Introduction
Chronic arterial obstruction is a slowly progressive narrowing or occlusion of arteries, most often in the lower limbs. Ischaemia develops over months or years and is partly compensated by collateral circulation. This topic covers four entities that share the final pathway of tissue ischaemia but differ in cause, vessel size and clinical course: Raynaud's syndrome and disease, Buerger's disease (thromboangiitis obliterans), obliterating atherosclerosis and diabetic angiopathy. Acute occlusion is covered in the previous topic.
General principles of chronic limb ischaemia
Clinical staging of chronic peripheral arterial disease is usually done by the Fontaine classification:
- Stage I: asymptomatic, with reduced or absent pulses or an arterial bruit.
- Stage IIa: claudication with walking distance over 200 m.
- Stage IIb: claudication with walking distance under 200 m.
- Stage III: ischaemic rest pain, typically at night, relieved by hanging the leg down.
- Stage IV: ulceration or gangrene.
The ankle-brachial index (ABI) is the first objective test. An ABI below 0.9 indicates significant arterial disease. A very high value above about 1.3 suggests non-compressible, calcified vessels and makes the result unreliable, which is typical in diabetes. Duplex ultrasound, CT or MR angiography and, when intervention is planned, digital subtraction angiography define the level and extent of the lesions.