Peripheral Arterial Disease
Atherosclerotic narrowing of the lower-limb arteries that limits blood flow to exercising, then resting, muscle in a dose-dependent way, producing intermittent claudication and, once supply can no longer meet resting demand, critical limb ischaemia with rest pain, ulceration and gangrene.
In a nutshell
PAD is atherosclerosis narrowing lower-limb arteries so that flow can meet resting but not exercising demand, producing claudication; once resting demand also cannot be met, critical limb ischaemia follows with rest pain, ulceration and gangrene.
Classic presentation
Cramping calf pain on walking a reproducible distance, relieved promptly by rest, in a smoker with reduced pulses and cool, pale skin.
Key points
- Claudication is a supply-demand mismatch: fixed stenosis cannot increase flow to meet exercise demand, so pain is reproducible and rest-relieved.
- Critical limb ischaemia is the same mechanism at a lower threshold: supply now fails to meet resting demand, so pain is constant, worse at night, and eased by dependency.
- ABPI quantifies severity directly: below 0.9 suggests PAD, below 0.5 suggests critical limb ischaemia, above 1.3 suggests calcified vessels, common in diabetes, and is unreliable.
- Fontaine staging maps disease progression onto falling supply and determines management: exercise and risk factor control for claudication, urgent revascularisation for critical limb ischaemia.
- Arterial ulcers occur distally and at pressure points, are painful and punched-out with a pale base, a distinct mechanism from venous ulcers.
- PAD signals systemic atherosclerosis: cardiovascular risk assessment and secondary prevention matter as much as the leg itself.
First-line investigation
Ankle-brachial pressure index: directly quantifies the perfusion deficit driving symptoms.
First-line management
Best medical therapy (antiplatelet, statin, smoking cessation, risk factor control) plus a supervised exercise programme for claudication; urgent revascularisation for critical limb ischaemia.
Exam traps
- A high ABPI above 1.3 does not mean healthy vessels: it usually means calcified, incompressible arteries, common in diabetes, and is falsely reassuring.
- Rest pain relieved by hanging the leg over the bed is a hallmark of critical limb ischaemia, not a benign finding: do not mistake it for comfort-seeking.
- Claudication is treated with exercise first, not straight to angioplasty: reserve revascularisation for lifestyle-limiting symptoms despite best medical therapy, or for critical limb ischaemia.
Educational content pending clinical review. Not medical advice.