Cardiovascular · Year 1 · from Cardiovascular

Case 2: Acute Limb Ischemia - The "Six Ps"

Clinical Image

Source: Wikimedia Commons - Arterial embolism - CC BY-SA 3.0

Patient Presentation

A 72-year-old woman is brought to the emergency department with sudden onset of severe pain in her left leg that began 4 hours ago while she was watching television. She describes the leg as feeling "cold and numb." She has a history of atrial fibrillation and stopped taking her warfarin 2 weeks ago because she ran out and forgot to refill it.

Demographics

  • Age: 72 years
  • Sex: Female
  • Past Medical History: Atrial fibrillation, hypertension, heart failure with preserved ejection fraction
  • Medications: (Should be on) Warfarin, metoprolol, lisinopril, furosemide
  • Social History: Never smoker

Chief Complaint

Sudden severe left leg pain with coldness and numbness for 4 hours

Physical Examination

  • Blood pressure: 142/88 mmHg
  • Heart rate: 94 bpm, irregularly irregular
  • Left lower extremity:
  • Pain: Severe, out of proportion to examination
  • Pallor: Markedly pale, waxy appearance
  • Pulselessness: No palpable femoral, popliteal, or pedal pulses
  • Poikilothermia: Cold to touch, clear demarcation at mid-thigh
  • Paresthesias: Decreased sensation to light touch below knee
  • Paralysis: Weak ankle dorsiflexion (concerning sign)
  • Right lower extremity: Normal pulses, warm, normal sensation

Workup

  • ECG: Atrial fibrillation with controlled ventricular rate
  • INR: 1.1 (subtherapeutic - off warfarin)
  • Lactate: 3.2 mmol/L (elevated)
  • CK: 450 U/L (mildly elevated, early rhabdomyolysis)
  • Creatinine: Normal baseline
  • Echocardiography: Dilated left atrium, no definite thrombus visualized
  • CT angiography (if time permits and not delaying intervention): Embolus at left common femoral artery bifurcation

Diagnosis

Acute Limb Ischemia (Rutherford Class IIb - Immediately Threatened) due to Cardiogenic Embolism from Atrial Fibrillation

Treatment

  1. Immediate: IV heparin anticoagulation
  2. Urgent surgical intervention (within hours):
  • Surgical embolectomy via femoral cutdown with Fogarty catheter
  • Fasciotomy if compartment syndrome suspected
  1. Intraoperative angiography to confirm complete revascularization
  2. Postoperative monitoring for reperfusion injury:
  • Hyperkalemia
  • Metabolic acidosis
  • Myoglobinuria
  1. Long-term anticoagulation for atrial fibrillation (transition to DOAC or warfarin)
  2. Cardiology follow-up for AF management

Physiological Principles Demonstrated

  • Embolic vs. thrombotic occlusion: Sudden onset without prior claudication suggests embolism. Atrial fibrillation is the most common source of arterial embolism.
  • Time-critical nature: Muscle can tolerate approximately 6 hours of ischemia before irreversible damage. Motor weakness (paralysis) indicates advanced ischemia and immediate threat.
  • Reperfusion injury: Restoration of blood flow can cause compartment syndrome, release of myoglobin (rhabdomyolysis), potassium (hyperkalemia), and lactate (acidosis).
  • Rutherford classification guides management: Class IIb (immediately threatened with motor deficit) requires emergent intervention within hours.

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