A 58-year-old African American male presents with cramping of his calves after walking about 2 city blocks; the left calf is cramping worse than the right. It abates when he stops walking, but recurs when he resumes walking. There are no symptoms at rest, but the pain is worsened by a faster pace or going up an incline or stairs and is associated with left forefoot numbness when severe. The pain is not positional and is not present when the patient is sitting or standing without walking. There is no back pain. He is treated for hypertension and dyslipidemia and has a 20-pack-year smoking history.
This patient has intermittent claudication (IC), which is the mildest symptomatic presentation of peripheral arterial disease (PAD). PAD isolated to the femoropopliteal segment is typically asymptomatic (75% of the time) or may present with IC.1 IC is defined classically as reproducible pain in a muscle group brought on by a consistent amount of exercise (eg, a defined distance of walking) and relieved by rest. In the setting of femoropopliteal PAD, the pain is located in the calf muscles and is caused by a hemodynamically significant arterial obstruction that prevents increased blood flow in the setting of calf muscle exercise and decreased vascular resistance. By Ohm’s law (pressure = blood flow × vascular resistance), when resistance drops and flow cannot increase, the result is a decrease in pressure distal to the obstruction and ischemic pain.
The prevalence of PAD in the United States is 4.3%, with between 8 and 12 million people affected. Age is an important risk factor, with a prevalence of >15% in those over age 70 years.2,3 PAD prevalence is expected to rise as the population ages and the rates of diabetes and obesity increase. In 2001, Medicare expenditures for PAD topped $4 billion, with a significant portion of this cost related to revascularization procedures.2,4
Other risk factors for PAD mirror those for coronary artery disease, since the common denominator of the 2 diseases is atherosclerosis. Male sex, tobacco use, hypertension, dyslipidemia, and African American race are all well-established risk factors for PAD and, specifically, IC.5
Although limb morbidity related to IC is relatively benign, overall cardiovascular morbidity and mortality in patients with IC are significant. Overall, 75% of patients with IC will remain stable or improve, whereas 25% may worsen. Only 1% to 3% will progress to critical limb ischemia (defined as rest pain or tissue loss) and less than 2% will progress to major amputation. However, 5-year risk of stroke or myocardial infarction in patients with IC is 20%, and overall 5-year cardiovascular mortality is 10% to 15%.6,7 Thus, perhaps the most ...