Shape phenotype of thigh fat and muscle and risk of major adverse cardiovascular events after fragility hip fracture

Abstract

Abstract Background Although sarcopenia has been recognized as a predictor of mortality in elderly patients with hip fracture, the association of thigh fat and muscle with cardiovascular (CV) outcome remains unclear. We examined the impact of computed tomography (CT)‐derived shape features of thigh fat and muscle on major adverse CV events (MACE) in elderly patients with hip fracture. Methods We conducted a retrospective analysis of consecutive patients aged ≥65 years who presented with hip fracture confirmed on pelvic bone CT scan and underwent hip fracture surgery at our institution from April 2019 to December 2021. The cross‐sectional area (CSA) and compactness (CM) of both the muscle and fat at the upper‐thigh level were calculated from two‐dimensional CT images using AVIEW Research (v1.1.38, Coreline Soft, Co. Ltd, Seoul, South Korea). The shape features of thigh fat and muscle were categorized into four groups based on the combination of CSA and CM: fat CSA (fat area [FA])/fat CM (FCM), muscle CSA (muscle area [MA])/muscle CM (MCM), FA/MCM and MA/FCM. In each of them, subjects were categorized into four subgroups: high CSA/high CM, high CSA/low CM, low CSA/high CM and low CSA/low CM. The primary outcome was MACE after 30 days of surgery, defined as a composite of all‐cause death, acute myocardial infarction, stroke or hospitalization for heart failure. Results Of 356 patients enrolled (median age, 82 years; 76.7% females), 72 (20.2%) had MACE over a median follow‐up of 13.1 months (ranges 5.9–21.0 months). Patients with MACE had a significantly lower median FA (193.7 vs. 226.2 cm2, P < 0.0001) and FCM (0.443 vs. 0.513, P = 0.001) compared with those without MACE, but no significant differences were found in MA, MCM and FA–MA ratio between the two groups. In a multivariate Cox regression analysis, low FA (<240.1 cm2) (adjusted hazard ratio [HR] 2.99, 95% confidence interval [CI] 1.39–6.44, P = 0.005) and low FCM (<0.477) (adjusted HR 2.00, 95% CI 1.10–3.63, P = 0.023) were associated with an increased risk of MACE. Among the shape phenotypes of thigh fat and muscle, the thigh fat phenotype of low FA/low FCM (adjusted HR 3.13, 95% CI 1.81–5.42, P < 0.0001 [reference, high FA/high FCM]) was found to be an independent predictor of MACE. Conclusions In elderly patients with fragility hip fracture, thigh CT‐derived measures of FA and FCM may provide useful prognostic information for predicting adverse CV outcomes.

Keywords

• compactness
• cross‐sectional area
• elderly
• fat
• fragility hip fracture
• major adverse cardiovascular events