A blockage of an artery in the lungs by fat, air, clumped tumor cells, or blood clot .

Alternative Names

Venous thrombo-embolism; Lung blood clot; Fat embolus; Air embolus; Tumor embolus

Causes, incidence, and risk factors

Pulmonary emboli are blockages of the blood vessels of the lungs (pulmonary vessels). Most often, they are caused by blood clots from the veins, especially veins in the legs or in the pelvis (hips). More rarely, air bubbles, fat droplets, amniotic fluid, or clumps of parasites or tumor cells may obstruct the pulmonary vessels. The most common cause of a pulmonary embolism is a blood clot in the veins of the legs, called a deep vein thrombosis ( DVT ). Many resolve on their own, though some may cause severe illness or even death. The risk factors include prolonged bed rest or inactivity (including long trips in planes, cars, or trains), oral contraceptive use, surgery (especially pelvic surgery), child birth, massive trauma, burns, cancer , stroke , heart attack , heart surgery, and fractures of the hips or femur. Persons with certain clotting disorders may also have a higher risk.

Signs and tests

Tests to evaluate the function of the lungs:

arterial blood gases

pulse oximetry

Tests to detect the location and extent of embolism :

chest X-ray

pulmonary ventilation/perfusion scan

pulmonary angiogram

Tests to detect

DVT (a common cause):

Doppler ultrasound exam of an extremity

blood flow studies

venography of the legs

plethysmography

of the legs

An ECG may show abnormalities caused by strain on the heart. This disease may also alter the results of the following tests:

echocardiogram

D-dimer level

chest CAT scan

chest MRI scan

Treatment

Emergency treatment and hospitalization are necessary. In cases of severe, life-threatening pulmonary embolism, definitive treatment consists of dissolving the clot with thrombolytic therapy. Anticoagulant therapy prevents the formation of more clots and allows the body to re-absorb the existing clots faster. Thrombolytic therapy (clot-dissolving medication) includes streptokinase, urokinase, or t-PA. Anticoagulation therapy (clot-preventing medication) consists of heparin by intravenous infusion initially, then oral warfarin (Coumadin). Subcutaneous low-molecular weight heparin is often substituted for intravenous heparin in many circumstances. In patients for whom anticoagulation therapy is contraindicated, an inferior vena cava filter (IVC filter) may be placed. This device, placed in the main central vein in the abdomen, is designed to block large clots from traveling into the pulmonary vessels. Oxygen therapy may be required to maintain normal oxygen concentrations. Surgery in patients at great risk for recurrent embolism is sometimes indicated.

Expectations (prognosis)

It is difficult to assess the prognosis of pulmonary embolism, because many cases are never diagnosed. Often, the prognosis is related to the disease that puts the person at risk for pulmonary embolism (cancer, major surgery, trauma, etc.). In cases of severe pulmonary embolism, where shock and heart failure occur, the death rate may be greater than 50%.

Complications

palpitations

heart failure or shock

respiratory distress (severe breathing difficulty)

sudden death

hemorrhage (usually a complication of thrombolytic or anticoagulation therapy)

pulmonary hypertension

with recurrent pulmonary embolism

Calling your health care provider

Go to the emergency room or call the local emergency number (such as 911) if symptoms of pulmonary embolus occur.

Prevention

Prevention of deep venous thrombosis ( DVT ) among patients who are at risk is very important. Walking and activity as soon as possible after surgery or during a prolonged medical illness can reduce the risk for pulmonary embolus. Subcutaneous heparin therapy (low doses of heparin injected under the skin) may be used for those on prolonged bedrest. Other preventive measures include compression stockings (plastic sleeves that fit around the legs and help circulate the blood).