Longitudinal changes in skeletal muscle mass after surgery for acute type A aortic dissection

Introduction Loss of skeletal muscle mass is associated with adverse survival and functional outcomes. Patients with acute type A aortic dissection (ATAAD) are exposed to profound systemic inflammation and postoperative immobility, yet the longitudinal changes in skeletal muscle mass remain poorly characterised. Purpose To examine short- and long-term changes in skeletal muscle mass and identify factors associated with muscle loss in patients undergoing surgery for ATAAD. Methods This retrospective cohort study included patients who underwent ATAAD surgery between April 2014 and December 2020. Skeletal muscle mass was assessed using computed tomography images obtained preoperatively, at 1 week after surgery, and at 1 year after surgery. The psoas muscle mass index (PMI) was measured at the L4 vertebral level with height normalisation. PMI across time points was compared using repeated-measures ANOVA with Bonferroni correction. Factors associated with acute (preoperative to 1 week) and long-term (preoperative to 1 year) PMI decline were examined using multiple linear regression. Results A total of 281 patients (median age 69 years; 52% male) were analysed. PMI values were 6.7 ± 2.0 cm²/m² preoperatively, 6.5 ± 1.8 cm²/m² at 1 week, and 6.3 ± 1.8 cm²/m² at 1 year. Although no significant difference was observed between preoperative and 1 week PMI (p = 0.054), PMI at 1 year was significantly decreased compared with both preoperative (p < 0.001) and 1 week values (p = 0.001). Independent factors associated with acute PMI decline were male, lower body mass index, higher preoperative PMI, and higher Acute Physiology and Chronic Health Evaluation II score. For long-term PMI decline, the same factors remained significant, with delirium and later initiation of mobilisation additionally identified as independent factors (all p < 0.05). Acute PMI change was strongly associated with long-term change (β: 0.69, 95% CI: 0.60–0.77, p < 0.001). Conclusions After ATAAD surgery, skeletal muscle mass is relatively preserved in the acute postoperative period but declines significantly by 1 year. Baseline characteristics were associated with both short- and long-term muscle loss, while perioperative factors such as delirium and later initiation of mobilisation were particularly related to long-term decline. Early postoperative changes may help identify patients at risk of sustained muscle deterioration.