Pulmonary embolism differentials
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Differential Diagnosis of Pulmonary Embolism
PE is notoriously difficult to diagnose clinically because its presenting symptoms - dyspnea, chest pain, tachycardia, and hypoxemia - overlap with many common and life-threatening conditions. No single symptom or sign is sufficiently predictive; diagnosis requires structured pretest probability assessment (Wells or Geneva score) combined with D-dimer and imaging.
"PE may mimic a large spectrum of diseases." - Fuster and Hurst's The Heart, 15th Ed.
The Key Differentials (Organized by System)
1. Cardiovascular - Highest Priority
| Condition | Key Distinguishing Features |
|---|---|
| Acute Coronary Syndrome (STEMI/NSTEMI) | Crushing/pressure chest pain, radiation to jaw/arm, ECG ST changes, troponin rise. Note: PE can also raise troponin (RV strain). ECG helps exclude acute MI. |
| Aortic Dissection | Tearing/ripping pain radiating to the back, widened mediastinum on CXR, unequal blood pressures. Both can cause shock and hypoxemia. |
| Decompensated Heart Failure | Orthopnea, PND, bilateral crackles, S3, elevated BNP, cardiomegaly. PE can also cause right heart failure and elevated BNP. |
| Pericarditis / Pericardial Effusion | Positional/pleuritic chest pain (worse supine, better leaning forward), friction rub, diffuse ST elevation with PR depression on ECG. PE can rarely mimic pericarditis. |
| Cardiac Arrhythmia | Palpitations, lightheadedness, irregular pulse on exam. Note: PE causes sinus tachycardia and new arrhythmias. |
2. Pulmonary
| Condition | Key Distinguishing Features |
|---|---|
| Pneumonia (CAP, TB, PJP, aspiration) | Fever, productive cough, consolidation on CXR, egophony, leukocytosis. The most common PE mimic. |
| Pneumothorax | Sudden pleuritic chest pain + dyspnea, decreased breath sounds, tracheal deviation, visible on CXR. Shares sudden onset with PE. |
| COPD Exacerbation | Known COPD history, wheeze, increased sputum, hypercapnia. PE is an important trigger of COPD exacerbation and must be excluded. |
| Asthma | Wheeze, atopy history, response to bronchodilators. PE can cause mild wheeze (~15% of cases). |
| Pulmonary Hypertension (primary) | Gradual onset dyspnea, RV strain on ECG/echo, no acute precipitant. Chronic PE (CTEPH) can be mistaken for idiopathic PAH. |
| Pleural Effusion / Pleurisy | Pleuritic pain, reduced breath sounds, dullness to percussion. PE itself causes effusion via pulmonary infarction. |
| Intrathoracic Malignancy | Mass on CXR/CT, systemic symptoms (weight loss, anorexia). Malignancy also predisposes to PE. |
| Acute Bronchitis | Cough-predominant, no hemoptysis or pleurisy, afebrile or mildly febrile, normal D-dimer. |
3. Musculoskeletal
| Condition | Key Distinguishing Features |
|---|---|
| Costochondritis / Musculoskeletal Pain | Reproducible chest wall tenderness on palpation. Critically: pulmonary infarction from PE can also cause chest wall tenderness, making this a dangerous mimic. |
| Rib Fracture | Trauma history, point tenderness, visible on CXR. |
4. Other Life-Threatening Conditions
| Condition | Key Distinguishing Features |
|---|---|
| Esophageal Perforation (Boerhaave syndrome) | History of forceful vomiting, subcutaneous emphysema, mediastinal air on CXR/CT. Misdiagnosis rate >50% due to broad overlap. |
| Acute Abdomen (hepatobiliary, splenic) | Right upper quadrant or epigastric pain, tenderness, elevated LFTs or lipase. |
| Preeclampsia (in pregnancy) | Hypertension, proteinuria, edema. PE must be excluded alongside eclampsia in dyspneic pregnant patients. |
5. Non-Organic / Functional
| Condition | Key Distinguishing Features |
|---|---|
| Anxiety / Panic Disorder | Normal O2 saturation, normal ECG and CXR, reproducible with hyperventilation, responds to anxiolytics. PE must always be excluded first before attributing dyspnea to anxiety. |
Clinical Clues Pointing Toward PE
- Sudden onset dyspnea (most common symptom, >50%)
- Pleuritic chest pain
- Unilateral leg swelling/DVT signs
- Risk factors: recent surgery/immobilization, malignancy, prior VTE, estrogen use, prolonged travel
- Near-normal CXR in the setting of severe respiratory compromise (classic)
- Sinus tachycardia + T-wave inversions V1-V4 / S1Q3T3 on ECG (right heart strain)
Key Investigations to Differentiate
- D-Dimer: High sensitivity; use to rule out in low/intermediate pretest probability. Elevated in many conditions (sepsis, cancer, pregnancy, trauma) - not specific.
- CT Pulmonary Angiography (CTPA): Gold standard for imaging.
- V/Q scan: Alternative when contrast contraindicated.
- ECG: Excludes STEMI and pericarditis; may show PE-related right heart strain.
- Troponin / BNP: Elevated in PE (RV strain), ACS, and heart failure - must be interpreted in context.
- Echocardiography: RV dilation/dysfunction suggests massive PE.
Sources:
- Braunwald's Heart Disease, Table 87.5 - Differential Diagnosis of Pulmonary Embolism
- Fuster and Hurst's The Heart, 15th Ed., p. 1768 - Differential Diagnosis section
- Goldman-Cecil Medicine, p. 802 - Clinical Manifestations
- Rosen's Emergency Medicine - Differential Diagnoses across multiple chapters
- Symptom to Diagnosis: An Evidence-Based Guide, 4th Ed., Table 15-2
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