Pulmonary Embolism

Pulmonary Embolism is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • Pulmonary embolism (PE) is the most serious presentation of venous thromboembolism (VTE).
  • Classified based on severity:
    • Low-risk PE: acute and absence of clinical markers of adverse prognosis (1)
    • Submassive PE: no systemic hypotension, but there is either myocardial necrosis (elevated troponin) or right ventricle (RV) dysfunction (RV dilation or systolic dysfunction on echocardiography [Echo], RV/LV ratio >1 on CT, elevation of B-type natriuretic peptide [BNP] or N-terminal pro-BNP, or consistent ECG changes) (1,2)
    • Massive PE: hemodynamic instability with sustained hypotension; pulselessness; or persistent bradycardia, cardiogenic shock, acute manifesting RV failure (1)

Epidemiology

Case fatality rates vary widely (1–60%); case fatality rate is approximately 11% at 2 weeks (1,2).

Incidence
  • Approximately 30 to 80/100,000, with higher incidence in African Americans and lower in Asians; >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 and cancer patients
    • 1:1,000 pregnancies (including postpartum)

Etiology and Pathophysiology

  • Venous stasis, endothelial damage, and changes in coagulation properties trigger 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).
  • The most common source (85%) of PE is proximal lower extremity deep vein thrombosis.

Genetics
  • 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 VTE
  • Prothrombin G20210A: 3% of Caucasians; rare in African American, Asian, and Native American; 6% in patients with VTE
  • Rarely, deficiencies in protein C, S, and antithrombin

Risk Factors

  • Older age, obesity, prolonged immobilization, surgery, major trauma, joint replacement, spinal cord injury, cancer, hormonal replacement therapy, pregnancy/puerperium, previous thrombosis, antiphospholipid syndrome, genetics
  • Oral contraceptive is the most frequent VTE risk factor in fertile women (1).

General Prevention

  • Low VTE risk: early ambulation after surgery, compression stockings, and intermittent pneumatic compression
  • Intermediate VTE risk: low-molecular-weight heparin (LMWH), unfractionated heparin (UFH), or fondaparinux
  • Hip or knee arthroplasty (high VTE risk): 10 or more days prophylaxis with LMWH, fondaparinux, apixaban, dabigatran, rivaroxaban, or low-dose UFH
  • Spinal cord injury, hip fracture surgery, and trauma surgery (high VTE risk): 28 to 35 days with LMWH, fondaparinux, UFH, or vitamin K antagonists (VKA)
  • Long-distance travel (>8 hours): hydration, walking, avoidance of constrictive clothing and frequent calf exercises, compression stockings below knee
  • Patients with factor V Leiden, prothrombin G20210A with no previous thrombosis do not need prophylaxis.

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