Michael Hunter, MD on Medika Life

Long Covid: Could This Be Why?

MICROCLOTS. COULD THEY EXPLAIN the mystery of why some who get a COVID19 infection suffer for long periods? Three hundred three million cases worldwide and 5.5 million deaths.

“The purpose of literature is to turn blood into ink.”
― T.S. Eliot

The numbers are staggering. But it doesn’t end there — Upwards of 100 million people worldwide already suffer from so-called long Covid. This number is almost certainly a significant underestimate.

meta-analysis suggests that worldwide, long Covid (to be more precise, post-acute sequelae of COVID-19) represents a significant fraction of cases. Approximately 43 percent of COVID-19 tested positive cases (and more than half of those hospitalized with COVID-19) suffer from it.

There may be some geographic differences. In North America, the proportion is just under one-third (30 percent) compared with half of the cases in Asia. Admittedly, researchers based these estimates on more severe cases, but you get the point — Long COVID is a significant problem.

Today we explore long Covid before turning to a potential explanation for why the phenomenon occurs.

Long COVID — What is it?

Fortunately, most of us who get coronavirus disease 2019 (COVID-19) will recover completely, often within a few weeks. On the other hand, some individuals (including some who have had only mild episodes of the disease) continue to have symptoms after the initial recovery.

These so-called long haulers have long COVID-19, living with COVID-19 effects that last for more than a month after you have been diagnosed with the virus.

The Mayo Clinic (USA) offers these insights: Older folks and those with many severe medical conditions are the most likely to suffer long-term from COVID-19 symptoms. But even young and healthy individuals can feel unwell for long periods. Here are some common symptoms:

  • Fatigue
  • Shortness of breath or difficulty breathing, cough, chest pain
  • Joint or muscle pain
  • Memory, concentration, or sleep problems
  • Headache
  • Fast or pounding heartbeat
  • Loss of smell or taste
  • Depression or anxiety
  • Fever
  • Dizziness when you stand
  • Worsened symptoms after physical or mental activities
Photo by DESIGNECOLOGIST on Unsplash

Long COVID — Organ damage

Think COVID-19, and lung probably come to mind. But we need to think more broadly — the novel coronavirus can attack many organs, including the kidneys, heart, and brain.

Chronic problems can include breathing problems, heart issues, kidney impairment, stroke, temporary paralysis, etc. Moreover, some suffer from multisystem inflammatory syndrome, with some organs and tissues severely inflamed.

Many of those who have severe lung problems acutely develop chronic fatigue syndrome. This syndrome involves extreme tiredness that worsens with mental or physical activity, and rest is not palliative.

Long Covid — Psychological problems

Perhaps not surprisingly, those who suffer severe symptoms requiring a stay in a hospital intensive care unit (ICU) may later have anxiety, depression, or post-traumatic stress syndrome (PTSD).

I want to emphasize that most people who have COVID-19 recover within weeks. Still, the potential long-term problems from the virus make it even more critical to reduce the spread of the disease. We still have much to learn about the long-term implications of COVID-19 infection.

Long COVID — Why?

In an insightful piece published in The Guardian, Dr. Resia Pretorius reminds us of this: COVID-19 is not simply a lung disease but affects blood flow and coagulation (blood clotting) systems. Dr. Pretorius is the head of the physiological sciences department at Stellenbosch University (South Africa).

Now, this:

“My lab has found significant microclot formation in patients with acute Covid-19 and those with long Covid-19. Unfortunately, routine blood tests miss these signs.”

We all typically form clots, for example, after cutting ourselves. The body then efficiently breaks down those clots via fibrinolysis. Fibrin is the central substance in that process.

Persistent microclots in the blood of those with long COVID-19 are resistant to fibrinolysis or clot destruction. Dr. Pretorious and her research team discovered high levels of various inflammatory molecules trapped in the microclots. These substances included:

  • plasminogen (a precursor or plasmin — which breaks clot down by attacking fibrin)
  • fibrinogen (forms fibrin, the main protein in a blood clot that helps stop bleeding)
  • von Willebrand factor (works by affecting the adherence of clot-related platelets to one another)
  • alpha-2 antiplasmin (a molecule preventing microclot breakdown)

Our tissues may not get enough oxygen with persistent microclots and hyperactivated platelets (also a key to clotting). A significant lack of oxygen can lead to troubling symptoms. Unfortunately, the researcher reminds us that there are no routine pathology tests to diagnose such patients. The usual tests do not find the inflammatory molecules described above.

Photo by Pawel Czerwinski on Unsplash

Long COVID — What to do

Someday, we may routinely use strategies targeting clot-causing platelets and other clot-causing substances. Perhaps we will use dialysis-style treatment to filter our microclots and inflammatory substances. Here’s a video on this approach from the British Broadcasting Corporation:

In addition, there is hope that we will find a biomarker for long Covid.

“The blood jet is poetry,
There is no stopping it.

“Kindness” written 01 February 1963.
– Sylvia Plath, Ariel

Thank you for joining me today.


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Michael Hunter, MD
Michael Hunter, MD
I received an undergraduate degree from Harvard, a medical degree from Yale, and trained in radiation oncology at the University of Pennsylvania. I practice radiation oncology in the Seattle area.

Michael Hunter, MD

I received an undergraduate degree from Harvard, a medical degree from Yale, and trained in radiation oncology at the University of Pennsylvania. I practice radiation oncology in the Seattle area.

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