Pulmonary Embolism PART I (Overview)

Summary

This video breaks down pulmonary embolism clearly and concisely: its common signs (sudden dyspnea, pleuritic chest pain, tachycardia, hypotension and DVT signs), major risk factors (surgery, immobility, malignancy, pregnancy, cardiopulmonary disease and thrombophilias), and how most emboli arise from lower-limb DVTs. It explains Virchow’s triad and thrombus formation, then follows an embolus from the leg through the IVC to the right heart and pulmonary arteries. The pathophysiology covers raised pulmonary pressures, right-ventricular strain and V/Q mismatch with hypoxemia and respiratory alkalosis. Practical investigations (CXR, ECG, D-dimer, CTPA, V/Q scan, bedside echo) and diagnostic challenges are also summarized.

Takeaways

• 🫁 Pulmonary embolism (PE) is a blockage of the pulmonary arteries, most commonly caused by thrombi (blood clots) originating from the deep veins of the lower limbs.
• 💉 Around 90–95% of pulmonary emboli result from deep vein thrombosis (DVT), making DVT a key underlying cause.
• ⚠️ Major risk factors for PE include recent surgery (especially abdominal, pelvic, orthopedic, and obstetric), pregnancy, immobility, malignancy, advanced age, and thrombotic disorders.
• 🩸 Virchow’s Triad describes the three main mechanisms promoting thrombus formation: abnormal blood flow (stasis), hypercoagulability, and vessel wall injury.
• 🧬 Once formed, a thrombus can resolve, propagate, embolize, recanalize, or organize within the vessel wall; embolization is the process that causes PE.
• ❤️ When a thrombus embolizes to the pulmonary circulation, it increases pulmonary vascular resistance and right ventricular pressure, potentially leading to right heart failure and systemic hypotension.
• 🌬️ In the lungs, PE causes ventilation–perfusion (V/Q) mismatch and inflammation, resulting in hypoxemia, hypocapnia, and respiratory alkalosis detectable on arterial blood gas tests.
• 📋 Common clinical signs and symptoms include dyspnea, pleuritic chest pain, tachycardia, hypotension, and leg swelling or pain due to DVT.
• 🩻 Investigations for PE include chest X-ray (often normal but may show wedge-shaped opacity or elevated hemidiaphragm), ECG (sinus tachycardia, right ventricular strain, or S1Q3T3 pattern), and D-dimer assay.
• 🖥️ CT pulmonary angiogram is the gold standard diagnostic test for confirming PE, while V/Q scanning, echocardiography, and D-dimer testing can support diagnosis or risk assessment.
• 🧠 Clinical diagnosis of PE is challenging because its symptoms overlap with other cardiopulmonary conditions, so identifying risk factors is essential for accurate assessment and management.

Q & A

What are the primary signs and symptoms of pulmonary embolism (PE)?

The primary signs and symptoms of pulmonary embolism include dyspnea (difficulty breathing), chest pain, tachycardia (increased heart rate), hypotension (low blood pressure), and signs of deep vein thrombosis (DVT), such as swollen and painful lower legs.

What is the most common cause of pulmonary embolism?

The most common cause of pulmonary embolism is deep vein thrombosis (DVT), which accounts for about 90-95% of cases. The thrombus (blood clot) from deep veins, usually in the legs, breaks off and lodges in the pulmonary arteries, blocking blood flow to the lungs.

What are some key risk factors for developing a pulmonary embolism?

Risk factors for pulmonary embolism include major surgeries (especially abdominal, pelvic, or orthopedic surgeries), pregnancy, cardiorespiratory conditions (e.g., COPD, congestive heart failure), varicose veins, fractures, malignancy, increasing age, immobility, and thrombotic disorders.

What are the three main factors involved in Virchow’s Triad, which contribute to thrombus formation?

Virchow’s Triad includes three factors that contribute to thrombus formation: abnormal blood flow (e.g., stasis), hypercoagulability (e.g., thrombophilia), and altered vessel walls (e.g., endothelial injury). These factors increase the likelihood of clot formation in the veins.

What happens to the thrombus after it forms in the deep veins?

After a thrombus forms in the deep veins, it can follow five possible outcomes: it can resolve (disappear), propagate (grow larger), embolize (break off and travel to the lungs), recanalize (develop holes and change structure), or organize (integrate into the vessel wall).

How does a pulmonary embolism affect the cardiovascular system?

A pulmonary embolism increases pulmonary vascular pressure, which can backflow into the right side of the heart. This causes right ventricular pressure to rise, leading to right ventricular dilation and potential right-sided heart failure. This in turn decreases cardiac output and blood pressure, resulting in hypotension.

What respiratory changes occur in the lungs as a result of pulmonary embolism?

In the lungs, a pulmonary embolism causes a ventilation-perfusion (V/Q) mismatch and inflammation. This results in impaired gas exchange, leading to hypoxemia (low oxygen levels) and hypocapnia (low carbon dioxide levels). In response, hyperventilation and respiratory alkalosis can occur.

How is pulmonary embolism diagnosed, and what tests are commonly used?

Pulmonary embolism is diagnosed through a combination of clinical assessment, risk factors, and investigations. Key diagnostic tests include a CT pulmonary angiogram (the gold standard), ECG (to rule out other conditions like myocardial infarction), D-dimer testing (to assess for clot presence), and chest X-rays (used to exclude other lung conditions).

What role does the ECG play in diagnosing pulmonary embolism?

While an ECG is typically used to exclude other conditions like myocardial infarction, it can show signs suggestive of pulmonary embolism. These may include sinus tachycardia, right ventricular strain (e.g., inverted T-waves in V1-V4), and the S1Q3T3 pattern, which reflects right heart strain due to PE.

What is the significance of the D-dimer test in diagnosing pulmonary embolism?

The D-dimer test measures the presence of fibrin degradation products, which are elevated when a thrombus is present. A high D-dimer level suggests the possibility of a pulmonary embolism, though it is not specific. A normal D-dimer can help rule out PE, particularly in low-risk patients.