Pulmonary Embolism: Symptoms and Risk Factors

A pulmonary embolism (PE) is a blood clot in the lungs. Blood clots can form in any blood vessel in the body, but they tend to form in the deep veins in the legs. Sometimes a piece of the clot can break loose. When this happens, the clot can travel through the veins and circulate with the blood. It tends to get stuck when it reaches the lungs, where the blood vessels naturally branch off into smaller vessels.

A PE isn’t a common condition. Only about 1 or 2 people out of 1000 will get a PE. But a PE can be serious, especially if the blood clot is large. It not only interferes with blood flow in the lungs, but it can also significantly impact the heart’s ability to function. So it’s important to diagnose a PE before it causes more serious problems. 

Here we’ll talk about symptoms of PEs, risk factors, and diagnosis.

Symptoms of a pulmonary embolism 

The symptoms of a PE can vary from person to person. Some people experience significant chest pain, which can happen when a part of the lung doesn’t get enough blood flow. Other people may not have any chest pain but notice mild weakness or dizziness. And others may only notice swelling in their legs, either from the original blood clot or a change in their heart function.

This is all to say that there’s no way to diagnose a PE on symptoms alone. But some of the more common symptoms include: 

• Chest pain: When a PE causes chest pain, it often feels like a sharp, focused pain that worsens when you take a deep breath. But others may experience this as a dull pain or tightness in the chest.

• Shortness of breath: This develops when the blood clot prevents the lungs from getting oxygen into the blood. Some people with a PE feel short of breath all the time, others only notice it on exertion, like when walking up steps.

• Lightheadedness or fainting: This can happen if the blood clot lowers your blood pressure. Low oxygen levels also contribute. 

• Bloody cough: This can occur if the blood clot irritates blood vessels in the lungs. While a lot of other conditions can also cause this symptom, with a PE you might see small specks of blood when coughing.

• Fast pulse: The heart tends to beat faster when there’s a blood clot in the lungs, so you might feel like your heart is racing.

Since PEs often come from a deep vein thrombosis (DVT) in the legs, some people may have symptoms of a blood clot in one of their legs. These symptoms might be pain, swelling, or redness of the leg. If you have any of the above symptoms and new symptoms in one of your legs, this is particularly concerning for a DVT and PE. 

Quiz: Do I have DVT?

Risk factors for pulmonary embolism 

There are many different conditions that can cause symptoms similar to a PE. So sometimes it also helps to know if you’re at increased risk of a blood clot for some reason. This can help you and your provider figure out if you should do more tests.

Certain conditions and situations increase the risk for a PE when they make your blood more likely to clot. This can be because there’s something wrong with the normal blood clotting processes or because the blood is pooling and stagnant inside the vein. 

You’re at increased risk for PEs if your blood clots more readily than normal. This is called a “hypercoagulable state.” Some things that cause this are:

• Inherited blood clotting disorders, like factor V Leiden

• Cancer

• Liver disease

• Some autoimmune diseases, like antiphospholipid syndrome

• Hormone therapy or birth control pills 

• Pregnancy

Areas of decreased blood flow can also lead to blood clots. Blood cells are more likely to stick together and clot when blood pools in a vein instead of flowing through it. Things that can cause this include:

• Immobilization: When muscles contract, they help squeeze blood through the veins. When you don’t move, your muscles don’t help with blood flow.

• Surgery: You’re often less active after surgery, which puts you at risk of blood clots. This is especially true after a joint surgery, like a knee or hip replacement.

• Long plane rides: This can cause blood clots because you sit for a long period of time. This is more likely to happen if you’re at risk for blood clots for other reasons.

• Venous insufficiency: This is a condition in which valves in the veins that stop blood from flowing backward don’t work as well, leading to blood pooling in the legs.

Diagnosis of a pulmonary embolism

The diagnosis of a PE starts before any testing. This is because a PE is a rare diagnosis, and the testing can be time consuming and expensive. So medical providers want to make sure there’s a good reason to suspect a PE before they put you through any unnecessary testing.

If you’re experiencing some of the above symptoms, your provider will start by looking for more clues that you could have a PE. This includes things like your:

• Age

• Other medical conditions

• Risk factors for a PE

• Vital signs (like heart rate and oxygen level)

• Signs of a DVT on a physical exam 

If you’re at low risk for a PE and there are no other clues pointing toward the diagnosis, this may be enough to rule out the diagnosis without doing extensive testing. 

Other times, your provider may recommend a D-dimer test, a blood test that can determine if you need more testing. It looks at the way your blood is clotting. A low D-dimer means you probably don’t have a blood clot. A higher D-dimer doesn’t necessarily mean you have a PE, it just means you need more testing. 

If you and your provider have good reason to think you might have a PE, or if your D-dimer is elevated, there are two main ways to diagnose a PE:

1. CT scan of the chest: This is a 3-D X-ray of the arteries that lead to the lungs. You get contrast dye through an intravenous (IV) line, which outlines any blood clots in the lungs. 

2. Ventilation-perfusion scan: During this test you inhale a special substance that lights up the lungs. You also get the same substance through an IV to light up the blood vessels. Then a machine scans the lungs to look for areas where there’s a mismatch between blood flow and air supply. Mismatched areas suggest a blood clot.

Fortunately, there’s treatment for a PE. In most cases anticoagulant medications can easily treat a PE. Your provider will get you the medications you need to take care of the problem.

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Written by:

Michael Dreis, MD

Dr. Dreis is an emergency medicine physician currently practicing in Milwaukee, Wisconsin. He went to medical school at the University of Wisconsin – Madison and completed his residency at Henry Ford Hospital in Detroit, Michigan.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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