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Peripheral artery disease
Definition and epidemiology
Peripheral artery disease (PAD) is the manifestation of atherosclerosis of the peripheral arteries supplying the legs and feet. Atherosclerosis diminishes perfusion of the legs and feet, in most cases only during activity, but in severe cases even in rest. As an atherosclerotic disease, it mostly co-exists with other atherosclerotic diseases like coronary artery disease and cerebrovascular disease. Peripheral artery disease is a disease of elderly smokers.
Risk factors are the same as for atherosclerosis in general, including smoking, hypertension, dyslipidaemia, and diabetes mellitus.
Peripheral artery disease classically presents with intermittent claudication. This is a crampy pain which occurs after physical activity like walking, and which resolves after rest. The condition is sometimes called “window shopper’s disease” as people stop walking after a while before resting, often pretending to stop to look at products in shop windows.
Skin affected by ischaemia is cold and thin, may be “shiny”, has decreased hair growth, decreased nail growth, and shows muscle atrophy. Ischaemia severely impairs wound healing properties, and accidental injuries to ischaemic areas may heal slowly or not at all.
In severe cases (Fontaine stage III and IV), ischaemia in rest is severe enough to cause pain in rest, ulcers, gangrene, or necrosis. These are indicative of critical limb ischaemia, which need urgent treatment.
The location of the symptoms depends on the location of the atherosclerotic narrowing:
- Aortoiliac disease (affection of the abdominal aorta or common iliac) – Affection of buttocks, hip, thighs. Erectile dysfunction
- Common femoral artery – Affection of thigh
- Superficial femoral artery – Affection of upper 2/3 of calf
- Popliteal artery – Affection of lower 1/3 of calf
- Tibial or peroneal artery – Affection of foot
The Fontaine classification classifies PAD according to the severity of the symptoms:
- Stage I – asymptomatic
- Stage II – pain on exertion
- Stage IIa – Claudication at walking distance > 200 m
- Stage IIb – claudication at walking distance < 200 m
- Stage III – pain at rest
- Stage IV – necrosis/gangrene/ulcers
Diagnosis and evaluation
Physical examination is important and may show signs of chronic ischaemia. Feeling for peripheral pulses is important, including comparing both sides and comparing to the upper limb. Decreased pulse is a characteristic finding. A bruit may be auscultated above the affected artery. Pain in rest which improves with the limb hanging low (like from the bed) is characteristic, as gravity improves blood flow.
Measurement of the ankle-brachial index or toe-brachial index is essential and gives a good objective measurement of lower limb perfusion. See topic A7.
The diagnosis of Fontaine stage I – II can be made clinically based on the presence of typical risk factors and clinical features.
Imaging is used in severe cases for preoperative planning. Doppler ultrasonography and angiography are used, either DSA or CT or MR angiography.
Treatment involves lifestyle changes, exercise, medical treatment, as well as revascularisation procedures in severe cases. Smoking cessation is especially obligatory, as the disease will progress regardless of measures taken as long as smoking continues.
Graded exercise therapy involves the patient walking up to the point where the pain occurs (and preferably a little more than that), before resting and repeating again. This should be performed for 30 minutes 3 – 5 times a week. Graded exercise therapy stimulates development of collateral circulation, which can significantly increase the distance which the patient can walk without pain.
Medical treatment involves antithrombotic therapy (aspirin/clopidogrel) and statins in all cases, as well as antihypertensives and antidiabetics to control risk factors, if necessary.
Surgical treatment involves endovascular and/or open surgery. It is indicated if the patient has severe symptoms which don’t improve after conservative treatment, or if the patient has Fontaine stage III or IV PAD. Critical limb ischaemia must be treated urgently to prevent loss of limbs.
Endovascular procedures include balloon angioplasty, stenting, and/or atherectomy (“shaving” off atherosclerotic plaques). Open surgical procedures involve bypassing the occlusion with the great saphenous vein or artificial prosthesis. Hybrid procedures combine both endovascular and open surgical techniques.
Bypass operations are named after the two arteries they connect via a graft. For example, femoro-popliteal bypass (often called a fem-pop) involves using a graft to connect the femoral artery and popliteal artery, bypassing a stenotic segment.
Both anatomical and extra-anatomical bypasses exist. Anatomical bypass operations involve connecting a graft between two arteries which are normally connected, like aorto-iliac bypass and femoro-popliteal bypass. Extra-anatomical bypasses involve connecting a graft between two arteries which are not normally connected, like axillo-femoral bypass and femoro-femoral (crossover) bypass.
The last choice of treatment, if a limb can’t be salvaged, is amputation.