The prevalence of peripheral atherosclerosis, commonly referred to as peripheral arterial disease (PAD), is estimated to affect over 8 million adults in the United States.1 According to the National Heart Lung and Blood Institute, it affects 5% of adults over 50 years of age and 20% of adults over 65 years of age.1 Early detection and diagnosis of atherosclerotic disease is imperative as cardiovascular disease is the main cause of mortality in developed countries. Atherosclerotic disease is the culprit of 40% of deaths in both men and women.2 Although race and ethnicity are not independent risk factors for PAD, the disease has a higher prevalence in certain groups including Blacks and people of Hispanic origin.3 PAD occurs equally in men and postmenopausal women, but men are more likely to have symptoms.4
PAD is usually not considered immediately as the cause of leg pain in the elderly. It can go undiagnosed for long periods of time, which worsens the associated disease processes.5 Patients with undiagnosed PAD may suffer poor outcomes including cardiovascular events such as myocardial infarction or stroke, nonhealing lower extremity wounds, and amputations.
Pathophysiology and clarification of terms
Atherosclerosis, which falls under the umbrella term, "arteriosclerosis" (abnormal thickening and hardening of the arterial walls), is a progressive condition characterized by the buildup of fatty plaques in the inner linings of the artery walls. It is a systemic disease of multifaceted etiology. Hypertension, hypercholesterolemia, diabetes mellitus, and smoking are modifiable risk factors. Age and sex are nonmodifiable risk factors.2 Occlusive PAD of the lower extremities accounts for 85% to 90% of all PAD.6 These fatty deposits restrict the blood circulation going to the legs and feet creating vascular problems such as nonhealing wounds (see Major lower limb arteries).
Peripheral vascular disease (PVD) is a general term used to include all of the noncardiac conditions that can affect circulation outside of the heart and brain, including PAD. It is characterized by narrowing of the vessels that carry blood to the legs and arms. Causes can be venous, arterial, or lymphatic in nature. Examples of venous PVD includes deep vein thrombosis, varicose veins, and chronic venous insufficiency. Lymphedema is an example of PVD that affects the lymphatic vessels. PAD includes peripheral artery atherosclerosis, Buerger's disease, Raynaud's phenomenon, and thromboembolic disorders. Even though the term PAD has a much more specific meaning, the terms PVD and PAD are often used interchangeably. Other causes of PVD include trauma, irregular anatomy of muscles or ligaments, and infection.5
It is estimated that approximately one-third of patients with PAD present with intermittent claudication.7 Intermittent claudication is typically characterized by pain or cramping in a single lower extremity brought on by walking or exercise and relieved by rest. The pain typically localizes distal to the occluded artery. Therefore, a femoral or popliteal artery occlusion would manifest as calf claudication. The gastrocnemius muscle uses the highest amount of oxygen during exertion, which explains why this is the most common location for claudication to present. This pain usually limits exertional efforts.7,8
Some patients with PAD may present with no signs or symptoms.2 This is especially true for sedentary patients. Therefore, the primary care provider must initiate screening for patients at risk for PAD (see Signs and symptoms of PAD).
Other conditions may mimic intermittent claudication. Venous obstruction and lumbosacral nerve root pain should be ruled out (see Differential diagnosis of lower extremity pain). The primary care provider should obtain a detailed history of the precipitating factors. The intensity of the exercise at which the pain begins will help to classify the severity of the condition. It is important to recognize that ischemic leg pain at rest suggests total occlusion of the artery and should be urgently referred to the ED. Anticoagulation or revascularization may be able to save the extremity.7
The Trans-Atlantic Inter-Society Consensus (TASC) is an international task force that recognizes PAD as a growing healthcare concern. The TASC uses evidence-based research to provide an international consensus on the diagnosis and treatment of PAD.9
The TASC defines increased risk for PAD as the presence of one of the following:
- Patients with diabetes and one additional risk factor (smoking, dyslipidemia, hypertension, or homocysteinemia)
- Age 50 to 69 years with history of smoking or diabetes
- Age 70 years and older
- Abnormal lower extremity pulses
- Leg symptoms with exertion or ischemic rest pain
- Known coronary, carotid, or renal atherosclerosis.9
Screening and diagnosis
Once the primary care provider identifies a patient at risk for PAD, a thorough physical exam should be performed including palpation of pulses and auscultation for bruits.8,10 Diminished pulses and audible bruits have been found to be indicators of PAD. Careful inspection of the skin and connective tissue is also important. Poor circulation can lead to skin and muscle breakdown, including changes in color and temperature, nonhealing leg ulcers, brittle nails, hair loss of the affected extremity, and muscle atrophy.7 In addition, ankle/brachial index (ABI) measurements should be used for screening.8,11 Taking ABI measurements is a simple, relatively inexpensive, noninvasive procedure that can initially be performed in the primary care office. However, diagnostic ABI measurements require a Doppler and a certain level of technical skill; therefore, patients are usually referred out of office for this procedure.12
Oscillometric (non-Doppler) systolic measurements are reliable in the exclusion of PAD;13 however, Doppler ABI measurements can provide highly specific diagnostic information. Both Doppler and non-Doppler ABI measurements involve dividing the brachial systolic blood pressure into the systolic blood pressure of the ankle. Using both methods, the brachial blood pressure is obtained, inflating the pneumatic cuff and auscultaing for Korotkoff sounds.12 This is done twice and the higher of the two systolic values is used. The inflatable cuff is also used in obtaining the pressure in the lower extremity. However, using the Doppler ABI method, the pulse is auscultated using the Doppler probe in the areas of the posterior tibial and dorsalis pedis arteries. The systolic pressure is obtained twice in each of these two areas. The highest of the four readings is the numerator in the equation.7
Example ABI (ratio of systolic BP [SBP] in the ankle divided by the systolic BP in the arm):
This is categorized as moderate PAD and would warrant a referral.
