A 58-year-old man with a history of recent orthopedic surgery presents with acute onset dyspnea and chest pain. Imaging confirms pulmonary embolism. Which is the most common source of thromboembolism in this patient?

Explanation

## Most Common Source of Pulmonary Embolism **Key Point:** Deep vein thrombosis (DVT) of the lower extremities accounts for approximately 90–95% of clinically significant pulmonary emboli. The remaining 5–10% originate from the right heart chambers, pelvic veins, or upper extremity veins. ### Pathophysiology of DVT-to-PE Progression Thrombi form in the deep veins of the legs (particularly the popliteal, femoral, and iliac veins) due to: - Venous stasis (immobility, surgery, malignancy) - Endothelial injury (trauma, central lines, previous thrombosis) - Hypercoagulability (malignancy, thrombophilia, postoperative state) Once formed, these thrombi can dislodge and travel through the right heart to lodge in the pulmonary arterial tree. ### Why Lower Limb DVT is Most Common | Feature | Lower Limb DVT | Right Heart Thrombus | PFO Paradoxical Embolism | |---------|---|---|---| | Frequency as PE source | 90–95% | 5–10% | <1% | | Risk factors | Immobility, surgery, malignancy | RV dysfunction, AF, MI | Hypercoagulable state + cardiac defect | | Clinical detection | Leg swelling, pain, Wells score | Echo findings, hemodynamic instability | Cryptogenic stroke history | **Clinical Pearl:** In this patient with recent orthopedic surgery, immobilization and endothelial injury from the procedure create a prothrombotic milieu. The lower limbs are the most common site of DVT formation. **High-Yield:** Always examine for signs of DVT (unilateral leg edema, calf tenderness, positive Homan's sign) in any patient presenting with PE. Compression ultrasound of the legs is the first-line imaging modality to identify the source. **Mnemonic — Virchow's Triad:** **VEH** = **V**enous stasis, **E**ndothelial injury, **H**ypercoagulability. All three are present in the postoperative patient.