Peripheral arterial disease

Pathophysiology - Clogged Pipes 101

• Atherosclerosis is the primary cause, leading to stenosis or occlusion.
• Major Risk Factors: Smoking (strongest), Diabetes Mellitus, Hyperlipidemia, Hypertension.
• Process: Endothelial injury → lipid deposition (LDLs) → foam cell & plaque formation → narrowed lumen → ↓ blood flow (ischemia).
• Most Common Sites: Superficial femoral artery (SFA) in Hunter's canal, followed by the popliteal artery.

⭐ Leriche Syndrome Triad (Aortoiliac occlusion):

1. Bilateral hip, thigh, and buttock claudication
2. Impotence
3. Symmetric atrophy of the bilateral lower extremities.

Clinical Features - The Leg's Complaint

• Intermittent Claudication: Reproducible muscle pain (calf, thigh, buttock) on exertion, promptly relieved by rest.
• Rest Pain: Severe, nocturnal forefoot pain, relieved by dependency (hanging foot off bed). A key feature of Critical Limb Ischemia (CLI).
• Physical Signs:
  • Shiny, atrophic skin with hair loss.
  • Dependent rubor and elevation pallor.
  • Cool skin; diminished or absent pulses.
• Tissue Loss (Advanced Disease):
  • Arterial Ulcers: Deep, "punched-out," painful lesions on distal toes or pressure points.
  • Gangrene.

⭐ The location of arterial ulcers (e.g., tips of the toes, pressure points) is a key differentiator from venous ulcers (typically over the medial malleolus).

Diagnosis - Checking the Flow

• Ankle-Brachial Index (ABI): Best initial, non-invasive test.
  • Calculated as $ABI = \frac{\text{Highest Ankle SBP}}{\text{Highest Brachial SBP}}$.
  • Interpretation:
    • < 0.9: Diagnostic of PAD.
    • < 0.4: Severe disease / Critical Limb Ischemia (CLI).
    • > 1.4: Calcified, non-compressible vessels (e.g., advanced age, diabetes).

⭐ An Ankle-Brachial Index (ABI) of <0.9 is the simple, non-invasive, first-line test for diagnosing PAD.

• Imaging:
  • Doppler US: Localizes lesions.
  • CTA/MRA: Gold standard for anatomical detail before revascularization.

Management - Restoring the Rush

⭐ A supervised exercise program is a highly effective, first-line intervention for intermittent claudication that can improve symptoms and walking distance significantly.

• Conservative Management

  • Risk Factor Modification: Smoking cessation is paramount. Also manage HTN, DM, HLD.
  • Supervised Exercise Therapy: Walk until near-maximal claudication pain, rest, repeat.

• Medical Management

  • Antiplatelet Therapy: Aspirin or Clopidogrel to reduce MI/stroke risk.
  • Statins: All patients with PAD should be on a statin, regardless of LDL level.
  • Cilostazol: Phosphodiesterase inhibitor; most effective medical therapy for claudication symptoms.

• Surgical Intervention

  • Revascularization: For limb-threatening ischemia or debilitating, refractory symptoms.
    • Percutaneous: Angioplasty ± Stenting
    • Surgical: Bypass grafting (e.g., fem-pop)
  • Amputation: For non-salvageable limbs (gangrene, intractable pain).

High-Yield Points - ⚡ Biggest Takeaways

• Atherosclerosis of the lower extremities is the primary cause, most commonly affecting the superficial femoral artery.
• Intermittent claudication is the hallmark symptom: reproducible leg pain with exertion that is relieved by rest.
• An Ankle-Brachial Index (ABI) < 0.9 is the main screening and diagnostic test.
• Cilostazol is the most effective medical therapy specifically for claudication symptoms.
• Aspirin and statins are critical for reducing cardiovascular risk, including MI and stroke.
• Critical limb ischemia presents as rest pain, non-healing arterial ulcers, or gangrene.