ABSTRACT
Introduction: The progression of pathophysiological pulmonary changes in patients following acute COVID-19 is not well established. Method(s): Patients hospitalised with COVID-19 pneumonia without signs of ILD, had MRI exams at a median of 6 (n=9), 12 (n=9), 25 (n=7), and 52 (n=3) weeks. MRI sequences included: dynamic contrast enhanced (DCE) lung perfusion,129 Xe diffusion weighted (DW-MRI), 129Xe ventilation and 129Xe 3D dissolved phase imaging. Result(s): 9 patients (age 56+/-9 years;7 male;1 required treatment in an ICU) were recruited. Median RBC:TP was abnormally low at all visits compared to reference age and sex matched data. An individual's RBC:TP was significantly and positively associated with an increase in their pulmonary blood volume (p=0.026). For patients with 52 week data available, one showed a continued increase in RBC:TP, 2 patients maintained a low RBC:TP (Figure 1). Ventilation defect percentage, and ventilation heterogeneity significantly decreased at 25 weeks compared to 6 129 129 129 weeks (p=0.010 and p=0.048). DW-MRI was normal at all visits. Dissolved phase xenon imaging showed RBC:TP significantly increased at 12 and 25 weeks compared to 6 weeks (p=0.048). Conclusion(s): In patients recovering after COVID-19, poor gas transfer is reflected by impaired xenon transfer, which improves alongside pulmonary blood volume.
ABSTRACT
The long-term effects of coronavirus disease 2019 (COVID- 19) pneumonia on the lungs and pulmonary circulation require further characterization. We assessed progression of pathophysiological pulmonary changes during 1 year of follow-up of patients who had been hospitalized because of COVID-19. After discharge, recruited patients had up to four MRI examinations at a median of 6 (n=9), 12 (n=9), 25 (n=7) and 52 (n=3) weeks. Lung MRI examinations included: ultra-short echo time (UTE), dynamic contrastenhanced (DCE) lung perfusion, 129Xe diffusion weighted (DW-MRI), 129Xe ventilation and 129Xe 3D dissolved phase imaging. Nine patients (age 56 +/-9 years;six male) were recruited. Ventilation defect percentage and whole lung coefficient of variation of lung ventilation decreased significantly at 25 weeks (visit 3) compared with visit 1 at 6 weeks (p=0.010 and p=0.048). The UTE imaging indicated no evidence of lung scarring, and DW-MRI indicated normal lung microstructure across all visits. Dissolved phase xenon imaging showed that RBC:TP increased significantly at visits 2 and 3 compared with visit 1 (p=0.048). Median RBC:TP was abnormally low at all visits compared with reference age- and sex-matched data. An individual's RBC:TP was associated significantly and positively with an increase in their pulmonary blood volume (p=0.026). For patients with 52-week data available, one showed a continued improvement in RBC:TP;however, two of the patients maintained a low RBC:TP. In patients recovering from COVID-19, xenon gas transfer improves alongside pulmonary blood volume. Further work is needed to establish the proportion of post-COVID-19 patients who have longer-term impairment in xenon transfer and to correlate changes in lung MRI parameters with symptoms, lung function tests and other imaging modalities. Persistent impairment of xenon transfer might represent a physiological mechanism underlying ongoing symptoms in some patients and might indicate damage to the pulmonary microcirculation.
ABSTRACT
S75 Figure 1Difference between the fibrotic and inflammatory groups in mean 129Xe ADC (a) and LmD (b) at baseline study visit[Figure omitted. See PDF]Conclusions129Xe DW-MRI could have a role in differentiating changes in the airway microstructure between fibrotic and inflammatory ILD. 129Xe RBC:TP has sensitivity to longitudinal change with a decline in gas exchange observed in the fibrotic group but not in the inflammatory group.