Management of Peripheral Arterial Disease
David C. Brewster
During the last decade, the treatment of peripheral arterial insufficiency (PAD) has undergone substantial change and improvements. Plaque regression has now been demonstrated with aggressive lipid-lowering therapy (see Chapter 27), and in properly selected patients, percutaneous transluminal angioplasty (PTA) with and without intraluminal stenting may achieve results that approach those of bypass surgery. In addition, great progress has been made in arterial reconstructive surgery for severe cases, making possible the salvage of limbs that would have otherwise required amputation. The wealth of available therapeutic options and a relatively favorable natural history provide the symptomatic patient with substantial opportunity for improvement. The primary physician needs to know the natural history of arterial occlusive disease in order to optimize the timing and intensity of therapy. Also essential to ensuring proper selection, implementation, and coordination of care is knowledge of the techniques, efficacies, and indications for conservative therapy (including risk-factor modification), angioplasty, and bypass surgery.
Prognosis for the Limb
The prognoses for the limb and symptoms in patients presenting with claudication are quite favorable. Clinical course correlates well with the clinical severity of disease as measured by distance walked before onset of claudication and by physical findings; persons with the worst prognosis have ischemic ulcers or rest pain in the setting of long-standing diabetes mellitus or persistent smoking. In general, greater than 80% of patients with claudication alone remain stable or improve, and only approximately 5% progress to limb loss. Almost no patients who cease smoking require amputation, whereas in contrast, more than 10% who continue to smoke lose a limb. Observed outcomes at 5 years are stable symptoms in 70% to 80%, worsening claudication in 10% to 20%, and progression to critical limb ischemia or limb loss in 1% to 2% of patients. Not surprisingly, most amputations occur in the high-risk group, but even in severe cases, nearly 70% stay the same or improve and only 15% come to amputation, underscoring the fact that progression to loss of limb is hardly inevitable.
Overall Prognosis
Although prognosis for the limb is generally favorable, mortality rates—both overall and cardiovascular—are high, reflecting the severity of underlying systemic atherosclerotic disease. The risk of dying from cardiovascular cause is sixfold greater in those with PAD than in those of similar age, sex, and lipid profile without it. All-cause mortality increases threefold, due almost entirely to the increase in cardiovascular risk. Combined mortality rates are in the range of 30%, 50%, and 70% at 5, 10, and 15 years after the onset of symptoms, respectively, which represent a relative risk about three times that for patients of similar age and gender. Concurrent disease of the coronary arteries, cerebral vasculature, or aorta accounts for most of the increased mortality, underscoring the systemic nature of atherosclerosis and its adverse effect on prognosis. The prevalence of systemic atherosclerosis in patients with peripheral arterial insufficiency should not be surprising, given that up to 80% of such patients give a history of smoking, 40% have hypertension, 30% have lipid abnormalities, and 20% have diabetes.
The underdiagnosis of PAD in primary care practice is well-documented. Not only does failure to recognize the condition lead to missed opportunities for symptomatic improvement; it also leads to failure to recognize and treat underlying systemic atherosclerotic disease that may compromise survival. A careful comprehensive cardiovascular history and physical examination in addition to a detailed look at the peripheral vasculature are essential. Patients who are clinically suspected can undergo noninvasive testing by Doppler ultrasound to confirm clinically significant disease, followed if necessary by noninvasive radiologic imaging (e.g., computed tomographic angiography [CTA\, magnetic resonance angiography [MRA]) or formal angiography (see Chapter 23) if interventional therapy is being contemplated.
In the Patient with Suspected Atherosclerotic Disease
A full review of atherosclerotic risk factors is essential, as are a detailed history and physical examination for findings indicative of poor prognosis (e.g., rest pain, dependent rubor, cold extremity, painful ulceration, gangrenous or necrotic tissue). Patients with such evidence of more advanced disease should be referred promptly for noninvasive Doppler ultrasound study to identify candidates for angiography and surgical intervention (see Chapter 23). Because evidence of peripheral vascular disease is a strong predictor of concurrent cardiovascular disease with its attendant morbidity and mortality, a thorough cardiac assessment is essential (see Chapter 36), especially if surgical intervention is being contemplated (see later discussion).
In the Patient with Diabetes
A thorough history and physical examination, supplemented by a Doppler flow study, have been shown to be predictive of outcome and can help to direct management. Physicians encountering a diabetic with a foot ulcer should inquire into previous amputation and painful skin ulceration. Evaluation for superimposed infection is particularly important. If there has been previous amputation, the likelihood ratio for an adverse outcome is 4.0 and the patient should be considered for aggressive therapy (e.g., revascularization). If there is neither previous amputation nor findings to suggest more advanced limb-threatening ischemia, an initial conservative (medical) approach is reasonable.
PRINCIPLES OF MANAGEMENT (1, 2 and 3,6,7,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28 and 29)
Medical Management
The basic objectives of medical management are to control or limit disease progression, increase exercise tolerance, and minimize the risk of complications. The most important methods for achieving these objectives are cessation of cigarette smoking, regular daily exercise, and meticulous foot care.
Smoking Cessation (see Chapter 54)
Smoking cessation ranks as a major treatment priority. Smoking hastens the progression of atherosclerosis and may further impair blood flow by inducing vasoconstriction. Among initially healthy women, smoking induces a dose-dependent 3- to 14-fold increase in the risk of developing symptomatic PAD. Cessation markedly reduces but does not entirely eliminate the risk. In persons with symptomatic disease, cessation reduces rest pain, claudication, risk of amputation, and the need for bypass surgery. The risk of repeat occlusion after angioplasty or bypass falls by more than two thirds in those who quit. Moreover, quitting decreases overall cardiovascular morbidity and mortality.
The chances of successfully quitting are greatest when a smoker becomes symptomatic from a complication of smoking; the physician’s influence is considerable in this context. The details of a comprehensive smoking cessation program are presented elsewhere (see Chapter 54), but a few considerations are relevant for persons with peripheral artery disease. Nicotine gum or transdermal patch can serve as a useful cessation aid by minimizing nicotine withdrawal; however, nicotine may induce vasospasm. Although nicotine therapy is probably not contraindicated in claudication because vasospasm usually does not play a major role, the gum or patch, if used, should be prescribed and monitored with care.
Exercise
Daily exercise, especially walking, remains a cornerstone of the treatment program. Mechanisms include improvements in flow-mediated arterial dilation (endothelial function), muscle metabolism, peak oxygen consumption, red cell movement, and pain threshold. Physical training significantly increases pain-free walking distance, 6-minute walk performance, brachial artery flow-mediated dilation, and quality of life. The best results are achieved with supervised group programs, but a home-based program complemented by group support can also achieve significant improvement. Results are best in patients with stable peripheral artery disease with or without intermittent claudication symptoms. Persons with rest pain, ulceration, unstable angina, congestive heart failure, severe lung disease, or arthritis may have more difficulty achieving best outcomes. Benefit becomes evident within 3 months of initiating an exercise program.
Regularity of exercise is more important than intensity or duration, although at least 30 min/d of continuous leg exercise appears to be necessary. Walking is optimal, but any form of dynamic exercise will suffice, including stationary bicycling, stair climbing, engaging in water aerobics, or using low-impact aerobic training equipment. Adding some resistance training improves functional capacity, particularly stair climbing. An exercise program can also reduce cardiovascular risk significantly (see Chapters 18 and 31).
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