pulmonary embolism

pulmonary embolism
Field	Pulmonology, Cardiology, Hematology

pulmonary embolism. It is a critical cardiovascular emergency where a blockage, typically a blood clot, travels to the arteries of the lungs. This condition is a common complication of deep vein thrombosis and represents a major cause of morbidity and mortality worldwide. Prompt diagnosis and treatment are essential to prevent severe outcomes like right heart failure or sudden death.

Signs and symptoms

The clinical presentation is highly variable, ranging from asymptomatic to catastrophic cardiovascular collapse. Common symptoms include sudden onset dyspnea, pleuritic chest pain, and cough, which may be accompanied by hemoptysis. Patients may exhibit signs of right ventricular strain such as elevated jugular venous pressure, a loud P2, or a right-sided S3 gallop. Severe cases can present with syncope, hypotension, or cardiac arrest, mimicking other emergencies like myocardial infarction or aortic dissection. The classic triad of dyspnea, chest pain, and hemoptysis is present in only a minority of cases.

Risk factors

The primary risk factors are encapsulated in Virchow's triad of venous stasis, hypercoagulability, and endothelial injury. Specific predisposing conditions include prolonged immobilization, as seen after major surgery or during long-haul flights, active malignancy, and inherited thrombophilias like factor V Leiden or prothrombin G20210A mutation. Other significant risks encompass trauma, especially fractures of the pelvis or long bones, pregnancy, the use of estrogen-containing medications, and certain medical conditions like heart failure or inflammatory bowel disease. The risk is notably elevated in patients with a prior history of venous thromboembolism.

Pathophysiology

The obstruction most commonly originates from a dislodged thrombus in the deep veins of the legs or pelvis, a condition known as deep vein thrombosis. The embolus travels through the right side of the heart and lodges in the pulmonary arterial tree. This causes mechanical obstruction, leading to increased pulmonary vascular resistance, which in turn elevates right ventricular afterload. The resultant pressure overload can cause acute cor pulmonale and right ventricular failure. Furthermore, the release of vasoactive mediators from platelets contributes to pulmonary vasoconstriction and ventilation-perfusion mismatch, exacerbating hypoxemia.

Diagnosis

Diagnosis requires a combination of clinical assessment, biomarker testing, and imaging. Initial evaluation often involves calculating a clinical probability score, such as the Wells criteria or Revised Geneva score. Elevated levels of D-dimer are sensitive but non-specific. The cornerstone of imaging is CT pulmonary angiography, which directly visualizes thrombi in the pulmonary arteries. Ventilation-perfusion scanning remains an option, particularly in patients with contraindications to contrast. Other modalities include echocardiography, which may show right ventricular dysfunction, and compression ultrasonography of the legs to identify a source deep vein thrombosis.

Treatment

Immediate management focuses on hemodynamic stabilization and initiation of anticoagulation. For most patients, initial therapy involves parenteral anticoagulants like low molecular weight heparin, fondaparinux, or unfractionated heparin. This is typically bridged to long-term oral anticoagulation with warfarin or a direct oral anticoagulant such as apixaban or rivaroxaban. In cases of massive embolism with hypotension, systemic thrombolysis with agents like alteplase is indicated. For patients with contraindications to thrombolysis or who remain unstable, catheter-directed therapies or surgical pulmonary embolectomy may be life-saving. Inferior vena cava filters are considered when anticoagulation is contraindicated.

Prognosis

The prognosis varies widely based on the clot burden, the patient's underlying cardiopulmonary reserve, and the timeliness of intervention. Early mortality risk is often stratified using tools like the Pulmonary Embolism Severity Index. With appropriate treatment, most patients survive the acute event, but they face risks of recurrence and long-term complications. A significant subset develops chronic thromboembolic pulmonary hypertension, which may require evaluation at specialized centers like UCSD for potential pulmonary thromboendarterectomy. Long-term anticoagulation therapy is crucial to reduce the risk of recurrent venous thromboembolism.

Category:Cardiovascular diseases Category:Medical emergencies Category:Lung disorders