What is pulmonary embolism?
Pulmonary embolism is the sudden blockage of a major blood vessel (artery) in the lung, usually by a blood clot . In most cases, the clots are small and are not deadly, but they can damage the lung. But if the clot is large and stops blood flow to the lung, it can be deadly. Quick treatment could save your life or reduce the risk of future problems.
What are the symptoms?
The most common symptoms are:
Pulmonary embolism can also cause more general symptoms. For example, you may feel anxious or on edge, sweat a lot, feel lightheaded or faint, or have a fast heart rate or palpitations .
If you have symptoms like these, you need to see a doctor right away, especially if they are sudden and severe.
What causes pulmonary embolism?
In most cases, pulmonary embolism is caused by a blood clot in the leg that breaks loose and travels to the lungs. A blood clot in a vein close to the skin is not likely to cause problems. But having blood clots in deep veins ( deep vein thrombosis ) can lead to pulmonary embolism. More than 300,000 people each year have deep vein thrombosis or a pulmonary embolism. 1
Other things can block an artery, such as tumors, air bubbles, amniotic fluid , or fat that is released into the blood vessels when a bone is broken. But these are rare.
What increases your risk of pulmonary embolism?
Anything that makes you more likely to form blood clots increases your risk of pulmonary embolism. Some people are born with blood that clots too quickly. Other things that can increase your risk include:
You are also at higher risk for blood clots if you are an older adult (especially older than 70) or extremely overweight ( obese ).
How is pulmonary embolism diagnosed?
It may be hard to diagnose pulmonary embolism, because the symptoms are like those of many other problems, such as a heart attack , a panic attack , or pneumonia . A doctor will start by doing a physical exam and asking questions about your past health and your symptoms. This helps the doctor decide if you are at high risk for pulmonary embolism.
Based on your risk, you might have tests to look for blood clots or rule out other causes of your symptoms. Common tests include blood tests, ultrasound , spiral CT scan , electrocardiogram (EKG, ECG) , and MRI .
How is it treated?
Doctors usually treat pulmonary embolism with medicines called anticoagulants . They are often called blood thinners, but they don't really thin the blood. They help prevent new clots and keep existing clots from growing.
At first, the doctor may give you a shot of heparin, a blood thinner that works quickly. Then you may take warfarin (such as Coumadin), a blood thinner that you take as a pill. Most people take warfarin for a few months. People at high risk for blood clots may need it for the rest of their lives.
If symptoms are severe and life-threatening, "clot-busting" drugs called thrombolytics may be used. These medicines can dissolve clots quickly, but they increase the risk of serious bleeding. Another option is surgery to remove the clot (embolectomy).
Some people can't take blood thinners, or they form clots in spite of taking the medicine. To prevent future problems, they may have a filter put into the large vein (vena cava) that carries blood from the lower body to the heart. A vena cava filter helps keep blood clots from reaching the lungs.
If you have had pulmonary embolism once, you are more likely to have it again. Blood thinners can help reduce your risk, but they increase your risk of bleeding. If your doctor prescribes blood thinners, be sure you understand how to take your medicine safely, and see your doctor for regular blood tests.
You can reduce your risk of pulmonary embolism by doing things that help prevent blood clots in your legs.
Frequently Asked Questions
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Pulmonary embolism is caused by a blocked artery in the lungs. The most common cause of such a blockage is a blood clot that forms in a deep vein in the leg and travels to the lungs, where it becomes lodged in a smaller lung artery.
Almost all blood clots that cause pulmonary embolism are formed in the deep leg veins. Clots also can form in the deep veins of the arms or pelvis.
Occasionally blood clots develop in surface veins , but these clots rarely lead to pulmonary embolism.
In rare cases, pulmonary embolism may be caused by other substances, including:
The symptoms of pulmonary embolism may include:
Pulmonary embolism may be hard to diagnose because its symptoms may occur with or are similar to other conditions, such as a heart attack, asthma, a panic attack, or pneumonia. Also, some people with pulmonary embolism don't have symptoms.
If a large blood clot blocks the artery in the lung, blood flow may be completely stopped, causing sudden death. A smaller clot reduces the blood flow and may cause damage to lung tissue. But if the clot dissolves on its own, it may not cause any major problems.
Symptoms of pulmonary embolism usually begin suddenly. Reduced blood flow to one or both lungs can cause shortness of breath and a rapid heart rate. Inflammation of the tissue covering the lungs and chest wall (pleura) can cause sharp chest pain.
