Calf muscle hemoglobin oxygen saturation in patients with peripheral artery disease who have different types of exertional leg pain

Background: This study compared calf muscle hemoglobin oxygen saturation (Sto ₂) and exercise performance during standardized treadmill exercise in patients with peripheral artery disease (PAD) who describe different types of exertional leg pain and compared secondary outcomes consisting of daily ambulatory activity and exercise performance during a 6-minute walk test (6MWT). Methods: Leg pain symptoms were evaluated in 114 patients with PAD using the San Diego Claudication Questionnaire, by which atypical exertional leg pain was defined in 31, claudication in 37, and leg pain on exertion and rest in 46. Patients were evaluated on a standardized, graded treadmill test during which calf muscle Sto ₂ was continuously monitored. The 6MWT distance, Walking Impairment Questionnaire (WIQ), and ambulatory activity were monitored during 1 week. Results: All patients experienced symptoms during the treadmill test consistent with claudication. The groups were not significantly different on the primary outcomes of time to reach the minimum calf muscle Sto ₂ (P =.350) or peak walking time (P =.238) during treadmill exercise. Patients with atypical leg pain had the highest daily ambulatory activity for total strides per day (P =.032), average daily cadence (P =.010), maximum cadences for durations between 5 minutes (P =.035) and 60 minutes (P =.029), speed score on the WIQ (P =.006), and lowest rating of perceived exertion at the end of the 6MWT (P =.017). Conclusions: PAD patients with atypical leg pain have vascular-mediated limitations in exercise performance during standardized treadmill testing similar to patients with claudication and patients with leg pain on exertion and rest but have higher levels of daily ambulatory activity in the community setting and higher perceived ambulatory function.