Pulmonary Embolism

Blockage of a pulmonary artery by an embolus

Aetiology

  • A PE is usually (95%) the result of a DVT - Virchow’s triad
  • Atrial fibrillation can cause PE - blood clots form in the atria due to stasis, and then embolize to the pulmonary arteries

Clinical presentation

Symptoms

  • Dyspnoea - often acute onset
  • Pleuritic chest pain
  • Symptoms of DVT - leg pain, swelling etc.
  • Collapse (/sudden death)
  • Fever
  • Haemoptysis

Signs

  • Tachycardia
  • Hypoxia
  • Cyanosis
  • Low BP

Investigations

  • If Wells score indicates a PE is likely - perform a CTPA
  • If Wells score indicates a PE is unlikely - perform D-dimer and if positive perform a CTPA
  • A V/Q scan is an alternative to a CTPA used in patients with renal impairment, contrast allergy or at risk from radiation where a CTPA is unsuitable
    • Try to avoid using CTPA for pregnant women (use USS or V/Q), however if patient is very unwell CTPA is the best modality so accept risk of radiation

Other imaging

  • CXR - will be normal early on in PE (before infarction), often used to rule out other causes, ‘wedge-shaped infarct’ indicates PE
  • USS leg - if radiation to be avoided or DVT suspected

Other tests

  • ECG - sinus tachycardia, S1Q3T3 (right heart strain pattern)
  • Troponin - may be raised due to strain on right ventricle, raised troponin is associated with worse outcomes
  • ABG - type I resp failure, respiratory alkalosis
  • Investigate underlying cause - USS, cancer screen, autoantibodies (SLE), thrombophilia screen

Management

Acute management

  • Anticoagulation - apixaban or rivaroxaban (DOACs) first line
    • May be outpatient if patient considered low-risk
    • If neither apixaban or rivaroxaban are suitable then either LMWH followed by dabigatran or edoxaban OR LMWH followed by a vitamin K antagonist (VKA, i.e. warfarin)
  • Thrombolysis is recommended as the first-line treatment for massive PE where there is circulatory failure (e.g. hypotension)

Secondary prevention

  • The options for long term anticoagulation are warfarin, a DOAC or LMWH
  • Treatment with a should be continued for at least three months
    • Provoked DVT with reversible factors - 3 months
    • Provoked DVT with irreversible factors, or unprovoked DVT - 3-6 months, potentially life-long depending on patient factors (e.g. genetic clotting disorder)
      •