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Chronic ischemia of the lower extremities is extremely prevalent in Western societies and accounts for a significant amount of morbidity and mortality. Atherosclerosis, although not the only cause of chronic lower extremity ischemia, is, by far, the most common. Together with critical ischemia of the heart, brain, and abdominal organs, atherosclerotic peripheral vascular disease constitutes the leading cause of death in the United States.1 As the mean age of the population increases, the number of individuals with atherosclerotic lesions of the lower extremities also rises. Patients with peripheral arterial disease (PAD) are at significantly higher risk of death compared to healthy controls from cardiovascular morbidity and mortality, as well as at increased risk of impaired functional status.2 A basic understanding of the pathogenesis, presentation, diagnosis, and treatment of chronic peripheral vascular disease is an integral part of medical and surgical practice in the United States.
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In order to gauge the prevalence of PAD in asymptomatic subjects, several epidemiological studies have been done using ankle–brachial index (ABI) as a measure of arterial stenosis. ABI is obtained using a standard blood pressure cuff placed just above the ankle. A Doppler is used to measure the systolic pressure of posterior tibial and dorsalis pedis arteries of each leg. The higher of the systolic pressures in each leg (DP vs. PT) is divided by the higher systolic pressure of either arm. An ABI of ≤0.90 indicates hemodynamically significant stenosis. The National Health and Nutritional Examination Survey included 2174 asymptomatic subjects aged ≥40 years. The prevalence of PAD, defined by an ABI of ≤0.90, ranged from 2.5% in people aged 50 to 59 years to 14.5% in people aged >70 years.3 All told, PAD affects a total of around 10 million people. This translates to around 3% to 10% of the general population, with this percentage increasing to 15% to 20% in people older than 70 years (Figure 35-1).4,5,6
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Despite aggressive screening policies with ABI, studies show that the number of people in the general population with PAD is grossly underestimated. This is, in part, because of the limitations of ABI alone in diagnosing PAD in some patients.7 This underestimation could indicate that the prevalence of this already widespread disease is actually much higher. Exercise testing in a noninvasive vascular laboratory setting should be considered in patients for whom the clinical suspicion of PAD is high, yet they have a normal or indeterminate ABI.8
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BASIC CONSIDERATIONS AND RISK FACTORS
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Atherosclerosis is a chronic inflammatory condition that affects the intima of elastic and muscular arteries of the body in a segmental fashion. Atherosclerosis is evident from ...