Peripheral Arterial Disease

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Merck Manuals Professional EditionMerck ManualsFree - In Google PlayView MERCK MANUALProfessional VersionTap to switch to the Consumer VersionShareEmailLinkedInFacebookGoogle+TwitterPeripheral Arterial Disease(Peripheral Vascular Disease)By Koon K. Teo, MBBCh, PhD, Population Health Research Institute; Department of Medicine, McMaster University, Hamilton, Ontario, Canada CLICK HERE FOR Patient EducationPeripheral arterial disease (PAD) is atherosclerosis of the extremities (virtually always lower) causing ischemia. Mild PAD may be asymptomatic or cause intermittent claudication; severe PAD may cause rest pain with skin atrophy, hair loss, cyanosis, ischemic ulcers, and gangrene. Diagnosis is by history, physical examination, and measurement of the ankle-brachial index. Treatment of mild PAD includes risk factor modification, exercise, antiplatelet drugs, and cilostazol or possibly pentoxifylline as needed for symptoms. Severe PAD usually requires angioplasty or surgical bypass and may require amputation. Prognosis is generally good with treatment, although mortality rate is relatively high because coronary artery or cerebrovascular disease often coexists.Overview of Peripheral Arterial DiseaseOverview of Peripheral Arterial DiseaseOverview of Peripheral Arterial DiseaseEtiologyPrevalence of peripheral arterial disease is about 12% in the US; men are affected more commonly than women. Risk factors are the same as those for atherosclerosis: increasing age, hypertension, diabetes, dyslipidemia (high low-density lipoprotein [LDL] cholesterol, low high-density lipoprotein [HDL] cholesterol), cigarette smoking (including passive smoking) or other forms of tobacco use, and a family history of atherosclerosis. Obesity, male sex, and a high homocysteine level are also risk factors.Atherosclerosis is a systemic disorder; 50 to 75% of patients with PAD also have clinically significant coronary artery disease (CAD) or cerebrovascular disease. However, CAD may be silent in part because PAD may prevent patients from exerting themselves enough to trigger angina.Symptoms and SignsTypically, PAD causes intermittent claudication, which is a painful, aching, cramping, uncomfortable, or tired feeling in the legs that occurs during walking and is relieved by rest. Claudication usually occurs in the calves but can occur in the feet, thighs, hips, buttocks, or, rarely, arms. Claudication is a manifestation of exercise-induced reversible ischemia, similar to angina pectoris. As PAD progresses, the distance that can be walked without symptoms may decrease, and patients with severe PAD may experience pain during rest, reflecting irreversible ischemia. Rest pain is usually worse distally, is aggravated by leg elevation (often causing pain at night), and lessens when the leg is below heart level. The pain may be burning, tightening, or aching, although this finding is nonspecific.About 20% of patients with peripheral arterial disease are asymptomatic, sometimes because they are not active enough to trigger leg ischemia. Some patients have atypical symptoms (eg, nonspecific exercise intolerance, hip or other joint pain).Mild PAD often causes no signs. Moderate to severe PAD commonly causes diminished or absent peripheral (popliteal, tibialis posterior, dorsalis pedis) pulses; Doppler ultrasonography can often detect blood flow when pulses cannot be palpated.When below heart level, the foot may appear dusky red (called dependent rubor). In some patients, elevating the foot causes loss of color and worsens ischemic pain; when the foot is lowered, venous filling is prolonged (> 15 sec). Edema is usually not present unless the patient has kept the leg immobile and in a dependent position to relieve pain. Patients with chronic PAD may have thin, pale (atrophic) skin with hair thinning or loss. Distal legs and feet may feel cool. The affected leg may sweat excessively and become cyanotic, probably because of sympathetic nerve overactivity. Peripheral Arterial Disease—Skin Changes Peripheral Arterial Disease—Skin ChangesPeripheral Arterial Disease—Skin ChangesDR P. MARAZZI/SCIENCE PHOTO LIBRARYAs ischemia worsens, ulcers may appear (typically on the toes or heel, occasionally on the leg or foot), especially after local trauma. The