A pulmonary embolism occurs when a lung artery is blocked by a blood clot. The blockage is often caused by one or more blood clots that travel to the lungs from another part of the body.
A pulmonary embolism is a problem of the vascular system, the network of blood vessels that includes the arteries, veins and capillaries that carry blood to and from the heart. Vascular problems are common, such as the narrowing and hardening of arteries (atherosclerosis ), or the weakening of blood vessel walls, which can rupture and cause serious internal bleeding, or become inflamed due to the presence of a blood clot (thrombophlebitis). Blood clots can form in the deep veins of the body, most commonly in the veins of the legs, a serious condition called deep vein thrombosis (DVT). A pulmonary
embolism is a complication of DVT, and results when a blood clot breaks free, travels through the bloodstream, and lodges in a lung artery. A clot that forms in one part of the body and travels in the bloodstream to another part of the body is called an embolus, hence the name embolism.
In the United States, pulmonary embolism is one of the most common causes of mortality, being second only to coronary artery disease as a cause of sudden unexpected death at any age. Incidence is high in all racial groups. Over 50,000 people die every year as a result of a pulmonary embolism. According to the National Heart, Lung and Blood Institute (NHLBI) at least 100,000 cases of pulmonary embolism occur each year in the United States. The condition is the third most common cause of death in hospitalized patients. If untreated, about 30% of patients with pulmonary embolism die. Most of those who die do so within the first few hours of the event.
QUESTIONS TO ASK YOUR DOCTOR
- What causes a pulmonary embolism?
- What are the warning signs?
- Can it happen again?
- How can I prevent it?
- What does treatment involve?
- What is thrombolytic therapy?
Causes and symptoms
The type of clot that is likely to cause a pulmonary embolism commonly originates in the deep muscle veins as a result of DVT which usually develops in the leg or pelvic veins. Less commonly, DVT can also sometimes occur in arm veins.
The symptoms pulmonary embolism depend on the location and size of the blood clot. They may include:
- shortness of breath
- chest pain, also extending to shoulder, arm, neck, and jaw
- coughing or spitting up blood
- lightheadedness or fainting
- rapid heartbeat
Pulmonary embolism is difficult to diagnose because the condition has no clear—cut specific indicators. Some tests used for diagnosis may include:
- Chest x ray;
- Electrocardiography (ECG), a test that measures the electrical activity of the heart;
- D-dimer immunosorbent assay, a blood test that shows an increase in the levels of the clot-dissolving D-dimer protein which may rise after pulmonary embolism;
- Spiral computed tomography (CT), an imaging technique used to visualize the blood vessels in the lungs as 2-dimensional slices;
- Lung scanning, a technique that uses small amounts of radioactive tracers to measure blood flow in the lungs and air intake;
- Pulmonary angiography, a procedure to x ray lung blood vessels;
- Duplex ultrasound, a technique that measures the speed of blood flow and images the structure of leg veins.
Prompt treatment is essential for pulmonary embolism. Immediate treatment usually includes injectable anticoagulant medications, such as heparin, followed by warfarin, an anticoagulant taken by mouth, to stabilize the clot, prevent it from enlarging, and restore a normal blood flow in the lungs. Oxygen and sedatives may also be provided to make the patient more comfortable.
Caffeine and alcohol intake should be limited as they contribute to high blood pressure , a risk factor for pulmonary embolism. NHLBI nutrition research has developed Dietary Approaches to Stop Hypertension (DASH) that recommend a diet including large amounts of fruits and vegetables as well as low—fat or fat-free dairy products. Diets rich in potassium, calcium and magnesium, and low in sodium (2,400 mg or less) have also been shown to play an important role in maintaining normal blood pressure levels.
When the pulmonary embolism is large, thrombolytic therapy may be used to dissolve the clot. In this approach, a vascular surgeon injects clot-dissolving medications through a catheter directly into the clot. The surgeon may also attempt to remove the clot using a catheter technique, called suction thrombectomy. In this procedure, a catheter is inserted through blood vessels and guided to the pulmonary embolism. A salt solution is then injected into the blocked artery. The water pressure pulls the clot toward the tip of the catheter and breaks it up.
Patients who survive an acute pulmonary embolism are at high risk for experiencing another one and for the development of pulmonary hypertension . They are also at risk of enlargement of the right ventricle of the heart due to resistance of the passage of blood through the lungs (cor pulmonale).
Maintaining ideal body weight with a healthy nutritional program and exercise is generally believed likely to reduce the likelihood of DVT, the precursor condition. Some measures can also help prevent pulmonary embolisms, such as wearing elastic compression stockings, which prevent blood from accumulating in the veins, or walking or flexing legs every hour on long air or car trips. People who travel are also advised to drink plenty of fluids, because dehydration can increase the tendency of the blood to clot.
Angiography —Injection of contrast dye into a large blood vessel to help visualize the blood vessels and the blood flow within them.
Anticoagulant —A medication that helps prevent blood clots from forming. Also called a blood thinner.
Atherosclerosis —Clogging, narrowing, and hardening of arteries.
Computerized tomography (CT) —The use of x rays and computers to create images that show cross-sections, or slices, of the body.
Cor pulmonale —Enlargement of the right ventricle of the heart due to resistance of the passage of blood through the lungs.
Embolism —Sudden blockage of an artery by a clot or foreign material which has been brought to its site by the bloodstream.
Embolus —A blood clot that forms in one part of the body and travels in the bloodstream to another part of the body.
Deep vein thrombosis (DVT) —A blood clot that forms in a vein deep in the body.
Hypertension —Abnormally high blood pressure.
Thrombophlebitis —Swelling of a vein caused by a blood clot.
Ultrasound —The use of ultrasonic waves to image an internal body structure.
Vascular system —Network of blood vessels in the body, including the arteries, veins and capillaries that carry blood to and from the heart.
Pulmonary embolism becomes increasingly common with age, yet the diagnosis is missed more often in the geriatric population, largely because respiratory symptoms are often dismissed as chronic in this age group.
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American Heart Association (AHA), 7272 Greenville Avenue, Dallas, TX, 75231, (800)AHA-USA-1, http://www.americanheart.org.
Monique Laberge Ph.D.