Promoting Exercise Therapy in Peripheral Artery Disease: Time to Get Moving

We are at an exciting time in the management of patients with peripheral artery disease (PAD). The access to exercise therapy is rapidly expanding due to several important developments. Though the persistent advocacy efforts of the American Heart Association (AHA) and many others including the late Dr. Alan Hirsch, the Centers for Medicare and Medicaid Services (CMS) made a national coverage decision for supervised exercise therapy (SET) for patients with PAD and claudication in 2017.¹ Innovative approaches to deliver exercise interventions that use new wearable technologies offer home-based therapies. The AHA scientific statement “Optimal Exercise Programs for Patients with Peripheral Artery Disease” provides a detailed overview of the available evidence that forms the basis for current programs and the research areas that will advance this field.²

Patients with PAD suffer from leg pain and disability that lowers quality of life. A key treatment goal for patients with PAD is improving walking capacity to preserve function. Patients with PAD have increased rates of functional decline even in the absence of classic claudication symptoms.³ The presence of walking limitation is associated with poor clinical outcomes across multiple domains. The benefits of SET in patients with PAD and claudication have been well-established for decades. The 2016 AHA/ACC Guidelines for the management of patients with lower extremity PAD give SET a Class I recommendation based on randomized clinical trial data demonstrating an improvement in functional outcomes.⁴

The benefits of exercise therapy for patients with PAD derive from an array of physiologic changes. A combination of blood flow limitation, alterations in vascular function and skeletal muscle dysfunction contribute to leg symptoms and functional impairment in patients with PAD. Reactive oxygen species and inflammation alter calf muscle structure and function characterized by mitochondrial dysfunction.5 Exercise therapy does not change ankle brachial index but augments walking capacity through a diverse set of mechanisms including reducing inflammation, improving endothelial function, and enhancing skeletal muscle function.⁶ It is promising to consider that further research into the pathways leading to improved function with exercise could identify additional therapies that would augment the exercise effect.

Several approaches have been used in the research setting to measure the benefits of exercise therapy in PAD. Treadmill based performance measures are commonly employed and permit objective, comparable assessment. However, several complementary approaches including the six-minute walk test and wearable activity monitors may reflect more accurately functional capacity in daily life.⁷ Validated questionnaires are available to determine self-reported walking ability and quality of life that complement objective walking based measures.⁸ Efforts are currently ongoing to develop patient-centered outcomes across the spectrum of clinical PAD including claudication and critical limb ischemia. These functional and patient-reported outcomes are an essential component to assess PAD therapies including revascularization approaches.

The statement reviews the available evidence for the optimal design of an effective SET program. Though there is an importance of individualizing the program to match the patient, several key elements are emphasized. Progressive exercise sessions should have the goal of achieving 30-45 minutes of treadmill walking with an intensity to induce mild claudication at 5 minutes and moderate claudication at 10 minutes and typically occur three times per week for at least 12 weeks. Following SET, a maintenance exercise program extends the benefits.

There is been considerable focus on the question of choosing between exercise therapy and revascularization for patients with PAD. However, available evidence supports a multi-faceted treatment strategy for claudication. Use of SET is recommended as initial therapy.⁴ Studies comparing SET with revascularization for claudication symptoms indicates that both approaches enhance functional capacity in patients with aortoiliac and/or femoral-popliteal occlusive disease and that the two therapies have additive benefits.^9,10 Thus, in select patients, revascularization may be used to augment the effects of SET. In all intervention studies for patients with claudication, functional assessments should be included as measures of therapeutic efficacy.

The recent coverage decision by CMS is an essential step forward, but challenges still exist in getting patients with PAD to exercise programs. The burden of traveling to the exercise facility three times a week limits participation and drop out related to discomfort with exercise limits efficacy.¹¹ Home-based exercise programs hold promise to offer an alternative potentially less burdensome approach. It is well-established that simply telling patients to go home and exercise is not effective. However, several studies indicate that structured home-based exercise interventions increase walking ability particularly programs that incorporate behavioral coaching and some visits to a center.¹² Based on these trials, the AHA/ACC 2016 guideline give home-based exercise a Class IIa, Level of Evidence A recommendation as a reasonable intervention for patients with PAD.⁴ In the SET setting, alternative approaches to traditional treadmill programs may benefit selected patients including pain-free walking, leg cycling, and arm aerobic exercise. These alternative strategies have a Class IIa, LOE A recommendation that they may be beneficial to improve functional status in patients with claudication.⁴

Exercise therapy is of proven benefit for patients with PAD and now it is available to so many more patients through CMS coverage. The critical next steps are increasing implementation through creation of more clinical SET programs, encouraging patient participation, and developing approaches to deliver effective exercise interventions in the community. Identification of patients with PAD requires improved awareness in our patient and caregiver communities. The AHA has launched several awareness and education campaigns including ‘Top 3 Reasons to Take Your Socks Off,’¹³ a PAD Toolkit¹⁴, and inclusion of a PAD patient advocate in the Go Red for Women campaign.¹⁵ It is time to get our patients with PAD exercising and this statement provides a scientific map for program development and a concept of the future in this field.