Without treatment, pulmonary embolism is likely to come back.
Complications of pulmonary embolism
Doctors will consider aggressive steps when they are treating a large, life-threatening pulmonary embolism.
Chronic or recurring pulmonary embolism
Blood clots that cause pulmonary embolism may dissolve on their own. But if you have had pulmonary embolism, you have an increased risk of a repeat episode if you do not receive treatment. If pulmonary embolism is diagnosed promptly, treatment with anticoagulant medicines (usually heparin and warfarin) may prevent new blood clots from forming.
The risk of having another pulmonary embolism caused by something other than blood clots varies. Substances that are reabsorbed into the body, such as air, fat, or amniotic fluid, usually do not increase the risk of having another episode. Cancer increases the risk of blood clots.
Having multiple episodes of pulmonary embolism can severely reduce blood flow through the lungs and heart. Over time, this increases blood pressure in the lungs (pulmonary hypertension), eventually leading to right-sided heart failure and possibly death.
What Increases Your Risk
For more information on risk factors for blood clots in the legs, see the topic Deep Vein Thrombosis.
Risk factors for developing clots include having slowed blood flow, abnormal clotting, and a blood vessel injury.
Slowed blood flow
When blood does not circulate normally, clots are more likely to develop. Reduced circulation may result from:
Some people have blood that clots too easily or too quickly. People with this problem are more likely to form larger clots that can break loose and travel to the lungs. Conditions that may cause increased clotting include:
Injury to the blood vessel wall
Blood is more likely to clot in veins and arteries shortly after they are injured. Injury to a vein can be caused by:
Other risk factors include:
When To Call a Doctor
Call 911 or other emergency services immediately if you think you have symptoms of pulmonary embolism. Symptoms include:
Call your doctor right away if you have symptoms of a blood clot in the leg. These symptoms may include:
Blood clots in the deep veins of the leg are the most common cause of pulmonary embolism. For more information on these types of blood clots, see the topic Deep Vein Thrombosis.
If you think you may have pulmonary embolism, call your doctor or go to the emergency room at the nearest hospital. Watchful waiting is not appropriate for pulmonary embolism.
Who to see
Health professionals who can diagnose pulmonary embolism include:
To prepare for your appointment, see the topic Making the Most of Your Appointment.
Exams and Tests
Diagnosing pulmonary embolism is difficult, because there are many other medical conditions, such as a heart attack or an anxiety attack, that can cause similar symptoms.
Diagnosis depends on an accurate and thorough medical history and ruling out other conditions. Your doctor will need to know about your symptoms and risk factors for pulmonary embolism. This information, combined with a careful physical exam, will point to the initial tests that are best suited to diagnose a deep vein thrombosis or pulmonary embolism.
Tests that are often done if you have shortness of breath or chest pain include:
Further testing may include:
After your doctor has determined that you have a pulmonary embolism, other tests can help guide treatment and suggest how well you will recover. These tests may include:
Treatment of pulmonary embolism focuses on preventing future pulmonary embolism by using anticoagulant medicines. Anticoagulants prevent existing blood clots from growing larger and help prevent new ones from developing.
If symptoms are severe and life-threatening, immediate and sometimes aggressive treatment is needed. Aggressive treatment may include thrombolytic medicines, which can dissolve a blood clot quickly but also increase the risk of severe bleeding. Another option for life-threatening, large pulmonary embolism is surgical removal of the clot, called an embolectomy. This surgery is only available at a few large hospitals.
Some people may also benefit from having a vena cava filter inserted into the large central vein of the body. This filter can help prevent blood clots from reaching the lungs. It is used when anticoagulants are not an option, when clots form despite anticoagulant use, or when there is an increased risk of death or a severely restricted lifestyle if another pulmonary embolism occurs.
The risk of forming another blood clot is highest in the weeks after the first episode of pulmonary embolism. This risk decreases over time. But the risk remains high for months and sometimes years, depending upon what caused the pulmonary embolism. People with recurrent blood clots and/or pulmonary embolism may have to take anticoagulants daily for the rest of their lives. Anticoagulant medicines also are often used for people who are not active due to illness or injury, or people who are having surgery on the legs, hips, belly, or brain.
Other preventive methods may also be used, such as:
Take steps to prevent blood clots from travel, such as drinking fluids and walking around every hour. Because of long periods of inactivity, you are at higher risk for blood clots when you are traveling.
