Pulmonary embolism
Think of it in anyone with unexplained breathlessness, low oxygen or a fast pulse. Use the Wells score to choose D-dimer or CTPA, start anticoagulation early, and thrombolyse a PE that drops the BP.
A 54-year-old woman is 6 days after a hip operation. She suddenly feels breathless with sharp pain on the right when she breathes in. Pulse 118, RR 26, SpO₂ 89% on air, BP 124/78. Her chest sounds clear. Her left calf is swollen.
How do you confirm the diagnosis, and do you start treatment before the scan?
- Oxygen and monitorSpO₂ 94–98%. ECG, BP, pulse.
- Shocked?Systolic below 90: massive PE. Senior now, bedside echo, consider thrombolysis.
- Two-level Wells scoreDecides the next test.
- PE likely: CTPAPE unlikely: D-dimer first, CTPA only if positive.
- Start anticoagulationIf the CTPA will be delayed and there is no bleeding risk.
- BloodsCBC, creatinine, LFTs, clotting, troponin, BNP if available.
- Look for the causeSurgery, immobility, cancer, pregnancy, pill, previous clot.
- Plan the duration3 months at least. Longer if no clear cause.
- Systolic BP below 90 or collapse
- Cardiac arrest
- Raised troponin or a dilated right ventricle on echo
- Low oxygen with a clear chest
- Tearing pain or unequal pulses (dissection mimic)
- Massive PE
- Intermediate-high-risk PE
- Aortic dissection
- Heart attack, tamponade or pneumothorax mimicking PE
- PE in pregnancy
| Wells above 4 | PE likely: CTPA (immediate, or anticoagulate while waiting) |
| Wells 4 or less | PE unlikely: D-dimer. Negative: PE excluded. Positive: CTPA |
| Massive PE | Systolic below 90 or shock: thrombolysis on senior decision (doses in the treatment section) |
| Anticoagulation | Apixaban or rivaroxaban for most. Enoxaparin in pregnancy and some cancers |
| Duration | At least 3 months |
Check every dose against a current drug reference and your hospital protocol.
On this page
What it is
A clot, usually from the deep veins of the leg or pelvis, travels to the lungs and blocks a pulmonary artery. Small clots cause pleuritic pain and breathlessness. A large clot strains the right side of the heart and can cause collapse and death.
Risk factors: recent surgery (especially hip, knee, pelvic and abdominal), immobility, long travel, cancer, pregnancy and the 6 weeks after delivery, the combined pill, previous clots, obesity, and inherited clotting problems.
Recognising it
- Sudden breathlessness, often with a clear chest on listening.
- Pleuritic chest pain, coughing blood.
- Fast pulse, fast breathing, low SpO₂.
- Fainting or collapse (large PE).
- A swollen, tender calf (DVT).
- Signs are often few: think of PE whenever the breathlessness or low oxygen is not explained.
Two-level Wells score
| Feature | Points |
|---|---|
| Signs of DVT (leg swelling and tenderness) | 3 |
| PE more likely than another diagnosis | 3 |
| Heart rate above 100 | 1.5 |
| Immobilised 3 days or more, or surgery in the last 4 weeks | 1.5 |
| Previous DVT or PE | 1.5 |
| Coughing blood | 1 |
| Cancer (treated in last 6 months or palliative) | 1 |
- CTPA now
- If it will be delayed: start anticoagulation while waiting
- D-dimer
- Negative: PE excluded, look for another cause
- Positive: CTPA
- D-dimer rises with age, infection, pregnancy, surgery and cancer. A positive result means little; a negative result in a low-probability patient excludes PE.
- Kidney failure or contrast allergy: a V/Q scan instead of CTPA, where available.
- Unstable patient: do not send to CT. A bedside echo showing a dilated right ventricle supports treating for massive PE.
