Overview

Blood clots in the lungs, medically known as pulmonary embolism (PE), occur when one or more arteries in the lungs become blocked by a blood clot. This condition is potentially life-threatening and requires immediate medical attention. The clot typically originates from the deep veins of the legs or pelvis (a condition called deep vein thrombosis, or DVT) and travels through the bloodstream to the lungs. Pulmonary embolism can vary in severity, from small clots causing minimal symptoms to large clots that can cause severe complications or sudden death if left untreated.

Causes

The primary cause of pulmonary embolism is the migration of a blood clot from another part of the body, most commonly from the legs. Common causes and risk factors include:

• Deep vein thrombosis (DVT): The most common source of pulmonary embolism, where clots form in the deep veins of the legs or pelvis.
• Prolonged immobility: Long periods of inactivity, such as during long flights or bed rest, can slow blood flow and increase clot risk.
• Surgery: Especially orthopedic surgeries (hip, knee), which can lead to clot formation.
• Trauma or injury: Physical injuries, especially to the legs or pelvis, can lead to clots.
• Cancer: Certain cancers increase clotting tendencies in the body.
• Smoking: Smoking damages blood vessels and increases clotting risk.
• Hormonal therapy: Use of birth control pills or hormone replacement therapy can slightly increase the risk of clots.
• Obesity: Excess body weight contributes to clotting risk by slowing blood circulation.
• Genetic clotting disorders: Conditions like Factor V Leiden or prothrombin gene mutation increase clotting tendency.

Symptoms

The symptoms of pulmonary embolism can appear suddenly and vary depending on the size and number of clots:

• Shortness of breath: The most common symptom, often developing quickly and worsening with exertion.
• Chest pain: Sharp, stabbing pain that may worsen when breathing deeply (pleuritic chest pain).
• Rapid heartbeat: Increased heart rate (tachycardia) as the heart compensates for reduced oxygen.
• Cough: A dry cough or coughing up blood (hemoptysis).
• Feeling faint or dizziness: May be due to decreased oxygen levels or low blood pressure.
• Swelling and pain in the leg: If associated with DVT, usually in the calf or thigh.
• Anxiety or restlessness: Some patients feel a sense of impending doom or anxiety.

Diagnosis

Diagnosing pulmonary embolism involves a combination of clinical assessment and diagnostic testing:

• Physical examination: Doctors assess vital signs and look for signs of DVT or respiratory distress.
• D-dimer test: A blood test that measures clot-degradation products; elevated levels may indicate clotting activity.
• CT pulmonary angiography (CTPA): The most commonly used imaging test that provides detailed images of pulmonary arteries.
• Ventilation-perfusion (V/Q) scan: Used in cases where CT is contraindicated, this scan evaluates airflow and blood flow in the lungs.
• Ultrasound of the legs: To detect DVT as a source of embolism.
• Echocardiogram: Evaluates the heart’s function and may show signs of right heart strain due to PE.
• Electrocardiogram (ECG): Helps rule out other causes of chest pain like heart attack, though PE can also cause ECG changes.

Treatment

Treatment for pulmonary embolism focuses on stopping clot growth, preventing new clots, and improving oxygenation:

• Anticoagulant therapy: Blood thinners like heparin, low molecular weight heparin, or direct oral anticoagulants (DOACs) such as apixaban or rivaroxaban are standard treatments.
• Thrombolytic therapy: In severe cases, clot-dissolving medications (like alteplase) are used for life-threatening PE.
• Oxygen therapy: Supplemental oxygen helps maintain adequate oxygen levels.
• Inferior vena cava (IVC) filter: A filter may be placed in the large abdominal vein to prevent clots from reaching the lungs when anticoagulation is contraindicated.
• Surgical or catheter-directed embolectomy: In rare, severe cases, the clot may be removed surgically or via catheter-based methods.
• Treatment of underlying causes: Managing DVT, lifestyle changes, and addressing contributing factors are essential to prevent recurrence.

Prognosis

The prognosis of blood clots in the lungs depends on the size of the clot, overall health, and how quickly treatment is initiated:

• Favorable outcome with early treatment: Most patients recover fully if PE is diagnosed and treated promptly.
• Risk of complications: Severe cases can lead to pulmonary hypertension or chronic thromboembolic pulmonary hypertension (CTEPH).
• Risk of recurrence: Without long-term management, there is a risk of future clots.
• Mortality risk: Untreated PE can be fatal; however, with treatment, the risk of death drops significantly.
• Long-term management: Many patients require anticoagulation for months or indefinitely, depending on the cause and recurrence risk.

Overall, early diagnosis, timely medical intervention, and preventive measures can greatly improve the outlook for individuals with pulmonary embolism.