Aetiology

Peripheral arterial disease (PAD) is most commonly caused by atherosclerosis.[2]​ Rarer causes of claudication are aortic coarctation, arterial fibrodysplasia, arterial tumour, arterial dissection, arterial embolism, thrombosis, vasospasm, and trauma. Other rare causes are Takayasu's arteritis, temporal arteritis, thoracic outlet obstruction, and Buerger's disease. Adventitial cystic disease, occluded limb aneurysms, popliteal artery entrapment, iliac endofibrosis, ergot toxicity, radiation fibrosis, and retroperitoneal fibrosis can also cause PAD. These can usually be distinguished based on clinical history and examination.

Pathophysiology

The pathophysiology of PAD is as diverse as the diseases it encompasses, but it centres on damage, inflammation, and structural defects of blood vessels. It includes atherosclerosis, degenerative diseases, dysplastic disorders, vascular inflammation, and thrombosis as well as thromboembolism.

Other factors include deconditioning, metabolic changes such as accumulation of acylcarnitines and adenosine diphosphate, impaired synthesis of phosphocreatine, and skeletal muscle injury characterised by muscle fibre loss.[11]

Classification

Fontaine stages

There are 4 increasing stages of severity:[1]

  • Stage I: asymptomatic

  • Stage IIa: mild claudication

  • Stage IIb: moderate to severe claudication

  • Stage III: ischaemia rest pain

  • Stage IV: ulceration or gangrene.

Rutherford categories

There are a total of 7 increasing categories of severity:[1]

  • Grade 0, category 0: asymptomatic

  • Grade I, category 1: mild claudication

  • Grade I, category 2: moderate claudication

  • Grade I, category 3: severe claudication

  • Grade II, category 4: ischaemia rest pain

  • Grade III, category 5: minor tissue loss

  • Grade IV, category 6: major tissue loss.

Asymptomatic/claudication/critical limb ischaemia/acute limb ischaemia

The American College of Cardiology/American Heart Association practice guidelines use the following divisions:[2]

Asymptomatic:

  • Absence of leg claudication symptoms.

Chronic symptomatic PAD:

  • Inadequate blood flow during exercise, causing fatigue, discomfort, or pain.

Chronic limb-threatening ischaemia (CLTI)

  • Compromise of blood flow to an extremity, causing limb pain at rest. Patients can develop ulcers or gangrene.

Acute limb ischaemia (ALI):

  • A sudden decrease in limb perfusion that threatens limb viability. Associated with the '6 Ps': pain, paralysis, paraesthesias, pulselessness, pallor, and poikilothermia.

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