Peripheral Arterial Disease (PAD)

Lecture Overview

• Discussion on PAD as part of clinical medicine series.
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• Mention of resources: website with notes, illustrations, prep courses, and merchandise.

Types of PAD

1. Thrombotic PAD
   • Caused by plaques and thrombi (clots) on plaques.
2. Embolic PAD
   • Caused by clots that travel and block peripheral arteries.
3. Vasospastic PAD
   • Caused by intense vasoconstriction, often in critical care.

Affected Peripheral Arteries

• Lower extremities more common than upper extremities.
• Key vessels affected:
  • Aorto-iliac arteries
  • Femoral-popliteal arteries
  • Tibiofibular arteries

Pathophysiology

• Narrowing of vessel lumen leading to reduced oxygen supply, ischemia, and potentially infarction.
• Atherosclerosis: Main cause of plaque formation.
  • Risk Factors: SAD CHF (Smoking, Advanced Age, Diabetes, Dyslipidemia, Hypertension, Family History)
• Complications: Claudication, Critical Limb Ischemia (CLI), Acute Limb Ischemia (ALI)

Embolic PAD

• Clots originated as thrombi and traveled (emboli).
• Causes: atrial fibrillation, post-MI left ventricular aneurysm, abdominal aortic aneurysm (AAA).
• Leads to tissue ischemia and complications similar to thrombotic PAD.

Vasospastic PAD

• Massive vasoconstriction, commonly in fingers and toes.
• Causes: Critical illness, shock, use of vasopressors (e.g., norepinephrine, epinephrine).
• Symptoms: Decreased pulses, skin discoloration, digital necrosis.

Symptoms and Presentation

1. Claudication

   • Pain in muscles during exertion due to reduced oxygen supply.
   • Location-specific pain:
     • Aorto-iliac: Hip and buttock
     • Femoral-popliteal: Calf
     • Tibiofibular: Foot
   • Intermittent and improves with rest.

2. Critical Limb Ischemia (CLI)

   • Severe reduction in blood supply.
   • Pain at rest, more chronic (>2 weeks).
   • Associated symptoms: Hair loss, skin atrophy, arterial ulcers, gangrene.

3. Acute Limb Ischemia (ALI)

   • Often due to embolic PAD or thrombotic PAD (plaque rupture with clot formation).
   • Sudden, severe ischemia causing: pain, paralysis, paresthesias, pulselessness, pallor (5Ps).
   • Possible gangrene if untreated.

Diagnosis

• Ankle Brachial Index (ABI):
  • Comparing ankle and brachial blood pressures.
  • Normal: 1 to 1.4
  • PAD: ≤0.9
  • Severe PAD: <0.4
• Further Assessment:
  • Duplex arterial ultrasound (if risk of contrast nephropathy).
  • Angiography (CT, MRI, or digital subtraction angiogram).

Treatment

1. Severe Cases (gangrenous limbs, critical/acute limb ischemia):

   • Amputation (above/below knee).
   • Revascularization (stenting, grafting, endarterectomy).
   • Acute limb ischemia: Heparin and thromboembolecomy, possibly TPA.

2. Non-Critical Cases (intermittent claudication):

   • Modify risk factors (stop smoking, manage diabetes, control cholesterol and blood pressure).
   • Antiplatelets (e.g., aspirin).
   • Exercise therapy.
   • Cilostazol (anti-platelet and vasodilator).

Summary

• PAD affects lower extremities, primarily involving thrombotic, embolic, and vasospastic mechanisms.
• Symptoms range from claudication to critical and acute limb ischemia, with potential severe complications if untreated.
• Diagnosis involves ABI and possibly further imaging, while treatment depends on severity and may involve lifestyle changes, medications, and surgical interventions.