What Causes Pulmonary Embolism? Understanding the Key Risk Factors and Triggers
Pulmonary embolism (PE) is a potentially life-threatening condition that occurs when a blood clot or other substance blocks one of the pulmonary arteries in the lungs. While many people associate PE with blood clots, there are several underlying causes and risk factors that contribute to its development. Understanding these triggers is essential for early detection, prevention, and effective treatment.
Deep Vein Thrombosis: The Most Common Cause
Deep vein thrombosis (DVT), particularly in the lower limbs, is the leading cause of pulmonary embolism. When a blood clot forms in a deep vein—usually in the legs—it can break loose and travel through the bloodstream to the lungs. Once it reaches the pulmonary circulation, it may become lodged in a smaller artery, obstructing blood flow and causing sudden respiratory distress. This process explains why prolonged immobility, long-haul flights, and post-surgical recovery are high-risk scenarios for DVT-related PE.
Air Embolism During Medical Procedures
Although less common, air embolism during intravenous therapy or surgical procedures can also lead to pulmonary embolism. If a significant volume of air enters the venous system—such as during improper IV administration or central line placement—it can travel to the right side of the heart and then into the pulmonary artery. Even small amounts of air can be dangerous if introduced rapidly, disrupting oxygen exchange and potentially leading to cardiovascular collapse.
Amniotic Fluid Embolism in Childbirth
Pregnant women face a unique risk during labor and delivery. Amniotic fluid embolism (AFE) occurs when amniotic fluid, fetal cells, or other debris enter the maternal bloodstream, triggering a severe allergic-like reaction and clotting abnormalities. Although rare, AFE is a critical emergency that can result in sudden pulmonary hypertension, respiratory failure, and cardiac arrest—mimicking the symptoms of a massive pulmonary embolism.
Fat Embolism Following Trauma or Surgery
Severe fractures, especially of long bones like the femur, or major orthopedic surgeries can release fat globules from bone marrow into the circulatory system. These fat particles can migrate to the lungs and block pulmonary vessels, leading to fat embolism syndrome. Symptoms often include shortness of breath, confusion, and petechial rash, typically appearing 1–3 days after the injury. Prompt recognition is vital to prevent complications.
Genetic Predisposition and Family History
Some individuals are genetically more susceptible to developing blood clots due to inherited conditions such as Factor V Leiden mutation, protein C or S deficiency, or antithrombin III deficiency. These disorders increase the blood's tendency to clot, raising the lifetime risk of deep vein thrombosis and subsequent pulmonary embolism. Anyone with a family history of unexplained clots should consider genetic screening and discuss preventive strategies with their healthcare provider.
Complications from Medical Treatments
Certain medical interventions carry an unexpected risk. For example, patients undergoing treatment for gastrointestinal bleeding—particularly those receiving sclerotherapy injections to seal bleeding varices—may inadvertently develop pulmonary embolism. The injected sclerosing agents can sometimes trigger local inflammation or clot formation, which may dislodge and travel to the lungs. While rare, this highlights the importance of careful monitoring during and after invasive procedures.
Prevention and Early Detection Are Key
Recognizing the diverse causes of pulmonary embolism empowers both patients and clinicians to take proactive steps. Lifestyle modifications, compression therapy, anticoagulant medications, and vigilant post-operative care can significantly reduce the risk. If you experience sudden chest pain, difficulty breathing, or unexplained coughing—especially after surgery or trauma—seek immediate medical attention. Early diagnosis saves lives.