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Peripheral Artery Disease (PAD)

Clinical Subject Page

Peripheral Artery Disease (PAD)

ICD-10

I73.9

Specialty

Cardiology

Onset

Chronic

Reviewed

June 2026

On This Page

Overview

Peripheral artery disease (PAD) is a chronic atherosclerotic disease causing narrowing or occlusion of peripheral arteries, most commonly in the lower extremities, resulting in reduced blood flow and limb ischemia.

Etiology & Risk Factors

  • Etiology of Peripheral Artery Disease (PAD)

    • Atherosclerosis (most common)
    • Diabetes mellitus
    • Chronic kidney disease
    • Vasculitis
    • Thromboembolism
    • Radiation-induced vascular disease
    • Buerger disease (thromboangiitis obliterans)

    Risk Factors. for Peripheral Artery Disease (PAD)

    • Smoking (strongest modifiable risk factor)
    • Diabetes mellitus
    • Hypertension
    • Hyperlipidemia
    • Older age
    • Family history
    • Chronic kidney disease
    • Obesity

Pathophysiology

            1. Peripheral artery disease (PAD) is caused by progressive atherosclerosis of the peripheral arteries, leading to reduced blood flow and oxygen delivery to the limbs, especially during exercise.

              Mechanism

              Atherosclerotic risk factors:

              • Smoking
              • Diabetes
              • Hypertension
              • Hyperlipidemia

              This causes:

              • Endothelial injury
              • Atherosclerotic plaque formation
              • Progressive arterial narrowing (stenosis)

              As the disease progresses:

              • Reduced arterial blood flow
              • Inadequate oxygen delivery during exercise
              • Limb ischemia
              • Tissue ischemia at rest in advanced disease
              • Non-healing ulcers and gangrene

              Simple Flow

              Risk factors → Endothelial injury → Atherosclerotic plaque formation → Progressive arterial narrowing → ↓ Limb blood flow → Ischemia → Intermittent claudication → Critical limb ischemia (advanced disease)

Clinical Presentation

  1. Symptoms

    • Intermittent claudication
    • Leg fatigue during walking
    • Rest pain (advanced disease)
    • Non-healing foot ulcers
    • Cold feet
    • Numbness

    Signs

    • Diminished or absent peripheral pulses
    • Cool extremity
    • Pallor on elevation
    • Dependent rubor
    • Delayed capillary refill
    • Hair loss
    • Shiny skin
    • Ischemic ulcers

History Taking

  • Key Questions

    • Leg pain while walking?
    • How far can you walk before pain starts?
    • Does pain improve with rest?
    • Rest pain?
    • Non-healing wounds?
    • Smoking history?
    • Diabetes?
    • Previous cardiovascular disease?
    • History of stroke or MI?

    Red Flags

    • Rest pain
    • Tissue loss
    • Gangrene
    • Sudden limb pain
    • Acute limb ischemia

Classification

Peripheral Arterial Disease (PAD) · Classification

SEVERITY IS GRADED BY SYMPTOM PATTERN, NOT JUST IMAGING Two main classification systems are used in clinical practice — Fontaine (simpler, 4-stage, common in Europe) and Rutherford (more detailed, 7-category, widely used for trial reporting and vascular surgery planning). Both progress from asymptomatic disease to tissue loss.
Fontaine Classification
I
Asymptomatic
Subclinical disease detected by reduced ABI or imaging; no claudication symptoms reported.
Stage I
II
Intermittent Claudication
IIa: claudication after >200m. IIb: claudication after <200m. Pain reproducibly relieved by rest.
Stage II
III
Rest Pain
Ischaemic pain at rest, classically worse at night/when supine, improved by dependency (hanging leg off bed).
Critical limb ischaemia
IV
Ulceration / Gangrene
Tissue loss — ischaemic ulcers, necrosis, or gangrene. Limb-threatening; urgent vascular referral required.
Critical limb ischaemia
Rutherford Grade Category Clinical Description Equivalent Fontaine
0 0 Asymptomatic — no haemodynamically significant disease Stage I
I 1 Mild claudication Stage IIa
I 2 Moderate claudication Stage IIa/IIb
I 3 Severe claudication Stage IIb
II 4 Ischaemic rest pain Stage III
III 5 Minor tissue loss — non-healing ulcer, focal gangrene with diffuse pedal ischaemia Stage IV
III 6 Major tissue loss — extending above transmetatarsal level, functional foot no longer salvageable Stage IV
Ankle-Brachial Index (ABI)
>1.40 — non-compressible vessels (calcification) — consider toe-brachial index instead, common in diabetes/CKD
1.00–1.40 — normal
0.91–0.99 — borderline
0.41–0.90 — mild-to-moderate PAD (claudication range)
≤0.40 — severe PAD, associated with rest pain/tissue loss (critical limb ischaemia)
Acute Limb Ischaemia (separate entity)
The 6 P's — Pain, Pallor, Pulselessness, Paraesthesia, Paralysis, Perishingly cold
Rutherford Acute Classification — I (viable), IIa (marginally threatened), IIb (immediately threatened), III (irreversible)
Cause — embolic (cardiac source, e.g. AF) vs thrombotic (acute-on-chronic PAD)
Management — surgical/vascular emergency; urgent revascularisation (embolectomy, thrombolysis, bypass) within hours to salvage the limb

