Venous thromboembolism

VTE Pathophysiology - The Clot Thickens

• Virchow's Triad underpins VTE development, where ≥2 factors are often present.

• Stasis: Post-op immobility, paralysis, prolonged travel.
• Endothelial Injury: Surgery, trauma, central venous catheters.
• Hypercoagulability:
  • Inherited: Factor V Leiden, Prothrombin G20210A mutation.
  • Acquired: Malignancy, pregnancy, OCPs, Antiphospholipid Syndrome.

⭐ Factor V Leiden is the most common inherited thrombophilia, causing resistance to activated Protein C, a natural anticoagulant.

VTE Diagnosis - Spot the Clot

• Clinical Probability Assessment:
  • Wells' Score: Stratifies risk for DVT/PE. Key criteria include:
    • Clinical signs of DVT (leg swelling, tenderness)
    • Immobilization or surgery in the last 4 weeks
    • Previous DVT/PE
    • Malignancy
• Initial Lab Work:
  • D-Dimer: A fibrin degradation product. High sensitivity, low specificity.
    • Useful to rule out VTE in low-probability patients (if negative).
    • A positive result is non-specific and requires imaging.

• Confirmatory Imaging:
  • DVT: Compression ultrasonography is the first-line test.
  • PE: CT Pulmonary Angiography (CTPA) is the gold standard.
    • 💡 V/Q scan is an alternative if CTPA is contraindicated (e.g., renal failure, contrast allergy).

⭐ PERC Rule (Pulmonary Embolism Rule-out Criteria): In low-risk patients, if all 8 criteria are met (Age <50, HR <100, SaO2 >94%, no unilateral leg swelling, no hemoptysis, no recent surgery/trauma, no prior PE/DVT, no hormone use), PE can be excluded without D-dimer testing.

VTE Management - Clotbusters

• Mechanism: Thrombolytics (e.g., Alteplase/tPA, Reteplase) activate plasminogen to plasmin, which degrades fibrin and dissolves the clot.
• Primary Indication: Reserved for massive PE with hemodynamic instability (e.g., persistent hypotension SBP <90 mmHg, shock) or limb-threatening DVT (phlegmasia cerulea dolens).
• Administration:
  • Systemic IV infusion is the standard approach.
  • Catheter-directed thrombolysis offers a lower-dose, targeted alternative, potentially reducing systemic bleeding risk.
• Key Absolute Contraindications:
  • Any prior intracranial hemorrhage
  • Active bleeding
  • Recent major surgery or trauma (<3 weeks)
  • Ischemic stroke within 3 months

⭐ The most feared complication of thrombolysis is intracranial hemorrhage. A meticulous screening for contraindications is critical before administration.

VTE Prophylaxis - Pre-emptive Strike

• Goal: Prevent DVT/PE in at-risk hospitalized patients.
• Risk Assessment: Use validated scores (e.g., Padua Prediction Score for medical pts, Caprini for surgical pts).

• Pharmacologic Options:

  • LMWH (e.g., Enoxaparin 40 mg SC daily)
  • UFH (e.g., 5000 units SC q8-12h)
  • DOACs (e.g., Apixaban, Rivaroxaban)

• Mechanical Options:

  • Intermittent pneumatic compression (IPC) devices.
  • Graduated compression stockings (GCS).

⭐ High-Yield: In patients with high bleeding risk (e.g., active bleed, severe thrombocytopenia <50,000/μL), mechanical prophylaxis is preferred over anticoagulants.

High‑Yield Points - ⚡ Biggest Takeaways

• Virchow's triad is key: stasis, hypercoagulability, and endothelial injury.
• Use Wells score to risk-stratify. A low score plus a negative D-dimer reliably rules out VTE.
• CT pulmonary angiography (CTPA) is the gold standard for diagnosing PE.
• Compression ultrasound is the first-line imaging for suspected DVT.
• Treat acutely with heparins or DOACs; bridge to warfarin or continue DOACs for long-term therapy.
• Massive PE with hemodynamic instability requires emergent thrombolysis.
• IVC filters are reserved for when anticoagulation is contraindicated or fails.