Investigations
| Test | Why | What to look for |
|---|---|---|
| ECG | Exclude MI, look for strain | Sinus tachycardia (most common), right heart strain, new AF. S1Q3T3 is uncommon |
| Chest X-ray | Other causes | Often normal. Helps exclude pneumothorax and pneumonia |
| ABG | Severity | Low oxygen, low CO₂ |
| CTPA | Diagnosis | Clot in the pulmonary arteries, right ventricle size |
| Echo | Unstable patients | Dilated right ventricle |
| Troponin, BNP | Risk | Raised: right heart strain, higher risk |
| CBC, creatinine, LFTs, clotting | Before anticoagulation | Platelets, kidney function for DOAC dosing |
| Leg ultrasound | If CTPA cannot be done | DVT confirms the need to treat |
Risk and treatment
- Systolic below 90 or shock
- Senior and ICU now
- Thrombolysis unless contraindicated
- IV unfractionated heparin
- Normal BP, but right ventricular strain on CT or echo, or raised troponin
- Anticoagulate, monitor closely in HDU
- Thrombolyse if the BP falls
- Normal BP, no strain
- Anticoagulation
- Some can go home early with follow-up
After recent major surgery, thrombolysis carries a high risk of bleeding. In the case above, the decision belongs to the senior team.
Special situations
- Pregnancy: enoxaparin by weight. DOACs and warfarin are not used. CTPA or V/Q is still done if needed: the risk of missing a PE is greater than the radiation risk.
- Cancer: a DOAC or enoxaparin, per oncology and bleeding risk.
- Kidney failure: dose adjust, or use heparin or warfarin.
How long to treat
- Clear temporary cause (surgery, injury, pregnancy): usually 3 months.
- No clear cause, or ongoing risk (cancer, previous clots): often longer or indefinite, on specialist advice.
- Unprovoked PE: ask about symptoms of cancer and examine. Further tests as guided.
Common mistakes
- Sending a D-dimer when the Wells score is high (go straight to CTPA).
- Sending a D-dimer in a pregnant or post-operative patient and being confused by a positive result.
- Waiting hours for a CTPA without starting anticoagulation.
- Sending an unstable patient to CT.
- Forgetting to check the creatinine before choosing a DOAC dose.
Frequently asked questions
What is the two-level Wells score for PE?
A score using signs of DVT, PE being the most likely diagnosis, heart rate above 100, immobilisation or recent surgery, previous clot, coughing blood and cancer. Above 4 means PE is likely; 4 or less means PE is unlikely.
What is the apixaban dose for PE?
10 mg twice daily for 7 days, then 5 mg twice daily, for at least 3 months.
When is thrombolysis given for PE?
For high-risk (massive) PE with shock or systolic BP below 90, unless there is a contraindication. It is a senior decision.
What is the immediate treatment for pulmonary embolism?
Oxygen and anticoagulation (for example apixaban or enoxaparin), started as soon as PE is likely if there is no bleeding risk. Massive PE with low BP is treated with thrombolysis unless contraindicated.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A 45-year-old woman has a Wells score of 7.5 for pulmonary embolism. CT pulmonary angiography is not available until tomorrow morning. She has no bleeding risk. What is the best management now?
Answer: Start anticoagulation now and arrange the CTPA. When PE is likely and imaging is delayed, give interim anticoagulation unless contraindicated.
- Thrombolysis: She is not shocked.
- Aspirin only: Not treatment for PE.
- Wait for the CTPA before any treatment: High probability: treat while waiting.
- D-dimer first, then decide: D-dimer is for low-probability patients.
2. A patient with low clinical probability (Wells 1) for PE has a negative D-dimer. What does this mean?
Answer: PE is excluded. A negative D-dimer in a low-probability patient safely rules out PE.
- CTPA is still needed: Not with low probability and negative D-dimer.
- Repeat D-dimer daily: Unnecessary.
- V/Q scan: Not needed.
- Start anticoagulation: Not indicated.
3. A patient with suspected PE has BP 78/50 and a dilated right ventricle on bedside echo. What is the best treatment?
Answer: Systemic thrombolysis. Massive (high-risk) PE with shock: systemic thrombolysis unless contraindicated, with unfractionated heparin.
- Fluids 3 litres rapidly: Large volumes can worsen RV failure.
