Peripheral Vascular Disease — MRCS Part B Surgical pathology

A vascular station covering chronic and acute limb ischaemia, from the claudicant in clinic to the white leg on the ward.

Chronic limb ischaemia

Atherosclerosis narrowing the aorto-iliac, femoropopliteal or crural arteries. Intermittent claudication is muscle pain brought on by a reproducible distance of walking and relieved within minutes by standing still; the calf for a superficial femoral lesion, the thigh and buttock (with impotence: Leriche's syndrome) for an aorto-iliac one. Critical limb ischaemia is rest pain for more than two weeks, typically in the forefoot at night and relieved by hanging the leg down, or ulceration or gangrene, with an ankle pressure under 50 mmHg or a toe pressure under 30. Risk factors: smoking above all, diabetes, hypertension, hyperlipidaemia, age, male sex, renal failure and a family history.

Classification

Fontaine: I asymptomatic, IIa claudication over 200 m, IIb under 200 m, III rest pain, IV ulcer or gangrene. Rutherford grades the same course from 0 to 6. The ankle-brachial pressure index supports the clinical picture: under 0.9 is disease, under 0.5 is severe, over 1.3 is calcified and uninterpretable (diabetes, renal failure).

Investigation and treatment

Duplex ultrasound first; CT or MR angiography to plan intervention; catheter angiography when treating. Every patient gets best medical therapy: stop smoking, a statin, an antiplatelet, blood pressure and diabetes control, and supervised exercise, which improves claudication distance as much as an angioplasty in many. Revascularisation — angioplasty with or without a stent for short lesions, bypass for long occlusions — is for lifestyle-limiting claudication that has failed exercise, and for critical ischaemia, where the alternative is amputation.

Prognosis

Most claudicants stay stable or improve; about a quarter deteriorate and only a few percent lose the leg within five years. Their real risk is elsewhere: cardiovascular death at two to three times the rate of the population. Critical ischaemia is different: without revascularisation a large proportion lose the limb within a year, and about a quarter die.

Acute limb ischaemia

A sudden fall in perfusion threatening the limb, within two weeks of onset. Causes: embolism (atrial fibrillation, a mural thrombus after infarction, a proximal aneurysm), thrombosis of a diseased artery or a graft, trauma and dissection. The six Ps: pain, pallor, pulselessness, perishing cold, paraesthesia and paralysis; the last two mean the nerves and muscle are failing and the limb has hours. Fixed mottling and a tense, tender calf mean it is already lost.

Management: heparin at once, oxygen, analgesia, and a vascular surgeon. An embolus in a previously normal leg is removed with a Fogarty catheter under local anaesthetic; thrombosis on top of disease needs imaging and either thrombolysis, angioplasty or bypass. Fasciotomies after reperfusion of a leg that has been ischaemic for more than a few hours, and watch for the reperfusion syndrome: hyperkalaemia, acidosis and myoglobinuria.

Upper limb and Raynaud's

Raynaud's disease is episodic vasospasm of the digits on cold or emotion, with the sequence white, blue then red; primary in young women, or secondary to connective tissue disease, vibration, beta-blockers or atherosclerosis. Other causes of upper limb ischaemia: embolism, thoracic outlet compression by a cervical rib with a subclavian aneurysm, arteritis (Takayasu, giant cell), Buerger's disease in smokers, and iatrogenic injury from cannulae and lines.