Lung perfusion scan: the added value in post SARS-COV-2 pneumonia

ABSTRACT

Background-Aim: Post-mortem studies showed that in patients with COVID-19 the poor prognosis is due not only to the worsening of the ventilation function but it can be related to the perfusion impairment due to massive pulmonary thrombosis or micro-thromboembolism. We aimed to investigate the clinical impact of lung perfusion (Q) scintigraphy in patients discharged after COVID-19 disease but still symptomatic for dyspnea. Methods: 33 patients (pts), discharged at least 1 month after COVID- 19, underwent Q scan at T0 (1-3 months after acute disease) and at T1 (after 6 months if lung perfusion defects were evident at T0). Inclusion criteria were (1) residual dyspnea mild (12/33pts), at minimal motor activity (9/33) and after prolonged effort (12/33), (2) No thromboembolism at CT pulmonary angiography during hospitalization. Exclusion criteria were previous history of lung disease (e.g. Cancer, COPD, emphysema) or abnormal pulmonary CT findings (e.g. lung bullae). Planar and Q-SPECT/CT images were obtained for evaluation of lobar or segmental or subsegmental peripheral perfusion defects for each bronchopulmonary segment. Perfusion images were qualitatively and semiquantitatively analysed. Q-lung software by GE Healthcare was used for SPECT/CT images for obtaining percent evaluation of pulmonary lobar perfusion (counts/volume % for each lobe), considering as normal a value of defect within - 5%/each lobe, if represented in ≥ 1 lobe. Q-scan was then compared with high resolution CT (HRCT) obtained during hospitalization in the acute phase (T-acute) and repeated after 1-3 months (T0). Significant pulmonary perfusion defects at Q scan were considered for addressing targeted therapy. Results: At T0 preserved lung perfusion was observed in 17/33 pts, thus excluding the vascular cause for the symptoms. Lung perfusion defects were detected in 16/33 patients who underwent T0 and T1 control. Defects were scored as following severe (7 pts with dyspnea at minimal motor activity), at least one wedge-shaped peripheral defect estimated as ≥ 50% of a pulmonary segment without corresponding HRCT abnormalities, suggesting a new CTPA within 3 months and an appropriate therapeutic strategy;moderate (6 pts with dyspnea after prolonged effort) consisting in multiple (>3) subsegmental defects;-mild (3 pts with mild dyspnea ≤ 3 sub-segmental defects). At T1 lung perfusion improvement (≥ 10% vs pathological lobe in T0), was observed in a total of 8/16 pts. Conclusions: In the age of precision medicine, Q scan-SPECT/CT in pts with recent COVID-19 can address clinical knowledge and management of SARS-CoV-2-induced lung abnormalities, suggesting the differential diagnosis with respiratory disease of different etiology and the appropriate patient-centered therapeutic strategies.