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Tuesday, March 29, 2011

Arterial ischemia

A 72-year-old man is evaluated in the office for bilateral leg pain and cramping after walking briskly up an incline. The pain is in the distal thigh and calf and is worse on the right side. He has no pain when walking downhill. The patient has a 100-pack-year smoking history, type 2 diabetes mellitus, hypertension, and heart failure. His medications are captopril, furosemide, atenolol, atorvastatin, metformin, and aspirin.

On physical examination, the blood pressure is 146/68 mm Hg and heart rate 82/min and regular. The lungs are clear. Cardiac examination reveals an S4. There is a right femoral artery bruit with absent pulses and mild dependent rubor. Ankle-brachial index is 0.8.

Which of the following is the most likely cause of this patient's symptoms?
A Arterial ischemia
B Osteoarthritis
C Peripheral neuropathy
D Right popliteal venous thrombosis
E Spinal stenosis

Key Points

* Most patients with peripheral vascular disease have an ankle-brachial index (ABI) <0.9, and those with severe disease (rest ischemia) have an ABI <0.4.
* An ABI >1.3 indicates vascular calcification.

Answer and Critique (Correct Answer = A)

The patient's history of exercise-induced leg pain, its relief with rest or walking downhill, vascular bruit and absent pulses on physical examination, dependent rubor, and several major risk factors for atherosclerotic artery disease all point to arterial ischemia as the cause of his symptoms. Determination of the ankle-brachial index (ABI) is a common initial test in the evaluation for peripheral vascular disease. With a Doppler probe, the ABI is measured as the ratio of the highest right/left dorsalis pedis/posterior tibial artery systolic pressure divided by the highest right/left brachial artery systolic pressure. A normal ABI is 1.0 to 1.3. Most patients with peripheral vascular disease have an ABI <0.9, and those with severe disease (rest ischemia) have an ABI of <0.4. An ABI >1.3 suggests a calcified, noncompressible vessel, most commonly seen in patients with long-standing diabetes mellitus and hypertension.

Peripheral neuropathy would be unlikely to present as pain with exercise. Spinal stenosis commonly presents as pain with standing and after walking a variable distance, most prominently with spinal extension, and is usually relieved by flexing forward, sitting, or lying down. Like spinal stenosis, osteoarthritis may cause pain on walking but is usually independent of grade; neither condition can account for the patient's other findings including bruit, diminished pulses, dependent rubor, and abnormal ABI. Popliteal venous thrombosis may present with localized pain and erythema, but the pain would not be exertional and cannot account for bilateral pain or the physical examination findings.

1. Khan NA, Rahim SA, Anand SS, Simel DL, Panju A. Does the clinical examination predict lower extremity peripheral arterial disease? JAMA. 2006;295:536-46

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