Peripheral artery disease (PAD) refers to varied pathologies such as atherosclerosis and vasculitis involving the peripheral circulation separate from cardiac and cranial arteries and affects more than 8.5 million Americans and 200 million people worldwide.¹ It occurs commonly in conjunction with CAD. Unfortunately, it is all too frequently underdiagnosed and untreated,² resulting in potentially avoidable lower limb amputations, myocardial infarctions, and cerebral vascular accidents. Individuals with symptoms and signs of PAD have an increased risk for heart disease and stroke³ and must be encouraged to seek medical attention for evaluation and ruling out of associated cardiovascular disease. According to the American Heart Association, individuals with PAD have four to five times’ greater risk for myocardial infarction and a cerebral vascular accident because atherosclerosis is a disease of the entire cardiovascular system. Nearly a quarter of individuals with claudication due to PAD will die within 5 years because of a myocardial infarction or stroke. Interestingly, patients with documented PAD have a 1 year higher incidence of fatal myocardial infarction than those with preexisting CAD.⁴

Appropriately, the patient diagnosed with PAD should be screened for CAD, and, conversely, the patient diagnosed with CAD should be screened for PAD. Kowantor et al.⁵ reported that 26% of 1,340 patients with documented CAD presented with undiagnosed PAD. Arterial fatty plaque buildup in vessels of patients with atherosclerosis reduces the flow of blood in the lower extremities and feet, and at a critical threshold, ischemic-related signs and symptoms will begin to manifest. Progression of untreated disease may ultimately reach a point of critical limb ischemia, which all too frequently results in loss of limb or ultimately life. The lower extremity signs and symptoms are generally subtle at first but eventually become obvious and ultimately debilitating. Unfortunately, the underlying systemic atherosclerotic disease may be previously unrecognized, resulting in serious comorbidities in the heart, brain, kidney, and other internal organs. Well-established risk factors for CAD and stroke such as family history, hyperlipidemia, hypertension, diabetes, and smoking likewise increase one’s risk for PAD.

The main symptoms of PAD may include, in proportion to disease severity, claudication, fatigue, achiness, burning, and discomfort in the buttocks, thighs, and calves. Erectile dysfunction may also result. These symptoms first appear during extensive walking or exercise, and disappear after several minutes of rest. As the PAD progresses, symptoms will occur with less exercise or activity and with an earlier onset. Claudication pain may be likened to symptoms of angina seen in patients with CAD. The most commonly utilized system to classify intermittent claudication and lower extremity ischemia is the Rutherford classification, which is divided into seven stages (see Table 3-1).⁶ Lower extremity ischemia leading to extremity numbness or intense pain at rest with ultimate tissue necrosis has been informally referred to as a heart attack of the foot. These symptoms frequently intensify with elevation of the limb, and it is not uncommon to observe the patient maintain the affected limb(s) in a position of dependency. The presence of pain at rest can be classified as a situation of critical limb ischemia where some type of intervention is urgently or emergently necessary to prevent necrosis of tissue and potential loss of limb.

Clinical findings consistent with PAD include decreased posterior tibial (PT) and/or dorsalis pedis (DP) blood pressure, weak or nonpalpable pulses, arterial bruits, increased capillary fill time, dermal atrophy, coolness of the skin, increase in temperature gradient, lower extremity hair loss, pallor on elevation, or cyanosis. The end-stage critically ischemia limb will frequently manifest dependent edema and a ruborous-like
hue resulting from the chronically dilated microvascular structures. The development of nonhealing ulcers or frank gangrene is further evidence of critical limb ischemia requiring urgent or emergent intervention (Fig. 3-1).

Noninvasive testing for PAD includes the ankle-brachial index (ABI), which is a painless office-based examination that compares the ratio of blood pressure in the distal lower extremity to that in the upper extremity. This inexpensive test takes only a few minutes and can easily be performed by the health care professional. Guidelines of the American College of Cardiology and American Heart Association recommend its use for screening individuals at high risk such as those over 65 years old or over 50 years old in diabetics or smokers.⁴ The appropriate method to measure ABI is to have the patient lying flat, with Doppler measurements obtained following 5 to 10 minutes of rest.⁷ Cuff width should be at least 40% of limb circumference. Systolic blood pressure (SBP) is measured in each arm and ankle including the DP and PT arteries. ABI of each leg is then calculated by dividing the higher of the PT or DP pressure by the higher of the right or left arm SBP (Fig. 3-2).

Normally, the ankle blood pressure is at least 90% of the upper extremity pressure; with severe arterial narrowing, the ankle pressure may be reduced to less than 50%. Low ABI has been established as an independent risk factor of CAD.⁸,⁹,¹⁰ Conversely, Allison et al.¹¹ showed that an abnormally high ABI (which is due to inelasticity of the arterial wall secondary to plaque buildup) is also associated with increased risk of CAD. The test can also be performed postexercise on a treadmill to better detect milder disease.

If the ABI is abnormal in the presence of symptoms, further testing is generally indicated to better evaluate the magnitude and precise location of the disease. Segmental pressures, pulse volume recording, ultrasonography in conjunction with Doppler imaging (duplex scan), and transcutaneous oximetry are other noninvasive techniques that evaluate arterial flow and/or tissue perfusion. Segmental pressures or sound waves measuring the blood flow in an artery can indirectly indicate the extent and location of a blockage. Computed Tomography and magnetic resonance angiography are additional noninvasive techniques demonstrating the extent of the disease. Invasive testing including angiography is the most specific test for determining the specific location and severity of occlusive lesions. Intravascular ultrasound is a newer technique that can image directly a blockage without subjecting the patient to radiographic dyes. This is beneficial in patients with allergies or renal disease.

The management of early PAD is centered on goals of reducing risks of further progression of atherosclerosis and most notably lessening the incidence of acute coronary syndromes and cerebral vascular accidents. With respect to the
lower extremity disease, the goal is to improve function and preserve the limb itself. Accordingly, cardiovascular risk factors such as hypertension, hyperlipidemia, and hyperglycemia must be controlled. Lifestyle modifications including smoking cessation and supervised exercise programs are also essential. The use of antiplatelet agents must be weighed against the risk of increased bleeding. Revascularization procedures are indicated for limb salvage in patients with activity-altering claudication, ulcerations, or gangrene. They are also indicated in patients who have failed medical management and lifestyle modifications where the procedure can reasonably be expected to result in increased functionality. In addition to classic open surgical bypass procedures, the trend has been decidedly toward endovascular interventions including angioplasties, atherectomy, bare metal and drug-eluting stents, and, most recently, drug-eluting balloons. Appropriate cardiac interventions are also frequently required where indicated.

Although generalized atherosclerosis is associated with poor long-term prognosis, the early identification and intervention can improve both quality of life and longevity.