Pulmonary embolism: Symptoms, causes, risk factors, and treatment

A pulmonary embolism (PE) is a blood clot that blocks the flow of blood to part of one lung. Many people with this condition have two or more clots in one or both lungs. Symptoms of a pulmonary embolism can be subtle: for example, shortness of breath on exertion or intermittent chest pains. The condition can also cause more pronounced symptoms like severe chest pain with difficulty taking a deep breath. A pulmonary embolism is a serious and potentially life-threatening condition, but there are ways to help prevent it.

What is a pulmonary embolism?

A pulmonary embolism most often starts as a clot inside a leg vein. It can also start inside an arm vein or pelvic vein. This type of clot is called a deep vein thrombosis (DVT).

Sometimes, a portion or all of the DVT can break away and travel through the bloodstream. If the clot makes its way to blood vessels in the lungs and interferes with blood flow, it is called a pulmonary embolism. Another name for this type of clot is a thromboembolism.

Because almost all pulmonary emboli originate from a DVT, and the risk factors and treatment of both are similar, doctors often use the umbrella term venous thromboembolic (VTE) disease to cover both conditions.

Veins carry blood through the right side of the heart and into the lungs, where the blood picks up oxygen and gets rid of carbon dioxide in a process called gas exchange. A pulmonary embolism prevents the normal flow of blood and gas exchange.

Pulmonary emboli affect about 900,000 people in the U.S. each year. They can happen to anyone at any stage of life, even very healthy people. Depending on the size of the clot and which blood vessels are blocked, a pulmonary embolism can be life-threatening.

What is a saddle pulmonary embolism?

A saddle pulmonary embolism is a large blood clot that gets stuck where the main artery in the lungs, called the pulmonary artery, branches left and right to bring blood to each lung.

A saddle pulmonary embolism is a rare type of pulmonary embolism, affecting less than 3% of people with a PE. A saddle pulmonary embolism can cause a pulmonary infarction, in which part of the lung tissue dies from lack of oxygen.

Common pulmonary embolism symptoms

In some cases, pulmonary embolism symptoms can happen all at once. In other cases, symptoms may start slowly and get worse as time goes on.

Common symptoms of a pulmonary embolism include:

• shortness of breath or rapid breathing
• palpitations from a fast heartbeat
• chest pain, especially when you breathe in deeply.

Symptoms suggestive of a larger pulmonary embolism (such as a saddle embolism) or multiple pulmonary emboli include:

• feeling lightheaded or fainting

• coughing up blood

• bluish nails or lips
• feeling anxiety or dread.

How long can you have a pulmonary embolism without knowing?

Many people with a pulmonary embolism do not notice symptoms, or the symptoms are so mild they don't recognize them as potentially due to a serious condition.

But by knowing the causes, risk factors, and signs of a DVT, you can take steps to prevent a DVT and treat a DVT at the earliest symptoms, before it can lead to a pulmonary embolism.

What causes a pulmonary embolism?

Almost all pulmonary emboli start as a DVT. Some people are at higher risk for DVTs because of their family history, lifestyle, or certain medical conditions and situations.

Most DVTs occur when blood flow in the veins of the legs is slowed. Ordinarily, as you walk around, your leg muscles squeeze your veins and keep blood flowing back to the heart. But if you don't move your legs for many hours, blood flow in the veins of your legs may slow so much that clots form.

In some cases, clots can develop in the lungs' blood vessels instead of in the legs or arms.

Risk factors for a pulmonary embolism

Risk factors for a pulmonary embolism include:

• being hospitalized or confined to bed for more than a few days
• sitting in a plane, car, or train for more than a few hours without walking
• breaking a leg or having a major injury
• having a hip or knee replacement
• having a venous catheter, which is a tube put into a vein to give fluids and medications or for medical tests
• having cancer or receiving chemotherapy
• being pregnant, when the weight of the fetus presses on veins in the pelvis and slows blood flow in the legs
• being obese
• smoking, which damages and narrows blood vessels
• taking birth control pills
• taking hormone replacement therapy
• having heart failure or severe chronic lung disease
• having inflammatory bowel disease (ulcerative colitis or Crohn's disease)
• having blood that is more likely to form clots, a condition called thrombophilia.

You also are at higher risk if you've had a deep vein thrombosis or pulmonary embolism in the past. About 33% of people who had a DVT or PE will have another one within 10 years.

Diagnosing a pulmonary embolism

It sometimes can be hard for a doctor to diagnose a pulmonary embolism. If your doctor suspects pulmonary embolism based on your symptoms, he or she will assess your personal risk for pulmonary embolism, and will evaluate whether you have another condition, such as pneumonia, that may cause similar symptoms.

Based on this assessment, your doctor may:

• place a device called a pulse oximeter on your finger to measure your oxygen level. Your doctor may also have you walk around while wearing the device to see if exercise causes your oxygen level to drop.
• order a blood test to measure the level of a substance called D-dimer that usually rises abnormally in people with a DVT or PE
• order an ultrasound of your legs to look for a DVT
• order a chest CT scan to look for pulmonary emboli.

Alternative diagnostic tests that are rarely needed include a ventilation perfusion (V/Q) scan, a chest MRI, or a lung angiogram.

Pulmonary embolism treatment

The main treatment for DVT and PE is an anticoagulant drug. Although often called blood thinners, anticoagulants do not actually thin the blood. They block certain proteins that cause unwanted blood clots while the body's natural process dissolves the clot.

The choice of initial drug treatment depends on the severity of symptoms and risk of complications. For smaller pulmonary emboli, doctors usually prescribe a direct-acting oral anticoagulant (DOAC). The four DOACs currently FDA-approved to treat pulmonary emboli are:

• apixaban (Eliquis)
• dabigatran (Pradaxa)
• edoxaban (Savaysa, Lixiana)
• rivaroxaban (Xarelto).

People with a large pulmonary embolism such as a saddle embolism will need to be hospitalized. They may be treated with intravenous (IV) heparin, or with injections of a different kind of heparin under the skin. Some patients will need an IV clot-dissolving drug (known as thrombolysis) or a procedure to remove the large clot.

Before the availability of DOACs, the only oral drug to treat DVT and PE was warfarin (Coumadin). Certain patients, such as those who have had heart valve replacement or are very prone to forming blood clots, cannot take a DOAC. Also, DOACs are much more expensive than warfarin. For these reasons, your doctor may prescribe warfarin for treatment of pulmonary embolism and prevention of recurrence.

Preventing pulmonary emboli

The best way to prevent pulmonary emboli is to prevent blood clots from forming.

Preventing a pulmonary embolism also involves recognizing signs that a DVT may be forming, such as:

• swelling in your leg or arm with or without pain
• having one leg or arm that seems larger than the other.

If you have these symptoms, see a doctor right away.

To help prevent a DVT that may lead to a PE, take breaks to walk around during car, plane, or train travel. Wearing compression stockings can help as well.

You also can make some lifestyle changes to help lower your risk of a pulmonary embolism, such as:

• eating healthy foods
• being physically active
• maintaining a healthy weight
• not smoking.

People with a pulmonary embolism need to take an anticoagulant drug for at least three months (most doctors recommend six months). People who have blood abnormalities that put them at especially high risk of a second pulmonary embolism, and those who have had two or more separate episodes, may need to take an anticoagulant drug indefinitely.