Pulmonary Embolism
Last Update 1st September 2026
Pulmonary Embolism
Clinical presentation
PE should be suspected in all patients who present with new or worsening dyspnoea, chest pain or hypotension without alternative cause. The threshold for further investigation should be low because of the nonspecific nature of symptoms and signs and because the consequences of a missed diagnosis can be dire.
Symptoms:
- Dyspnoea and/or chest pain, acute or subacute over days to weeks
- Pleuritic chest pain and haemoptysis — more typical of peripheral emboli
- Isolated dyspnoea — more typical of larger, central emboli
- Palpitations, pre-syncope or syncope
- Unilateral leg or arm pain, tightness or swelling suggesting concurrent DVT
Signs are nonspecific: tachypnoea, tachycardia, hypotension, and signs of right ventricular failure. PE is more likely if oxygen saturation is below 95% or heart rate above 100 beats per minute. Presentation with haemodynamic instability or syncope is rare and indicates central or extensive PE.
About two thirds of patients with PE will also have a DVT.
ECG is worth doing but is neither sensitive nor specific. Sinus tachycardia is the most common ECG abnormality in PE. Others: RBBB pattern, anterior and inferior T-wave inversion, right axis deviation, dominant R in V1, P pulmonale, and the classic-but-uncommon S1Q3T3.
Risk factors
Cumulative, and used mainly to score pre-test probability.
- Strong (OR >10) — hip or leg fracture, hip or knee replacement, major surgery with GA ≥30 min, major trauma, spinal cord injury
- Moderate (OR 2–9) — surgery with GA <30 min, chemotherapy, chronic heart or respiratory failure, inflammatory bowel disease, the combined oral contraceptive pill, pregnancy and postpartum, previous VTE, malignancy, recent hospitalisation, antiphospholipid syndrome
- Weak (OR <2) — prolonged sitting including car or air travel, increasing age, laparoscopic surgery, obesity, varicose veins
- Hereditary — antithrombin deficiency (RR 5–10), protein C deficiency (RR 4–6.5), protein S deficiency (RR 1–10), factor V Leiden (RR 3–5), prothrombin gene mutation (RR 2–3)
Investigations
Only about 20% of patients with a clinically suspected VTE have it objectively confirmed, so a clinical prediction rule is what keeps imaging proportionate.
Simplified Wells score — 1 point each for clinical signs and symptoms of DVT, immobility or surgery in the previous four weeks, previous VTE, haemoptysis, malignancy, an alternative diagnosis less likely than PE, and heart rate >100. Score 0–1 = unlikely; ≥2 = likely. The simplified Geneva score is an alternative. Neither excludes VTE on its own.
PERC is a rule-out tool, applicable to patients aged under 50 when the estimated rate of PE is low — under 15%, which describes most Australian general practice. All seven must be satisfied:
- Age <50 years
- Pulse <100
- Oxygen saturation >95% on room air
- No exogenous oestrogen
- No prior VTE
- No surgery or trauma in the previous four weeks
- No unilateral leg swelling
If one or more criteria are not met, PE cannot be ruled out and further assessment is required.
D-dimer. High sensitivity, low specificity — it is almost always raised in acute thrombosis but also in sepsis, malignancy, pregnancy and trauma. A low Wells score and a negative D-dimer can safely and efficiently exclude PE in primary care without the need for imaging. A high Wells or Geneva score goes straight to imaging — don’t order a D-dimer to talk yourself out of it.
Imaging. CTPA is preferred in most patients: a negative scan excludes PE, it rarely returns an inconclusive result, and it may give an alternative diagnosis. V/Q is for renal impairment and is preferred in pregnancy, but up to 55% of V/Q scans are non-diagnostic. Lower-limb Doppler alone cannot rule out PE. Echocardiography helps in the haemodynamically unstable patient too sick for CT, by showing right ventricular dysfunction.
Initial management
Refer emergently (ambulance, 000) if hypoxic or haemodynamically unstable — shock, or systolic BP <90 mmHg. Send with IV access, oxygen and analgesia available.
