Why PE Is a Core OSCE Topic
Pulmonary embolism kills approximately 25,000 people in the UK annually and is frequently missed because its presentation is non-specific. OSCEs examine PE in acute management stations, data interpretation (applying the Wells score and interpreting CTPA reports), and prescribing scenarios (anticoagulate this patient). Examiners test systematic risk stratification, correct investigation sequencing, and safe prescribing.
⚠️ Red Flag
Massive PE (haemodynamically unstable) is immediately life-threatening. Any patient with suspected PE who has SBP below 90 mmHg, HR above 100 bpm, or syncope should be escalated urgently. This is the one situation where you consider thrombolysis without waiting for CTPA confirmation.
Presentation — The Triad and Beyond
Classic triad (present together in only 20% of cases):
- Dyspnoea
- Pleuritic chest pain
- Haemoptysis
Other features:
- Tachycardia (most sensitive sign — present in over 90%)
- Tachypnoea
- Low-grade fever
- Pleural rub
- Signs of DVT (unilateral leg swelling, calf tenderness, erythema) — present in 40-50%
Wells PE Score — Pre-test Probability
| Clinical feature | Points |
|---|---|
| Clinical signs and symptoms of DVT (leg swelling + tenderness) | 3 |
| PE is the most likely diagnosis or equally likely | 3 |
| Heart rate above 100 bpm | 1.5 |
| Immobilisation (3 or more days bedrest) or surgery in past 4 weeks | 1.5 |
| Previous DVT or PE | 1.5 |
| Haemoptysis | 1 |
| Active malignancy (treatment ongoing or within 6 months, or palliative) | 1 |
| Total | Probability | 2-level classification |
|---|---|---|
| 0-1 | Low | PE unlikely (below 5) |
| 2-6 | Intermediate | PE likely (5 or above) |
| 7 or above | High | PE likely (5 or above) |
Investigation Pathway (BTS 2023)
🧠 Mnemonic
Two-level Wells pathway:
- PE unlikely (below 5): D-dimer first
- Negative D-dimer: PE excluded — no imaging needed
- Positive D-dimer: CTPA
- PE likely (5 or above): CTPA directly — do not waste time on D-dimer
D-dimer
- High sensitivity, low specificity — a normal D-dimer effectively excludes PE in low/intermediate probability; a raised D-dimer does not confirm PE
- Age-adjusted D-dimer threshold (ADJUST-PE): in patients over 50 years, threshold = age x 10 micrograms/L (e.g., 70-year-old: threshold = 700 micrograms/L)
- D-dimer is raised in: infection, pregnancy, post-operative state, malignancy, atrial fibrillation, increasing age — making it non-specific in hospitalised patients
CTPA (CT Pulmonary Angiography)
- Gold standard investigation for PE
- Identifies filling defects within pulmonary arteries
- Also identifies alternative diagnoses (pneumonia, aortic dissection, malignancy)
- Contrast contraindicated in: severe renal impairment (eGFR below 30), confirmed contrast allergy — use V/Q scan instead
V/Q Scan (Ventilation/Perfusion)
- Alternative to CTPA in contrast allergy, renal failure, or pregnancy
- Results reported as normal (excludes PE), high probability (treat as PE), or indeterminate
ECG in PE
🧠 Mnemonic
S1Q3T3 — classic but present in under 20% of cases:
- S wave in lead I
- Q wave in lead III
- T wave inversion in lead III
More common ECG findings: sinus tachycardia (most common), right heart strain (T-wave inversion V1-V4, right bundle branch block), right axis deviation. A normal ECG does not exclude PE.
Severity Assessment — PESI Score
The Pulmonary Embolism Severity Index guides admission vs outpatient management.
Simplified PESI (sPESI):
- Age above 80: 1 point
- Cancer: 1 point
- Chronic cardiorespiratory disease: 1 point
- HR above 110: 1 point
- SBP below 100 mmHg: 1 point
- SpO2 below 90%: 1 point
Score 0 = low risk → consider outpatient treatment. Score 1 or above = admit.
