Peripheral arterial disease and ankle-brachial index

What it is

Chronic limb ischemia is the inability of the arterial supply to meet the cellular metabolic demand. The Fontaine classification:

• Grade I: asymptomatic
• Grade II: intermittent claudication
• Grade III: rest pain
• Grade IV: ulcer or gangrene

Grade III and Grade IV together are critical limb ischemia.

Causes and risk

Causes are atherosclerosis, vasculitis and artery entrapment. Major risk factors are smoking and diabetes. Minor risk factors are hypertension, dyslipidemia, obesity, a sedentary lifestyle, and a personal or family history of CAD or CVD. Another list groups the causes as vascular, that is DVT, Beurger disease and Takayasu; neurospinal, that is disc disease and spinal stenosis; and neuropathic, that is DM. Claudication with normal peripheral pulses has its own short list of causes: neurogenic claudication from spinal stenosis, anaemia, and B-blockers.

How it presents

Claudication is cramping muscular pain on exertion, distal to the site of obstruction, appearing during exercise after a fixed claudication distance and relieved by a short rest, sitting or standing, of 2-5 min. It is reproducible: the same distance elicits pain in the same location, and the same rest relieves it. Numbness and paraesthesia go with it, the foot and leg may be cold, pulses are absent or weak below the level of disease, and bruits are present. Perfusion signs are hair loss, hypertrophic nails, atrophic muscles, slow capillary refill, skin ulceration, and pallor with elevation with rubor on dependency. Critical limb ischemia reads differently: the pain is continuous and severe, aching rather than cramping, felt in the forefoot, more at night, waking the person from sleep, increased by movement or pressure, and relieved by hanging the leg out of bed. The foot shows tissue loss with ulceration or gangrene, thin shiny cold skin, loss of subcutaneous fat and muscle wasting, and elevation to 20 may cause pallor. The level of occlusion sets the site: aorto-iliac gives claudication in both buttocks, thighs and calf with absent femoral, popliteal and distal pulses and impotence; iliac or common femoral gives unilateral thigh and calf claudication with unilateral loss of femoral and distal pulses; superficial femoral or popliteal gives unilateral calf claudication with absent distal pulses; and tibial and peroneal disease gives claudication in calf and foot with absent ankle pulses. Leriche syndrome is chronic aortoiliac occlusive disease presenting with a triad: claudication of the buttocks and thighs, decreased femoral pulses, and impotence. It is elsewhere given as bilateral buttock pain and erectile impotence due to common iliac disease. The critically ischaemic limb is set out as 6 Ps: pain, pallor, pulseless, perishingly cold, paraesthesia, and paralysis, which is the best indicator of danger to the limb. The arterial ulcer is set beside the venous one. The venous ulcer sits in the medial gaiter region of the leg, has sloped edges, is not severe in pain unless there is excessive oedema or infection, is usually associated with limb oedema, and carries venous eczema, haemosiderosis and atrophie blanche; behind it stand varicose veins and DVTs. The arterial ulcer sits on the feet and toes and at the ankle over the lateral malleolus, is punched-out, is painful, oedema with it is uncommon, and it carries trophic changes and gangrene.