Improving Walking in Peripheral Artery Disease

Peripheral artery disease (PAD) is a cardiovascular disease manifesting from systemic atherosclerosis that blocks the leg arteries and results in insufficient blood flow to the lower extremities. Limb ischemia from PAD is the most common disorder treated within the vascular surgical service of the Omaha Veterans Affairs Medical Center. PAD also accounts for one-third of the operations performed in the VA Medical Centers nationwide. The risk of mortality of Veterans with PAD is substantial; nearly 30% of Veterans with PAD died within 3.8 years of diagnosis. This project aims to establish the feasibility and acceptability of specially designed assistive shoes in patients with PAD and to determine if there are any potential benefits of using these shoes over standard shoes. These assistive shoes may enable patients to carry out desired activities of daily living with less pain and more physical activity. Increasing physical activity will decrease morbidity and mortality. If proven beneficial, the findings will lead to a novel and conservative rehabilitation protocol that directly benefits Veterans nationwide.

The long-term goal of this project is to improve mobility, functional independence, and quality of life in patients with peripheral artery disease (PAD) by using specially designed assistive shoes. PAD is a manifestation of systemic atherosclerosis producing blockages in the leg arteries, resulting in insufficient blood flow to the lower extremities. Limb ischemia from PAD is the most common disorder treated within the vascular surgical service of the Omaha Veterans Affairs Medical Center. PAD also accounts for one-third of the operations performed nationwide in the VA. Walking induced muscle pain known as intermittent claudication is the most common PAD symptom. Claudicating patients with PAD walk slower, have reduced quality of life and lose independence in performing activities of daily living. The investigators have identified consistent deficits of the ankle plantarflexors to effectively push-off during walking. Currently, there is a critical treatment gap for patients whose disease presentation does not warrant an operative approach, but who desire to restore their functional independence and walking ability. Specially designed assistive shoes (carbon fiber: CF; spring-loaded: SL) with specific mechanical properties to absorb and release energy, have been shown to promote push-off efficiency in walkers and runners. These shoes may lead to improved push-off in populations with reduced ankle push-off capacity, but this has not been tested yet. This work proposes to evaluate patient preferences in terms of using assistive shoes and whether these shoes improve walking performance in claudicating patients with PAD. The investigators hypothesize that assistive shoes (CF and SL) will lead to improved walking performance in patients with PAD as compared to standard shoes. The investigators also hypothesize that subject reported preference of assistive shoes (CF and SL) will be positive based on comfort, fatigue, ease of walking, and feasibility. These hypotheses will be tested by the following three specific aims:

Aim 1: Determine the acute improvement in walking performance (claudication walking distances, vertical ground reaction force, and muscle oxygenation) in patients with PAD while using their standard shoes versus the assistive shoes.

Aim 2: Determine the subject-reported preference of assistive shoes. Aim 3: Determine the progressive improvements in physical activity, quality of life, and walking distance after a three-month assistive shoe intervention.

Twenty patients with PAD will be recruited for Aims 1 and 2. For Aim 1, each subject will walk on a pressure instrumented treadmill while performing a progressive treadmill test with a near infrared spectroscopy sensor on the calf for each shoe condition: i) standard, ii) CF, and iii) SL. Walking performance will be evaluated in terms of claudication walking distances, vertical ground reaction force, and muscle oxygenation. All outcomes will be compared across these three types of shoes. Aim 2 will primarily focus on qualitative measurements of subject reported preference to identify whether assistive shoes are feasible for patients with PAD to use. Visual-analog scales, rate of perceived exertion, and interviews will be used to assess comfort, fatigue, intensity, and feasibility after each condition of Aim 1. Five patients from Aims 1 and 2 who are satisfied with CL and another five who are satisfied with SL, will be recruited for Aim 3. Patients will wear the assistive shoes of their choice for regular daily use for three months as a conservative intervention. Physical activity, quality of life, and walking distances will be assessed prior to the start of the intervention and after three months of intervention. Overall, the aims will demonstrate feasibility and acceptability of assistive shoes in patients with PAD. Results will support a full clinical trial, and guide necessary intervention length and potential rehabilitation recommendations.

Eligibility Criteria:
Inclusion Criteria:

At entry into the study, all patients must:

* be able to give written, informed consent
* demonstrate positive history of chronic claudication
* have an ankle brachial index \< 0.90 at rest
* have a stable blood pressure regimen, stable lipid regimen, stable diabetes regimen and risk factor control for 6 weeks

Exclusion Criteria:

Any potential subjects will be excluded if they have:

* rest pain or tissue loss due to peripheral artery disease (Fontaine stage III and IV)
* acute lower extremity ischemic event secondary to thromboembolic disease or acute trauma
* walking capacity significantly limited by conditions other than claudication including leg (joint/musculoskeletal, neurologic) and systemic (heart, lung disease) pathology