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Pulmonary Embolism

From Mediwikis

CT Scan showing Pulmonary Embolism

Thrombus formed in the systemic veins (10% in the right heart) may dislodge and embolise into the pulmonary arterial system. 10% of pulmonary emboli are fatal. Clot forms as a result of a combination of sluggish blood flow, local injury/compression of the vein and a hypercoagulable state. After pulmonary embolism, lung tissue is ventilated but not perfused - producing an intrapulmonary dead space and resulting in impaired gas exchange.

Symptoms and Signs

  • Sudden onset unexplained dyspnoea

When infarction has occurred:

  • Pleuritic chest pain
  • Haemoptysis

Small/Medium Pulmonary Embolism

Embolus -> terminal pulmonary vessel.
An overview of Pulmonary Embolism, courtesy of AllAccessMedicine.
  • Pleuritic chest pain
  • Breathlessness
  • Haemoptysis (30%)
  • Fever
  • Tachypnoeic
  • Localised pleural rub
  • Coarse crackles
  • Pleural effusion

Massive Pulmonary Embolism

Rare sudden collapse. Acute obstruction of right ventricular outflow tract.

  • Severe central chest pain (cardiac ischaemia due to decreased coronary blood flow)
  • Shocked, pale, sweaty
  • Syncope (reduced cardiac output)
  • Shock
    • Tachypnoeic
    • Tachycardia
    • Hypotension
    • Peripheral shutdown
  • Raised JVP
  • Right ventricular heave
  • Gallop rhythm (3/4 sounds - heart failure)

Multiple Recurrent Pulmonary Emboli

Multiple occlusions of pulmonary vasculature, causing pulmonary hypertension.

  • Gradual breathlessness (over weeks - months)
  • Weakness
  • Syncope on exertion
  • Angina
  • Right ventricular overload
  • Right ventricular heave
  • Loud pulmonary second sound


Small/Medium Pulmonary Emboli

  • Chest X-Ray
    • Normal
  • ECG
    • Normal
    • Sinus tachycardia
  • Blood tests
    • Increased WCC, ESR and lactate dehydrogenase (pulmonary infarction)
  • Plasma D-Dimer
    • If undetectable, excludes diagnosis of pulmonary embolism
  • Radionuclide Ventilation/Perfusion Scan (V/Q Scan)
  • Ultrasound
    • Clots in pelvic veins
  • CT/MRI scan
    • Medium-sized pulmonary emboli

Massive Pulmonary Emboli

  • Chest X-Ray
    • Pulmonary oligaemia
    • Dilatation of pulmonary artery in hila
  • ECG
    • Right atrial dilatation - tall peaked T waves in lead II
    • Right ventricular strain and dilatation - right axis deviation, RBBB, T wave inversion
  • Blood gases
    • Hypoxia
    • Hypocapnia
  • Echocardiogram
    • Vigorously contracting left ventricle
    • Clot in right ventricular outflow tract
  • Pulmonary angiography (if surgery is considered)

Multiple Recurrent Pulmonary Emboli

  • Chest X-Ray
    • Enlarged pulmonary arterioles with oligaemic lung fields
  • ECG
    • Pulmonary hypertension - right axis deviation, right ventricular hypertrophy
  • Leg imaging - Ultrasound & Venography
    • Thrombi
    • Radionuclide Ventilation/Perfusion Scan (V/Q Scan)



  • High flow O2 (unless significant chronic lung disease)
  • Bed rest
  • Analgesia
  • IV fluids
  • Inotropic agents - improve pumping of right heart

Dissolution of Thrombus

If major embolism:

  • Fibrinolytic therapy (e.g. - streptokinase IV infusion)

Prevention of Further Emboli

  • IV heparin
  • Oral anticoagulants
  • Physiotherapy