Chapter 31-14: Pulmonary Embolism (PE)

TEXTBOOK PRESENTATION

PE is covered extensively in Chapter 15-11: Pulmonary Embolism. This discussion will focus on patients who experience syncope due to PE.

The classic presentation of a patient with PE and syncope is an older patient with risk factors for venous thromboembolic disease with the sudden onset of chest pain, dyspnea, and sudden loss of consciousness.

DISEASE HIGHLIGHTS

1. PE is a more common cause of syncope than commonly appreciated. PE was diagnosed in 17% of patients admitted for their first episode of syncope who did not have an obvious cause (eg, dehydration, vasovagal).

2. Syncope complicates PE in 9–24% of patients.

3. Syncope is secondary to massive embolization (involving > 50% of the pulmonary vascular bed), critically limiting blood return to the LV, reducing cardiac output, causing hypotension and syncope.

EVIDENCE-BASED DIAGNOSIS

1. Echocardiography reveals RV dysfunction in 88–94% of patients with PE and syncope (due to the extent of embolization required for syncope to occur).

2. Patients with PE and syncope who survive to arrive at the hospital have often stabilized (probably due to clot fragmentation and improved LV return), may be hemodynamically stable and relatively asymptomatic.

3. 25% of patients with PE and syncope had no other symptoms or signs suggestive of PE (increasing the likelihood of missed diagnoses).

   PE should be considered in patients with syncope of unknown origin, even in the absence of other clinical symptoms and signs.

4. Patients with PE and syncope may have typical risk factors, associated symptoms (eg, chest pain or dyspnea) and signs suggesting PE.

5. Findings suggestive of PE in such patients with syncope include tachypnea (LR+, 6.4) and unilateral leg swelling (LR+, 8.9).

6. Other findings that might suggest PE include

   1. Persistent hypotension

   2. Hypoxia (PaO₂ < 60 mm Hg)

   3. ECG findings (S1Q3T3 pattern, right axis deviation, or right BBB)

   4. Radiographic findings (an unexplained pleural effusion or infiltrate suggestive of pulmonary infarction)

   5. Echocardiographic findings of right atrial or right ventricular enlargement

7. D-dimer assays and CT angiogram are the most commonly used tests to evaluate patients with possible PE.

TREATMENT

See Treatment.