How to assess for Peripheral Artery Disease (PAD)?

How to Assess for Peripheral Artery Disease (PAD)

Begin by identifying at-risk patients through targeted screening criteria, then confirm the diagnosis with ankle-brachial index (ABI) testing—the resting ABI is the primary diagnostic test and may be the only test needed to establish PAD and initiate treatment. 1, 2

Patient Identification: Who Should Be Assessed

Screen patients meeting any of these criteria 1, 2:

• Age ≥65 years (all patients) 1, 2
• Age 50-64 years with atherosclerotic risk factors: diabetes, smoking history, dyslipidemia, hypertension, chronic kidney disease, or family history of PAD 1, 2
• Age <50 years with diabetes plus one additional atherosclerotic risk factor 1
• Known atherosclerotic disease in other vascular beds (coronary, carotid, subclavian, renal, mesenteric arteries, or abdominal aortic aneurysm) 1, 2

Step 1: Clinical History

Obtain a comprehensive medical history focusing on these specific symptoms 1:

Classic Claudication Characteristics

• Pain type: Aching, burning, cramping, discomfort, or fatigue in muscles 1
• Location: Buttock, thigh, calf, or ankle 1
• Onset pattern: Reproducibly triggered by walking a specific distance or uphill 1
• Relief pattern: Resolves within 10 minutes of rest without position change 1

Critical pitfall: Only 10-11% of PAD patients present with classic claudication—most have atypical symptoms or are asymptomatic. 1, 3

Other Important Symptoms

• Atypical exertional leg symptoms: Muscular discomfort requiring >10 minutes rest, leg weakness, numbness, or fatigue during walking without pain 1
• Ischemic rest pain in the lower extremities 1
• Nonhealing or slow-healing lower extremity wounds 1
• Erectile dysfunction (associated finding) 1

Step 2: Physical Examination

Perform a comprehensive vascular examination 1:

Pulse Palpation (Grade Each Pulse)

Palpate all four lower extremity pulses bilaterally 1, 4:

• Femoral artery
• Popliteal artery
• Dorsalis pedis artery
• Posterior tibial artery

Grading system: 0 = absent, 1 = diminished, 2 = normal, 3 = bounding 1

Key finding: If all four pedal pulses are present bilaterally, PAD is unlikely. 4 The presence of both pedal pulses and absence of femoral bruits has 98.3% specificity and 94.9% negative predictive value for excluding PAD. 5

Auscultation

• Listen for femoral bruits (indicates stenosis) 1
• A femoral bruit has a likelihood ratio of 4.80 for PAD diagnosis 6

Inspection of Legs and Feet

Look for 1:

• Nonhealing wounds or ulcers
• Gangrene
• Asymmetric hair growth
• Nail bed changes
• Calf muscle atrophy
• Elevation pallor or dependent rubor

Bilateral Arm Blood Pressure

Measure blood pressure in both arms at initial assessment 1

• An inter-arm difference >15-20 mmHg suggests subclavian or innominate artery stenosis 1
• Use the higher arm pressure for accurate ABI calculation 1

Step 3: Diagnostic Testing Algorithm

Primary Test: Resting Ankle-Brachial Index (ABI)

The resting ABI is the initial and often only diagnostic test needed. 1, 2

How to perform 1:

• Measure systolic blood pressures at both brachial arteries
• Measure systolic blood pressures at both dorsalis pedis and posterior tibial arteries using Doppler
• Calculate ABI for each leg: divide the higher of dorsalis pedis or posterior tibial pressure by the higher of the two arm pressures

Interpretation 2, 4:

• ABI ≤0.90: PAD confirmed (abnormal)
• ABI 0.91-0.99: Borderline
• ABI 1.00-1.40: Normal
• ABI >1.40: Noncompressible arteries (proceed to toe-brachial index)

When Resting ABI is Normal or Borderline: Exercise Treadmill ABI

Perform exercise treadmill ABI testing when 1, 2:

• Resting ABI is normal (0.91-1.40) or borderline AND patient has exertional leg symptoms
• Need to objectively quantify functional limitation in symptomatic patients

Diagnostic criterion: Post-exercise ABI decrease >20% from baseline confirms PAD 2, 4

When ABI >1.40 (Noncompressible Arteries): Toe-Brachial Index (TBI)

Use TBI in these situations 1, 2:

• ABI >1.40 (common in diabetes and chronic kidney disease due to arterial calcification)
• Suspected critical limb ischemia

Interpretation: TBI <0.70 indicates PAD 2, 4

Critical pitfall: Not using TBI in diabetic or renal disease patients with noncompressible arteries leads to missed diagnoses. 2

Additional Perfusion Assessment (For Critical Limb Ischemia)

When evaluating chronic wounds or critical limb ischemia, assess 2:

• Ankle pressure <50 mmHg
• Toe pressure <30 mmHg
• Transcutaneous oxygen pressure (TcPO2) <30 mmHg
• Apply WIfI classification (Wound, Ischemia, foot Infection) to estimate amputation risk 2

Step 4: Anatomic Imaging (Only When Revascularization Considered)

Do NOT obtain anatomic imaging for 2, 4:

• Asymptomatic PAD patients
• Patients managed with medical therapy alone

For symptomatic patients being considered for revascularization 4:

1. First-line: Duplex ultrasound to diagnose anatomic location and stenosis severity
2. Alternatives: MRA with gadolinium or CTA
3. Invasive angiography: Reserved for patients undergoing intervention

Common Pitfalls to Avoid

1. Relying solely on classic claudication symptoms for diagnosis—this misses 89-90% of PAD patients 2, 3
2. Failing to measure bilateral arm blood pressures leads to inaccurate ABI calculations 2
3. Not performing exercise ABI when resting ABI is normal but clinical suspicion is high 2
4. Using ABI alone in diabetic or chronic kidney disease patients without considering TBI when arteries are noncompressible 2
5. Ordering anatomic imaging in asymptomatic patients or those not being considered for revascularization 2, 4
6. Accepting normal resting ABI as excluding PAD when patient has typical exertional symptoms—exercise testing is needed 2