# Clinical Cases: Peripheral Vascular Disease

## Case 1: Critical Limb Ischemia - Advanced Peripheral Arterial Disease

### Clinical Image
![Critical Limb Ischemia](case_01_image.jpg)
*Source: [Wikimedia Commons - Peripheral arterial disease](https://commons.wikimedia.org/wiki/File:Gangran_foot.jpg) - CC BY-SA 3.0*

### Patient Presentation
A 68-year-old man presents with worsening pain in his right foot that has been present for 3 weeks. The pain is constant, worst at night, and only partially relieved by hanging his leg over the side of the bed. He has a non-healing ulcer on his right great toe that developed 6 weeks ago after he stubbed his toe. He has a 50-pack-year smoking history and quit 2 years ago after a "mini-stroke."

### Demographics
- Age: 68 years
- Sex: Male
- Past Medical History: Type 2 diabetes, hypertension, hyperlipidemia, TIA 2 years ago
- Medications: Metformin, lisinopril, atorvastatin, aspirin
- Social History: Former smoker (50 pack-years), quit 2 years ago

### Chief Complaint
Rest pain in right foot and non-healing toe ulcer

### Physical Examination
- Blood pressure: 148/82 mmHg
- Heart rate: 78 bpm
- Right lower extremity:
  - Dependent rubor, elevation pallor
  - Cool to touch compared to left
  - Hair loss on lower leg and foot
  - Shiny, atrophic skin
  - Ulcer on plantar surface of great toe (2 cm, punched-out, pale base)
  - Femoral pulse: 2+ (palpable)
  - Popliteal pulse: 1+ (diminished)
  - Dorsalis pedis and posterior tibial: Absent
- Left lower extremity: Reduced but palpable pedal pulses

### Workup
- Ankle-brachial index (ABI): Right 0.32, Left 0.68
- Toe-brachial index: Right 0.25 (severe disease)
- Arterial duplex ultrasound: Severe stenoses in right superficial femoral and popliteal arteries, occluded anterior tibial artery
- CT angiography: Confirms multilevel disease; AT artery occluded, PT artery 90% stenosed, peroneal artery patent
- HbA1c: 8.2%
- Wound culture: No evidence of osteomyelitis on MRI

### Diagnosis
Critical Limb Ischemia (Rutherford Category 5) with tissue loss, secondary to multilevel peripheral arterial disease

### Treatment
1. Pain management and wound care
2. Urgent revascularization consultation:
   - Options: Endovascular intervention vs. surgical bypass
   - Decision based on anatomy (TASC classification) and patient factors
3. Antiplatelet therapy (aspirin + clopidogrel perioperatively)
4. High-intensity statin therapy
5. Strict glycemic control
6. Smoking cessation reinforcement (already quit)
7. Wound care with offloading
8. If revascularization not possible or fails: amputation consultation

### Physiological Principles Demonstrated
- **Critical limb ischemia criteria**: Rest pain plus tissue loss (ulceration or gangrene) indicates blood flow insufficient to meet metabolic demands even at rest.
- **Dependent rubor**: Maximally dilated capillaries from chronic ischemia fill with deoxygenated blood when dependent, producing the characteristic color that blanches with elevation.
- **ABI interpretation**: ABI <0.40 indicates severe disease. Values <0.5 are associated with rest pain, and values <0.3-0.4 often indicate critical ischemia.
- **Limb salvage urgency**: Without revascularization, CLI has a 1-year amputation rate of 25-40% and mortality of 20-25%. Prompt intervention is essential.

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

### Clinical Image
![Acute Limb Ischemia](case_01_image.jpg)
*Source: [Wikimedia Commons - Arterial embolism](https://commons.wikimedia.org/wiki/File:Acutelimbischemia.jpg) - 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
3. Intraoperative angiography to confirm complete revascularization
4. Postoperative monitoring for reperfusion injury:
   - Hyperkalemia
   - Metabolic acidosis
   - Myoglobinuria
5. Long-term anticoagulation for atrial fibrillation (transition to DOAC or warfarin)
6. 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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## Case 3: Deep Vein Thrombosis and Pulmonary Embolism - Virchow's Triad

### Clinical Image
![Deep Vein Thrombosis](case_01_image.jpg)
*Source: [Wikimedia Commons - DVT](https://commons.wikimedia.org/wiki/File:Deep_vein_thrombosis_of_the_right_leg.jpg) - CC BY-SA 3.0*

### Patient Presentation
A 45-year-old woman presents to the emergency department with 3 days of left leg swelling and pain. Yesterday she developed shortness of breath with exertion. She returned from a 12-hour flight from Australia 5 days ago. She also mentions she was started on hormone replacement therapy 3 months ago for menopausal symptoms.

### Demographics
- Age: 45 years
- Sex: Female
- Past Medical History: Surgical menopause (hysterectomy 6 months ago for fibroids)
- Medications: Estrogen replacement therapy
- Social History: Occasional alcohol, no smoking

### Chief Complaint
Left leg swelling and pain for 3 days, shortness of breath for 1 day

### Physical Examination
- Blood pressure: 118/76 mmHg
- Heart rate: 105 bpm
- Respiratory rate: 22/min
- Oxygen saturation: 92% on room air
- Left lower extremity:
  - Circumferential swelling (3 cm larger than right at mid-calf)
  - Warmth and erythema
  - Tenderness along the medial thigh
  - Positive Homan's sign (nonspecific)
  - Pitting edema
- Cardiovascular: Tachycardic, regular rhythm
- Respiratory: Clear to auscultation, mild tachypnea

### Workup
- Wells Score for DVT: 4 (moderate-high probability)
- Wells Score for PE: 4.5 (moderate probability)
- D-dimer: 3,450 ng/mL (elevated)
- Compression ultrasound: Non-compressible left common femoral and popliteal veins with echogenic thrombus
- CT pulmonary angiography: Bilateral segmental pulmonary emboli; no RV strain
- Troponin: Mildly elevated
- BNP: 180 pg/mL (mildly elevated)
- Echocardiography: Normal RV size and function

### Diagnosis
Proximal Deep Vein Thrombosis with Submassive (Intermediate-Low Risk) Pulmonary Embolism

### Treatment
1. Anticoagulation initiated immediately:
   - Options: LMWH bridge to warfarin, or DOAC monotherapy (rivaroxaban or apixaban)
2. Duration: Minimum 3 months; extended duration consideration given provoked by modifiable factors
3. Discontinue estrogen therapy (major risk factor)
4. Risk stratification: Intermediate-low risk PE (positive biomarkers but no RV dysfunction) - does not require thrombolysis
5. Graduated compression stockings for DVT symptoms
6. Early ambulation (bed rest not required)
7. Outpatient follow-up; consider IVC filter only if anticoagulation contraindicated

### Physiological Principles Demonstrated
- **Virchow's triad**: This patient demonstrates all three components:
  - Stasis: Prolonged immobility during long-haul flight
  - Endothelial injury: Recent surgery (hysterectomy)
  - Hypercoagulability: Exogenous estrogen therapy
- **DVT and PE connection**: Over 90% of pulmonary emboli originate from lower extremity or pelvic DVT, emphasizing that DVT and PE are the same disease process.
- **Risk stratification**: Not all PEs require aggressive intervention. Hemodynamic stability and RV function determine management intensity.
- **Provoked vs. unprovoked**: This VTE is provoked by identifiable transient risk factors (travel, estrogen), informing duration of anticoagulation and recurrence risk.