Peripheral arterial disease (PAD) of the lower extremities affects nearly 8 to 12 million adults in the United States.1 The age-adjusted prevalence of PAD is approximately 12% and accounts for significant morbidity and health care expenditure among the elderly. This disorder affects men and women equally.2,3,4,5 Symptomatic PAD causes functional impairment and reduced mobility, and asymptomatic PAD may eventually progress to symptomatic PAD. Regardless of symptom status, PAD predicts future cardiovascular events such as myocardial infarction (MI), stroke, and death.
Diagnosis of Lower Extremity PAD
Although history suggestive of classic walking-induced lower extremity pain with resolution at rest and physical examination demonstrating absent or diminished pulses of lower extremities is sufficient to diagnose PAD, only 10% of patients with PAD may present with this classic presentation.6,7 An ankle–brachial index (ABI), defined as the ratio of ankle to brachial systolic blood pressure, of ≤0.90 is 90% sensitive and 95% specific for the diagnosis of PAD.8 Severe PAD is defined as ABI ≤ 0.40 and is associated with rest pain or ischemic ulceration.
Risk Factors of Lower Extremity PAD
A constellation of data from several studies9,10,11,12,13 provides evidence that risk factors for PAD are essentially the same as those for coronary artery disease (CAD) with few exceptions. Therefore, age (>40 years), family history, diabetes, hyperlipidemia, cigarette smoking, and hypertension are the major risk factors for PAD. Cigarette smoking and diabetes are probably the most important of these risk factors. The most common form of dyslipidemia causing PAD is the combination of elevated triglycerides and low high-density lipoprotein level (HDL)—a pattern most commonly seen among patients with uncontrolled diabetes ("metabolic dyslipidemia"). Female diabetic patients are more prone to develop PAD compared to male diabetic patients, and in women, it manifests as peroneal and tibial PAD. Smoking, on the other hand, causes mostly aortoiliac disease. Women with a history of heavy smoking often develop a distinct hypoplastic aortoiliac syndrome. In addition to these traditional risk factors, several other novel risk factors are found to be associated with increased risk of PAD. Elevated levels of lipoprotein (a), homocysteine, apolipoprotein (apo) A-1, apoB-100, high sensitive C-reactive protein, and fibrinogen predispose patients to PAD.14 Impaired renal function has also been found to be a risk factor for developing PAD.15
Prevalence of Lower Extremity CAD in PAD
As the risk factors for PAD and CAD are very similar, there is a common association of these two disorders16 (Table 13-1). However, depending on the methods used to diagnose and define CAD, the prevalence of CAD in PAD has been reported from 14% to 90%. When only clinical symptoms of angina and electrocardiograms were used to diagnose CAD among PAD patients, CAD prevalence was found ...