Changes in pulmonary microcirculation after COVID-19

The endothelium is a tissue most vulnerable to the SARS-CoV-2 virus. Systemic endothelial dysfunction leads to the development of endothelitis which causes the main manifestations of the disease and systemic disturbance of microcirculation in various organs. Pulmonary microcirculatory damage, the most striking clinical manifestation, was the reason to perform SPECT to detect microcirculation disorders.

Aim. To assess microcirculatory changes in the lungs of patients who had no previous respiratory diseases and had a COVID-19 infection at different times from the onset of the disease.

Methods. SPECT data were analyzed in 136 patients who had a proven coronavirus infection of varying severity from May 2020 to June 2021.

Results. All patients showed changes in microcirculation in the lungs in the post-COVID period. The severity of microcirculation disorders had a significant correlation (r_s = 0.76; p = 0.01) with the degree of damage to the pulmonary parenchyma and an average correlation (r_s = 0.48; p = 0.05) with the timing of the post-COVID period and the degree of residual lesions on CT (r_s = 0.49; p = 0.01). The examined patients with persistent clinical complaints had pulmonary microcirculatory lesions, which may indicate the development of vasculitis, at all stages of the post-COVID period. Despite regression of the lesions confirmed by CT in 3 to 6 months after the acute COVID-19 infection, specialists from Russian and other countries report that 30–36% of patients develop pulmonary fibrosis. Similar changes were identified in 19.1% of the examined patients in our study.

Conclusion. Microcirculation disorders are detected in all patients in the post-COVID period, irrespective of the severity according to CT. Progressive decrease in microcirculation in the lower parts of the lungs, local zones of hypoperfusion with the critically low accumulation of radiopharmaceuticals, persistent areas of compaction of the lung tissue (so-called “ground glass”), reticular changes, and the development of traction bronchiectasis, a decrease in the diffusion capacity of the lungs and alveolar volume may indicate fibrotic lesions with subsequent development of virus-associated interstitial lung disease.

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