Anticoagulation — NICE 2023
First-line: DOAC (direct oral anticoagulant)
| Drug | Dosing |
|---|---|
| Apixaban | 10 mg BD for 7 days, then 5 mg BD |
| Rivaroxaban | 15 mg BD for 21 days, then 20 mg OD |
- DOACs are preferred over LMWH bridging to warfarin for most patients
- LMWH (tinzaparin, dalteparin) used in: pregnancy, active cancer (DOAC increasingly used in cancer), renal impairment (eGFR below 15), antiphospholipid syndrome
Duration:
- Provoked PE (surgery, immobility, trauma): 3 months
- Unprovoked PE or active cancer: 6 months minimum, consider extended treatment
- Recurrent unprovoked VTE: lifelong anticoagulation discussion
Massive PE Management
Haemodynamically unstable PE (SBP below 90 mmHg, HR above 100, syncope, cardiac arrest):
- 1High-flow oxygen, IV access x2
- 2Fluid bolus 500 mL cautiously (RV is preload-dependent but overdistension worsens function)
- 3Systemic thrombolysis: alteplase 100 mg over 2 hours (or 0.6 mg/kg over 15 minutes in cardiac arrest)
- 4If thrombolysis contraindicated: surgical embolectomy or catheter-directed thrombolysis
- 5ITU admission, vasopressors (noradrenaline or vasopressin)
Frequently Asked Questions
"What is the difference between DVT and PE investigation pathways?"
DVT investigation uses the Wells DVT score (not the Wells PE score) and compression Doppler ultrasound of the leg veins. PE investigation uses the Wells PE score and CTPA or V/Q scan. Both pathways use D-dimer as a rule-out tool in low-probability cases. A confirmed DVT in a patient with respiratory symptoms warrants CTPA to exclude concurrent PE.
"Why is D-dimer not useful in hospitalised patients?"
D-dimer is elevated by many conditions that cause fibrin degradation: infection, surgery, trauma, pregnancy, malignancy, and increasing age all raise D-dimer non-specifically. In a hospitalised patient who is unwell for another reason, a raised D-dimer adds little diagnostic value. The Wells score should be used to determine whether CTPA is more appropriate than starting with D-dimer.
"What are the absolute contraindications to thrombolysis in PE?"
The same as for stroke thrombolysis: prior haemorrhagic stroke (any time), ischaemic stroke within 3 months, active bleeding, recent major surgery or trauma within 3 weeks, aortic dissection, intracranial neoplasm. In massive PE with imminent cardiac arrest, the benefit-risk ratio shifts dramatically in favour of thrombolysis even with relative contraindications.
"When can PE be treated as an outpatient?"
Outpatient treatment is safe for haemodynamically stable patients with sPESI of 0 who have adequate home circumstances, can self-administer or take oral anticoagulation reliably, have no significant comorbidity, and have good access to medical care if they deteriorate. The HOME-PE trial supports early discharge for low-risk PE. CTPA must still be performed to confirm the diagnosis before discharge.
"What is chronic thromboembolic pulmonary hypertension (CTEPH)?"
CTEPH is a long-term complication of PE where organised thrombus obstructs pulmonary arteries, causing progressive pulmonary hypertension. It affects approximately 3-5% of PE patients. Features: progressive exertional dyspnoea months to years after an acute PE, right heart failure signs. Investigation: V/Q scan (more sensitive than CTPA for chronic disease), right heart catheterisation. Treatment: pulmonary endarterectomy (surgical) or balloon pulmonary angioplasty; riociguat for inoperable cases.
Related Posts
- Chest Pain History OSCE — differentiating PE chest pain from other causes
- Deep Vein Thrombosis OSCE — DVT assessment and management as part of the VTE spectrum
- Blood Results Interpretation OSCE — interpreting D-dimer, troponin, and BNP in PE