Phase-resolved Functional Lung MRI Reveals Distinct Lung Perfusion Phenotype in Children and Adolescents with Post-COVID-19 Condition.

Background Although measurable organic dysfunctions are frequently absent in pediatric patients with post-COVID-19 condition (PCC), this condition adversely affects quality of life. Free-breathing phase-resolved functional lung (PREFUL) MRI may be useful for assessing lung function in pediatric patients with PCC. Purpose To detect lung changes in children and adolescents with PCC compared with healthy control participants using PREFUL MRI. Materials and Methods In this single-center, prospective, cross-sectional study conducted between April 2022 and April 2023, children and adolescents (age ≤17 years) with PCC and age- and sex-matched healthy participants underwent MRI. Subgroup analysis was performed in participants with PCC who had cardiopulmonary symptoms. Regional ventilation, flow-volume loop correlation metric (FVL-CM), quantified perfusion, ventilation and perfusion defect percentages, and ventilation-perfusion ratios were compared between participants with PCC and controls using the Wilcoxon signed rank test. Correlation of imaging parameters with spirometry, heart rate, respiratory rate, and Bell score (fatigue severity) in participants with PCC was assessed using the Spearman rank correlation coefficient. Results The final study sample included 54 participants (27 participants with PCC and 27 matched control participants; median age, 15 years [IQR, 11-17 years]; 14 male participants). Twenty-one participants had cardiopulmonary symptoms. Participants with PCC had lower regional ventilation (median, 0.2 mL/mL [IQR, 0.1-0.2 mL/mL] vs 0.2 mL/mL [IQR, 0.2-0.2 mL/mL]; = .047) and quantified perfusion (49 mL/min per 100 mL [IQR, 33-60 mL/min per 100 mL] vs 78 mL/min per 100 mL [IQR, 59-89 mL/min per 100 mL]; < .001). Participants with PCC and cardiopulmonary symptoms had lower FVL-CMs (median, 0.99 arbitrary units [au] [IQR, 0.98-0.99 au] vs 0.99 au [IQR, 0.99-0.99 au]; = .01) and higher ventilation defect (median, 7.6% [IQR, 4.5%-15.1%] vs 5.4% [IQR, 2.7%-7.1%]; = .047) and perfusion defect percentage (median, 3.2% [IQR, 2.4%-4.2%] vs 2.3% [IQR, 1.8%-3.5%]; = .02) compared with matched control participants. In participants with PCC, greater lung perfusion correlated with increased chronic fatigue severity (ρ = 0.48; = .009) and higher ventilation-perfusion mismatch correlated with increased heart rate (ρ = 0.44; = .02). Conclusion Free-breathing phase-resolved functional lung MRI-derived parameters helped identify a distinct phenotype of lung perfusion in children and adolescents with PCC and were correlated with heart rate and chronic fatigue severity. Clinical trial registration no. DRKS00028963 © RSNA, 2025 See also the editorial by Parraga and Svenningsen in this issue.