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- Pulmonary embolism (PE) is the most serious presentation of venous thromboembolism (VTE).
- Mortality exceeds 15% during the first 3 months. In 25% of patients, first manifestation is sudden death.
Case fatality rate 1–60%. For patients with intermediate risk, mortality rate is 3–15% if right ventricular (RV) dilation or dysfunction. If hemodynamically unstable, mortality is >15% due to worsening RV failure and cardiogenic shock.
- Approximately 60 to 70 per 100,000, with >100,000 cases annually in the United States
- Incidence increases with age, most occurring at 60 to 70 years of age.
- 250,000 hospitalizations per year in the United States, 10–60% in hospitalized patients
- Highest risk for orthopedic patients
- 1:1,000 pregnancies (including postpartum)
Etiology and Pathophysiology
- Venous stasis, endothelial damage, and changes in coagulation properties trigger formation of thrombus (1).
- Causes increased pulmonary vascular resistance, impaired gas exchange, and decreased pulmonary compliance. RV failure due to pressure overload is usually the primary cause of death (1).
- DVT in the proximal veins is the most common source of PE, up to 85% of the cases.
- Factor V Leiden: Most common thrombophilia. +5.5% in Caucasian, 2.2% in Hispanics, 1.2% in African American, 0.5% in Asian; associated with 20% of all VTE
- Prothrombin G20210A: 3% of Caucasians, rare in African American, Asian, and Native American; 6% in patients with VTE
- Deficiencies in protein C, S, and antithrombin
- Acquired: age, immobilization, surgery, major trauma, lower limb fractures, joint replacement, spinal cord injury, cancer, hormonal replacement therapy, pregnancy/puerperium, previous thrombosis, paroxysmal nocturnal hemoglobinuria, antiphospholipid syndrome, prolonged travel
- Oral contraceptive is the most frequent medication (1).
- Inherited: antithrombin deficiency, protein C or S deficiency, factor V Leiden, prothrombin gene mutation G20210A (1)
- Mechanical thromboprophylaxis: early ambulation after surgery, compression stockings, and intermittent pneumatic compression
- Intermediate risk: general, gynecologic, or urologic surgery; prophylaxis is recommended with low-molecular-weight heparin (LMWH), unfractionated heparin (UFH), or fondaparinux.
- High risk: 10 or more days prophylaxis in hip or knee arthroplasty, with LMWH, fondaparinux, apixaban, dabigatran, rivaroxaban, or low-dose UFH. 28 to 35 days with LMWH, fondaparinux, UFH, or vitamin K antagonists (VKA) in hip fracture surgery; LMWH or UFH in major trauma, spinal cord injury
- Long-distance travel (>8 hours): hydration, walking, avoidance of constrictive clothing and frequent calf exercises; if additional risk factors, then compression stockings below knee
- Patients with factor V Leiden, prothrombin G20210A with no previous thrombosis do not need long-term daily prophylaxis.