- Oral rivaroxaban: Not for massive PE.
- Enoxaparin and ward care: Massive PE needs reperfusion.
- IVC filter first: Not first.
4. A 45-year-old has a unilateral swollen calf 3 cm larger than the other, pitting oedema and recent long-haul travel; two-level Wells score is ‘likely’. What is the next step?
Answer: Proximal leg vein ultrasound. Suspected DVT: two-level Wells score. ‘Likely’ (≥ 2) → proximal leg vein ultrasound within 4 hours (interim anticoagulation if delayed); if negative, D-dimer — positive → repeat scan in 6–8 days. ‘Unlikely’ → D-dimer; negative excludes DVT, positive → ultrasound. D-dimer is sensitive but non-specific (raised in pregnancy, infection, cancer, surgery, age). Treatment: DOAC (apixaban/rivaroxaban) for ≥ 3 months for provoked DVT.
- D-dimer only and discharge if positive: A positive D-dimer does not allow discharge.
- CT pulmonary angiogram: There are no PE symptoms.
- Venography as first-line: Venography is invasive.
5. A 50-year-old has a proximal DVT 3 weeks after knee arthroscopy (provoked). Renal function is normal. What is the treatment and duration?
Answer: DOAC for 3 months. Proximal DVT: confirm with compression ultrasound (Wells score + D-dimer guide). Treat with a DOAC (apixaban, rivaroxaban) or LMWH → warfarin. Provoked (surgery, trauma, immobility) → 3 months. Unprovoked → consider extended anticoagulation balancing bleeding risk. Cancer-associated → DOAC/LMWH ≥ 6 months. IVC filter only if anticoagulation contraindicated. Compression stockings for symptoms.
- Lifelong warfarin: Lifelong treatment is not needed for a provoked DVT.
- Aspirin only: Aspirin is not adequate.
- IVC filter for all: A filter is only for contraindication to anticoagulation.
6. What is the most common source of a pulmonary embolus?
Answer: Proximal deep leg and pelvic veins. Most pulmonary emboli arise from deep vein thrombosis in the proximal leg veins (femoral, popliteal and iliac). Calf-vein clots often resolve but can extend upwards. Superficial veins rarely cause significant emboli.
- Great saphenous vein of the thigh: A superficial vein; clots here rarely embolise.
- Deep veins of the upper limb: An uncommon source (lines, effort thrombosis).
- Thrombus in the right atrium: Atrial thrombi usually embolise to the systemic circulation (stroke) from the left side.
- Tributaries of the portal vein: Portal clots stay in the liver circulation.
7. In Virchow's triad, which factor is most important for thrombosis in arteries and the heart?
Answer: Endothelial injury. Virchow's triad: endothelial injury, abnormal flow (stasis or turbulence) and hypercoagulability. Endothelial injury is dominant in the heart and arteries (atherosclerotic plaque rupture, myocardial infarction, vasculitis). Stasis is most important in veins (DVT).
- Stasis of blood: Dominant in venous thrombosis.
- Hypercoagulability: Important in inherited conditions (factor V Leiden).
- Raised haematocrit: A contributor to hyperviscosity.
- Low platelet count: Causes bleeding, not thrombosis.
References and dose sources
- NICE NG158: Venous thromboembolic diseases, diagnosis and management
- ESC 2019 guidelines on acute pulmonary embolism
- Apixaban dosing: Drugs.com: Apixaban dosage (see also our apixaban dose page)
- Rivaroxaban dosing: Drugs.com: Rivaroxaban dosage (see also our rivaroxaban dose page)
- Enoxaparin dosing: Drugs.com: Enoxaparin dosage (see also our enoxaparin dose page)
- Warfarin dosing: Drugs.com: Warfarin dosage (see also our warfarin dose page)
- Alteplase dosing: Drugs.com: Alteplase dosage (see also our alteplase dose page)
- Streptokinase dosing: Drugs.com: Streptokinase (see also our streptokinase dose page)
- Heparin (unfractionated) dosing: Drugs.com: Heparin dosage (see also our heparin (unfractionated) dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.