Investigations Approach

Peripheral Arterial Disease · Investigations Approach

THE FIRST QUESTION IS: IS THIS CHRONIC PAD OR ACUTE LIMB ISCHAEMIA? Chronic, stable claudication follows a structured outpatient workup (ABI → imaging → cardiovascular risk assessment). A sudden, severely ischaemic limb with the 6 P's bypasses stepwise workup entirely — it is a surgical emergency requiring immediate imaging and revascularisation.
Suspected PAD → Assess onset, severity, and limb viability
CHRONIC / STABLE PAD
1
Clinical assessmentHistory (claudication distance, rest pain), pulse exam, inspection for ulcers/colour change, capillary refill.
2
Ankle-Brachial Index (ABI)First-line objective test. ≤0.90 confirms PAD. If >1.40 (non-compressible), use toe-brachial index instead.
3
Exercise ABI (if resting normal but symptoms suggestive)Treadmill testing unmasks PAD when resting ABI is falsely normal/borderline.
4
Imaging if intervention being consideredDuplex ultrasound first-line; CT or MR angiography for surgical/endovascular planning.
5
Cardiovascular risk workupPAD = marker of systemic atherosclerosis — lipids, HbA1c, BP, smoking status; consider carotid/coronary screening.
ACUTE LIMB ISCHAEMIA
1
Assess the 6 P's immediatelyPain, Pallor, Pulselessness, Paraesthesia, Paralysis, Perishingly cold — determines limb viability and urgency.
2
Skip stepwise workup — call vascular surgery immediatelyNo role for routine ABI/duplex delay if limb is threatened — time is tissue.
3
Bedside handheld DopplerConfirms absent/reduced flow at bedside without delaying definitive care.
4
Urgent CT angiographyDefines level of occlusion for surgical/endovascular planning — done in parallel with surgical referral, not before it.
5
Identify causeECG/echo for embolic source (e.g. AF) vs underlying chronic PAD with acute thrombosis — guides definitive treatment choice.
Investigation Role
Ankle-Brachial Index First-line, bedside, diagnostic and severity marker for chronic PAD; not used in acute limb ischaemia workup
Duplex Ultrasound Non-invasive first-line imaging; localises stenosis/occlusion, assesses flow velocity and vessel patency
CT Angiography Detailed anatomical mapping for revascularisation planning; investigation of choice in acute limb ischaemia
MR Angiography Alternative to CT if contrast/radiation contraindicated; avoid gadolinium in severe renal impairment
Digital Subtraction Angiography Gold standard but invasive; usually reserved for concurrent endovascular intervention
Handheld Doppler Rapid bedside confirmation of arterial signal presence/absence in acute or chronic settings
Supporting Bloods
Lipid profile — atherosclerotic risk assessment
HbA1c/fasting glucose — diabetes is a major PAD risk factor and accelerant
FBC — anaemia can worsen claudication symptoms; polycythaemia/thrombocytosis in acute thrombosis workup
U&E/creatinine — baseline before contrast imaging; renal disease shares risk factors with PAD
Coagulation/thrombophilia screen — in acute limb ischaemia without clear embolic source, especially in younger patients
Pitfalls to Avoid
Don't trust a normal resting ABI if symptoms are convincing — consider exercise ABI before excluding PAD
Falsely elevated ABI — calcified, non-compressible vessels (diabetes, CKD, elderly) give artificially high readings; use toe-brachial index
Don't delay vascular referral for imaging in suspected acute limb ischaemia with a threatened limb
Always assess for systemic atherosclerosis once PAD confirmed — coronary and cerebrovascular disease frequently coexist

Diagnosis

      • Diagnosis of Peripheral Artery Disease (PAD)  is based on:

        • Clinical symptoms
        • ABI ≤0.90
        • Duplex ultrasound
        • CT/MR angiography when revascularization is planned
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Management

Lifestyle Modification

  • Smoking cessation
  • Supervised exercise therapy
  • Weight control
  • Foot care

Medications

  • Antiplatelet therapy (Aspirin or Clopidogrel)
  • High-intensity statin
  • ACE inhibitor/ARB (if indicated)
  • Cilostazol (for claudication, if no heart failure)

Revascularization

  • Endovascular angioplasty ± stenting
  • Surgical bypass
  • Amputation (non-salvageable limb)

Complications

    • Critical limb ischemia
    • Non-healing ulcers
    • Gangrene
    • Limb amputation
    • Acute limb ischemia
    • Myocardial infarction
    • Stroke

Prognosis

  • Stable with risk-factor modification and medical therapy.
  • Patients with Peripheral Artery Disease (PAD) have a significantly increased risk of cardiovascular events.
  • Critical limb ischemia carries a high risk of amputation and mortality.

Key Points / Clinical Pearls

  • Smoking is the strongest modifiable risk factor for Peripheral Artery Disease (PAD).
  • Atherosclerosis is the most common cause of PAD.
  • ABI is the first-line diagnostic test (ABI ≤0.90 confirms PAD).
  • Intermittent claudication is the classic presentation.
  • All patients require aggressive cardiovascular risk reduction.
  • Critical limb ischemia is a vascular emergency requiring urgent revascularization.