Overview
Definition
Obstruction of the pulmonary artery or one of its branches by a thrombus that originated elsewhere in the body.
Epidemiology
A leading cause of preventable hospital death.
Etiology & Risk Factors
- Most commonly caused by a DVT from the lower extremities that breaks loose and embolizes to the pulmonary circulation.
- Risk factors are the same as DVT (Virchow's Triad).
Clinical Symptoms
- Sudden onset of dyspnea (shortness of breath) - most common symptom
- Pleuritic chest pain (sharp pain worse with deep inspiration)
- Tachypnea (rapid breathing) - most common sign
- Tachycardia, cough (sometimes with hemoptysis)
- Massive PE: Severe hypotension, syncope, right heart failure (cor pulmonale)
Clinical Approach
Diagnosis
- Wells Score / PERC Rule to determine probability
- CT Pulmonary Angiography (CTPA): Gold Standard diagnostic test
- V/Q Scan (Ventilation-Perfusion scan): Used if CT is contraindicated (e.g., severe renal failure, allergy to contrast)
- ECG: Usually shows sinus tachycardia. S1Q3T3 pattern is the 'classic' board answer but is actually rare (indicates acute right heart strain).
Management
- Hemodynamically Stable: Anticoagulation (DOACs, LMWH, or IV Heparin)
- Hemodynamically Unstable (Massive PE with shock): Thrombolytic therapy (tPA / Alteplase) to actively dissolve the clot, or surgical embolectomy
Complications
- Sudden cardiac death
- Pulmonary hypertension (chronic thromboembolic pulmonary hypertension - CTEPH)