Peripheral arterial disease

Diagnosis

See chart, "Differential Diagnosis of PAD," from PIER's module on peripheral arterial disease.

The most common initial complaint in patients who are symptomatic is exertional lower-extremity cramping relieved by rest. PAD also presents as diffuse limb pain, fatigue, or weakness. Since many older patients lack awareness of PAD, including its indicators and its significant associated disability, ask patients specifically about the following symptoms:

• leg fatigue with ambulation,
• leg pain with ambulation, including classic claudication,
• leg numbness at rest and with ambulation,
• constant leg pain, particularly in the forefoot,
• impotence,
• nonhealing ulcers, and
• cool distal extremities.

If there is pain, ask about its specific site. The claudication site can serve as a rough guide to corresponding location of ischemia in the following manner:

• buttock and hip claudication corresponds to aortoiliac,
• thigh to common femoral artery or aortoiliac,
• upper calf to superficial femoral artery,
• lower calf to popliteal artery, and
• foot to tibial or peroneal artery.

Palpate for the presence or absence of peripheral pulses, particularly the brachial, femoral and pedal arteries, and auscultate the abdominal aorta and femoral arteries for bruits in all at-risk patients. Inspect legs and feet for skin color changes, ulceration and signs of infection. Bruits, ulcers between or on the tips of the toes, hair loss on the legs or dry skin can raise suspicion, but are not specific to PAD.

Calculate ABI to confirm a diagnosis of PAD and ascertain its severity. A normal ABI is 1.0 to 1.3, and an ABI below 0.9 has 95% sensitivity and 100% specificity for detection of a greater than 50% angiographic stenosis of a major vessel. An ABI lower than 0.4 indicates severe ischemia and has been associated with a midterm mortality rate as high as 25%. An elevated ABI (>1.6), which indicates a calcified, noncompressible vessel, is also associated with an increased mortality risk.

Darkened skin and blood blisters on the toes and top of a foot caused by ischemia

Order the following ABI and imaging studies from an Intersocietal Commission for the Accreditation of Vascular Laboratories (ICAVL)-accredited laboratory:

• Segmental pressure and waveform analysis for patients with moderate (ABI <0.59 to >0.40) to severe (ABI <0.39) PAD,
• Exercise or stress ABI in patients with claudication symptoms but an ABI >0.90,
• Digital subtraction arteriography of limbs in patients with indications for intervention. This remains the gold standard.
• Magnetic resonance arteriography for patients with contrast allergy or at high risk for contrast nephropathy, and
• CT angiography for patients who have prohibitive arterial access sites, and for interventional planning for suspected aortoiliac arterial disease.

Because MRA and CT angiography are more variable than DSA, determine the level of expertise of the providers who will perform these imaging techniques.

If ABI is normal, but a patient exhibits symptoms of claudication, order an exercise protocol ABI. An ABI that decreases by 20% following exercise indicates PAD, while a normal ABI following exercise suggests another cause for the patient’s symptoms. This is sensitive particularly for aortoiliac stenosis. Other, nonarterial causes of extremity pain include deep venous thrombosis, musculoskeletal disorders such as fibromyalgia or polymyalgia rheumatica, peripheral neuropathy, osteoarthritis, degenerative disc disease, venous insufficiency, popliteal entrapment syndrome, chronic exertional compartment syndrome and spinal stenosis. Buerger’s disease (thromboarteritis obliterans) is a rare variant of PAD characterized by aggressive arteriolar occlusion in male smokers.

Since patients with PAD also may have concomitant systemic diseases, such as anemia, hypertension, diabetes and renal impairment or an underlying hypercoagulable disorder, order the following blood studies in eligible patients with newly diagnosed PAD:

• Complete blood count,
• electrolytes,
• creatinine,
• coagulation panel (protime, activated partial thromboplastin time, platelets),
• urinalysis to evaluate for renal, glucose or hematologic abnormalities
• glycosylated hemoglobin (HbA1C) and
• lipid panel.

For patients under age 50 and those with unexplained failed bypasses, consider testing for hypercoagulable disorders, including hyperhomocystinemia, activated protein C resistance and Prothrombin 202010A.

If a patient needs additional diagnostic testing because symptoms suggest PAD, but ABI is normal, consult a vascular specialist.

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• Feb 2010
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