Pulmonary Embolism Evaluation
Pulmonary embolism (PE) is a potentially serious condition in which a blood clot lodges in one of the arteries of the lungs, blocking blood flow. Most pulmonary emboli arise from clots that form in the deep veins of the legs or pelvis (deep vein thrombosis) and travel to the lungs. PE can range from small clots with few or no symptoms to large emboli that cause severe breathing difficulty or strain on the heart. Imaging—primarily CT pulmonary angiography—plays a central role in evaluating suspected PE, along with clinical assessment and laboratory testing.
What is it?
A pulmonary embolism occurs when a blood clot—or, less commonly, fat, air, tumor, or other material—lodges in one of the arteries supplying the lungs. This blocks the flow of blood through that artery and reduces the lung’s ability to deliver oxygen to the body. Most pulmonary emboli arise from blood clots that form in the deep veins of the legs (deep vein thrombosis, or DVT) or, less commonly, the pelvis or upper extremities. These clots can break off and travel through the bloodstream until they become lodged in the lung’s arteries.
Several factors increase the risk of pulmonary embolism. Major risk factors include prior DVT or PE, recent surgery (especially of the hip, knee, or abdomen), prolonged immobility (such as long flights or hospitalization), cancer, pregnancy and the postpartum period, hormonal therapy (oral contraceptives or hormone replacement), heart failure, severe infection, and inherited clotting disorders (thrombophilias). Additional contributors include smoking, obesity, increasing age, and certain autoimmune conditions.
Symptoms can vary widely depending on the size, location, and number of clots, as well as the patient’s underlying health. The most common symptoms include sudden shortness of breath, chest pain (often sharp and worse with deep breathing), rapid heart rate, and cough (which may include blood). Some patients also notice leg swelling, redness, or pain consistent with deep vein thrombosis. Smaller emboli can produce subtle symptoms or may even be discovered incidentally. Larger or “massive” pulmonary emboli can cause severe shortness of breath, low blood pressure, fainting, and, in severe cases, cardiac arrest. Patients with chronic recurrent emboli may develop pulmonary hypertension and progressive breathing difficulty.
Evaluation of suspected pulmonary embolism is guided by the patient’s clinical presentation and risk factors. Structured scoring systems (such as the Wells or Geneva score) help assess the likelihood of PE and guide testing. The D-dimer blood test is often used in lower-risk patients; a normal value can help rule out PE without imaging, while elevated levels are less specific and typically prompt further evaluation. CT pulmonary angiography (CTPA) is the primary imaging test for diagnosing PE; it uses intravenous contrast to visualize the pulmonary arteries and directly detect clots. Ventilation-perfusion (V/Q) scanning is an alternative—particularly for patients who cannot receive iodinated contrast or who are pregnant—and assesses the match between airflow and blood flow in the lungs. Ultrasound of the legs is often used to identify deep vein thrombosis, which strongly supports the diagnosis when PE is clinically suspected. Echocardiography helps assess strain on the right side of the heart and is particularly important in severe or unstable cases. ECG, basic blood work, and pulse oximetry are routinely used in the overall assessment.
Important to Know
Pulmonary embolism is a time-sensitive diagnosis that requires prompt evaluation and treatment, often in the emergency department. The mainstay of treatment for most patients is anticoagulation with blood-thinning medications, which prevents clots from growing and reduces the risk of additional emboli. Several types of anticoagulants are available, and the choice depends on individual factors such as kidney function, pregnancy, cancer, bleeding risk, and patient preferences.
For patients with severe or “massive” pulmonary embolism—including those with low blood pressure or significant heart strain—more aggressive treatments may be considered. These can include thrombolytic (“clot-busting”) therapy, catheter-directed treatments to break up or remove clot, or, in selected critical cases, surgical removal of the clot. Supportive care, including supplemental oxygen, fluids, and treatment of associated conditions, is also important.
Treatment of underlying risk factors—such as managing cancer, treating infections, encouraging early mobilization after surgery, and addressing modifiable contributors—is an essential part of care. Inferior vena cava (IVC) filters may be considered for selected patients who cannot tolerate anticoagulation or who develop recurrent emboli despite adequate treatment.
The duration of anticoagulation depends on the circumstances of the PE: provoked emboli (clearly related to a temporary risk factor such as surgery) often require shorter courses, while unprovoked or recurrent emboli, ongoing risk factors (such as active cancer), or certain inherited clotting conditions may require longer or even indefinite anticoagulation. Decisions are individualized in collaboration with hematologists, pulmonologists, and primary care clinicians.
Most patients with treated pulmonary embolism recover well, although some develop chronic complications such as post-thrombotic syndrome of the legs or chronic thromboembolic pulmonary hypertension. Follow-up after PE is important to monitor for symptoms, adjust treatment, and address ongoing risk factors.
Red flag symptoms include sudden severe shortness of breath, severe chest pain, fainting or near-fainting, coughing up blood, rapid heart rate with confusion or low blood pressure, or sudden collapse. These warrant immediate emergency evaluation.