier is infected by SARS-CoV-2 as demonstrated by duodenal biopsies showing the presence of viral RNA inside the cytoplasm and nucleus of enterocytes.
It has been shown that this can lead to an increase in inflammation with IL-6 and TNFa levels.
AND hence we have the ‘gut-brain axis’ A network of autonomic nerves in the gut (second brain) that can cause inflammation& affect the actual brain via the Vagus nerve. VZV has been shown to be latent there, and more recently Sars-CoV-2 viral RNA. See potential mechanism.
It’s all interconnected.
If you have symptoms of POTS after Covid please ask to be tested. A simple 10-minute stand test can diagnose it. There is treatment. If you have symptoms of inappropriate sinus tachycardia, please ask to be tested- a 24-hour ECG monitor will do.
Last one- if you find yourself worse on activity (post exertional malaise) also get checked for POTS. I can’t remember the last time I saw one without the other. POTS > PEM
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