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Internal MedicinePulmonologyAcute Pulmonary Embolism

Acute Pulmonary Embolism

Must-Not-Miss / Red Flags

  • Massive PE: systolic BP 15 minutes or requiring vasopressors – immediate thrombolysis or embolectomy
  • Right ventricular strain on echo/CT: high‑risk submassive PE
  • Cardiac arrest: consider thrombolysis during CPR
Patient Explanation
“A blood clot has traveled to your lungs and is blocking blood flow. We’ll give you medicine to dissolve the clot and prevent new ones from forming.”
Board Fact
“The most common ECG finding in PE is sinus tachycardia; S1Q3T3 pattern is present in only 12% of cases.”
ICD-10
I26.99

Definition & Core Concept

Acute pulmonary embolism (PE) is an obstruction of the pulmonary artery or its branches by thrombus, most commonly originating from deep veins of the lower extremities, leading to V/Q mismatch and potentially life‑threatening hemodynamic compromise.

Epidemiology & Risk Factors

  • Annual incidence: 1‑2 per 1,000 adults
  • Third most common cardiovascular cause of death after MI and stroke
  • Risk factors: surgery, trauma, immobilization, malignancy, pregnancy, OCPs, thrombophilia

Pathophysiology (Rule of 3)

  1. Thrombus formation (Virchow’s triad: stasis, hypercoagulability, endothelial injury) in deep veins
  2. Embolization to pulmonary arteries → mechanical obstruction
  3. Release of vasoactive mediators (serotonin, thromboxane) → pulmonary vasoconstriction and bronchoconstriction → V/Q mismatch

Clinical Presentation

  • Sudden‑onset dyspnea, pleuritic chest pain, tachypnea, tachycardia
  • Hemoptysis (rare), syncope (massive PE)
  • Signs of DVT: unilateral leg swelling, tenderness, warmth

Diagnostic Workup

Wells criteria / PERC rule: estimate pre‑test probability. D‑dimer: high sensitivity; if negative and low probability, PE is ruled out. CT pulmonary angiography (CTPA): gold standard; filling defects in pulmonary arteries. Echocardiogram: RV dilation and dysfunction (McConnell’s sign). Bilateral leg ultrasound: for DVT.

Management Protocol

  1. Anticoagulation: start immediately with LMWH (Enoxaparin 1 mg/kg BID) or DOAC (Rivaroxaban 15 mg BID for 3 weeks then 20 mg daily, or Apixaban 10 mg BID ×7 days then 5 mg BID)
  2. Thrombolysis: Alteplase 100 mg IV over 2 hours for massive PE (with hypotension); consider for submassive PE with RV dysfunction and low bleeding risk
  3. Catheter‑directed thrombolysis or surgical embolectomy: if thrombolysis contraindicated or failed
  4. Oxygen: to maintain SpO₂ ≥92%

Complications & Prognosis

  • Chronic thromboembolic pulmonary hypertension (CTEPH)
  • Right ventricular failure
  • Cardiac arrest (from massive PE)

ICU Criteria

ICU admission if: massive PE (hypotension), submassive PE with RV dysfunction and elevated biomarkers, or requiring thrombolysis.

Clinical Vignette

A 55‑year‑old woman develops sudden dyspnea and right‑sided pleuritic chest pain 2 weeks after knee replacement surgery. CTPA shows bilateral segmental filling defects. BP is 110/70, HR 110, SpO₂ 91%.

Pearls & Pitfalls

  • A normal D‑dimer in a low‑probability patient effectively rules out PE – do not proceed to CTPA unnecessarily.
  • Always assess for DVT – the source of PE is usually the legs.

Discharge & Follow-Up

Anticoagulation for at least 3 months (longer if unprovoked or recurrent). Compression stockings for DVT. Monitor for bleeding complications. Screen for malignancy if unprovoked PE.

Literature & Guidelines

ESC 2024 Guidelines for the Diagnosis and Management of Acute PE. PMID: 38573409.

Personal Clinical Notes