Causes and Risk Factors
Family history and genetics are risk factors that are non-modifiable. If a close relative has or had the disease, there is a higher chance of developing PAD, and the same goes for cardiovascular disease.
Diseases that cause abnormal thickening of the blood and plasma cell disorders can increase the risk of PAD as the blood becomes more viscous and is more likely to form blood clots. Diabetes is a major risk factor for PAD. Up to half of people with PAD have diabetes. High blood sugar levels associated with diabetes can damage the blood vessels and the nerves that control the blood vessels. High cholesterol and high lipid levels are also linked with PAD. High levels of LDL cholesterol can lead to build-up of cholesterol and other fatty materials in the arteries, and high triglyceride levels also increase the likelihood of atherosclerosis and blood clotting.
High blood pressure or hypertension can also be linked to PAD. The high force levels of blood flow can lead to damage of the blood vessels which in turn can promote atherosclerosis. Another possible cause of PAD is inflammation of the blood vessels. High levels of homocysteine, which is an amino acid normally found in the blood, can cause PAD by damaging the inner lining of the artery. The higher the levels of homocysteine within the blood, usually the more narrow the arteries.
Peripheral arterial disease (PAD) is caused by the hardening of the arteries due to the build-up of fatty materials such as cholesterol. A condition called atherosclerosis, which is characterized by the narrowing and hardening of the arteries, is most commonly associated with PAD. This narrowing of the artery lumen restricts blood flow to the muscles during activity. When muscles have to work harder for blood during exercise, symptoms of PAD often surface.
Effects on Daily Activities and Mobility
In studies of physician office patients with PAD, only half are still walking more than the distance that causes them pain. In more advanced PAD, patients must stop and rest one or more times to relieve cramping pain in the legs in an effort to improve walking function, and they may also need to stand still and flex the foot or sit down to obtain relief.
Patients with peripheral artery disease (PAD) develop limitations in walking due to the severity of the disease. The pain in the calf or thigh muscles that occurs during walking and is relieved by rest is a classic symptom of intermittent claudication. This symptom occurs in approximately half of patients with PAD. The most severely affected patients have ischemic pain at rest or may have a sore on the foot or toes that is slow to heal. These patients often have to reduce their normal daily activities and may ultimately require amputation of a lower extremity. Intermittent claudication results from muscle ischemia caused by an atherosclerotic stenosis of the arteries supplying the lower extremities. Patients describe the level and distance of pain-free walking that they can achieve before the onset of claudication, using terms such as one, two, or three blocks.
Walking and Exercise Limitations
Though claudicants can increase their pain-free walking time with regular exercise by participating in structured community walking programs, they find it difficult to do so because it is often necessary to trade transportative walking activity or work-related walking for exercise.
In a study to quantify the daily step activity in PAD patients, it was shown that patients with intermittent claudication ambulate less than healthy elderly individuals and have a much more pronounced reduction in ambulatory activity compared to patients with disabling medical conditions such as chronic obstructive pulmonary disease and congestive heart failure. Importantly, patients with claudication spend the majority of their day performing sedentary activities. Step activity is monitored using accelerometers, and in a different study, it was demonstrated that in patients undergoing peripheral revascularization, the improvement in walking ability was not always reflected in increased movement and exercise, but rather increased the intensity of pain-free walking. These findings suggest that PAD patients need to be educated about the importance of regular exercise in improving claudication and overall cardiovascular health.
PAD patients have limitations in walking, mobility, and exercise due to the onset of leg pain, which occurs with muscle activity and is relieved with rest – a symptom known as intermittent claudication. This restriction inevitably leads to a sedentary lifestyle with detrimental effects. Patients with intermittent claudication walk approximately less than half the distance of age-matched healthy controls. Treadmill walking distances in claudicants are significantly reduced compared to age-matched controls, and patients often report weakness and discomfort in the legs when walking. These limitations are not only attributed to the severity of lower limb ischemia but also to the patients’ perceptions of their illness and expected walking ability.
Impact on Work and Productivity
The use of clinical measures to determine employment capabilities in those with PAD is still quite limited. The 6-minute walk test has been used to predict mortality and cardiovascular events in patients with PAD and provides an indication of functional capacity. A measurement of walking speed has also been proposed, and a significant gait abnormality in itself can be related to a lower extremity functional limitation. Understanding a patient’s ability to perform work and the way in which their job may be affecting their health is an important step in measuring the impact of PAD on work and productivity.
