Pulmonary Embolism (PE)

Understanding Pulmonary Embolism

A pulmonary embolism (PE) occurs when a blood clot travels to the lungs, usually from the legs (deep vein thrombosis or DVT). Before we examine how this condition appears on imaging, let's understand why rapid diagnosis and treatment are essential.

Here's how accurate CT pulmonary angiography is at diagnosing pulmonary embolism:

Think of pulmonary embolism like a traffic jam on a highway—when a clot blocks blood flow through pulmonary arteries, oxygen exchange is compromised and the right side of the heart must work harder. Large clots can be life-threatening, requiring immediate treatment.

What Is Pulmonary Embolism?

Pulmonary embolism is blockage of one or more pulmonary arteries by blood clots that most often originate from deep vein thrombosis in the legs or pelvis. PE ranges from small, clinically insignificant clots to massive, life-threatening events.

Risk factors for PE:

| Category | Risk Factors | |----------|--------------| | Provoking factors | Surgery, trauma, immobilization, pregnancy | | Medical conditions | Cancer, heart failure, stroke, obesity | | Genetic factors | Factor V Leiden, prothrombin mutation | | Medications | Estrogen-containing birth control, hormone therapy | | Lifestyle | Smoking, prolonged sitting/travel |

Why CT pulmonary angiography (CTPA) is gold standard:

• Direct visualization of clots in pulmonary arteries
• Can detect both large and small emboli
• Assesses for right heart strain
• Identifies alternative diagnoses if PE is absent
• Fast and widely available

How PE Appears on CT

CT pulmonary angiography with intravenous contrast is the first-line imaging test for suspected PE. It directly visualizes the pulmonary arteries to detect filling defects representing clots.

Key Findings Pattern

When evaluating for pulmonary embolism on CT, radiologists look for specific signs:

When Your Doctor Orders This Test

Here's a typical scenario where CT pulmonary angiography is ordered:

Common presenting symptoms:

• Sudden dyspnea (shortness of breath)
• Pleuritic chest pain (worse with breathing)
• Tachycardia (fast heart rate)
• Tachypnea (rapid breathing)
• Cough (may be dry or produce blood-tinged sputum)

Clinical prediction rules (PERC, Wells, Geneva):

• Help determine pre-test probability
• Guide decision on imaging vs. D-dimer
• Wells score: chest symptoms, DVT symptoms, tachycardia, immobilization, prior PE/DVT, hemoptysis, cancer

Red flags for massive/high-risk PE:

• Hypotension (systolic BP ＜90 mmHg)
• Cardiac arrest
• Shock
• Severe hypoxia
• Right heart strain markers

Differential Diagnosis

Several conditions can mimic pulmonary embolism:

How Accurate Is CT for Pulmonary Embolism?

CT pulmonary angiography is highly accurate for diagnosing PE:

What Happens Next?

Management depends on PE severity and hemodynamic stability:

Frequently Asked Questions

What causes pulmonary embolism?

Most PEs (90%) originate from deep vein thrombosis (DVT) in the legs or pelvis. Clots form when blood flow slows (immobilization), blood becomes more clot-prone (genetics, cancer, medications), or vessel walls are damaged (trauma, surgery). The clot breaks loose and travels through the heart to lodge in pulmonary arteries.

How long do I need to take blood thinners?

Duration depends on whether your PE was provoked (has a clear cause) or unprovoked. Provoked PE (after surgery, trauma, immobilization): typically 3 months. Unprovoked PE (no clear cause): often 6-12 months or indefinitely depending on bleeding risk and recurrence risk. Discuss with your doctor.

Can I fly after having a PE?

After PE diagnosis, most doctors recommend waiting 2-4 weeks before flying, once stable on anticoagulation. For long flights, wear compression stockings, stay hydrated, move around periodically, and possibly take a prophylactic dose of anticoagulation if high risk. Always consult your doctor before travel.

Will the clot completely dissolve?

In most cases, yes. The body's fibrinolytic system gradually breaks down clot over weeks to months. However, some clot may organize and persist, potentially leading to chronic thromboembolic pulmonary hypertension (CTEPH) in a small percentage of patients (1-5%). Follow-up imaging monitors for resolution.

Can PE be prevented?

Yes, especially in high-risk situations: during hospitalization or surgery, receive prophylactic blood thinners or compression devices. On long flights, move around regularly, stay hydrated, avoid alcohol. If you have DVT or PE history, maintain prescribed anticoagulation. Treat modifiable risk factors (smoking cessation, weight loss, control blood pressure).

References

Medical Disclaimer: This information is for educational purposes. Pulmonary embolism is a potentially life-threatening condition requiring immediate medical attention. Always seek emergency care for symptoms of PE.