🫁 Pulmonary Embolism — Overview
Pulmonary Embolism (PE) occurs when a blood clot (usually from a DVT in the legs or pelvis) travels to and occludes pulmonary arteries, causing haemodynamic compromise and respiratory failure.
PE is a leading cause of preventable hospital death. Massive PE (with haemodynamic instability) has up to 30–50% mortality. Prompt diagnosis and treatment are essential.
Clinical Presentations — Spectrum
| Category | Haemodynamics | Features | Mortality |
|---|
| Massive PE | Unstable: SBP <90 or drop ≥40 mmHg for >15 min | Shock, syncope, cardiac arrest (PEA) | 30–50% |
| Submassive PE | Stable but RV dysfunction present | Elevated troponin/BNP, RV dilation on echo/CT | 5–15% |
| Low-risk PE | Stable, no RV dysfunction | Dyspnoea, pleuritic chest pain, haemoptysis | <1% |
Classic PE Symptoms
- Dyspnoea — most common symptom (~73%); sudden onset
- Pleuritic chest pain — sharp, worse on inspiration; indicates peripheral infarction
- Haemoptysis — blood in sputum; pulmonary infarction
- Syncope / near-syncope — massive PE; sudden collapse
- Tachycardia, tachypnoea, hypoxaemia
- Leg swelling/pain from underlying DVT (~50% of cases)
- Low-grade fever (infarction)
PE can present as PEA (pulseless electrical activity) arrest. PEA in the absence of obvious reversible causes should prompt consideration of massive PE → empirical thrombolysis during CPR may be lifesaving.
ECG in PE
- Most common: sinus tachycardia (non-specific but important)
- S1Q3T3 pattern: deep S wave lead I, Q wave + T wave inversion lead III — classic but only ~20% of PE
- New right bundle branch block (RBBB) — RV strain
- T wave inversions V1–V4 — right heart strain pattern
- New AF — complication of acute PE
🔬 Diagnosis of PE
Wells PE Score
| Clinical Feature | Score |
|---|
| Clinical signs/symptoms of DVT (swollen leg, deep vein tenderness) | +3 |
| PE is #1 diagnosis OR equally likely as alternative | +3 |
| Heart rate >100 bpm | +1.5 |
| Immobilisation ≥3 days OR surgery within 4 weeks requiring GA | +1.5 |
| Previous documented DVT or PE | +1.5 |
| Haemoptysis | +1 |
| Active malignancy (treatment within 6 months or palliative) | +1 |
| Wells PE Score | Probability | PE Prevalence |
|---|
| ≥5 (PE likely) | High | ~40–67% |
| <5 (PE unlikely) | Low–moderate | ~8–12% |
Diagnostic Pathway
| Situation | Approach |
|---|
| HAEMODYNAMICALLY UNSTABLE — massive PE suspected | Do NOT delay for imaging; bedside ECHO (RV dilation = high suspicion); treat immediately; if arrest → empirical thrombolysis |
| Wells <5 (PE unlikely) | D-dimer: if negative = PE excluded; if positive → CTPA |
| Wells ≥5 (PE likely) | Go directly to CTPA — D-dimer is not useful |
CTPA — Gold Standard
- CT Pulmonary Angiogram: definitive investigation for PE
- Sensitivity ~96–100%, specificity ~98% for segmental PE and above
- Also identifies alternative diagnoses (pneumonia, aortic dissection, cardiac tamponade)
- V/Q scan: alternative if CTPA contraindicated (contrast allergy, severe renal impairment, pregnancy)
Additional Investigations — Risk Stratification
- Troponin: Elevated = RV myocardial injury → higher mortality
- BNP/NT-proBNP: Elevated = RV pressure overload → worse prognosis
- Echocardiogram: RV dilation, D-sign (septal flattening), McConnell's sign (RV free wall hypokinesis, preserved apex)
- ABG: ↓PaO₂ + ↓PaCO₂ + respiratory alkalosis (hyperventilation pattern)
Classic ABG in PE: Hypoxaemia + hypocapnia + respiratory alkalosis. The patient hyperventilates to compensate for hypoxia, blowing off CO₂ and causing alkalosis.
