Pulmonary embolism (PE) is the obstruction of the pulmonary arterial tree by thrombus (most commonly originating from a deep vein thrombosis of the lower limb or pelvic veins) 1,2. It is the third most common cause of acute cardiovascular death after myocardial infarction and stroke 1.

Clinical presentation

  • common symptoms: acute-onset dyspnoea (75–85%), pleuritic chest pain (40–65%), cough, haemoptysis, and presyncope or syncope

  • massive (high-risk) PE: sustained systemic hypotension (systolic BP <90 mmHg or a drop ≥40 mmHg for >15 minutes), obstructive shock, or pulseless electrical activity (PEA) cardiac arrest 1

Investigations

Pre-test probability & Laboratory

  • Wells score or revised Geneva score: used to stratify patients into "PE unlikely" vs "PE likely" 1,2

  • D-dimer: high negative predictive value in low/intermediate probability patients; age-adjusted threshold (age × 10 µg/L in patients aged >50 years) increases specificity without reducing sensitivity 1

  • ECG: sinus tachycardia is the most common finding; right ventricular strain patterns include T-wave inversion in V1–V4, incomplete/complete RBBB, and the classic S1Q3T3 pattern (<15% of cases) 1

Imaging

  • CT pulmonary angiography (CTPA): modality of choice; demonstrates intraluminal filling defects within the main ("saddle embolus"), lobar, segmental, or subsegmental pulmonary arteries ("polo mint sign" on axial slices and "railway track sign" on longitudinal views), alongside right ventricular strain (RV:LV diameter ratio >1.0 and interventricular septal bowing) 1,2

  • V/Q (ventilation-perfusion) scintigraphy: preferred in pregnancy or severe renal impairment when chest radiograph is normal 1

Management

  • low- and intermediate-risk PE: direct oral anticoagulants (DOACs such as apixaban or rivaroxaban) are first-line over vitamin K antagonists; low-molecular-weight heparin (LMWH) is preferred in pregnancy and active GI/urothelial malignancy 1,2

  • high-risk (massive) PE: immediate unfractionated heparin plus systemic thrombolysis (e.g. recombinant tissue plasminogen activator / alteplase), or surgical/catheter-directed embolectomy if thrombolysis is contraindicated 1

See also