Definition
Pulmonary embolism is a blockage of a pulmonary artery (or one of its branches) by a thrombus, usually originating from a deep vein thrombosis (DVT).
Risk Factors
Mnemonic:
THROMBOSIS
Trauma (esp. long bone fractures)
Hospitalisation or immobility
Recent surgery
Oestrogen (pregnancy, OCP, HRT)
Malignancy
Blood disorders (thrombophilia, antiphospholipid syndrome)
Obesity
Smoking
Infection/inflammation
Stasis (e.g. long flights)
Clinical features
Mnemonic:
PHD DADS
Pleuritic chest pain
Haemoptysis
Dyspnoea (sudden onset)
DVT signs (leg swelling/pain)
Anxiety (sense of doom)
Dizziness/syncope
Sinus tachycardia
Additional: low-grade fever, cyanosis, hypotension (if massive PE)
📊Diagnosis
Clinical Risk Stratification:
Wells Score → PE likely/unlikely
PERC rule (in low-risk patients)
D-dimer:
If PE unlikely, negative D-dimer excludes PE
Imaging:
CTPA: 1st line if stable & not pregnant
V/Q scan: preferred in pregnancy/renal impairment
Leg Doppler USS: if DVT suspected
ECG: sinus tachycardia, S1Q3T3 (rare), RBBB
CXR: usually normal; may show wedge infarct or effusion
ABG: may show hypoxia, low PaCO2
Management – Mnemonic: ABCDE + ACUTE PE
Initial (ABCDE approach):
Airway: ensure patency
Breathing: oxygen if hypoxic
Circulation: IV access, fluids if hypotensive
Disability: assess GCS
Exposure: leg exam for DVT, signs of bleeding
Definitive:
Anticoagulation: LMWH or DOAC (e.g. apixaban)
CTPA confirmation
Unfractionated heparin if high bleeding risk or renal failure
Thrombolysis: only for massive PE with haemodynamic instability
Echo: RV strain in severe cases
Complications
Death
Pulmonary infarction
Chronic thromboembolic pulmonary hypertension (CTEPH)
Right heart failure
🧐 Differentials
ACS (MI)
Pericarditis
Pneumothorax
Pneumonia
Anxiety/panic attack
🩺 Monitoring
Anticoagulation for 3+ months (longer if unprovoked or thrombophilia)
Monitor for bleeding, INR if warfarin used
Review for CTEPH symptoms
🔎 Key PARA Exam Traps
💡 Sudden dyspnoea + pleuritic chest pain ± haemoptysis = suspect PE
💡 Normal CXR does NOT exclude PE: CXR is often normal or non-specific
💡 Use Wells score to assess pre-test probability: Do not jump straight to D-dimer in high-risk patients
💡 D-dimer rules out PE only in low-risk patients: Raised D-dimer is non-specific
💡 CTPA is the imaging test of choice: V/Q scan if CTPA contraindicated (e.g. pregnancy, renal failure)
💡 ECG may show sinus tachycardia or S1Q3T3: Neither is sensitive or specific
💡 Massive PE causes hypotension and shock: Treat immediately — do not delay for imaging if unstable
💡 Thrombolysis is indicated in massive PE: Not routinely used in stable PE
💡 Pregnancy and recent surgery increase PE risk: Always assess risk factors
💡 Unprovoked PE → consider underlying malignancy
NICE NG158 (Venous thromboembolic diseases) – Last Updated: March 2020
- PARA-aligned, reviewed February 2026
PASSMAP ensures all content is NICE-aligned and reviewed for Physician Associate Registration Assessment (PARA) success.
Educational platform. Not medical advice.