Normal ABI measurements are between 1.0 and 1.3. Values above or below this range are considered abnormal (see Interpretation of ankle-brachial index). A value greater than 1.3 indicates calcification of the artery. Using the Doppler ABI method, a value below 0.9 has 95% sensitivity and close to 100% specificity for detecting PAD.7 With this degree of accuracy, verifying the diagnosis with angiography is usually not necessary.9
Management and treatment
Patients with PAD constitute a high-risk population. According to current cardiovascular risk stratification guidelines from the National Cholesterol Education Program Adult Treatment Panel report (ATP III), PAD is a coronary heart disease equivalent. PAD indicates a risk for major coronary events equal to that of established coronary heart disease: 20% per 10 years.14 Management of PAD in the primary care setting is focused on risk factor modification, lifestyle modification, prompt referral to cardiology and/or a vascular specialist, and pharmacologic therapy. The goals of treatment for PAD are to reduce cardiovascular morbidity and mortality and to improve quality of life by improving the patient's functional status and decreasing symptoms.7
Risk factors for PAD that must be addressed include diabetes, hyperlipidemia, hypertension, smoking, and age. Effective control of blood glucose levels has been shown to reduce the risk of microvascular complications.7 Optimizing treatment for hyperlipidemia with lipid-lowering drugs, primarily HMG-CoA reductase inhibitors (statins), has demonstrated increased benefit in claudication symptoms, walking ability, total walking distance, and leg functioning.14 In addition, lipid-lowering therapies with diet as well as pharmacotherapy reduce the progression of PAD. Lowering blood pressure to goal (less than 140/90 mm Hg for nondiabetic patients and less than 130/80 mm Hg for patients with diabetes) with angiotensive-converting enzyme inhibitors, beta-blockers, and other antihypertensive therapy reduces the risk of major cardiac and cerebrovascular diseases in patients with PAD.7,14
Lifestyle modifications should address smoking and exercise. Smoking cessation via primary care provider advice, nicotine replacement therapy, and bupropion should be strongly encouraged.8,14 There is evidence to show that quitting smoking can slow disease progression and reduce PAD symptoms. Exercise programs are also recommended as first-line treatment for patients experiencing claudication. Supervised exercise programs have demonstrated an increase in pain-free walking distance by 180%. In addition, patients who participated in these programs increased their walking time and walking distance. The benefits from exercise were derived from the formation of collateral blood supply, improved nitric oxide-dependent vasodilation, muscle metabolism, and decreased markers of systemic inflammation.15 An exercise goal of 30 minutes, three times a week for 6 months has been shown to improve walking efficiency.7 Because age is a nonmodifiable risk factor for PAD, the elderly will remain at risk. Overall, risk factor modification and control are effective forms of prevention.
Patients who have been screened for PAD and have an ABI of less than 0.90 and greater than 1.3 should be referred to cardiology and/or a vascular surgeon. Imaging tests useful in the diagnosis of PAD include ultrasound, magnetic resonance angiography, and computed tomographic angiography,4,8,11 although angiography may be reserved for those with advanced disease who are considering surgical intervention. Surgery and percutaneous interventions include peripheral catheter-based and endovascular interventions as well as surgical revascularizations.
Pharmacologic therapy reduces symptoms and slows the progression of the disease.7 Currently, only two drugs are FDA-approved for the treatment of intermittent claudication in PAD: pentoxifylline and cilostazol. Antiplatelet therapy with aspirin (75 to 325 mg) is recommended in patients with PAD as it reduces mortality in individuals with cardiovascular disease by 25%.14 Clopidogrel is more effective than aspirin in reducing the combined risk of ischemic stroke, myocardial infarction, or vascular death.7 Studies have shown that patients with PAD receive less intensive pharmacologic therapy compared to coronary heart disease patients despite evidence that it improves cardiovascular outcomes in PAD patients.16
Signs and symptoms of PAD5
- Shiny skin with hair loss
- Thickened, brittle toenails
- Extremity cool to touch
- Color pale on elevation and dusky red with dependency
- Decreased or absent lower extremity pulses
- Presence of bruit (aorta or femoral artery)
- Muscle atrophy in affected extremity
- Ulceration (generally involves the toes or areas of injury)
- Gangrene (severe sign)
- Pain with activity that is relieved with rest (intermittent claudication)
- Numbness of lower extremity
- Complaint of erectile dysfunction
1. National Heart Lung and Blood Institute. (2008). What is PAD?
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