Lung perfusion disturbances in nonhospitalized post‐COVID with dyspnea—A magnetic resonance imaging feasibility study

BACKGROUND: Dyspnea is common after COVID‐19. Though the underlying mechanisms are largely unknown, lung perfusion abnormalities could contribute to lingering dyspnea. OBJECTIVES: To detect pulmonary perfusion disturbances in nonhospitalized individuals with the post‐COVID condition and persistent dyspnea 4–13 months after the disease onset. METHODS: Individuals with dyspnea and matched healthy controls were recruited for dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI), a 6‐min walk test, and an assessment of dyspnea. The DCE‐MRI was quantified using two parametric values: mean time to peak (TTP) and TTP ratio, reflecting the total lung perfusion resistance and the fraction of lung with delayed perfusion, respectively. RESULTS: Twenty‐eight persons with persistent dyspnea (mean age 46.5 ± 8.0 years, 75% women) and 22 controls (mean age 44.1 ± 10.8 years, 73% women) were included. There was no systematic sex difference in dyspnea. The post‐COVID group had no focal perfusion deficits but had higher mean pulmonary TTP (0.43 ± 0.04 vs. 0.41 ± 0.03, p = 0.011) and TTP ratio (0.096 ± 0.052 vs. 0.068 ± 0.027, p = 0.032). Post‐COVID males had the highest mean TTP of 0.47 ± 0.02 and TTP ratio of 0.160 ± 0.039 compared to male controls and post‐COVID females (p = 0.001 and p < 0.001, respectively). Correlations between dyspnea and perfusion parameters were demonstrated in males (r = 0.83, p < 0.001 for mean TTP; r = 0.76, p = 0.003 for TTP ratio), but not in females. CONCLUSIONS: DCE‐MRI demonstrated late contrast bolus arrival in males with post‐COVID dyspnea, suggestive of primary vascular lesions or secondary effects of hypoxic vasoconstriction. Since this effect was not regularly observed in female patients, our findings suggest sex differences in the mechanisms underlying post‐COVID dyspnea, which warrants further investigation in dedicated trials.