Related Subjects: | Pulmonary Embolism | Wells Score for PE

🫁 Pulmonary Embolism Rule-out Criteria (PERC) Score

The PERC score is a validated clinical decision tool used in the emergency setting to safely exclude pulmonary embolism (PE) in low-risk patients without the need for further testing (like D-dimer or imaging). 👉 If all 8 criteria are negative and clinical suspicion is low (<15%), the risk of PE is <2% — no further workup is needed.

📋 PERC Criteria (8 Components)

✅ How to Use

• Step 1: Assess pre-test probability of PE using gestalt/Wells score. PERC is only valid in low pre-test probability (<15%).
• Step 2: Apply the 8 PERC criteria. If all 8 are negative → PE can be safely excluded, no D-dimer or imaging required.
• Step 3: If any criterion is positive → further testing needed (start with D-dimer).

⚠️ Limitations

• Not valid in moderate/high suspicion patients.
• Not validated in inpatients, pregnancy, or those with significant comorbidities.
• Use alongside clinical judgement — never replace it.

🧠 Teaching Commentary

The PERC score is about avoiding over-investigation. CT pulmonary angiography carries radiation and contrast risks, so PERC helps reduce unnecessary scans in genuinely low-risk patients. - Remember: PERC is applied after clinical assessment shows a low pre-test probability. - If your patient is “PERC-negative,” their risk of PE is so low that you can stop without further testing. - If “PERC-positive” (fails even one criterion), you must escalate to D-dimer (and possibly imaging).

💊 Management

• High-flow O₂, cardiac monitoring
• Stable PE: Wells + D-dimer/CTPA pathway. Anticoagulate early if high suspicion.
• Unstable PE: Oxygen, cautious fluids, vasopressors, thrombolysis (Alteplase 10 mg bolus + 90 mg/2h)
• Cardiac arrest (PEA): Suspect PE if very low ETCO₂. Give thrombolysis, continue CPR 60–90 min
• Interventions: Catheter-directed thrombolysis or surgical embolectomy if thrombolysis fails or contraindicated
• Anticoagulation: LMWH, UFH, or DOAC (Apixaban/Rivaroxaban). Warfarin 3–6 months for first unprovoked PE
• IVC filter: For contraindication to anticoagulation or recurrent PE despite therapy

🎯 Special Scenarios

• Cancer: Prefer DOACs (Apixaban, Rivaroxaban) but caution in GI malignancy
• Pregnancy: – CXR safe – USS Doppler first-line – V/Q or CTPA if needed – LMWH mainstay (Warfarin contraindicated) – Double dose Enoxaparin due to ↑ GFR

📚 References

• 2019 ESC Guidelines on Acute PE

Cases — Pulmonary Embolism (PE)

• Case 1 — Post-Operative PE 🏥: A 62-year-old woman, 7 days after hip replacement, develops sudden pleuritic chest pain and dyspnoea. Exam: tachycardia, O₂ sats 90% on air. CTPA: segmental pulmonary emboli. Diagnosis: Provoked PE post-surgery. Management: LMWH bridging → DOAC for 3 months; mechanical prophylaxis in future surgeries.
• Case 2 — Massive PE with Shock ⚡: A 55-year-old man with history of DVT presents with syncope, hypotension (BP 75/40), tachycardia, raised JVP, and loud P₂. CTPA: saddle embolus. Diagnosis: Massive PE with haemodynamic instability. Management: Immediate thrombolysis (alteplase); oxygen; IV fluids cautiously; consider surgical or catheter-directed thrombectomy if refractory.
• Case 3 — Submassive PE with RV Strain ❤️: A 48-year-old woman on long-haul flight develops progressive breathlessness. Exam: tachypnoea, tachycardia, O₂ sats 88% RA. CTPA: bilateral pulmonary emboli; echo: RV dilatation. Diagnosis: Submassive PE (RV dysfunction but stable BP). Management: Anticoagulation (DOAC); admit for monitoring; oxygen; consider thrombolysis if clinical deterioration.
• Case 4 — Unprovoked PE 🔍: A 35-year-old man with no recent travel, surgery, or immobility presents with pleuritic chest pain and haemoptysis. Wells score high. CTPA confirms left lower lobe PE. Diagnosis: Unprovoked PE — possible underlying thrombophilia or malignancy. Management: Anticoagulation (≥6 months or indefinite); malignancy screen (CT abdo/pelvis, PSA/CA markers as appropriate); thrombophilia testing if young/family history.
• Case 5 — PE with Recent Intracranial Haemorrhage 🧠: A 72-year-old man, 3 weeks after a spontaneous intracerebral haemorrhage, is admitted with acute dyspnoea and pleuritic chest pain. CTPA confirms right-sided pulmonary embolism. - Anticoagulation is contraindicated due to very high risk of re-bleeding. - Exam: stable but hypoxic, O₂ sats 88% on air. Diagnosis: Acute pulmonary embolism in patient with recent ICH (absolute contraindication to anticoagulation). Management: Supportive care (O₂, analgesia, fluids). Insert retrievable IVC filter to prevent recurrent embolisation. Once neurology team clears anticoagulation (typically ≥6 weeks post-ICH), start anticoagulation and plan filter retrieval.

Teaching Commentary 🧠

Pulmonary embolism = acute blockage of pulmonary arteries, usually from DVT. - Risk factors: surgery, immobility, pregnancy, cancer, thrombophilia, oestrogen therapy. - Clinical spectrum: from small, pleuritic PE → massive, obstructive shock. - Dx: Wells score, D-dimer, CTPA (or V/Q if renal failure/pregnancy). - Mx: Anticoagulation for all (DOACs first-line in UK unless contraindicated). Thrombolysis reserved for massive PE with haemodynamic compromise. Unprovoked PE → always screen for underlying cancer or clotting disorders.