10 PE (pulmonary embolism) facts and figures
In this article we will describe 10 key facts and figures about pulmonary embolism: focusing on its symptoms, causes and treatment.
A pulmonary embolism is when a blood clot blocks a blood vessel in your lungs. It can be life-threatening in some people, if not treated quickly.
1. Definition
Pulmonary embolism (PE) is the luminal obstruction of one or more pulmonary arteries; usually by an embolised venous thrombus, but can also be due to an embolised solid, liquid, or gas.
Most PEs originate as thrombi due to deep vein thrombosis (DVT), most frequently in the calf veins.
Other causes include:
- Fat embolism
- Air embolism
- Amniotic fluid embolism
- Septic emboli
- De novo thrombosis (rare).
Venous thromboembolism (VTE) is an umbrella term encompassing both pulmonary embolism (PE) and deep vein thrombosis (DVT).
2. Epidemiology
- If untreated, 20% of individuals with a deep vein thrombosis (DVT) will develop a pulmonary embolism
- 45-50% of people with PE have concurrent DVT
- Half of all pulmonary embolism cases occur in hospital inpatients
- In the UK, PE and DVT together make up the third most common cardiovascular disease (after acute myocardial infarction and stroke)
- Nearly 70,000 hospital episodes of PE were reported in the UK, between 2021-2022, resulting in over 35,000 admissions.
3. Symptoms
Common symptoms of PE include: a sudden (or gradual) onset of shortness of breath, pleuritic chest pain (that is worse when breathing in, moving and coughing; 40%), a tachycardia (rapid heart rate), lightheadedness, and sometimes haemoptysis (coughing up blood).
Pain, redness, and swelling in one leg (usually the calf) may also indicate a blood clot (deep vein thrombosis) that has led to a pulmonary embolism.
Massive pulmonary embolism. Clinical features of a massive PE include:
- Haemodynamic instability: hypotension and cardiogenic shock
- Syncope/collapse
- Elevated jugular venous pressure (JVP).
Note. Any patient with unexplained SOB and a normal chest x-ray should be considered (and treated) as having a PE until otherwise proven.
4. Causes
PEs can be caused by clotting disorders, injury to a vein, surgery, certain medications, and prolonged periods of immobility (e.g. long flights or bed rest).
Note. COVID-19. People who have severe symptoms of COVID-19 have an increased risk of DVT and PE.
5. Risk factors
Risk factors for DVT include age (especially over 60 years), obesity, smoking, cancer, heart failure, varicose veins, genetic predisposition, pregnancy/oral contraceptive (OC) or hormone replacement therapy (HRT), and a history (or family history) of DVT or PE.
6. Diagnosis
PE is diagnosed through various imaging tests, such as a CT pulmonary angiography (CTPA), a V/Q (ventilation-perfusion) scan, or a Doppler ultrasound of the legs to detect DVT.
Other investigations
These include ECG, chest x-ray and arterial blood gases (ABGs). Although there are typical abnormalities in all three, all three can be normal.
ECG
Possible ECG findings include:
- Sinus tachycardia: the most common finding
- Right ventricular strain pattern: T wave inversion in anterior leads (V1-V4) +/- inferior leads (II, III, aVF)
- Right bundle branch block (RBBB)
- Right axis deviation (RAD)
- The classic ‘S1Q3T3’ ECG change is only seen in <20% patients – large S wave in lead I, large Q wave in lead III, and inverted T wave in lead III.
Chest x-ray
Chest x-ray is used to exclude other possible differential diagnoses (e.g. pneumothorax and pneumonia), not to make the diagnosis of PE. Possible chest x-ray findings in PE include:
- Wedge-shaped pulmonary infarction: wedge-shaped opacification without air bronchograms
- Atelectasis
- Pleural effusion
- Raised hemidiaphragm.
Unusual signs on chest x-ray. Focal oligaemia, or the Westermark sign, is an area of increased lung transparency distal to an occluded vessel; pulmonary infarction appears on CXR as a pleural-based wedge shaped consolidation, or Hampton’s hump.
Two other signs reflecting vascular patterns may be observed: Fleischner’s sign, related to pulmonary artery enlargement; and Palla’s sign, indicating vascular prominence before an arterial occlusion.
Chest x-ray showing a pleural-based wedge-shaped consolidation in the right lower lobe (Hamptons’ hump; arrow), which was confirmed by CTPA to be a pulmonary infarction, in a patient with acute pulmonary embolism.
Chest x-ray showing enlargement of the main pulmonary artery (Fleischner’s sign; white arrow) and prominence of the right descending pulmonary artery (Palla’s sign; black arrows) in a patient with chronic pulmonary embolism.
Note. Most patients with PE have a normal chest x-ray.
D-dimer
The D-dimer test has a high sensitivity but low specificity for VTE (PE and DVT). Many conditions can result in an elevated D-dimer in the absence of VTE:
- Pregnancy
- AKI or AKI on CKD
- Malignancy
- Liver disease
- Severe infection or inflammatory disease
- Disseminated intravascular coagulation (DIC)
- Recent trauma/surgery/hospitalised patients.
Note 1. In these patients, D-dimer testing has no value in diagnosing VTE
Note 2. D-dimer has a good negative predictive value. A negative D-dimer almost certainly excludes PE (and DVT).
7. Complications
If untreated, PE can cause severe complications, including pulmonary hypertension, chronic thromboembolic pulmonary hypertension (CTEPH), heart failure, and death.
8. Treatment
Treatment typically involves anticoagulant medications like heparin, warfarin, or newer oral anticoagulants (NOACs) to prevent further clotting. In severe cases, thrombolytic therapy or surgical interventions like embolectomy may be necessary.
9. Prevention
Preventive measures include staying active, exercising regularly, maintaining a healthy weight, avoiding prolonged periods of immobility, wearing compression stockings; and, for high-risk individuals (or people who have had 2 or more DVT/PEs), taking blood thinners (warfarin, heparin, direct-acting oral anticoagulant (DOAC)).
Occasionally an inferior vena cava (IVC) filter – inserted by an interventional radiologist – is necessary to prevent further PEs from further DVTs.
Prevention while travelling
The risk of blood clots developing while traveling is low but increases as long-haul travel increases. The following to help prevent blood clots during travel:
- Drink plenty of fluids. Water is the best liquid for preventing dehydration, which can contribute to the development of blood clots. Avoid alcohol, which contributes to fluid loss
- Take a break from sitting. Move around the airplane cabin once an hour or so. If you’re driving, stop every so often and walk around the car a couple of times. Do a few deep knee bends
- Move in your seat. Bend and make circle movements with your ankles and raise your toes up and down every 15 to 30 minutes
- Wear support stockings. Your doctor may recommend these to help promote circulation and fluid movement in your legs.
10. Prognosis
The prognosis for PE is very variable. With prompt treatment, the outlook is generally good, but untreated PE can be fatal. Approximately one-third of untreated PE cases are fatal.
In England, 25,000 deaths per year are due to blood clots (PEs that developed after a DVT) that occurred whilst the person was in hospital.
Summary
We have described 10 PE (pulmonary embolism) facts and figures, focusing on its symptoms, causes and treatment. We hope it has been helpful.
Other resources
10 DVT facts
Pulmonary embolism (NHS England)