ulcers tend to be surrounded by black, necrotic tissue (dry gangrene). They are usually painful, but people with peripheral neuropathy due to diabetes or alcoholism may not feel them. Infection of ischemic ulcers (wet gangrene) occurs readily, causing rapidly progressive cellulitis.The level of arterial occlusion influences location of symptoms. Aortoiliac PAD may cause buttock, thigh, or calf claudication; hip pain; and, in men, erectile dysfunction (Leriche syndrome). In femoropopliteal PAD, claudication typically occurs in the calf; pulses below the femoral artery are weak or absent. In PAD of more distal arteries, femoropopliteal pulses may be present, but foot pulses are absent.Arterial occlusive disease occasionally affects the arms, epecially the left proximal subclavian artery, causing arm fatigue with exercise and occasionally embolization to the hands.DiagnosisAnkle-brachial BP indexUltrasonographyAngiography before surgery CT Scan of a Patient with Occlusion of Superficial Femoral Arteries CT Scan of a Patient with Occlusion of Superficial Femoral ArteriesCT Scan of a Patient with Occlusion of Superficial Femoral Arteries© 2017 Elliot K. Fishman, MD.Peripheral arterial disease is suspected clinically but is underrecognized because many patients have atypical symptoms or are not active enough to have symptoms. Spinal stenosis may also cause leg pain during walking but can be distinguished because the pain (called pseudoclaudication) requires sitting, not just rest, for relief, and distal pulses remain intact.Diagnosis is confirmed by noninvasive testing. First, bilateral arm and ankle systolic BP is measured; because ankle pulses may be difficult to palpate, a Doppler probe may be placed over the dorsalis pedis or posterior tibial arteries. Doppler ultrasonography is often used, because pressure gradients and pulse volume waveforms can help distinguish isolated aortoiliac PAD from femoropopliteal PAD and below-the-knee PAD.A low (≤ 0.90) ankle-brachial index (ratio of ankle to arm systolic BP) indicates PAD, which can be classified as mild (0.71 to 0.90), moderate (0.41 to 0.70), or severe (≤ 0.40). If the index is normal (0.91 to 1.30) but suspicion of PAD remains high, the index is determined after exercise stress testing. A high index (> 1.30) may indicate noncompressible leg vessels (as occurs in Mönckeberg arteriosclerosis with calcification of the arterial wall). If the index is > 1.30 but suspicion of PAD remains high, additional tests (eg, Doppler ultrasonography, measurement of BP in the first toe using toe cuffs) are done to check for arterial stenoses or occlusions. Ischemic lesions are unlikely to heal when systolic BP is < 55 mm Hg in patients without diabetes or < 70 mm Hg in patients with diabetes; below-the-knee amputations usually heal if BP is ≥ 70 mm Hg. Peripheral arterial insufficiency can also be assessed by transcutaneous oximetry (TcO2). A TcO2 level < 40 mm Hg is predictive of poor healing, and a value < 20 mm Hg is consistent with critical limb ischemia.Angiography provides details of the location and extent of arterial stenoses or occlusion; it is a prerequisite for surgical correction or percutaneous transluminal angioplasty (PTA). It is not a substitute for noninvasive testing because it provides no information about the functional significance of abnormal findings. Magnetic resonance angiography and CT angiography are noninvasive tests that may eventually supplant contrast angiography.TreatmentKey PointsPeripheral arterial disease (PAD) occurs almost always in the lower extremities.50 to 75% of patients also have significant cerebral and/or coronary atherosclerosis.When symptomatic, PAD causes intermittent claudication, which is discomfort in the legs that occurs during walking and is relieved by rest; it is a manifestation of exercise-induced reversible ischemia, similar to angina pectoris.Severe PAD may cause pain during rest, reflecting irreversible ischemia, or ischemic ulcers on the feet.A low (≤ 0.90) ankle-brachial index (ratio of ankle to arm systolic BP) indicates PAD.Modify atherosclerosis risk factors; give statins, antiplatelet drugs, and sometimes ACE inhibitors, pentoxifylline, or cilostazol.PTA with or without stent insertion may dilate vascular occlusions; sometimes surgery (endarterectomy or bypass grafting) is necessary.