New imaging technique clearly shows the source of Long COVID in the lungs

While COVID vaccines have saved millions of lives worldwide by reducing the overall severity of the disease, nearly one in 10 recoveries still have persistent symptoms after the original illness is over.

These patients present with a staggering array of over 200 symptoms including dizziness, diarrhea, shortness of breath, fatigue and debilitating brain fog that can last for months or even years.

Frustratingly, even long-term COVID patients who describe breathing problems show normal results on standard clinical breath tests, says respirologist Michael Nicholson of St Joseph’s Health Care London.

But a new imaging method has now unequivocally uncovered the cause of the breathing problem.

“The results allowed us to show that there is a physiological impact on [patient] lungs that correlated with their symptoms,” says Nicholson.

(Alexander Matheson)

The scans show the extensive damage COVID-19 can cause to our delicate respiratory system. Whether it’s the virus itself or the body’s response to it, some mechanism has effectively cut off the function of the patients’ pulmonary vessels, cutting off many of the smallest ones where all-important gas exchange takes place.

The researchers, led by Western University physicist Alexander Matheson, instructed 40 volunteers — 34 with post-acute COVID-19 syndrome and 6 without — to inhale a polarized xenon gas isotope. The gas resonates at a characteristic frequency in the MRI, allowing researchers to observe the activity of tiny airways and blood vessels in real time.

“For those who are symptomatic post-COVID, we see this abnormality in the exchange of oxygen across the alveolar membrane into the red blood cells, even if they didn’t have an infection severe enough to be hospitalized,” the medicine says Western University biophysicist Grace Parraga.

“What we saw on MRI was that the passage of oxygen into the red blood cells was suppressed in these symptomatic patients who had COVID-19 compared to healthy volunteers.”

Because flu symptoms are the most obvious and common sign of COVID-19, it’s often dismissed as just another respiratory disease, but COVID-19 is actually also a vascular disease, meaning it can affect the circulatory system. The virus particles directly target endothelial cells that line the walls of our blood vessels and heart.

The vascular damage is reflected by the MRI scans; CT scans also confirm the abnormalities in the finest blood vessels in our lungs.

In addition, a previous study has already shown a shift in blood distribution from smaller to larger blood vessels in the lungs of hospitalized COVID patients.

The team propose several possible mechanisms for the change in gas exchange they observed, shown in the diagram below.

Possible mechanisms for disturbed gas exchange. (Matherson et al., Radiology, 2022)

Vessels may lose flexibility leaving less blood for xenon to bind to (B), new blood flow patterns due to changes in vessels elsewhere may divert blood away from gas exchange regions (C) or there is a physical blockage , which prevents the blood from getting there (D).

Matheson and colleagues caution that the small sample size limits their ability to generalize, but urge further investigation. And whatever the mechanism behind it, it’s perfectly clear that catching the virus can really mess up the circulatory system.

Despite the easing of restrictions in many parts of the world, the global pandemic continues and any SARS-CoV-2 infection risks vascular damage, from clotting problems to heart disease.

“I was on oxygen for almost two months after COVID, and it took me almost three months to get to a place where I could walk without gasping for air,” explains one of the study participants, Olympic bobsleigh champion Alex Kopacz .

“The take-home message for me is that we need to remember that this virus can have very serious long-term consequences that are not trivial. In my case, before I got sick, I didn’t think it would really affect me.”

This study was published in radiology.

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