Chronic lower limb ischaemia
Treatment for Chronic lower limb ischaemia
Peripheral vascular disease commonly affects the arteries supplying the leg and is mostly caused by atherosclerosis. Restriction of blood flow, due to arterial stenosis or occlusion, often leads patients to complain of muscle pain on walking (intermittent claudication). Any further reduction in blood flow causes ischaemic pain at rest, which affects the foot. Ulceration and gangrene may then supervene and can result in loss of the limb if not treated. The Fontaine score is useful when classifying the severity of ischaemia.
Although many patients with claudication remain stable, about 150-200 per million of the population progress to critical limb ischaemia (Fontaine III or IV) each year. Many patients with critical limb ischaemia can undergo revascularisation, which has a reasonable chance of saving the limb. A recent audit by the Vascular Surgical Society found a success rate of over 70% for these patients. However, many patients still require major amputation.
Treatment for lower limb ischaemia
Intermittent claudication seems a relatively benign condition, although severe claudication may preclude patients from manual work. The risk of generalised vascular disease is probably more important. Patients with claudication have a three times higher risk of death compared with age matched controls. Modification of risk factors is therefore vital to reduce death from myocardial infarction and stroke. All patients should be advised to stop smoking and take regular exercise. They should also be screened for hyperlipidaemia and diabetes. Patients with peripheral vascular disease benefit from regular chiropody, and those with diabetes should attend a foot clinic. Obesity reduces exercise capacity, and losing weight will improve the walking distance.
Drug treatment
All patients with peripheral vascular disease benefit from aspirin (75-300 mg/day) because this reduces the risk of cardiovascular events. Patients who are intolerant of aspirin should take dipyridamole (200 mg, twice daily) or clopidogrel (75 mg/day). Naftidrofuryl may improve the walking distance of patients with moderate claudication (less than 500 m), but it is not known if it affects the outcome of the disease. The evidence to support naftidrofuryl is controversial, and patients prescribed it should be reassessed after three to six months.
Exercise programmes
A recent meta-analysis of 21 supervised exercise programmes showed that training for at least six months, by walking to near maximum pain tolerance, significantly improved pain free and maximum walking distances. The only controlled trial comparing an exercise programme with percutaneous transluminal angioplasty found that exercise was better. Exercise programmes are cheaper than percutaneous transluminal angioplasty or surgery, although long term compliance seems poor.
Endovascular techniques
The number of percutaneous transluminal angioplasties performed for claudication has risen steeply in recent years. In some situations endovascular techniques have virtually replaced conventional surgery. Percutaneous transluminal angioplasty seems best suited for stenoses or short occlusions of the iliac and superficial femoral vessels, with one year patency rates of 90% and 80% respectively. Angioplasty carries a small but definite risk of losing the limb because of thrombosis or embolisation, and patients should be informed of this risk.
Metallic stents push back the atheroma and improve on the initial lumen gain after angioplasty alone. The indications for iliac stents include a residual stenosis or dissection after angioplasty and long occlusions, but there seems little evidence to justify their routine use. Deployment of stents more distally has produced disappointing results due to high restenosis rates.
Surgery
The role of bypass for longer arterial occlusions remains poorly defined because of a lack of proper trials comparing it with percutaneous transluminal angioplasty and conservative treatment. Polyester (Dacron) aortobifemoral bypass grafts have five year patency rates of over 90% but are associated with a mortality of up to 5%. Complications include graft infection and postoperative impotence. Femoropopliteal bypass grafting, using autologous long saphenous vein, polyester, or polytetrafluoroethylene (Goretex) yields patency rates of less than 70% at five years. The early patency of prosthetic grafts seems similar to that of vein grafts, although the long term results seem less good. Femoropopliteal bypass grafts should rarely be used for patients with claudication.
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Tags: arterial stenosis, atherosclerosis, lower limb ischaemia, muscle pain