If you are already at high risk for pulmonary embolism or deep vein thrombosis, talk to your doctor before taking a long flight or car trip. Ask if you need to take any special precautions to prevent blood clots during travel.
Home treatment is not recommended for initial treatment for pulmonary embolism. But it is important for preventing more clots from developing and causing a deep vein thrombosis , which can lead to recurring pulmonary embolism.
Measures that reduce your risk for developing a deep vein thrombosis include the following:
For more information on how to prevent clots from developing, see the topic Deep Vein Thrombosis.
Medicines can help prevent repeated episodes of pulmonary embolism by preventing new blood clots from forming or preventing existing clots from getting larger.
Anticoagulants are prescribed when pulmonary embolism is diagnosed or strongly suspected. Normally, when an injury that causes bleeding occurs, the body sends out signals that cause the blood to clot at the wound. The clot naturally breaks down as the wound heals. A person who is prone to abnormal clotting has an imbalance between clot formation and clot breakdown. Anticoagulants prevent the production of certain proteins that are needed for blood to clot. Although anticoagulants can prevent new clots from forming and prevent existing clots from getting larger, they do not break up or dissolve existing blood clots.
Heparin and warfarin are the two main types of anticoagulants used to treat pulmonary embolism.
Heparin is an anticoagulant given by injection. It immediately affects the clotting system in your body. Oral anticoagulant medicine (warfarin) takes longer to start working.
Warfarin (such as Coumadin)
Warfarin is an anticoagulant that is taken in pill form. It is usually started while a person is still being treated with heparin because it takes several days for warfarin to build up to a level that's effective. When the warfarin is at a proper level, heparin is stopped and treatment with warfarin continues.
Typically, warfarin is given for at least 3 months after pulmonary embolism to reduce the risk of having another blood clot. Treatment with anticoagulants may continue throughout your life if the risk of having another pulmonary embolism remains high.
Because warfarin can increase the risk of birth defects, pregnant women with a risk of developing blood clots are limited to taking heparin.
Clot-dissolving (thrombolytic) medicines are not commonly used to treat pulmonary embolism. Although they can quickly dissolve a blood clot, thrombolytics also greatly increase the risk of serious bleeding. They are occasionally used to treat a life-threatening pulmonary embolism.
What to think about
After pulmonary embolism is diagnosed, a doctor considers:
If you have recently had a major stroke, surgery, or active internal bleeding, you usually cannot take anticoagulant or thrombolytic medicines. A vena cava filter may help to reduce the risk of another pulmonary embolism in this case.
Safety with anticoagulant medicine
When you take anticoagulants, you need to take extra steps to avoid bleeding problems.
If you take heparin:
If you take warfarin:
For more information, see:
Surgical removal of a clot is called an embolectomy. This type of treatment for pulmonary embolism is rarely used. It is considered for people who can't have other kinds of treatment or those whose clot is so dangerous that they can't wait for medicine to work. An embolectomy also may be an option for a person whose condition is stable but who shows signs of significant reduced blood flow in the pulmonary artery.
What to think about
Surgery increases the risk of forming new blood clots that can cause another pulmonary embolism.
Some people cannot take anticoagulant medicines, or they continue to develop blood clots despite taking the medicines. If surgery or medicines are not options, other methods of preventing pulmonary embolism may be considered, such as a vena cava filter.
Other treatment choices
A vena cava filter may be inserted in the large central vein that passes through the abdomen and returns blood from the body to the heart (vena cava). This filter can prevent blood clots in the leg or pelvic veins from traveling to the lungs and heart. These filters may be permanent or removable.
Studies have shown that vena cava filters help prevent pulmonary embolism. But they may be most effective when combined with anticoagulant therapy.
What to think about
Vena cava filters aren't recommended as the first treatment for pulmonary embolism. But they may be considered if you:
Vena cava filters may benefit people who have had a pulmonary embolism surgically removed (embolectomy) if another pulmonary embolism would likely be fatal or severely limit a person's lifestyle.
Vena cava filters can cause serious health problems if they break or become blocked with one or more blood clots.
Vena cava filters have not been shown to lower the death rate in people with pulmonary embolism.
Other Places To Get Help
Last Revised: May 8, 2012
U.S. Department of Health and Human Services (2008). The Surgeon General's call to action to prevent deep vein thrombosis and pulmonary embolism. Available online: http://www.surgeongeneral.gov/topics/deepvein.
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