🎯 Pathology

• blood clot (thrombus) in the deep veins of the legs dislodge (becomes an embolus) —> travels to the heart —> gets stuck in the pulmonary circulation —> reduced blood flow in the pulmonary circulation —> increased strain on the right side of the heart leading to pulmonary hypertension

• thrombus = blood clot

• embolus = dislodged blood clot in the bloodstream

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💡 Causes

• Virchow’s triad

  1. Blood stasis

     • obesity

     • long haul flights

     • recent surgery / prolonged bed rest / reduced mobility

  2. Blood hypercoagulability

     • thrombophilias —> factor V Leiden, prothrombin gene mutation, antiphospholipid syndrome

     • malignancy

     • drugs —> combined oral contraceptive pill (COCP) and hormone replacement therapy (HRT)

     • pregnancy (state of hypercoagulability to minimise blood loss)

  3. Endothelial injury

     • cigarette smoking

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🩺 Clinical features

• Small emboli —> can be asymptomatic

• Large emboli —> can be life-threatening

• symptoms

  • pleuritic chest pain (pain worse on inspiration)

  • shortness of breath

• signs

  • tachycardia, tachypnoea

  • hypotension in a saddle embolus

  • fever

  • haemoptysis

  • raised JVP

  • look for unilateral leg swelling (deep vein thrombosis)

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🕵️‍♂️ Investigations

• best initial tests

  • calculate Well’s score

    • if > 4 —> PE is likely

      • next step —> CT pulmonary angiogram with contrast

    • if ≤ 4 —> PE unlikely

      • next step —> D-dimer

      • if D-dimer is high (≥ 500 ng/mL) —> CT pulmonary angiogram with contrast

• other tests

  • ECG

    • most common rhythm —> sinus tachycardia

    • “classical” rhythm —> S1Q3T3 (deep S wave in lead I, Q wave in lead III, and an inverted I wave in lead III)

• ABG

  • low PaO2 and PaCO2 due to hyperventilation —> respiratory alkalosis

• chest x-ray

  • usually normal

  • may show Hampton’s hump (wedge-shaped infarct) and Westermark sign (collapse of the vessels distal to the PE)

• V/Q scan

  • used if CT pulmonary angiogram is contraindicated —> pregnancy, renal impairment

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💆‍♂️ Management​

• initial

  • ABCDE approach (includes providing oxygen and adequate analgesia)

• provoked PE (the cause is known)

  • 1st line

    • 3 months apixaban or rivaroxaban

• alternatives

  • low-molecular weight heparin (LMWH) followed by warfarin OR

  • LMWH followed by dabigatran or edoxaban

• unprovoked PE (the cause is unknown)

  • same as the above but for 6 months

• with active cancer

  • DOAC for 3-6 months

• for pregnancy

  • 1st line is LMWH (warfarin is contraindicated)!

• PE + haemodynamic instability

  • indication of a saddle embolus

  • 1st line is thrombolysis

• recurrent PEs

  • inferior vena cave filters

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🧲 High-yield tips

• “pleuritic chest pain + shortness of breath + unilateral leg swelling” —> raises suspicion of a PE

• if renal failure —> V/Q scan is better than CTPA

• if a PE is unprovoked —> get a CT thorax, abdomen and pelvis to exclude malignancy —> if no malignancy do a thrombophilia screen​