PE (pulmonary embolism) – medical revision notes
In this article we will describe 10 medical revision notes about pulmonary embolism: focusing on its symptoms, causes and treatment.
Key Points
- Pulmonary embolism (PE) is the occlusion of pulmonary arteries by thrombi that originate elsewhere, typically in large veins of the legs or pelvis
- Symptoms are nonspecific and include dyspnoea, pleuritic chest pain; and, in more severe cases, collapse or cardiorespiratory arrest. Signs are also nonspecific and may include tachypnoea, tachycardia; and in more severe cases, hypotension
- Diagnosis is best made by CT pulmonary angiography (CTPA)
- Treatment is with anticoagulants. Sometimes, clot dissolution with systemic or catheter-directed thrombolysis, or by removal of the clot via catheter suction thrombectomy or surgical resection, are required
- When anticoagulation is contraindicated, an inferior vena cava (IVC) filter should be considered.
1. Definition
Pulmonary embolism (PE) refers to the blockage of one or more pulmonary arteries, typically caused by an embolised venous thrombus. However, it can also result from the embolisation of solid, liquid, or gas materials.
Most pulmonary emboli originate from thrombi due to deep vein thrombosis (DVT), primarily in the calf veins. Other potential causes include:
- Fat embolism
- Air embolism
- Amniotic fluid embolism
- Septic emboli
- De novo thrombosis (rare)
Venous thromboembolism (VTE) is a collective term for both pulmonary embolism (PE) and deep vein thrombosis (DVT).
2. Epidemiology
- Untreated DVT: Approximately 20% of individuals with a DVT will go on to develop a PE
- Concurrent DVT: 45-50% of patients with PE also have a DVT
- Hospital Acquired: Half of all cases of PE occur in hospital inpatients
- Prevalence in the UK: PE and DVT together are the third most common cardiovascular conditions after acute myocardial infarction and stroke
- Recent Data: Nearly 70,000 hospital episodes of PE were reported in the UK from 2021-2022, leading to over 35,000 admissions.
3. Risk factors
- Age: Particularly over 60 years
- Obesity
- Smoking
- Cancer
- Heart failure
- Varicose veins
- Genetic predisposition
- Pregnancy, oral contraceptive (OC), or hormone replacement therapy (HRT)
- History or family history of DVT or PE
4. Causes
Pulmonary embolisms can arise from:
- Clotting disorders
- Injury to a vein
- Surgical procedures
- Certain medications
- Prolonged immobility (e.g. long journeys, bed rest).
Note: Individuals with severe COVID-19 symptoms have an increased risk of DVT and PE.
5. Symptoms
Symptoms of PE are often non-specific and can include:
- Sudden (or gradual) onset of shortness of breath
- Pleuritic chest pain (worsening with inspiration, movement, and coughing)
- Tachycardia (rapid heart rate)
- Lightheadedness
- Haemoptysis (coughing up blood)
Signs of DVT: Pain, redness, and swelling in one leg (typically the calf) may indicate a clot leading to a pulmonary embolism.
Massive pulmonary embolism
Clinical features may include:
- Haemodynamic instability (hypotension and cardiogenic shock)
- Syncope or collapse
- Elevated jugular venous pressure (JVP)
Note: Any patient presenting with unexplained shortness of breath and a normal chest x-ray should be considered (and treated) as having a PE until proven otherwise.
6. Diagnosis
PE can be diagnosed using various imaging tests, including:
- CT pulmonary angiography (CTPA)
- V/Q (ventilation-perfusion) scan
- Doppler ultrasound of the legs for DVT detection.
Other investigations include:
- ECG
- Chest x-ray
- Arterial blood gases (ABGs)
While abnormalities are often present, all tests can yield normal results.
ECG
- Normal (most common)
- Sinus tachycardia
- Right ventricular strain pattern: T wave inversion in anterior leads (V1-V4) and possibly inferior leads (II, III, aVF)
- Right bundle branch block (RBBB)
- Right axis deviation (RAD)
- The classic ‘S1Q3T3’ change occurs in less than 20% of patients.
Chest x-ray
This is used to exclude differential diagnoses (e.g. pneumothorax, pneumonia).
But. Possible findings in PE include:
- Wedge-shaped pulmonary infarction (without air bronchograms)
- Atelectasis
- Pleural effusion
- Raised hemidiaphragm
Unusual signs may include:
- Westermark sign: An area of increased lung transparency distal to an occluded vessel.
- Hampton’s hump: A pleural-based wedge-shaped consolidation indicating pulmonary infarction.
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 present with a normal chest x-ray. In fact a normal chest x-ray should make you consider PE as a diagnosis more carefully.
D-dimer
- High sensitivity but low specificity for VTE (PE and DVT)
- Elevated D-dimer can occur in other conditions like pregnancy, AKI, malignancy, liver disease, severe infection, DIC, or recent trauma/surgery.
Note 1: D-dimer testing is not useful for diagnosing VTE in patients with these conditions
Note 2: A negative D-dimer effectively excludes PE (and DVT) – i.e. has good negative predictive value.
Differential diagnosis
- Pneumothorax
- Pneumonia
- Pleural effusion
- Pleuritis or pericarditis (infection or inflammation).
7. Treatment
Treatment generally involves anticoagulant medication, such as:
- Heparin
- Warfarin
- New oral anticoagulants (NOACs)
In severe cases, thrombolytic therapy or surgical interventions (e.g. embolectomy) may be required.
Note. If you suspect massive PE, get the patient to ICU and in front of a cardiothoracic surgeon. They may need urgent thoracotomy.
8. Complications
Untreated PE can lead to severe complications, including:
- Pulmonary hypertension
- Chronic thromboembolic pulmonary hypertension (CTEPH)
- Heart failure
- Death.
9. Prognosis
- The prognosis for PE varies widely
- With prompt treatment, the outlook is generally favourable; however, untreated PE can be fatal, with approximately one-third of untreated cases resulting in death
- In England, around 25,000 deaths per year are attributed to blood clots (PEs that developed following DVT) occurring in hospital settings.
10. Prevention
- Staying active and exercising regularly
- Maintaining a healthy weight
- Avoiding prolonged immobility
- Wearing compression stockings
- For high-risk individuals (or those with two or more DVT/PE episodes), using blood thinners (warfarin, heparin, direct-acting oral anticoagulants (DOACs))
In some cases, an inferior vena cava (IVC) filter may be inserted by an interventional radiologist to prevent further PEs from DVTs.
Hospital prevention
- Early mobilisation
- Anticoagulant administration
- Mechanical compression devices applied to the legs
Travel prevention
While the risk of developing blood clots during travel is low, it increases with long-haul journeys. To reduce risk during travel:
- Stay hydrated; drink plenty of water and avoid alcohol.
- Take breaks to move around: if on a flight, stand and walk every hour; if driving, stop regularly and walk around.
- Perform ankle exercises while seated.
- Wear support stockings to enhance circulation.
Summary
We have described 10 medical revision notes about PE (pulmonary embolism), focusing on its symptoms, causes and treatment. We hope it has been helpful.
Other resources
10 DVT medical revision notes
Pulmonary embolism (NHS England)
Review: Vyas, 2024
