A New Heat Therapy Device for Home-based Leg Heating in Patients With Lower-extremity Peripheral Artery Disease: a Pilot Study

Lower-extremity PAD is a manifestation of systemic atherosclerosis associated with increased risk of cardiovascular morbidity and mortality, diminished quality of life, physical functioning and psychological well-being. In 2015, an estimated 236 million people worldwide, most between 65 and 69 years of age, were living with PAD. Home-based leg heat therapy (HT) is emerging as a potential effective and practical treatment to increase leg blood flow and improve walking performance in patients with symptomatic PAD. In the first randomized sham-controlled trial to examine the benefits of supervised leg HT in patients with symptomatic PAD (90 min, 3 days/week for 6 weeks), we demonstrated that patients assigned to the leg heating group displayed a clinically meaningful improvement in perceived physical functioning. Building upon these findings, we recently completed a NIH-sponsored randomized clinical trial to examine the safety, tolerability, and effectiveness of home-based, unsupervised leg HT (90 min, 7 days/week for 8 weeks) in 34 patients with symptomatic PAD. Patients randomized to the HT group displayed an increase in 6-minute walk from baseline of 23 meters after 8 weeks of treatment, which is clinically meaningful for PAD patients. Importantly, home-based leg HT was also found to be safe (no skin injury), well-tolerated, and patient compliance was surprisingly high (96% completion of the prescribed treatment sessions).

Heat packs, electric heating pads, and electric blankets are widely available, but have high risk of contact burns, particularly in patients with peripheral neuropathy that is commonly associated with diabetes mellitus and PAD. An assembly of individual pads is difficult to apply and skin contact is unreliable. Water-circulating pads have been found to be safer than electric devices because they provide more reliable thermostatic control. PAD patients with diffuse bilateral disease often accompanied by neuropathy need a reliable system that is simple to operate, easy to put on, covers the entirety of both lower limbs and safely provides HT while avoiding skin injury. Currently, there is no commercially-available HT system for home-based therapy in elderly individuals, despite the documented benefits associated with repeated HT. To address this unmet clinical need, Aquilo Sports is developing a system that will monitor skin temperature and have an integrated shut-off feature to prevent skin burns, and record treatment sessions to confirm patient compliance. The system has undergone extensive independent validation testing and has been widely adopted by professional athletes. The garment is easily closed with a zipper and auto-adjusts pneumatically to different leg sizes.

Our objective is to establish evidence to support the safety and feasibility of the redeveloped Aquilo system during repeated home-based treatment in patients with PAD. Our approach to testing our hypothesis will be to ask 6 patients with PAD to undergo daily home-based leg HT (90 min/day, 7 days/week) for 12 weeks. The length of the intervention (12 weeks) was selected as it is similar to: 1) the duration of previous studies with other HT modalities showing beneficial effects in patients with PAD, 2) the recommended minimal duration of exercise training interventions, the gold standard treatment for PAD.

The primary study outcome is the change from baseline in walking performance on the 6-minute walk test at the 12-week follow-up. Secondary outcomes include plantar flexion power, as assessed using isokinetic dynamometry, sit-to-stand muscle power and perceived quality of life.The study coordinator will call patients weekly to record the occurrence of adverse events.