A pulmonary embolism (PE) is a blood clot in your lungs. The clot often forms in the deep veins of the legs. This condition is known as deep vein thrombosis (DVT).

If the clot breaks loose and moves through the bloodstream, it’s called a venous thromboembolism (VTE) and may represent a life-threatening condition. A PE is usually a VTE that travels from the leg to the lungs.

If you don’t get effective treatment for it, a PE can lead to pulmonary hypertension. This is a condition in which blood pressure in the arteries of the lungs increases to an unhealthy level.

It also strains the right side of the heart. When the heart has to work harder than normal for a long time, it can result in heart failure.

A majority of VTE cases develop during or after a stay in the hospital, usually after surgery. Many of these blood clots can be prevented with proper care in the hospital and at home after surgery.

When a clot blocks a pulmonary artery, one of the first symptoms is shortness of breath. A PE can also cause unusually rapid breathing. You might also feel chest pain with a PE.

A blood clot in the lungs can also reduce blood flow to the brain, making you feel a little lightheaded.

PE has many possible causes.

The most common cause is prolonged bed rest. When you don’t walk or move your legs for long periods, blood doesn’t circulate as well as it should. Blood pools or collects in the veins and blood clots can form.

Less common causes include bone marrow from a long, broken bone, as well as tissue from a tumor, and even air bubbles.

The veins are the blood vessels that return blood to the heart.

If a clot from a deep vein reaches the heart, the next stop is the lungs, where blood receives oxygen and gets rid of carbon dioxide. The blood vessels get very small. This can cause the clot to lodge in the vessel, blocking blood flow through the lungs.

Any surgery that requires you to lie in bed can raise your risk of a PE. Some operations are particularly risky, however. These include pelvic, hip, or knee surgery.

The risk with these operations isn’t just extended time in bed. The position necessary for the surgery may increase the risk for DVT and PE.

Keep these risk factors in mind:

  • A leg fracture or other injury that requires the legs to be immobile for a while can also raise your risk of a clot forming in your leg and possibly traveling to your lungs.
  • Many forms of cancer, including brain, lung, pancreatic, kidney, colon and ovarian cancers, cause the body to create a substance that increases the likelihood of blood clots.
  • If you’re a smoker, you’re at an increased risk for a PE.
  • Having overweight, including during pregnancy, is another risk factor.
  • Birth control pills and hormone replacement therapy can also put some women at higher risk.

Having heart or lung disease can make it more difficult to diagnose PE. Imaging studies are needed to confirm a suspected PE.

A blood test that looks for a substance called D-dimer may be done if you’re thought to be at low risk of having PE. It can indicate whether your blood is clotting somewhere.

If the D-dimer test is negative, you’re very unlikely to have PE and you may not need to undergo further testing. Recent surgery, pregnancy, trauma, and even advanced age can raise your level of D-dimer. When this test is positive, it’s usually confirmed through imaging studies.

A chest X-ray doesn’t identify a blood clot in the lungs, but it can help eliminate other possible reasons for your symptoms.

A pulmonary ventilation/perfusion (VQ) scan can give your healthcare provider a very detailed look at the blood vessels in your lungs.

The most common imaging study used to diagnose PE is a CT scan.

One of the first treatments for pulmonary embolism is anticoagulation therapy. You’ll probably start taking blood thinners immediately after receiving a PE diagnosis.

Blood thinners don’t break up or eliminate the existing PE, but they’ll help prevent additional clots from forming. Bleeding issues are the main side effects.

In time, your body usually causes the blood clot to break apart, and your bloodstream will absorb it.

If the PE is causing severe symptoms such as hypotension, or low blood pressure, you may also be treated with drugs that break up the clot.

The drugs can be given intravenously or through a catheter that’s threaded from a leg or neck vein to the site of the clot. Your healthcare provider may also use a tiny device inserted through the catheter to help break up the clot.

If you have chronic clots causing pulmonary hypertension, your healthcare provider can perform a surgical procedure called a pulmonary thromboendarterectomy (PTE). PTE is used to remove clots from the larger blood vessels in the lungs.

However, this is a high-risk procedure and only done at a few specialized centers.

If you’re going to have surgery, talk to your healthcare provider about your risk for PE and what you can do to reduce it. They may give you a blood-thinning medication, such as heparin, warfarin (Coumadin, Jantoven), or a warfarin alternative, before and after surgery.

These drugs help keep blood clots from forming in the body, but they can raise your risk for bleeding complications.

Here are some other important ways to avoid a PE:

  • Quit smoking if you smoke because it can damage your blood vessels and increase your odds of developing blood clots, hypertension (high blood pressure), and other problems.
  • If you have overweight or obesity, talk with your healthcare provider about ways to safely lose weight and maintain your healthy weight.

Staying as physically active as possible is also very important. Try to think of and treat exercise as something you do throughout the day and not just as a 30-minute workout.

The more time that you spend on your feet walking, dancing, or otherwise moving, the less likely blood will have the chance to pool and clot in your legs.

If your healthcare provider diagnoses PE early, they can effectively treat it.

See your healthcare provider immediately if you’ve had surgery and you experience the symptoms of PE or the symptoms of a blood clot in your leg, including:

  • swelling
  • pain
  • tenderness
  • warmth

Most patients with PE make a full recovery within weeks to months after starting treatment and don’t have any long-term effects.

Roughly 33 percent of people who have a blood clot are at an increased risk of having another within 10 years, according to the Centers for Disease Control and Prevention (CDC).

Paying close attention to symptoms and exercising your legs, may help you to avoid blood clots in your lungs or other places in your body.