The added value of lung perfusion scintigraphy semiquantitative measures in post-COVID patients with persistent dyspnea without pulmonary embolism

Background: Persistent dyspnea is frequent in post-COVID patients, even in the absence of pulmonary embolism (PE). In this scenario, the role of lung perfusion scintigraphy is unclear. The present study correlated scintigraphy-based semiquantitative perfusion parameters with chest high-resolution computed tomography (hrCT) volumetric indexes and clinical data in post-COVID patients with persistent dyspnea. Research design and methods: Sixty patients (30 post-COVID and 30 not previously affected by COVID-19) with persistent dyspnea submitted to lung perfusion scintigraphy and hrCT were retrospectively recruited. Perfusion rates of the pulmonary fields and hrCT-based normalized inflated, emphysematous, infiltrated, collapsed, and vascular lung volumes were calculated. Inflammatory and coagulation biomarkers were collected. PE at imaging was an exclusion criterion. Results: Compared to controls, reduced perfusion rates of the lower pulmonary fields and higher perfusion rates of the middle ones were observed in post-COVID patients, while hrCT findings were superimposable between the two groups. Perfusion rates of lower pulmonary fields were significantly associated only with abnormal lung volumes at hrCT. Conclusions: In post-COVID dyspnea without PE, lung perfusion scintigraphy may reveal a pulmonary involvement not detectable by hrCT. Post-COVID patients may show decreased perfusion rates of lower pulmonary fields in the presence of normal vascular density and markers of inflammation/coagulation.