PAD can impact an individual’s work and productivity in several ways. Pain and discomfort associated with walking, as well as the need to stop and rest, can affect those who are required to be on their feet for long periods. A study comparing 50 patients with Intermittent Claudication to matched controls without IC showed a 20% decrease in work hours per week in the patients with IC. Loss of working hours was attributed to leg pain and limitation in walking distance. Patients with limping and walking difficulties were also less likely to be working for financial gain compared to those without. Another study looking at employment status and working capabilities in 264 IC sufferers found that patients with IC had a significantly higher rate of unemployment, and half the patients reported becoming unemployed after the onset of IC. This was attributed to the fact that the functional loss of pain-free walking ability makes it difficult for patients to maintain employment, especially if their occupation involves manual labor. Having to stop due to leg pain during walking was also found to limit work performance in patients with IC.
Challenges in Performing Household Tasks
The provision of women with PAD reporting higher frequency of sedentary tasks to reduce lower limb leg pain is consistent with the traditional role allocation of housework occurring in many families. These barriers may prevent women from achieving preferred health-promoting activity levels, with detrimental consequences to rehabilitation and maintenance of health status. Although the relationships between activity make-up and health status in PAD populations are complex, any reduction in lower limb activity is likely to hasten functional decline. Participants identified several specific task-related barriers to housework occurring in individual rooms of the house.
The authors acknowledge the Social Model of Disability, which suggests that it is not the impairments of an individual that create disability, but rather the structure of society and the nature of its barriers (whether physical or attitudinal) which may exclude people with impairments from participation in everyday life. This model influenced our understanding of the data, which suggested that changes in housework activities were predominantly environmental and task-related, rather than related to personal changes in abilities.
There is little doubt that housework has been, at different times, the ultimate invention in labor-saving devices to reallocate labor from an unhealthful or less desirable task to a more healthful or desirable one. However, patients with disabilities may experience barriers in performing housework activities.
Management and Treatment Options
In those with PAD and comorbid conditions such as obesity, hypertension, and hyperlipidemia, aggressive medical management with control of these risk factors can be an effective means of improving functional status. A non-randomized trial was conducted to assess the effects of control of cardiovascular risk factors on the 4-year incidence of intermittent claudication and functional decline in 519 patients with PAD and abnormal distal pulse examination without limb-threatening ischemia. Patients who achieved four or more guideline-based risk factor targets had a 67% lower rate of new onset claudication and a 36% lower rate of functional decline compared to those who did not achieve any of the targets. This evidence suggests that control of cardiovascular risk factors can prevent functional decline in PAD.
As compared to patients with other cardiovascular diseases, those with PAD have been shown to have greater long-term improvement in functional status with changes in lifestyle. The Walking and Leg Circulation Study was a randomized trial comparing a home-based walking exercise program with supervised treadmill exercise and resistance training versus usual care in patients with PAD. After six months, patients in both exercise groups demonstrated significant improvements in treadmill walking distance and physical activity. The improvements in walking ability were associated with reductions in major mobility disability, and a two-year follow-up demonstrated sustained benefits of the exercise intervention. A subsequent study examined the effects of a home-based walking exercise program compared to endovascular revascularization on treadmill walking performance and functional status. After six months, patients in both treatment groups demonstrated similar significant improvements in walking performance and physical activity; however, those in the endovascular group experienced greater improvements in walking-specific quality of life.
A comprehensive management and treatment plan for peripheral arterial disease (PAD) consists of two major components: relief of symptoms with improvement in functional status, and prevention of cardiovascular events. The medical and revascularization treatment options outlined above are largely aimed at symptom relief and may not lead to substantial improvements in functional status. Conversely, lifestyle changes aimed at risk factor modification have been shown to improve functional status and possibly delay symptom progression of PAD.
