Longitudinal lung function assessment of patients hospitalised with COVID-19 using¹H and¹²⁹Xe lung MRI

Abstract

IntroductionMicrovascular abnormalities and impaired 129Xe gas transfer have been observed in patients with COVID-19. The progression of pathophysiological pulmonary changes during the post-acute period in these patients remains unclear.MethodsPatients who were hospitalised due to COVID-19 pneumonia underwent a pulmonary 1H and 129Xe MRI protocol at 6, 12, 25 and 50 weeks after hospital admission. The imaging protocol included: ultra-short echo time, dynamic contrast enhanced lung perfusion, 129Xe lung ventilation, 129Xe diffusion weighted and 129Xe 3D spectroscopic imaging of gas exchange.Results9 patients were recruited and underwent MRI at 6 (n=9), 12 (n=9), 25 (n=6) and 50 (n=3) weeks after hospital admission. At 6 weeks after hospital admission, patients demonstrated impaired 129Xe gas transfer (RBC:M) but normal lung microstructure (ADC, LmD). Minor ventilation abnormalities present in four patients were largely resolved in the 6–25 week period. At 12 week follow up, all patients with lung perfusion data available (n=6) showed an increase in both pulmonary blood volume and flow when compared to 6 weeks, though this was not statistically significant. At 12 and 25 week follow up, significant improvements in 129Xe gas transfer were observed compared to 6-week examinations, however 129Xe gas transfer remained abnormally low.ConclusionsThis study demonstrates that multinuclear MRI is sensitive to functional pulmonary changes in the follow up of patients who were hospitalised with COVID-19. Persistent impairment of xenon transfer may represent a physiological mechanism underlying ongoing symptoms in some patients and may indicate damage to the pulmonary microcirculation.

Review of Hyperpolarized Pulmonary Functional 129Xe MR for Long‐COVID

“…With respect to gas‐exchange, a combination of lung perfusion abnormalities and/or alveolar/interstitial endothelial changes may be mechanistically driving the observation of diminished RBC:membrane values. This is supported by the correlations detected for the changes in 129 Xe gas transfer with changes in pulmonary blood volume in one of the longitudinal studies 129 Xe gas‐exchange MRI 78 . Pilot dynamic contrast‐enhanced MRI evidence of pulmonary microvasculature abnormalities in 10 participants, after SARS‐CoV‐2 infection 90 also supports this hypothesis.…”

“…The most comprehensive longitudinal study of 129 Xe MRI gas-exchange values was reported in the original nine participants with COVID. 78 As shown in Fig. 7, at 12-week follow-up, there was improved 129 Xe MRI RBC:membrane, but no longitudinal change was detected between 12 and 52 weeks, and median values remained abnormally lower than expected and than an age-and sex-matched healthy volunteer group of 12 participants.…”

“…6) also had significantly worse 6MWD ( P = 0.003) and post‐exertional SpO 2 ( P = 0.03) and there were significant relationships for VDP with 6MWD ( ρ = −0.31; P = 0.02) and post‐exertional SpO 2 ( ρ = −0.43; P = 0.002). It is also worth noting that in UK participants with COVID, there was a longitudinal trend toward improved VDP at 12 and 24 weeks as compared to 6 weeks post‐infection 78 …”

“…The most comprehensive longitudinal study of 129 Xe MRI gas‐exchange values was reported in the original nine participants with COVID 78 . As shown in Fig.…”

“…It is also worth noting that in UK participants with COVID, there was a longitudinal trend toward improved VDP at 12 and 24 weeks as compared to 6 weeks post-infection. 78 Of the original 76 participants, 53 participants were evaluated 12 months later, roughly 1/3 hospitalized during their acute COVID-19 infection. Although normal at the baseline visit, surprisingly, FEV 1 (P = 0.001), FEV 1 /FVC (P = 0.003), and DL CO (P = 0.002) significantly improved 12 months later.…”