Clinical, radiological and pathological findings in patients with persistent lung disease following SARS-CoV-2 infection.

Some patients experience pulmonary sequelae after SARS-CoV-2 infection, ranging from self-limited abnormalities to major lung diseases. Morphological analysis of lung tissue may help our understanding of pathogenic mechanisms and help to provide consistent personalised management. The aim of this study was to ascertain morphological and immunomolecular features of lung tissue. Transbronchial lung cryobiopsy was carried out in patients with persistent symptoms and computed tomography suggestive of residual lung disease after recovery from SARS-CoV-2 infection. 164 patients were referred for suspected pulmonary sequelae after COVID-19; 10 patients with >5% parenchymal lung disease underwent lung biopsy. The histological pattern of lung disease was not homogeneous and three different case clusters could be identified, which was mirrored by their clinical and radiological features. Cluster 1 ("chronic fibrosing") was characterised by post-infection progression of pre-existing interstitial pneumonias. Cluster 2 ("acute/subacute injury") was characterised by different types and grades of lung injury, ranging from organising pneumonia and fibrosing nonspecific interstitial pneumonia to diffuse alveolar damage. Cluster 3 ("vascular changes") was characterised by diffuse vascular increase, dilatation and distortion (capillaries and venules) within otherwise normal parenchyma. Clusters 2 and 3 had immunophenotypical changes similar to those observed in early/mild COVID-19 pneumonias (abnormal expression of STAT3 in hyperplastic pneumocytes and PD-L1, IDO and STAT3 in endothelial cells). This is the first study correlating histological/immunohistochemical patterns with clinical and radiological pictures of patients with post-COVID lung disease. Different phenotypes with potentially different underlying pathogenic mechanisms have been identified.

Mid-term impact of mild-moderate COVID-19 on cardiorespiratory fitness in élite athletes.

BACKGROUND: Mid- and long-term sequelae of COVID-19 on cardiorespiratory fitness are unknown. Aim of the study was to assess the mid-term impact of mild-moderate COVID-19 on cardiorespiratory fitness evaluated by cardiopulmonary exercise testing (CPET) in élite athletes. METHODS: 13 elite cross-country skiers with previous mild-moderate COVID-19 symptoms underwent CPET before resuming seasonal training (COVID athletes). 13 élite detrained cross-country skiers, matched for principal confounding factors, were taken as controls (control group). Resting peripheral oxygen saturation, pulmonary function test, echocardiography, bioelectrical impedance analysis and CPET (modified XELG2, Woodway, USA) were performed in all participants. RESULTS: Median recovery time in COVID athletes was 34 days (IQR 33-38 days). COVID athletes reached earlier the onset of the aerobic threshold (4'48" vs. 6'28", R2=0.15, F=4.37, P<0.05) than controls, whereas the time to anaerobic threshold and maximal efforts did not significantly differ between groups. Oxygen consumption was lower at the aerobic threshold in COVID athletes than controls (VO2/kg 28.6 mL/min vs. 38.9 mL/min, R2=0.39, F=15.34, P<0.01), whereas no significant difference between groups was found both at the aerobic threshold and at peak exercise (all P<0.05). Findings from resting echocardiography and pulmonary function test were similar between the two groups. CONCLUSIONS: Élite cross-country athletes, previously affected by mild-moderate COVID-19, reached earlier the aerobic threshold than controls, whereas the remaining CPET parameters did not differ between groups. Such changes were not associated with any detectable difference in resting pulmonary and cardiac examination. Subjects affected by mild-moderate COVID-19 may require a longer time course of re-adaptation to aerobic exercise.

Medium-term impact of COVID-19 on pulmonary function, functional capacity and quality of life.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has spread worldwide, having a dramatic impact on healthcare systems. The aim of this study is to evaluate mid-term clinical impact of COVID-19 on respiratory function. METHODS: 379 patients were evaluated 4 months after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnosis. Patients were divided in two groups based on the presence of pneumonia during COVID-19. Clinical conditions, quality of life, symptomatology, 6-min walk test, pulmonary function test with spirometry and diffusing capacity of the lung for carbon monoxide were analysed. Data were compared to clinical evolution during COVID-19 (development of acute respiratory distress syndrome, need of invasive mechanical ventilation, partial oxygen saturation (S pO2 )/inspiratory oxygen fraction (F IO2 ) ratio and pneumonia severity index (PSI)). RESULTS: After a median 135 days, 260 (68.6%) out of 379 patients referred at least one symptom. Patients who developed pneumonia during COVID-19 showed lower S pO2 at rest (p<0.001), S pO2 during 6-min walk test (p<0.001), total lung capacity (p<0.001), airway occlusion pressure after 0.1 s (P 0.1) (p=0.02), P 0.1/maximal inspiratory pressure ratio (p=0.005) and higher Borg category-ratio scale (p=0.006) and modified Medical Research Council breathlessness scale (p=0.003), compared to patients without pneumonia. S pO2 /F IO2 ratio and PSI during SARS-CoV-2 pneumonia were directly associated with mid-term alteration of S pO2 at rest (p<0.001) and during 6-min walk test (p<0.001), residual volume (p<0.001), total lung capacity (p<0.001 and p=0.003, respectively) and forced vital capacity (p=0.004 and p=0.03, respectively). CONCLUSION: Lung damage during COVID-19 correlates to the reduction of pulmonary function 4 months after acute infection.

