Patient education: Pulmonary embolism (blood clot in the lung) (The Basics)

What is a pulmonary embolism? — A pulmonary embolism ("PE") is a blockage in 1 or more of the blood vessels that supply blood to the lungs. Most often, these blockages are caused by blood clots that form somewhere else and then travel to the lungs. In rare cases, blockages can also be caused by air bubbles, tiny globs of fat, or pieces of tumor that travel to the lungs.

Why are blood clots dangerous? — If a blood clot forms or gets stuck inside a blood vessel, it can clog the vessel and keep blood from getting where it needs to go. When that happens in the lungs, the lungs can get damaged. Having blocked arteries in the lung can also make it hard to breathe and can even lead to death.

Most blood clots in the lungs actually form in the legs or pelvic area and then travel to the lungs. When a clot forms in the deep veins of the leg, it is called "deep vein thrombosis" ("DVT") (figure 1). DVT can cause swelling, pain, warmth, and redness in the leg. If you have any of these symptoms, it's important to see a doctor right away. They can do tests to find out if you do have a clot and where it is. There are treatments that can help prevent a clot from getting bigger and traveling to the lungs.

What are the symptoms of blood clots in the lungs? — Common symptoms include:

●Panting, shortness of breath, or trouble breathing

●Sharp, knife-like chest pain when you breathe in or strain

●Coughing or coughing up blood

●Rapid heartbeat

If you get any of these symptoms, especially if they happen over a short period of time (hours or days) or get worse quickly, call for an ambulance (in the US and Canada, call 9-1-1). At the hospital, doctors can do tests to find out if you do have a clot. Blood clots in the lungs can lead to death. That's why it's important to act fast and find out if there is a clot.

Is there a test for PE? — Yes. There are several tests that doctors can use to find out if a person has a blood clot in a lung. The most common tests include:

●D-dimer blood test – D-dimer is a substance in the blood. The amount of D-dimer often goes up in people with a blood clot in a lung. This blood test is often done together with other tests.

●CT pulmonary angiography ("CT-PA") – A CT pulmonary angiogram is a special kind of X-ray that uses computers. During this test, a dye is injected into 1 of your veins. The dye shows up on X-rays and can show if any blood vessels are blocked.

●Ventilation/perfusion lung scan ("V/Q scan") – For this test, you breathe in a small amount of a radioactive substance. You also have a radioactive dye injected into 1 of your veins. Then, doctors look at how the different substances look on the scan. The scan can show if 1 of the arteries in the lung is blocked.

Less commonly, other tests are done, such as:

●Pulmonary angiography – For this test, you have a small tube called a catheter inserted into 1 of the large veins in your body, usually in your leg. Then, doctors gently push this tube up into your chest to where the major blood vessels of the lung are found. When the tube is in place, the doctors inject a dye that shows up on an X-ray.

●MRI pulmonary angiography ("MRI-PA") – An MRI is an imaging test that uses a magnet to create pictures. During this test, a dye is injected into 1 of your veins. The dye shows up on X-rays and can show if any blood vessels are blocked.

How is a PE treated? — Blood clots in the lungs are treated with medicines that keep clots from getting bigger. These medicines are called "anticoagulants." They are sometimes also called "blood thinners," although they do not actually thin the blood. Some come in shots, and others come in pills. PE is usually treated first in the hospital.

●If you have had a clot, your doctor will prescribe an anticoagulant medicine to lower your risk of getting more clots in the future. You will need to take the medicine for at least 3 months (and sometimes longer). Some people are first given a medicine that comes as a shot, called heparin. You might get this shot for a few days, or longer if for some reason you can't take pills.

●The medicines do not dissolve existing blood clots, but they do keep them from getting bigger. They also help keep new blood clots from forming. Taking the medicine for a few months is important because it gives your body time to dissolve the old clot. It's also important because people who have a clot are at risk of developing another clot, especially in the first few months.

●There are different oral medicines (pills) used to prevent and treat blood clots. They include apixaban (brand name: Eliquis), dabigatran (brand name: Pradaxa), edoxaban (brand names: Savaysa, Lixiana), rivaroxaban (brand name: Xarelto), and warfarin (brand name: Jantoven). Each medicine is different in the dose, how often you take it, the cost, and how your diet or other medicines might affect it (table 1). Your doctor can talk to you about your options and preferences.

If your doctor prescribes 1 of these medicines:

●Take it exactly as your doctor tells you to – If you forget or miss a dose, call your doctor to find out what to do. When you start taking the medicine, you will need to have your blood tested. If you take warfarin, you will need regular blood tests to check how your blood is clotting. This is important to make sure that you get the correct dose of warfarin for you.

●Follow your doctor's instructions about diet and medicines – Depending on which medicine you take, you might need to pay special attention to what you eat. Also, certain other medicines can affect the way these medicines work.

●Watch for signs of bleeding – Abnormal bleeding is a risk with any of the medicines used to prevent and treat blood clots. That's because while these medicines help prevent dangerous blood clots, they also make it harder for your body to control bleeding after an injury. Try to avoid getting injured, and tell your doctor right away if you do have signs of bleeding.

People who cannot take medicines to prevent and treat clots, or who do not get enough benefit from the medicines, can get a different treatment. This is called an "inferior vena cava filter" ("IVC filter"). The inferior vena cava is the large vein that carries blood from your legs and the lower half of your body back up to your heart. IVC filters go inside the inferior vena cava. They filter and trap any large clots that form below the location of the filter. Your doctor might suggest this if:

●You cannot safely take a medicine for blood clots.

●You form clots even while taking a medicine for blood clots.

●You have a dangerous bleeding problem while taking a medicine for blood clots.

●Your lungs and heart might not be able to handle another PE.

In some cases, a severe clot can cause low blood pressure and even shock. (Shock is when blood pressure gets too low, and not enough blood can get to the body's organs and tissues.) If this happens, doctors can give medicine to dissolve the clot. This is sometimes called "clot-busting" medicine, and is given through a catheter (a small tube inserted into the vein). In some cases, doctors will do surgery to remove the clot.

Can I do anything on my own to prevent blood clots? — Yes. People sometimes form clots because they have been sitting still for too long. People who travel on long airplane flights, for example, are at increased risk of blood clots. Some things that you can do to help prevent a clot during a long flight include:

●Stand up and walk around at least once every hour.

●Do not smoke just before your trip.

●Wear loose, comfortable clothes.

●Shift your position while seated, and move your legs and feet often.

●Wear knee-high compression stockings.

●Avoid alcohol and medicines that make you sleepy, because they can impair your ability to move around.

More on this topic

Patient education: Choosing an oral medicine for blood clots (The Basics)
Patient education: Taking oral medicines for blood clots (The Basics)
Patient education: Staying healthy when you travel (The Basics)
Patient education: What can go wrong after a heart attack? (The Basics)
Patient education: Factor V Leiden (The Basics)
Patient education: Deep vein thrombosis (blood clot in the leg) (The Basics)
Patient education: How to give an anticoagulant shot (The Basics)
Patient education: D-dimer test (The Basics)
Patient education: Lowering the risk of a blood clot (The Basics)
Patient education: Clot-dissolving medicines for heart attack or stroke (The Basics)
Patient education: Pulmonary embolism – Discharge instructions (The Basics)

Patient education: Lower extremity chronic venous disease (Beyond the Basics)
Patient education: Deep vein thrombosis (DVT) (Beyond the Basics)
Patient education: Pulmonary embolism (Beyond the Basics)
Patient education: Warfarin (Beyond the Basics)