Acute disease severity is associated with increased MRI pulmonary perfusion transit times at follow-up in male patients hospitalised due to COVID-19.

<bold>Aim:</bold> To evaluate the relationship between pulmonary perfusion and sex, age and disease severity in patients hospitalised due to COVID-19. <bold>Methods:</bold> Subjects underwent 3T MRI at 13 centres as part of the C-MORE study. Maps of relative pulmonary blood volume (rPBV), relative pulmonary blood flow (rPBF) and mean transit time (MTT) were calculated from contrast enhanced perfusion imaging. Kruskal-Wallis and Mann-Whitney U Tests were used to evaluate sex dependence and associations with WHO Clinical Progression Scale (“WHO score”) with a Bonferroni correction. A linear regression model tested the relationship between hospital duration, age and perfusion metrics. <bold>Results</bold> 198 patients had successful pulmonary perfusion analysis (WHO score 3-4: n=36, WHO score 5: n=105; WHO score 6: n=43; WHO score 7-9: n=14). Median hospital duration: 6 days (range 0-157, n=199), follow up time: 151 days (range 81-653). MTT and rPBF differed with sex. Male patients with WHO score 7-9 had significantly longer MTT than those with WHO score 3-4. Male patients with WHO score 5 had more heterogenous MTT (IQR MTT) than those with WHO score 3-4. In males, age and admission duration were significant predictors of MTT. In females <fig><object-id>erj;64/suppl_68/PA5261/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> admission duration and WHO score were not significant predictors of any perfusion metrics. <bold>Conclusion:</bold> MTT was associated with acute disease severity in male post-COVID patients.