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Acute limb ischemia secondary to thrombosis or embolism is a true medical emergency requiring immediate therapy for limb salvage. The term critical limb ischemia is used when chronic progressive peripheral arterial disease results in ischemic pain at rest, ulceration, or gangrene. Despite improvements in the management of peripheral arterial disease, current 1-year mortality after the onset of critical limb ischemia is in excess of 25%, and 25% of survivors require amputation.1,2 Diagnosis of acute limb ischemia is based primarily on findings of a detailed history and physical examination. Upon diagnosis, urgent involvement of both the radiologist and vascular surgeon is required in order to confirm the diagnosis and initiate treatment to restore blood flow to the affected limb. For a rapid and reliable diagnosis, a thorough understanding of the pathophysiology, etiology, and clinical presentation of occlusive arterial disease is required and can help guide management decisions.

According to the National Health and Nutrition Examination Survey (NHANES) data for 1999 to 2000, the prevalence of peripheral arterial disease (defined as an ankle-brachial index of <0.9) in the U.S. is 4.3% for those aged >40 years and 15.5% for those aged >70 years.3 The Peripheral Arterial Disease Awareness, Risk, and Treatment: New Resources for Survival (PARTNERS) study assessed the prevalence of occlusive arterial disease in high-risk populations—those aged >70 years and those aged >50 years with diabetes or a smoking history—and found the prevalence to be >29%.4

With objective noninvasive testing, peripheral arterial disease has been reported in 11% to 27% of elderly men and women, with both sexes affected equally.5

Symptoms of this disease increase with age and are two to four times more common in men than in women. Most of these patients have a long history of smoking, and it has been reported that >80% of patients with occlusive arterial disease are either former or current smokers.6 Other risk factors include diabetes, hyperlipidemia, hypertension, hyperhomocysteinemia, and an elevated C-reactive protein level. Of all the known risk factors for occlusive arterial disease, smoking and diabetes are pathophysiologically the most important. Between 40% and 60% of patients with occlusive arterial disease have either coronary or cerebrovascular disease.7 The severity of peripheral vascular disease is closely linked to the risk of myocardial infarction, ischemic stroke, and death from vascular disease.5 The most frequently diseased arteries leading to limb ischemia are, in order of occurrence, the femoropopliteal, tibial, aortoiliac, and brachiocephalic vessels.

Acute limb ischemia results from a lack of blood supply to meet tissue oxygen and nutrient requirements. As time proceeds, the depletion of oxygen and nutrients from the cellular microenvironment will ultimately lead to cell death and irreversible tissue damage. Peripheral nerves and skeletal muscle are more sensitive to ischemia, and irreversible changes occur in these tissues within 6 hours of anoxia at room temperature, likely due to differences in cellular respiration and oxygen requirements.

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