Determinants of Trunk Muscle Size Decrease in Patients with Type B Acute Aortic Dissection

Trunk muscle decrease is reportedly associated with an increased risk of multiple adverse clinical outcomes. Acute aortic dissection (AAD) involves a systemic inflammatory response which is associated with exaggerated muscle protein catabolism. AAD requires prolonged hospitalization and potentially exacerbates muscle size decrease.Cross-sectional areas (CSA) of both the bilateral psoas muscle area (PMA) and L4 vertebral body were determined using CT scans on admission to calculate the psoas-lumbar vertebral index (PLVI = bilateral PMA/L4 body CSA) in 141 hospitalized type B AAD patients. Serial CT scans within 30 days were performed to investigate PLVI change (%/day) calculated as: (PLVI at follow-up - PLVI at admission) /PLVI at admission × 100/follow-up interval (days). Patients were categorized into a large decrease of PLVI (LD) group and a modest decrease and increase of PLVI (MDI) group according to the median value of decreased PLVI change (-0.48%/day).A large PLVI decrease was correlated with a higher peak C-reactive protein (CRP) value (13.8 versus 10.9 mg/dL, P = 0.010), and larger false lumen (FL) diameter (13.6 versus 11.4 mm, P = 0.015). The days until ambulation and the length of hospital stay were slightly longer in the LD group than in the MDI group (days until ambulation, P = 0.111; length of hospital stay, P = 0.053). Logistic regression model analysis demonstrated a higher peak CRP level (OR = 3.43; 95% CI, 1.50-7.84) and larger %FL diameter (OR = 3.88; 95% CI, 1.55-9.69) were predictive of a large PLVI decrease.Our results indicate that a larger FL and subsequent exaggerated inflammatory response may result in a trunk muscle decrease in type B AAD patients.