Refer to ED if PE is likely on simplified Wells (≥2), or there will be a delay obtaining diagnostic imaging.
If there are delays in definitive investigation and bleeding risk is low, an initial therapeutic dose of low molecular weight heparin should be considered before transfer.
Community management is reasonable for a confirmed PE in a patient with a low simplified Wells score (0–1) who is well, with no clinical concerns and no red flags. If in doubt, refer.
If the patient is pregnant with suspected PE, contact the local obstetric team for advice.
Anticoagulation
Anticoagulation is indicated in almost all cases of PE because it is highly effective in preventing thrombus extension or recurrence.
DOACs are first-line for most patients — no routine monitoring, few interactions, and lower bleeding risk than warfarin. Apixaban and rivaroxaban are preferred because they need no parenteral lead-in.
- Apixaban — 10 mg orally twice daily for 7 days, then 5 mg twice daily. Consider 2.5 mg twice daily beyond 6 months. Contraindicated if CrCl <25 mL/min.
- Rivaroxaban — 15 mg orally twice daily for 21 days, then 20 mg once daily. Consider 10 mg daily beyond 6 months. Contraindicated if CrCl <15 mL/min.
Standard doses are used in obesity. Use CrCl, not eGFR, to assess renal function for DOAC dosing. Both are CYP3A4/P-gp substrates — watch for clarithromycin, ketoconazole and ritonavir (bleeding risk), and rifampicin and St John’s wort (loss of efficacy).
When not to use a DOAC:
- Pregnancy or breastfeeding — enoxaparin
- Antiphospholipid syndrome — warfarin plus enoxaparin, target INR 2–3, with enoxaparin for at least 5 days and until INR >2 on two consecutive days
- Severe renal impairment, mechanical heart valves, active clinically significant bleeding, a bleeding disorder, or hepatic disease with coagulopathy
- Cancer-associated VTE — most can now be treated with DOACs, with similar efficacy and safety to LMWH; the exception is unresected luminal genitourinary or gastrointestinal malignancy, where LMWH is still preferred because of higher bleeding risk
Warfarin may also be preferred in morbid obesity or severe renal impairment.
Duration of anticoagulation
All patients with PE should receive anticoagulant therapy for 3–6 months. After that:
- Provoked by a major reversible risk factor — stop at 3–6 months.
- Two or more unprovoked VTEs, or a non-reversible risk factor such as malignancy or antiphospholipid syndrome — continue indefinitely.
- First unprovoked or minimally provoked PE — genuine clinical equipoise. Recurrence after stopping is about 10% at one year and 30% at 3–5 years, against a bleeding risk on DOACs of roughly 1% per year. The trend is towards continuing; weigh patient preference.
Thrombophilia testing and follow-up imaging
Thrombophilia does not change initial management, and its influence on recurrence risk is minimal in most situations — thrombophilia testing is not recommended in most patients at presentation and is best deferred to the haematologist. Testing is more worthwhile in patients under 50 with a family history, and testing for antiphospholipid syndrome in unprovoked PE is reasonable because it changes both drug choice and duration.
Follow-up imaging, in the absence of new symptoms, should not be used to determine the duration of anticoagulation, since up to 50% have residual thrombosis after 3–6 months. Imaging at the end of the initial treatment period is for establishing a new baseline, not for deciding to stop.
Follow-up and complications
Patients on long-term anticoagulation need at least yearly review that the benefit still outweighs the risk, with 6–12-monthly renal and hepatic function on a DOAC.
Chronic thromboembolic pulmonary hypertension (CTEPH) affects up to 4% of patients after PE. Progressive or non-resolving exertional dyspnoea is the predominant symptom. Investigate with echocardiography and V/Q scanning, and refer to a specialist pulmonary hypertension centre if suspected.
Isolated subsegmental PE is a genuine grey area. Patients with adequate cardiopulmonary reserve and low recurrence risk can have anticoagulation withheld if serial bilateral compression ultrasound at day 1 and day 7 remains negative. Involve a haematologist or respiratory physician in that decision.