What is Peripheral Artery Disease (PAD) in a patient with intermittent lower leg pain and a history of smoking or other cardiovascular risk factors?

What is Peripheral Artery Disease (PAD)?

Peripheral artery disease is atherosclerotic blockage of the arteries supplying the lower extremities, affecting approximately 230 million people worldwide and 12-20% of Americans over age 60, characterized by reduced blood flow that causes intermittent claudication, ischemic rest pain, non-healing wounds, or may be entirely asymptomatic. 1, 2, 3

Core Pathophysiology

• PAD results from atherosclerotic plaque buildup causing arterial stenosis or occlusion in the abdominal aorta, iliac, and lower extremity arteries 1, 4, 2
• The disease reduces blood flow to the limbs, creating a mismatch between oxygen supply and demand during exertion or at rest in severe cases 1, 4
• Beyond simple flow limitation, PAD involves complex skeletal muscle metabolic dysfunction, neurological effects, and inflammatory processes 1

Clinical Presentations: The Spectrum

Only 10% of PAD patients experience classic intermittent claudication—the hallmark symptom of reproducible leg pain with walking that resolves within 10 minutes of rest. 3, 5

Symptom Distribution

• 40% are completely asymptomatic despite having objectively confirmed disease 3, 5
• 50% experience atypical leg symptoms that differ from classic claudication, including various forms of walking impairment 3
• 10% present with classic intermittent claudication (cramping, aching pain in calf, thigh, or buttock with exertion, relieved by rest) 3, 5
• A minority develop critical limb ischemia with ischemic rest pain, non-healing wounds, ulcerations, or gangrene 1, 4

Anatomic Correlation with Symptoms

• Iliac artery disease produces hip, buttock, thigh, and calf pain 1
• Femoral and popliteal artery disease typically causes calf pain 1
• Tibial artery disease may produce calf pain or, rarely, foot pain and numbness 1

Who Is at Risk?

The American College of Cardiology identifies specific populations requiring PAD assessment: 1

• Age ≥65 years (all individuals) 1
• Age 50-64 years with atherosclerosis risk factors (diabetes, smoking history, hyperlipidemia, hypertension) or family history of PAD 1
• Age <50 years with diabetes plus one additional atherosclerosis risk factor 1
• Any age with known atherosclerotic disease elsewhere (coronary, carotid, subclavian, renal, mesenteric stenosis, or abdominal aortic aneurysm) 1

Major Risk Factors

• Smoking (most significant modifiable risk factor) 1, 6, 3
• Diabetes mellitus (confers 10-fold increased risk when combined with other factors) 1, 6, 3
• Hyperlipidemia 1, 6, 3
• Hypertension 1, 6, 3
• Chronic kidney disease 3

Physical Examination Findings

Pulse Assessment

• Palpate femoral, popliteal, dorsalis pedis, and posterior tibial pulses 1
• Record numerically: 0 (absent), 1 (diminished), 2 (normal), 3 (bounding) 1

Inspection Requirements

• Remove shoes and socks completely 1
• Assess skin color, temperature, and integrity 1
• Look for distal hair loss, trophic skin changes, hypertrophic nails 1
• Inspect for ulcerations, particularly in intertriginous areas 1

Auscultation

• Listen for femoral bruits indicating turbulent flow from focal stenoses 1
• Check for carotid bruits as markers of systemic atherosclerosis 1

Blood Pressure Measurement

• Measure blood pressure in both arms at least once during initial assessment 1
• Inter-arm difference >15-20 mmHg suggests subclavian or innominate artery stenosis 1

Diagnostic Confirmation

The resting ankle-brachial index (ABI) is the initial and often only diagnostic test required to establish PAD diagnosis. 1, 5

ABI Interpretation

• <0.9 = PAD diagnosis confirmed 5
• <0.4 = Critical limb ischemia requiring urgent vascular specialist referral within 24 hours 7, 8
• Normal ABI with symptoms warrants exercise ABI testing 3

Special Consideration for Diabetics

• Medial arterial calcification can falsely elevate ABI in diabetic patients 7
• Measure toe-brachial index and transcutaneous oxygen pressure (TcPO2) when ABI appears normal despite clinical suspicion 7

The Critical Prognostic Reality

PAD patients face a 50% mortality rate at 5 years, primarily from myocardial infarction, stroke, and cardiovascular death—not from limb complications. 8, 4

• Cardiovascular ischemic events occur far more frequently than limb ischemic events in any PAD cohort 1
• PAD confers a 2-4 fold increased relative risk for cardiovascular events and all-cause mortality 5
• From the limb standpoint, prognosis is relatively favorable: claudication remains stable in 70-80% of patients over 10 years 4

Common Pitfalls to Avoid

• Never assume bilateral presentation excludes vascular disease—bilateral PAD is common 7
• Do not delay vascular assessment in diabetic patients with neuropathy, as presentation may be subtle with absent pain despite severe ischemia 7, 8
• Recognize that 40% of PAD patients have no leg symptoms, so screening should be based on risk factors, not symptoms alone 8, 3
• Distinguish PAD from pseudoclaudication (venous disease, spinal stenosis, chronic compartment syndrome, osteoarthritis)—vascular claudication improves within 10 minutes of rest, worsens with inclines, and is associated with diminished pulses 1, 7