Peripheral Artery Disease: Clinical Evaluation

Symptoms of Peripheral Artery Disease

The most commonly ascribed symptom that develops as a result of PAD is intermittent claudication. The word claudication derives from the Latin word claudicato , which was used to describe the limp gait of a lame horse. As defined in the Rose questionnaire, claudication is the development of an ischemic muscular pain on exertion. The pain can be characterized as aching, burning, heaviness, feeling leaden, tightness, or cramping. Pain should originate in a muscular bed, such as the calf, thigh, hip, or buttock, and not localize to a joint. The area of the worst blood flow limitation usually subtends the site of muscular discomfort. For example, patients who develop hip or buttock discomfort with walking most likely have distal aorta or iliac artery occlusive disease, whereas patients with calf claudication likely have superficial femoral or popliteal arterial stenoses or occlusions. The reduction of muscular work upon activity cessation rebalances the available blood supply with muscle demand and quickly resolves the pain.

Both time of activity to pain onset and time to pain resolution should be consistent and predictable. The distance walked to the onset of leg discomfort is called the initial claudication distance , and the maximal distance the patient can walk without stopping because of leg discomfort is called the absolute claudication distance . Several classification schemes are used to categorize the severity of claudication, including the Fontaine ( Table 18.1 ) and Rutherford classifications ( Table 18.2 ). When the interview is complete, the physician should have insight into the nature of discomfort, how long it has been present, the typical duration of exercise required to cause the discomfort, and the amount of rest necessary to relieve the symptoms.

Classic symptoms of claudication occur in a minority of patients with PAD, including those with functional limitations. The application of questionnaires for claudication, such as the World Health Organization (WHO)/Rose questionnaire or the Walking Impairment Questionnaire, may underestimate PAD prevalence by 50%. Data from McDermott et al. indicate that complaints other than claudication are common. They evaluated functional tolerance across a range of symptoms in cross-sectional analyses of patients with and without PAD. PAD patients demonstrated several types of leg discomfort, including leg pain at rest and with walking, pain with walking alone requiring cessation of activity, and pain patients could “walk through.” This variety of presentations would be missed with questioning only for classic symptoms. Moreover, the type of discomfort predicted function. Patients with pain at rest and with walking had worse functional capacity than those whose pain occurred with walking and stopped with walking cessation, and those who were able to “walk through” the pain. Quality of leg pain, whether it is atypical or classic, does not predict severity of reduction in limb perfusion pressure as measured by the ABI.

The presence of intermittent claudication has important prognostic implications regarding functional capacity and mortality. Three quarters of patients with intermittent claudication will have stable symptoms over the next 10 years; approximately 25% will progress to more disabling claudication or critical limb ischemia (CLI) requiring revascularization or culminating in amputation. Moreover, they will suffer a mortality more than twice that of the general population, approximating 15% to 30% at 5 years.

Differential Diagnosis of Claudication

Once exercise-related discomfort has been established, several alternate vascular and nonvascular diagnoses should be considered ( Box 18.1 ). Vascular disorders include popliteal artery entrapment (see Chapter 63 ), compartment syndrome, fibromuscular dysplasia (FMD), venous insufficiency (see Chapter 54 ), and vasculitis (see 39, 42 ). Popliteal artery entrapment typically occurs in very active persons or athletes. Because of an abnormal origin of the medial (or less commonly, lateral) head of the gastrocnemius muscle, the popliteal artery may be compressed with walking and yield symptoms of claudication. Endofibrosis of the external iliac artery (EIA), a rare occurrence in highly trained cyclists and other endurance athletes, may cause claudication.

FMD is a noninflammatory arterial occlusive disease that most commonly affects the renal and carotid arteries but may involve other arterial beds (see Chapter 58 ). Any of the arteries in the lower extremities may be affected, but the iliac arteries are the most common. Fibroplasias may involve the intimal, medial, or adventitial layer of the artery. The most common histological type is medial fibroplasia, which is the most frequent cause of the “string of beads” appearance of FMD on angiography, depicting areas of stenosis and dilatation. FMD has a predilection for the nonbranching points of vessels. The etiology of FMD remains unknown.

Increased calf muscle size with exercise may inhibit venous outflow, cause exertional compartment syndrome—in which tissue pressure is increased and microvascular flow is impeded—and bring about complaints of calf pain or tightness with exertion. Symptoms improve with leg elevation after exercise cessation. Venous claudication may occur as a result of iliofemoral thrombosis with poor collateral vein formation. When venous outflow is impaired, the increase in arterial inflow with exercise increases venous pressure markedly and causes a severe tightness or bursting sensation in the limb. Patients may report improvement in symptoms with leg elevation following exercise cessation. These patients frequently have leg edema. Vasculitides such as Takayasu arteritis, giant-cell arteritis (GCA), and thromboangiitis obliterans (TAO) are infrequent causes of claudication.

Nonvascular causes of exertional leg pain include lumbar radiculopathy, hip and knee arthritis, and myositis. Perhaps the most common nonvascular diagnosis is lumbar radiculopathy causing nerve-based pain. Patients may complain of leg pain or paresthesias as a result of compression of the lumbar nerve roots from disk herniation or degenerative osteophytes. The paresthesias or pain tend to affect the posterior aspect of the leg and occur with specific positions, such as standing, or develop at the beginning of ambulation. These symptoms may improve with continued walking or when leaning forward because pressure on the nerve roots is reduced.

Osteoarthritis of the hip or knee may cause pain associated with walking. The pain may be confused with intermittent claudication because it typically occurs with exercise. However, the discomfort is usually referable to a joint such as the hip or knee. It can be distinguished from claudication in that the level of activity required to precipitate symptoms varies and does not resolve rapidly with activity cessation.

Differential Diagnosis of Critical Limb Ischemia

The differential diagnosis of CLI includes vascular and nonvascular diseases ( Box 18.2 ). Atheroembolism, or blue toe syndrome , occurs when components of large-vessel atherosclerotic plaque embolize to distal vessels ( Fig. 18.2 ) (see Chapter 45 ). The embolized material is composed of fibroplatelet debris and cholesterol crystals. A common cause of atheroembolism is iatrogenic disruption of the vessel, whether from catheterization or surgery. Several features may help in differentiating atheroembolism from traditional CLI. Patients typically have pulses palpable down to the ankle, because the emboli require a patent pathway to distal portions of the extremities. Other clinical clues include new renal insufficiency and blood eosinophilia. On examination, the patient will have areas of cyanosis or violaceous discoloration of the toes or portions of the feet and areas of livedo reticularis.