Early effects of antifibrotic therapy on respiratory muscle stiffness and dyspnea in SSc-ILD: a shear wave elastography study

Abstract Systemic sclerosis-associated interstitial lung disease (SSc-ILD) is characterized by microvascular injury and progressive fibrosis leading to respiratory impairment. This study aimed to evaluate the effect of anti-fibrotic therapy on intercostal and diaphragmatic shear wave elastography (SWE) measurements in patients with SSc-ILD and to assess their relationship with pulmonary function tests and Borg dyspnea scores. 30 patients with SSc-ILD receiving stable background therapy and 30 healthy controls were evaluated prospectively between January and August 2025. Intercostal and diaphragmatic SWE, pulmonary function tests, and Borg dyspnea scores were obtained before and three months after initiation of anti-fibrotic therapy. At three months, SSc-ILD patients showed significant improvement in FVC and FEV₁ ( p = 0.009 and p = 0.02), while Borg scores and intercostal and diaphragmatic SWE values decreased (all p < 0.001). Elastography measurements regressed to levels comparable with controls. Changes in intercostal SWE correlated with ΔFVC and ΔFEV₁ ( R = –0.769, p < 0.001 and R = –0.492, p = 0.007), and ΔBorg correlated with both intercostal and diaphragmatic SWE ( R = 0.89 and R = 0.793, both p < 0.001). In multivariable analysis, elastographic improvement was the strongest determinant of dyspnea reduction ( p < 0.001). Anti-fibrotic therapy initiation was associated with early reductions in respiratory muscle elastographic stiffness parameters and dyspnea in SSc-ILD. These short-term changes may reflect early biomechanical or functional alterations rather than definitive structural remodeling.