💊 PE Management — Haemodynamically Stable
Immediate Supportive Care
- High-flow O₂ via non-rebreather mask — target SpO₂ ≥94%
- IV access × 2; cautious fluids (250–500 mL) if hypotensive — excess fluids worsen RV overload
- Continuous cardiac monitoring
- Analgesia for pleuritic pain (NSAIDs or opioids)
Start anticoagulation BEFORE CTPA if clinical probability is high and no contraindication.
Anticoagulation — First-Line
| Drug | Regimen | Notes |
|---|
| Rivaroxaban | 15 mg BD × 21 days → 20 mg OD | First-line DOAC; with food |
| Apixaban | 10 mg BD × 7 days → 5 mg BD | Preferred in CKD; no food requirement |
| Enoxaparin (LMWH) | 1 mg/kg SC BD | Cancer-associated PE; pregnancy |
| UFH infusion | 80 units/kg bolus → 18 units/kg/hr (aPTT target 60–100s) | Massive/submassive PE — rapid reversibility if thrombolysis needed |
Duration of Treatment
| Scenario | Duration |
|---|
| Provoked PE (surgery, trauma) | 3 months |
| First unprovoked PE | Minimum 3 months; consider extended/indefinite |
| Second PE event | Indefinite anticoagulation |
| Cancer-associated PE | Duration of cancer + minimum 3–6 months |
Low-Risk PE — Outpatient Management
- PESI class I–II or sPESI = 0: consider outpatient DOAC with close follow-up within 5 days
- Criteria: haemodynamically stable, adequate renal function, no significant comorbidity, good social support, can take oral medication
- Most GCC centres admit PE patients for ≥24 hours minimum for observation
🚨 Massive PE — Emergency Management
Massive PE = SBP <90 mmHg OR fall ≥40 mmHg for >15 min not explained by other cause → ACTIVATE RESUS TEAM
Immediate Resuscitation Steps
- Call for help — anaesthetics, ICU, cardiology
- 100% oxygen — prepare airway management
- IV UFH 80 units/kg bolus immediately
- Cautious IV fluid bolus 250–500 mL (avoid excess — worsens RV overload)
- Vasopressors (noradrenaline) if SBP <90 despite fluid
- Bedside echocardiography — confirm RV dilation, McConnell's sign
- CTPA if patient stable enough; if not → treat based on clinical/echo diagnosis
Systemic Thrombolysis — Alteplase
Alteplase dosing for massive PE:
• Standard: 10 mg IV bolus over 1–2 min, then 90 mg over 2 hours (total 100 mg)
• In cardiac arrest: 50 mg IV bolus → continue CPR ≥60–90 minutes
• Restart UFH 2 hours post-alteplase (once aPTT <80 seconds)
Contraindications to Thrombolysis
Absolute Contraindications
- Prior intracranial haemorrhage (ever)
- Intracranial structural disease (AVM, tumour)
- Ischaemic stroke within 3 months
- Active significant internal bleeding
- Head trauma within 3 months
- Suspected aortic dissection
Relative Contraindications (weigh risk/benefit in massive PE)
- Major surgery within 3 weeks
- Non-compressible vascular punctures
- Prolonged CPR (>10 minutes)
- Pregnancy
- Active peptic ulcer
- Severe hypertension (SBP >180)
In PEA cardiac arrest from PE: Thrombolysis takes priority over most relative contraindications. Give alteplase 50 mg bolus and continue CPR for ≥60–90 minutes for clot lysis.
Surgical / Interventional Options
- Surgical embolectomy: Open removal of clot — when thrombolysis fails or absolutely contraindicated; requires cardiothoracic surgical centre
- Catheter-directed thrombolysis: Low-dose local thrombolytic via catheter — option for submassive PE; lower systemic bleeding risk
- ECMO: Bridge to definitive therapy in refractory massive PE — available at major GCC cardiac centres (KFSH, Cleveland Clinic Abu Dhabi, HMC Doha)