Pulmonary Embolism

“A blockage of the artery of the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism)”

Risk Factors

• Modifiable:
  • Prolonged bed rest / reduced mobility
• Non-Modifiable:
  • Recent surgery
  • Thrombophilia
  • Leg fracture
  • Malignancy
  • Pregnancy/postpartum
  • Previous PE

Aetiology & Pathophysiology

• Venous thrombosis → clots break off and pass through veins to the right side of the heart → lodge in the pulmonary circulation
• Rare causes:
  • Right ventricular thrombus (post-MI)
  • Septic emboli (right-sided endocarditis)
  • Fat
  • Air
  • Amniotic fluid embolism
  • Neo-plastic cells
  • Parasites.

Clinical Presentation

Small emboli may be asymptomatic, whereas large emboli are often fatal.

Investigations

• Bloods:
  • FBC, U&E, baseline clotting, D-dimers
  • ABG – may show Low PaO2 and Low PaCO2
• Imaging:
  • Chest X-Ray – may be normal, or show:
    • Oligaemia of the affected segment
    • Dilated pulmonary artery
    • Linear atelectasis
    • Small pleural effusion
    • Wedge-shaped opacities
    • Cavitation (rare)
  • Chest CT pulmonary angiogram
• Special:
  • ECG – may be normal, or show:
    • Tachycardia
    • Right bundle branch block
    • Right ventricular strain (inverted T in V1 to V4)
    • The classical SI QIII TIII pattern is rare

Management

• Haemodynamically stable patient:
  • LMW Heparin OR Unfractionated Heparin if underlying renal impairment
  • Treat for 5 days
  • Then start DOAC or Warfarin
  • For Warfarin, stop Heparin when INR is 2-3 due to initial prothrombotic effect of Warfarin
  • Consider Vena Caval Filter if a contraindication to anticoagulation
• Haemodynamically unstable patient:
  • Thrombolysis for massive PE – Alteplase

Prevention

• Give Heparin to all immobile patients
• Stop HRT + COCP pre-op