Association of Computed Tomographic Leg Muscle Characteristics With Lower Limb and Cardiovascular Events in Patients With Peripheral Artery Disease

Background-Poor lower extremity physical performance is an independent predictor of unfavorable outcome in patients with peripheral artery disease (PAD); however, few studies have assessed muscle characteristics on imaging directly. Method and Results-A novel 3-dimensional semi-automated protocol was developed to estimate leg muscle volume and density (mean attenuation) from computed tomography images. Patients with PAD who underwent a lower extremity computed tomography scan at a tertiary vascular surgery center were included, and were followed up using hospital records and linked data as part of a retrospective cohort study. The primary outcomes were lower limb events (major amputation or peripheral revascularization) and cardiovascular events (myocardial infarction, stroke, or cardiovascular death). Two hundred and twenty-three patients with PAD were included (median age 69.0 years; 73% men) and followed for a median of 4.9 [2.6-7.0] years. During this time there were 99 index lower limb events and 97 cardiovascular events. Low leg muscle density was associated with increased risk of lower limb (rate ratio 1.41 [1.11-1.80] per SD reduction) and cardiovascular events (rate ratio 1.60 [1.29-1.99] per SD reduction). Low muscle density remained an independent predictor of cardiovascular (but not lower limb) events, after adjusting for age, sex, traditional cardiovascular risk factors, and angiographic PAD severity (rate ratio 1.39 [1.09-1.77] per lower SD). In contrast, leg muscle volume was not associated with outcomes after adjusting for risk factors and PAD severity. Conclusions-Low leg muscle density, but not volume, is a strong, independent predictor of major cardiovascular events among people with PAD. Further research is needed to understand the mechanisms underlying these associations.