The pathogenic role of epithelial and endothelial cells in early-phase COVID-19 pneumonia: victims and partners in crime.

Current understanding of the complex pathogenesis of COVID-19 interstitial pneumonia pathogenesis in the light of biopsies carried out in early/moderate phase and histology data obtained at postmortem analysis is discussed. In autopsies the most observed pattern is diffuse alveolar damage with alveolar-epithelial type-II cell hyperplasia, hyaline membranes, and frequent thromboembolic disease. However, these observations cannot explain some clinical, radiological and physiopathological features observed in SARS-CoV-2 interstitial pneumonia, including the occurrence of vascular enlargement on CT and preserved lung compliance in subjects even presenting with or developing respiratory failure. Histological investigation on early-phase pneumonia on perioperative samples and lung biopsies revealed peculiar morphological and morpho-phenotypical changes including hyper-expression of phosphorylated STAT3 and immune checkpoint molecules (PD-L1 and IDO) in alveolar-epithelial and endothelial cells. These features might explain in part these discrepancies.

Covid-19 Interstitial Pneumonia: Histological and Immunohistochemical Features on Cryobiopsies.

BACKGROUND: The pathogenetic steps leading to Covid-19 interstitial pneumonia remain to be clarified. Most postmortem studies to date reveal diffuse alveolar damage as the most relevant histologic pattern. Antemortem lung biopsy may however provide more precise data regarding the earlier stages of the disease, providing a basis for novel treatment approaches. OBJECTIVES: To ascertain the morphological and immunohistochemical features of lung samples obtained in patients with moderate Covid-19 pneumonia. METHODS: Transbronchial lung cryobiopsy was carried out in 12 Covid-19 patients within 20 days of symptom onset. RESULTS: Histopathologic changes included spots of patchy acute lung injury with alveolar type II cell hyperplasia, with no evidence of hyaline membranes. Strong nuclear expression of phosphorylated STAT3 was observed in >50% of AECII. Interalveolar capillaries showed enlarged lumen and were in part arranged in superposed rows. Pulmonary venules were characterized by luminal enlargement, thickened walls, and perivascular CD4+ T-cell infiltration. A strong nuclear expression of phosphorylated STAT3, associated with PD-L1 and IDO expression, was observed in endothelial cells of venules and interstitial capillaries. Alveolar spaces macrophages exhibited a peculiar phenotype (CD68, CD11c, CD14, CD205, CD206, CD123/IL3AR, and PD-L1). CONCLUSIONS: Morphologically distinct features were identified in early stages of Covid-19 pneumonia, with epithelial and endothelial cell abnormalities different from either classical interstitial lung diseases or diffuse alveolar damage. Alveolar type II cell hyperplasia was a prominent event in the majority of cases. Inflammatory cells expressed peculiar phenotypes. No evidence of hyaline membranes and endothelial changes characterized by IDO expression might in part explain the compliance and the characteristic pulmonary vasoplegia observed in less-advanced Covid-19 pneumonia.

Clinical, electromyographical, histopathological characteristics of COVID-19 related rhabdomyolysis.

Rhabdomyolysis is an uncommon complication of the coronavirus disease 2019 (COVID-19) infection. Previous reports have described its management and treatment in medical units, but have not discussed confirmatory tests or differential diagnosis. We report a case of a 58 year-old male patient, who was admitted for COVID-19 pneumonia and subsequently developed severe weakness, inability to move limbs, acute renal failure, significantly elevated myoglobin and creatinine kinase, and was diagnosed with rhabdomyolysis. Continuous renal replacement therapy, the treatment modality of choice over hyperhydration due to ongoing mechanical ventilation, was effective in resolving symptoms. No direct viral invasion of muscles was noted on biopsy. Here, we describe his symptoms, electromyography, and muscular biopsy results, and further discuss the possible differential diagnoses. Neuromuscular symptoms related to COVID-19 require careful clinical analysis. In addition, detailed reports of patients' course of illness and diagnoses will assist in improving care for affected patients.