Thoracic Skeletal Muscle and Exercise Capacity in Adults With Congenital Heart Disease: A Cross-Sectional Imaging Analysis.

BACKGROUND: The growing population of adults with congenital heart disease (ACHD) faces lifelong morbidities despite advancements in medical and surgical care. Sarcopenia, characterized by loss of muscle mass and strength, is linked to increased disability, poor quality of life and mortality. This study examines sex-specific thoracic skeletal muscle characteristics in ACHD patients using advanced imaging techniques, comparing them with healthy reference values and investigating their association with exercise capacity. MATERIAL AND METHODS: In this single-centre retrospective study, ACHD patients (age 18-50 years) who underwent both cardiopulmonary exercise tests and thoracic CT/MRI within a year were included. Skeletal muscle area (SMA) was manually measured and compared with healthy reference data. RESULTS: Among 60 ACHD patients (mean age 28.3 ± 8.3 years; 48% females), males exhibited significantly lower SMA (T10: 116.8 ± 24.6 cm2, p < 0.0001; T11: 114.4 ± 24.7 cm2, p = 0.0002) and skeletal muscle index (SMI) (T10: 37.2 ± 8 cm2/m2, p = 0.005; T11: 36.4 ± 8.1 cm2/m2, p = 0.0014) at T10 and T11 vertebral level, whereas females showed a reduction in SMA at T10 (79.7 ± 14.9 cm2, p = 0.0242) and T12 (74.2 ± 10.7 cm2, p = 0.0015) compared with healthy individuals. Females had significantly lower skeletal muscle radiation attenuation (SMRA) at T10 (16.3 ± 14.6 HU, p < 0.001), T11 (17.1 ± 10.3 HU, p < 0.001) and T12 (25 ± 10.7 HU, p < 0.001) levels, suggesting increased muscle fat content. Peak O2 pulse correlated with SMA at T10 (r = 0.57, R2 = 0.32, p ≤ 0.0001), T11 (r = 0.61, R2 = 0.38, p < 0.0001) and T12 (r = 0.73, R2 = 0.53, p = 0.001) levels. Similar correlations were observed between peak O2 pulse and SMI, whereas peak VO2 correlated with SMA at T10 (r = 0.27, R2 = 0.07, p = 0.0394) and T11 (r = 0.34, R2 = 0.11, p = 0.02) and SMRA across all levels (T10: r = 0.64, R2 = 0.41, p = 0.0076; T11: r = 0.85, R2 = 0.72, p = 0.0003; T12: r = 0.62, R2 = 0.38, p = 0.0327). SMA at T11 had a negative correlation with VE/VCO2 (r = -0.36, R2 = 0.13, p = 0.01). There was no correlation between the number of sternotomies and exercise parameters. Subjects with a pacemaker demonstrated significantly lower peak VO2 (p = 0.04) and VO2 at the anabolic threshold (p = 0.03) compared with ACHD patients without a pacemaker. CONCLUSIONS: Abnormal skeletal muscle parameters observed on thoracic cross-sectional imaging are associated with diminished exercise capacity in ACHD patients. Assessment of thoracic skeletal muscle characteristics may enable early detection of muscle loss, providing valuable insights into the complex factors contributing to exercise limitations in this population.