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Arterial Diseases of the Extremities

Chapter 292 | Harrison's 22e · Part 6 – Cardiovascular Disorders · Chapter 292

Key Clinical Points

  1. Peripheral artery disease (PAD) is a clinical disorder resulting from stenosis or occlusion in the aorta or limb arteries.
  2. Atherosclerosis is the primary cause of PAD in patients >40 years old, with high prevalence in the sixth and seventh decades of life.
  3. Intermittent claudication is the hallmark symptom, characterized by muscle pain/cramping during exercise relieved by rest; its location indicates the site of occlusion (e.g., calf → femoral-popliteal).
  4. Ankle-brachial index (ABI) is the primary noninvasive diagnostic tool: 1.00–1.40 is normal, 0.91–0.99 is borderline, and ≤0.90 is abnormal/diagnostic of PAD.
  5. Toe-brachial index (TBI) ≤0.70 is used when ABI is unreliable due to vascular calcification (e.g., in patients with diabetes or CKD).
  6. Severe ischemia may manifest as persistent rest pain or ischemic neuropathy (numbness and hyporeflexia).
  7. Physical signs of PAD include diminished pulses, bruits, muscle atrophy, and trophic changes (hair loss, thickened nails, skin changes).
  8. Raynaud phenomenon is a distinct condition involving episodic vasospasm triggered by cold or stress, categorized into primary and secondary forms.
  9. MRA, CTA, and catheter-based angiography are utilized for pre-revascularization planning to define anatomy.
  10. Atherosclerotic lesions occur preferentially at arterial branch points due to increased turbulence and altered shear stress.

DEFINITION & CLASSIFICATION

• Peripheral artery disease (PAD): Defined as a clinical disorder in which there is a stenosis or occlusion in the aorta or the arteries of the limbs.

• Primary Cause: Atherosclerosis is the leading cause of PAD in patients >40 years old.

EPIDEMIOLOGY

• Demographics: Highest prevalence of atherosclerotic PAD occurs in the sixth and seventh decades of life.

• Risk Factors: Prevalence is similar in men and women, but higher in patients identified as black than non-Hispanic white. Risk factors include: 1. Cigarette smoking 2. Diabetes mellitus 3. Hypercholesterolemia 4. Elevated lipoprotein(a) 5. Hypertension 6. Renal insufficiency

ETIOLOGY & PATHOPHYISIOLOGY

• Non-Atherosclerotic Causes: Thrombosis, embolism, vasculitis, fibromuscular dysplasia, entrapment, cystic adventitial disease, and trauma.

• Pathology of Atherosclerotic Lesions: Characterized by: 1. Calcification deposition 2. Thinning of the media 3. Patchy destruction of muscle and elastic fibers 4. Fragmentation of the internal elastic lamina 5. Thrombi composed of platelets and fibrin.

• Site Prevalence: Lesions occur preferentially at arterial branch points (sites of increased turbulence, altered shear stress, and intimal injury). Frequency of involvement: 1. Abdominal aorta and iliac arteries: 30% of symptomatic patients 2. Femoral and popliteal arteries: 80–90% of patients 3. Distal vessels (tibial and peroneal): 40–50% of patients.

CLINICAL FEATURES

• Symptoms: 1. Intermittent Claudication: The most typical symptom; defined as pain, ache, cramp, numbness, or a sense of fatigue in the muscles during exercise and relieved by rest. 2. Localization Mapping: - Buttock, hip, thigh → indicates aortoiliac disease. - Calf → indicates femoral-popliteal disease. 3. Severe Ischemia: - Persistent rest pain (occurs when blood flow cannot accommodate basal nutritional needs). - Ischemic neuropathy: Results in numbness and hyporeflexia.

• Physical Examination: 1. Palpation: Assessment of femoral, popliteal, dorsalis pedis, and posterior tibial pulses. 2. Auscultation: Evaluation of the abdomen and groin for bruits. 3. Inspection: Visual assessment of legs and feet.

• Physical Signs of PAD: 1. Vascular Findings: Decreased or absent pulses distal to obstruction; bruits over narrowed arteries. 2. Musculoskeletal/Trophic Changes: Muscle atrophy, hair loss, thickened nails, smooth and shiny skin, reduced skin temperature, pallor, or cyanosis. 3. Chronic Ischemia Signs (Figure 3): Erythema, scaling, and calluses on the soles of the feet.