Medications and Lifestyle Changes
As stated by Hirsch et al. (2006), the initial approach to patients with claudication due to PAD has been largely based on knowledge about modifying risk factors for atherosclerosis. Thus, advances in medical management of claudication have often drawn on experiences from trials in coronary artery disease and stroke patients. The goal of medical treatment of claudication is to improve functional capacity by increasing pain-free walking time, not total walking time, and to reduce the risk of cardiovascular events and death. A review by Olin and Sealove (2006) neatly summarizes current and emerging options for management. They state, “The medical management of patients with symptomatic PAD is best accomplished through a global reduction in cardiovascular risk combined with a systematic approach to improving walking distance…”. Although most medications used in the management of PAD do not specifically target the cause of claudication or functional limitation, aggressive cardiovascular secondary prevention with antiplatelet agents, statins, and ACE inhibitors is the primary therapeutic measure. High-dose statin therapy has been demonstrated to significantly improve treadmill walking distance, and reports from small studies suggest reductions in claudication symptoms and improved ankle-brachial pressure indices (ABPI). Supervised walking exercise and cilostazol are the only treatments proven to be superior to placebo for relief of claudication in limb and patient-oriented outcomes, but many patients are unable to access supervised exercise programs due to comorbidities or health service constraints. In this case, home-based exercise is an effective substitute and perhaps more cost-effective. Although the SCOT trial demonstrated that cilostazol is superior to clopidogrel for relief of intermittent claudication, there are concerns about cardiovascular safety and side effects of cilostazol (particularly in elderly patients) with an increase in all-cause mortality reported in the CSPS trial. A recent RCT and meta-analysis has provided evidence for the use of niacin in improving ABPI and total walking distance in PAD patients, and there is increasing interest in the effects of Rho kinase inhibitors on PAD. However, further studies are needed to explore the efficacy of these medications for claudication compared with existing treatments.
Surgical Interventions
Surgical interventions, such as angioplasty and surgery to bypass the blockage and improve blood flow, are often recommended for people with PAD. Angioplasty uses a small catheter with a balloon on the end to open or widen the blood vessel where it is narrowed or blocked. The catheter is guided to the blocked site and the balloon is inflated to flatten the plaque against the wall of the artery in this section. A vascular surgeon or interventional radiologist uses a catheter to conduct a minimally invasive procedure in which a small incision is made and a thin tube called a catheter is inserted into the artery and guided to the blockage. The surgeon will make a graft bypass using another blood vessel from another part of the body or a synthetic vessel to enable proper blood flow. This surgery is mostly conducted for blockages in the iliac artery or the arteries above the knee. These surgical procedures are useful ways to re-establish proper blood flow to the extremities, thus alleviate ischemic symptoms.
Rehabilitation and Physical Therapy
Pedometers, accelerometers, and other step activity monitoring devices can also be effective motivational tools to encourage progressive increase in physical activity and decrease in sedentary time in people with claudication. High-intensity strength training has also been shown to be beneficial for pain-free and maximum walking times, but can result in muscle soreness and damage for up to 3 days and be discouraging for some people with intermittent claudication. Aerobic exercise, especially interval training, has the most consistent effects on walking distances and may protect against decline in walking ability, but studies have shown it to be less effective if the patient does not reach exercise-induced leg ischemia. Patients are advised that discomfort during exercise sessions is not harmful and if past pain thresholds are maintained, there should be a subsequent increase in walking times over the following hours to days.
Supervised exercise therapy usually involves a 3-month program of regular treadmill exercise with walking to near maximal claudication pain maintained by the instruction to walk through the pain until they are unable to continue and have to rest. This is followed by mobilization to supervised treadmill walking up to 5 days per week for the patient. This better improves pain-free and maximal walking distances than unsupervised exercise rehabilitation. Alternate exercise therapies such as resistance training and upper body ergometers have also been evaluated and shown to be beneficial for people with intermittent claudication in small trials.
Exercise can be a very effective way of increasing an individual’s walking distance. Regular exercise increases the distance one can walk before pain forces them to stop. It also increases the time before the onset of pain during a fixed distance. Exercise could be less painful for people with intermittent claudication if they increase their walking distance at a slower pace. Supervised exercise programs could lead to more effective outcomes in increasing the pain-free walking distance. Although people with intermittent claudication may be reluctant to take up exercise due to the pain it causes in the short term, in the long term it offers the best way to manage and improve their condition.
