By Dr. Sérgio Silva [email protected]
Dr Sérgio Silva is a vascular surgeon, specialising in minimally invasive surgery, at the Department of Vascular Surgery at Hospital Particular do Algarve, both in Alvor and Faro.
A marker of systemic atherosclerosis
Atherothrombosis is a generalised process that occurs throughout the arterial tree. In the brain, atherothrombosis may result in a transient ischemic attack or ischemic stroke.
In the coronary arteries, it can lead to stable or unstable angina and, in the peripheral arteries, atherothrombosis causes leg-muscle ischemia (varying from asymptomatic to severe symptomatic disease).
Peripheral arterial disease (PAD) can be asymptomatic (pre-existing atherosclerosis as a diffuse marker of the disease, placing patients at risk of an ischemic event elsewhere in the vasculature) or symptomatic.
PAD may cause intermittent claudication, which is pain or weakness when walking that is relieved with rest. The muscle pain or weakness after exercise occurs most commonly to the calf, but can include also the buttocks, hips, thighs or the inferior back muscles.
Only 25 per cent of people with documented PAD are symptomatic. People with PAD may not walk far or fast enough to induce muscle ischemic symptoms because of comorbidities such as pulmonary disease or arthritis, may have atypical symptoms unrecognised as intermittent claudication, may fail to mention their symptoms to their physician, or may have sufficient collateral circulation to tolerate their arterial obstruction.
PAD patients also have a higher prevalence of cognitive impairment and erectile dysfunction.
If the arterial flow to the lower extremities cannot meet the needs of resting tissue metabolism, critical lower extremity ischemia occurs with pain at rest or tissue loss.
Critical ischemia causes rest pain in the toes or foot with progression to ulceration or gangrene. Chronic arterial insufficiency ulcers commonly develop at the ankle, heel or leg.
Diagnosis
Persons with PAD of the lower extremities have reduced or absent arterial pulses. Noninvasive tests used to assess lower extremity arterial blood flow include measurement of ankle and brachial artery systolic blood pressures, characterisation of velocity wave form, and duplex ultrasonography.
Duplex ultrasonography, computed tomographic angiography and magnetic resonance angiography are useful in assessing the anatomic location and severity of PAD and in selecting suitable candidates for endovascular or surgical revascularisation.
Risk factors
As would be expected, the risk factors for PAD are similar to those for atherosclerosis affecting the heart and brain. These risk factors include those related to lifestyle, such as smoking, diet and physical inactivity.
Common conditions such as diabetes and hypertension are also associated with increased risk of PAD. The role of infection in the development of atherosclerosis is currently the focus of much interest.
Homocysteinaemia, hypercholesterolaemia and hypercoagulable states also increase the risk of vascular disease. Thus, factors that can be controlled, such as diet and smoking, and factors that cannot be altered, such as genetic traits, gender and age, are all known to be associated with increased risk of PAD.
Although there are similarities in risk factors for atherosclerosis throughout the vasculature, the degree of risk associated with a given risk factor may differ for each arterial bed.
For example, smoking and diabetes are widely held to be the strongest risk factors for PAD. PAD patients are at high risk of ischemic events as PAD is a risk marker for MI and stroke.
Treatment
Medical management of peripheral arterial disease include: smoking cessation, reduction of hypertension to 140/90 mm Hg and to 130/80 mm Hg in patients with diabetes mellitus or chronic renal insufficiency, control of diabetes mellitus, reduction of cholesterol levels. Antiplatelet drug therapy for example with aspirin, treatment with an enzyme inhibitor, treatment with beta blockers in patients with coronary artery disease, use of statins and Naftidrofurylin for patients with intermittent claudication, exercise and foot care.
Lower extremity angioplasty and bypass surgery
Indications for lower extremity percutaneous transluminal angioplasty or bypass surgery are (1) incapacitating claudication in persons interfering with work or lifestyle; (2) limb salvage in persons with limb-threatening ischemia as manifested by rest pain, nonhealing ulcers, and/or infection or gangrene; and (3) vasculogenic impotence.
Percutaneous balloon angioplasty and/or stenting is indicated for stenoses, and short occlusion. This is a minimally invasive procedure, which can be done under local anesthesia. Surgical revascularisation (bypass) is often chosen for long occlusions, as it is a more risky procedure.
Amputation
Studies have demonstrated that both immediate and long-term survival are higher in patients having revascularisation rather than amputation for limb-threatening ischemia. However, amputation of lower extremities should be performed if tissue loss has progressed beyond the point of salvage, if surgery is too risky, if life expectancy is very low, or if functional limitations diminish the benefit of limb salvage.
Prognosis
PAD is often undiagnosed. For every 100 patients who present with intermittent claudication, there are approximately 100 more with symptoms who do not present to their physician, and another 100 with asymptomatic disease. Of the 100 patients presenting, only around 25 per cent will have deterioration of their condition locally. In contrast, after five years, only approximately 50 per cent will be alive without having had a cardiovascular event. Therefore, pharmacological therapy in PAD patients should aim to improve the symptoms and local prognosis, provide an adjuvant to interventional measures, and, most importantly, modify cardiovascular mortality and morbidity.