DIAGNOSTIC APPROACH

  1. Noninvasive Assessment: Used to establish diagnosis and assess severity.
  2. Ankle-Brachial Index (ABI):
  3. Calculation: Ratio of ankle systolic pressure to brachial artery systolic pressure.
  4. Normal: 1.00–1.40
  5. Borderline: 0.91–0.99
  6. Abnormal/Diagnostic of PAD: ≤0.90
  7. Toe-Brachial Index (TBI):
  8. Used when ABI is inaccurate due to vascular calcification (e.g., diabetes, CKD).
  9. Abnormal: ≤0.70
  10. Additional Noninvasive Tests:
  11. Segmental pressure measurements.
  12. Pulse volume recordings (blunted contour indicates significant PAD).
  13. Duplex ultrasonography (B-mode imaging and Doppler flow velocity analysis) to detect stenoses in native arteries and bypass grafts.
  14. Transcutaneous oximetry.
  15. Stress testing (treadmill):
  16. Purpose: Assess functional limitations.

  17. Finding: Decline of ABI immediately after exercise supports diagnosis in equivocal cases.

  18. Pre-revascularization Imaging: Used to define anatomy for endovascular and surgical planning.

  19. Magnetic resonance angiography (MRA) (Figure 1).
  20. Computed tomographic angiography (CTA).
  21. Conventional catheter-based angiography.

SPECIAL POPULATIONS

• Raynaud Phenomenon: Characterized by blanching, cyanosis, and rubor of the fingers or toes after cold exposure or emotional stress.

• Classification (Table 292-1): Secondary Raynaud phenomenon is associated with: 1. Collagen vascular diseases: scleroderma, systemic lupus erythematosus, rheumatoid arthritis, dermatomyositis, polymyositis, mixed connective tissue disease, Sjögren syndrome. 2. Arterial occlusive diseases: atherosclerosis of the extremities, thromboangiitis obliterans, acute arterial occlusion, thoracic outlet syndrome. 3. Pulmonary hypertension. 4. Neurologic disorders: intervertebral disk disease, syringomyelia, spinal cord tumors, stroke, poliomyelitis, carpal tunnel syndrome, complex regional pain syndrome. 5. Blood dyscrasias: cold agglutinins, cryoglobulinemia, cryofibrinogenemia, myeloproliferative disorders, lymphoplasmacytic lymphoma. 6. Trauma: vibration injury, hammer hand syndrome, electric shock, cold injury, typing, piano playing. 7. Drugs and toxins: ergot derivatives, methysergide, β-adrenergic receptor blockers, bleomycin, vinblastine, cisplatin, gemcitabine, vinyl chloride.

Reference Tables

TABLE 292-1 Classification of Raynaud Phenomenon Primary or idiopathic Raynaud phenomenon Secondary Raynaud phenomenon

Harrison's 22e, p.2177

  • Primary or idiopathic Raynaud phenomenon
  • Secondary Raynaud phenomenon
  • Collagen vascular diseases: scleroderma, systemic lupus erythematosus,
    rheumatoid arthritis, dermatomyositis, polymyositis, mixed connective tissue
    disease, Sjögren syndrome
  • Arterial occlusive diseases: atherosclerosis of the extremities,
    thromboangiitis obliterans, acute arterial occlusion, thoracic outlet syndrome
  • Pulmonary hypertension
  • Neurologic disorders: intervertebral disk disease, syringomyelia, spinal cord
    tumors, stroke, poliomyelitis, carpal tunnel syndrome, complex regional pain
    syndrome
  • Blood dyscrasias: cold agglutinins, cryoglobulinemia, cryofibrinogenemia,
    myeloproliferative disorders, lymphoplasmacytic lymphoma
  • Trauma: vibration injury, hammer hand syndrome, electric shock, cold injury,
    typing, piano playing
  • Drugs and toxins: ergot derivatives, methysergide, β-adrenergic receptor
    blockers, bleomycin, vinblastine, cisplatin, gemcitabine, vinyl chloride