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

The goal of the proposed pilot study is to evaluate the feasibility of a new leg heat therapy system treatment for patients with lower extremity PAD. The new system is comprised of leg-length water circulating pads surrounded by a separate pneumatic compression outer garment that compresses the pads against the skin for efficient heat transfer. The new leg garment is easily closed with a zipper. The air chambers automatically adjust the amount of air inflation enabling use of the garment independent of patient leg size. Six patients with PAD will be asked to complete daily (90 min/day) home-based leg HT for 12 weeks using the newly developed system. 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.

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.

Eligibility Criteria:
Inclusion Criteria:

* Men and women 60 years or older
* Resting ankle-brachial index (ABI) of 0.9 or less in at least one leg.
* Individuals with a resting ABI between 0.91 and 1.00 at baseline will be eligible if their ABI drops by 20% or greater following a heel-rise test.

Exclusion Criteria:

* Critical limb ischemia (ischemic rest pain or ischemia-related, non-healing wounds or tissue loss)
* Prior amputation
* Exercise tolerance limited by factors other than leg pain (e.g. angina, arthritis, severe lung disease, etc).
* Recent (\<3 months) lower-extremity revascularization or orthopedic surgery
* Use of walking aid other than a cane
* Active cancer
* Chronic kidney disease (eGFR \<30 by MDRD or Mayo or Cockcroft-Gault formula)
* Unable to fit into water-circulating trousers
* A Mini-Mental Status Examination score \<23
* Impaired thermal sensation in the leg
* Age lower than 60 yrs