Thread by @DrGrahamLJ

More on imaging in the context of #LongCOVID

A thread of summarising this key paper titled -

'Pulmonary circulation abnormalities in post-acute COVID-19 syndrome: dual-energy CT angiographic findings in 79 patients '


H/T M. Oudkerk (not on Twitter)doi.org/10.1007/s00330…

Objectives of the study

'To evaluate the frequency and pattern of pulmonary vascular abnormalities in the year following COVID-19'

Methods

Study of 79 patients remaining symptomatic >6 months after hospitalization for SARS-CoV-2 pneumonia who had been evaluated with dual-energy CT angiography

(The word 'pneumonia' here is a misleading, but it's what most researchers call it, so let's go with it.)

Results

Chronic (persistent) clots in lung blood vessels in 5%

Acute (recent) clots in lung blood vessels in 2.5%

This doesn't sound like much but it only refers to the clots that are visible. It is much greater than would be expected following a respiratory viral pneumonia.

Lung perfusion was abnormal in 87.4%

This is massive!

It means the blood vessels of the lungs remain abnormal in these people (hospitalized during acute CV)

Note: Conventional CT scans alone don't show perfusion defects. The study used Dual-Energy CT (also called spectral CT)

Here is a Dual-Energy CT scan from the study (at 32 weeks post infection)

On the left is the conventional CT element.
It looks normal!

On the right is the perfusion element of the same scan which shows an area of reduced perfusion.

Another Dual-Energy CT (at 24 weeks)

The conventional CT element shows an area of increased density near the edge of the lung.

Usually we would think this is due to inflammation of the small airways. But the perfusion element of the scan shows it is due to increased perfusion.

So, the perfusion abnormalities can be due to either reduced or increased perfusion.

This is also the case in patients with acute #COVID-19.

See Lang et al. https://t.co/raH2Wu7UxNncbi.nlm.nih.gov/pmc/articles/P…

Another Dual-Energy CT scan (at 32 weeks)

It shows a feature that is highly specific to acute phase COVID-19 lung disease. It is called 'vascular tree-in-bud'. It is a sign of disease of the small blood vessels in the lungs

This study found that this sign persists

This is important because vascular tree-in-bud is visible on the conventional CT element of the scan. However, without the perfusion element of the scan this would very easily be mistaken for inflammation in small airways by a radiologist not aware it is a feature of COVID AND LC

The study suggests this phenomenon is due to 'aberrant angiogenesis' (abnormal formation/repair of blood vessels)

The study suggests the perfusion defects are due to unresolved microthombi (clots) within the pulmonary capillaries (the smallest of all blood vessels).

This is exactly what is found on autopsy studies in those who die of acute #COVID! See Carsana et al
pubmed.ncbi.nlm.nih.gov/32526193/

Conclusion

The study shows 'numerous abnormalities at the level of lung microcirculation in the year following hospitalization'

AND ...

Conclusion

'Our results suggest the complementarity between HRCT and spectral imaging for proper understanding of post COVID-19 lung sequelae'

This means that all conventional imaging (such as CT or CTPA) can be misleadingly normal post acute COVID.

It aligns with other studies which suggest that some form of perfusion imaging is probably best. See this review ... ncbi.nlm.nih.gov/pmc/articles/P…

I want this post to be informative to doctors who have patients suffering following #COVID-19.

Not only is #LongCOVID real. It is visible!

Conventional imaging won't be abnormal in most, even those who were hospitalized with acute COVID-19.

Only some features are occasionally visible on conventional CT and the radiologist would need to be very alert.

Although treatment options are still being investigated, some are thought to be beneficial. (#teamclots)

Post-acute symptoms should be taken seriously. Imaging may not be informative, but this is not the patient's fault - the medical imaging is letting us and them down

Rule #1
If your patient has persistent symptoms post acute COVID, then please believe them

Rule #2
Imaging has a limited role and normal imaging should not be taken to mean there is no problem

Rule #3
Perfusion scanning is probably best for those with persistent respiratory symptoms

Rule #4
Believing your patient is more important than imaging
(It's the old adage: Treat your patient, not the imaging!)

Rule #5
COVID-19 is NOT pneumonia!
(Although this paper calls the acute phase disease a 'pneumonia', this is misleading. The disease is a pulmonary vasculopathy, a disease of the lung blood vessels.)

Rule #6
Acute #COVID-19 and #LongCOVID are the same disease. Some get better, some don't.
(The lung damage shows identical features in both phases of the disease)

Thanks for reading!