Tuesday, April 16, 2024
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How Covid-19 causes blood clots


I AM a general practitioner mainly working with elderly people and as such I have been on the front line, visiting nursing homes since the pandemic struck, and throughout the long months. I have been vaccinated, with a booster, or I would not be allowed to do my job. Which is an issue for another time.

There is another world that I inhabit, which is looking at heart disease, and researching and writing about it. In this world I am viewed as a maverick, because I dare to question the almighty cholesterol hypothesis.

Which means that I have become wearily familiar with two things. First, attacks from fellow medics and ‘experts’ in cardiovascular medicine, who tell me I am talking rubbish. Two, the fact that the world of medical research is . . . is . . . not quite the Olympian ideal that we may wish it to be. (He said, being polite.)

Which is why I wrote the book Doctoring Data, to try to help people make sense of various mad headlines on health matters such as ‘Eggs are bad for you’, ‘Eggs are a super-food and good for you’, ‘Eggs are bad for you again’. Also to lay bare some of the massive conflicts of interest and data manipulation.

In this world, I felt I was pretty well positioned to look at Covid-19 vaccines – what they do, how they work, and what problems they could cause. In particular the issue of blood clotting, because I believe that ‘abnormal’ blood clotting is the underlying cause of cardiovascular disease, and I have been researching this for more than 30 years.

Indeed, when Covid-19 struck, I was writing a chapter on how bacteria and viruses can increase the risk of blood clotting, leading to such terrible things as strokes and heart attacks.

I watched, Cassandra-like, as researchers wrote in seeming amazement at how Covid-19 was mainly killing people through blood clots. Furthermore, children were developing an auto-immune condition leading to inflammation in blood vessels, known as vasculitis (‘vascular’ = blood vessels ‘itis’ = inflammation), 

I was researching an auto-immune disease that causes vasculitis in children called Kawasaki’s disease. It was clear that the two things were pretty much the same. Kawasaki’s disease causes a red-hot vasculitis that damages blood vessels and can, in some cases, lead to heart attacks in children aged four or five. The cause is unknown, but many researchers believe a viral infection triggers the process.

How does Covid-19 cause vasculitis and blood clots? In super-short version, the SARS-CoV-2 virus enters cells by locking on to a receptor that sits on the cell membrane surface. It is called the ACE2 receptor. With no ACE2 receptor the virus cannot gain entry to a cell.

Cells lining the lungs have many ACE2 receptors, as do the cells lining all blood vessels. As do cells in the heart – myocardial cells and pericardial cells. This is because ACE2 reception plays a critical role in controlling blood pressure and suchlike. Also, the conversion of angiotensin I to angiotensin II happens in the lungs (the ‘A’ in ACE2 stands for angiotensin). I am dancing on a world of complexity here, without, I hope, falling in.

So, cells with lots of ACE2 receptors on them will get infected with SARS-CoV-2. The virus will replicate within these cells, before thousands of newly made viruses burst out. Lung cells go first, so this is where the main problems start, and why the lungs can fill up with fluid and other ‘wreckage’.

Then, the cells lining all blood vessels get into the act. Of course, the immune system is not sitting about doing nothing. Infected cells send out distress messages letting the immune system know that that the virus has gained entry. The immune system comes across the virus in the bloodstream and mounts an attack. The whole system starts to get revved up. Specific anti-SARS-CoV-2 antibodies begin to be manufactured – this can take a couple of weeks.

(Caveat: here I am mainly talking about what happens in ‘severe’ cases; the vast majority of people have a far, far, milder ‘infection’. I do not wish to worry anyone unnecessarily.)

The cells lining blood vessels are now damaged and dying. Also, they begin to become the focus of attacks for the immune system. The only way killer cells and suchlike can get at a virus within a cell is to kill the cell first. Your immune system begins to see the cells lining your blood vessels as ‘the enemy’: seek out and destroy.

At the same time the blood clotting system is activated. The immune system and the blood clotting system are intimately connected. In more primitive animals, they are same thing. Once your immune system is on hyper-killer alert, you blood is far more ready to clot.

Added to all this, the spike protein of SARS-CoV-2 is a powerful stimulator of blood clotting, as discussed in the paper SARS-CoV-2spike S1 subunit induces hypercoagulability’

In short, there are many different ways in which Covid-19 stimulates blood clotting. For example:

·       If you damage the cells lining blood vessels (endothelial cells) this stimulates blood clots to form at those points

·       Activation of the immune system means the blood is more ready to clot

·       The spike proteins on SARS-CoV-2 viruses actively stimulate blood clots

Which obviously raises the question: can the vaccines also do the same thing? I will consider this in a further article.

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Malcolm Kendrick
Malcolm Kendrick
Malcolm Kendrick is a Scottish doctor, author, speaker and sceptic. His latest book ‘The enduring mystery of heart disease – The Clot Thickens’ has recently been published.

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