🫁 Pulmonary Embolism (PE): A Silent Killer

Pulmonary embolism (PE) is a potentially fatal condition caused by the obstruction of the pulmonary arteries, most commonly due to a thrombus originating in the deep veins of the lower limbs. Timely recognition and treatment are critical to improving patient outcomes.

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1️⃣ Etiology & Pathogenesis

The most common cause of PE is thrombotic embolism, typically arising from a deep vein thrombosis (DVT) in the femoral or iliac veins. The underlying risk factors are best explained by Virchow’s Triad:

• Hypercoagulability: Seen in malignancy, inherited thrombophilias
• Venous stasis: Long periods of immobility, recent surgery or travel
• Endothelial injury: Trauma, central lines

Other, less common causes include:

• Fat embolism – usually following long bone fractures
• Air embolism – can occur during central venous catheterization
• Amniotic fluid embolism – associated with labor and delivery

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2️⃣ Clinical Presentation

PE presents with a wide range of symptoms. An easy-to-remember mnemonic is STOP CLOT:

• S – Swelling in legs (suggestive of DVT)
• T – Tenderness/cramping in calves
• O – Out of breath (dyspnea, hypoxia)
• P – Pass out (syncope or presyncope)
• C – Chest pain (typically pleuritic)
• L – Leg discoloration (mottled or cyanotic)
• O – Overdrive heart rate (tachycardia)
• T – Time to act (seek urgent medical help)

Physical exam and vitals may show:

• Tachypnea, tachycardia, hypoxia
• Jugular venous distension (suggesting right heart strain)
• Signs of DVT: swelling, tenderness, and redness of the leg
• Heart sounds: split S2, murmur of tricuspid regurgitation

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3️⃣ Risk Stratification: The Wells Score

The Wells Score is a validated clinical prediction tool for assessing PE probability.

• > 4 points → High probability → Proceed directly to CT pulmonary angiogram (CTPA)
• ≤ 4 points → Low/moderate probability → Check D-dimer:
  • If positive, proceed to CTPA
  • If negative, PE is unlikely

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4️⃣ Investigations

A stepwise diagnostic approach includes:

• ABG: Hypoxemia with respiratory alkalosis (↓ PaO₂ and ↓ PaCO₂)
• ECG: May show sinus tachycardia, S1Q3T3 pattern, RBBB, or right axis deviation
• CXR: Often normal, but may reveal classic signs:
  • Hampton’s Hump (wedge-shaped infarct)
  • Westermark Sign (oligemia)
  • Fleischner Sign (prominent pulmonary artery)
• Echocardiogram: May reveal right ventricular dilation and tricuspid regurgitation

The gold standard for diagnosis remains CT Pulmonary Angiography (CTPA).

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5️⃣ Management

Management depends on the severity and hemodynamic status of the patient.

• Anticoagulation: First-line in most cases. Options include LMWH, DOACs, or unfractionated heparin.
  • Duration: Typically 3 months if provoked, lifelong if unprovoked or recurrent.
• IV Thrombolysis: Reserved for massive PE with hemodynamic instability.
• Surgical or catheter-directed embolectomy: For cases unresponsive to thrombolysis.
• IVC filter: Considered when anticoagulation is contraindicated.

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🧠 Conclusion

Pulmonary embolism is a serious, life-threatening condition that requires high clinical suspicion and swift action. Understanding the risk factors, recognizing key symptoms, and following a structured diagnostic and treatment plan can dramatically improve patient outcomes.

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📘 Want to dive deeper?
Download our High-Yield Respiratory Handbook from our website to explore more clinical topics in detail.

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