Peripheral arterial disease (PAD) is one of the several terms referring to a partial or complete obstruction of one or more arteries below the aortic bifurcation. Although the term PAD is sometimes inclusive of all peripheral arteries and/or any etiology, in this chapter PAD refers to atherosclerotic occlusive disease of lower extremity arteries. Other terms used for this affliction in the literature are peripheral vascular disease (PVD), peripheral arterial occlusive disease (PAOD), and lower extremity arterial disease (LEAD).
The epidemiologic data regarding this condition have evolved dramatically over the past three decades. Initially, only symptomatic PAD was studied. However, with the development of investigative methods applicable in epidemiology, several studies have suggested that during the natural course of this disease, symptomatic PAD is preceded by a long period of asymptomatic disease. These studies showed that asymptomatic PAD is not innocuous, since patients at this initial stage of the disease are already at a higher risk of cardiovascular events. Consequently, the more recent studies have used objective investigation methods and typically include both symptomatic and asymptomatic forms of the disease. This has led to better estimates of PAD prevalence and incidence. PAD that exhibits typical symptomatology, usually in the form of leg pain brought about by walking, has been conservatively estimated to reduce the quality of life in at least 2 million Americans and in some cases leads to revascularization or amputation.1 Recent estimates place the total number of persons with PAD in the United States at more than 8 million.2
SYMPTOMS AND MEASURES OF PAD IN EPIDEMIOLOGY
It was recognized as long ago as the 18th century that an insufficient blood supply to the legs could cause pain and dysfunction. This type of pain is known as intermittent claudication (IC) and is characterized as leg muscle pain occurring when walking and relieved at rest. IC is generally indicative of exercise-induced ischemic pain.
Early studies focused primarily on claudication as the chief symptomatic manifestation of PAD. A number of patient questionnaires have been developed to uniformly identify claudication and to distinguish it from other types of leg pain. The first of these was the Rose questionnaire, also referred to as the World Health Organization questionnaire.3 However, despite initial good results of the questionnaire to accurately detect PAD, this questionnaire is known as to present a low sensitivity, from 68% down to 9% in different studies.4 Two attempts have been made to improve the diagnostic performances. The Edinburgh Claudication Questionnaire5 is a modification of the Rose questionnaire, presenting 47% to 91% sensitivity and 95% to 99% specificity in different studies.5,6,7 The San Diego Claudication Questionnaire is another modified version of the Rose questionnaire and additionally captures information on the laterality of symptoms.8 The interviewer administered form of the San Diego Claudication Questionnaire is presented in Table 1-1.