Chest CT-scan myosteatosis assessment, prevalence and impact in patients with persistent dyspnea after COVID-19 infection

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Introduction: Long COVID is characterized by persistent symptoms, including dyspnea, lasting months post-infection. Muscle strenght, a key contributor to reduced exercise capacity, may significantly impact these patients. Chest computed tomography (CT) enables the assessment of sarcopenia by evaluating muscle surface and myosteatosis which is characterized by fat infiltration and reduced muscle density. Methods: This monocentric observational study included patients with persistent dyspnea at 3 months post-COVID. Patients were admitted for day hospital care in pulmonology, where they underwent thoracic CT, pulmonary function tests, and exercise testing. Myosteatosis at L3 and T4 was quantified, and associations with clinical and functional parameters were analyzed. Results: At evaluation, among the 86 patients, 59% were female, the mean age was 56 years, and mean BMI was 27 kg/m². They reported a mean mMRC dyspnea scale at 2 and exhibited mostly normal pulmonary function at rest. L3 myosteatosis (34%) was associated with lower PaO₂ (75 vs. 87 mmHg, p=0.009), reduced DLCO, and poorer exercise performance (VO₂max, 6MWT distance). Patients with the lowest T4 muscle density had more severe initial COVID-19, higher rates of pulmonary sequelae, lower oxygen saturation, and greater physical limitations. A T4 muscle density threshold of 48 Hounsfield units identified the most vulnerable patients. Conclusion: T4 muscle density correlates strongly with L3 and enhances risk stratification. Chest CT-based myosteatosis assessment may aid in identifying Long COVID patients at risk of persistent respiratory and functional impairment, guiding targeted rehabilitation strategies.

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