Abstract 4145636: Associaion Between Daily Steps And Calf Muscle Oxygen Saturation In Patients With Symptomatic Peripheral Artery Disease

Purposes: We determined whether patients with peripheral artery disease (PAD) who walked at least 7,000 steps/day had better microvascular function, assessed by calf muscle oxygen saturation (StO 2 ), and more favorable vascular biomarkers than patients who walked less than 7,000 steps/day. A secondary aim was to determine whether group differences in calf muscle StO 2 and vascular biomarkers persisted after adjusting for severity of PAD, and demographic and clinical characteristics. Methods: Five hundred and sixteen patients were assessed on daily ambulatory activity for one week with a step activity monitor, and were grouped according to whether they walked fewer than 7,000 steps/day (Group 1; n=306) or for 7,000 steps/day or greater (Group 2; n=210). Patients performed a standardized Gardner-Skinner graded treadmill test, and calf muscle StO 2 was continuously measured over the medial gastrocnemius muscle of the more symptomatic leg using near-infrared spectrometry. Additionally, patients had blood samples drawn for measurement of high-sensitivity C-reactive protein (HsCRP). Results: Exercise time to reach the minimum calf muscle StO 2 was significantly longer (p=0.025) in Group 2 (297±339 sec) than in Group 1 (210±232 sec). Additionally, HsCRP was significantly lower (p<0.001) in Group 2 (4.0±4.5 mg/L) than in Group 1 (6.8±10.7 mg/L). In multivariable linear regression models, exercise time to minimum calf muscle StO 2 was significantly associated with physical activity group status after adjusting for ankle/brachial index (Model 1) (p=0.032), and after adjusting for age, race, sex, education, and body mass index (Model 2) (p=0.044). HsCRP was significantly associated with physical activity group status after adjusting for Model 1 (p<0.001), Model 2 (p<0.001), and the two models combined (Model 3) (p<0.001). Conclusions: Walking at least 7,000 steps/day was associated with better microvascular function in the calf muscle during exercise and with lower vascular inflammation in patients with symptomatic PAD. The clinical significance is that community-based walking for at least 7,000 steps/day is a simple goal that is associated with more favorable vascular outcomes in patients with symptomatic PAD.