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Diagnosing Pulmonary Embolism

NYU Langone doctors can quickly identify pulmonary embolism, a blockage in the lungs that can be life threatening. This condition is usually caused by blood clots that develop in the veins of a leg, a related condition known as deep vein thrombosis.

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If not treated quickly, one or more clots can break loose and travel through the bloodstream to the lungs, where they lodge and limit or stop blood flow. This starves lung tissue of blood, making it difficult or impossible for your lungs to provide oxygen to the rest of your body. When pulmonary embolism occurs, it requires immediate emergency medical attention.

Venous thromboembolism is an umbrella term that encompasses deep vein thrombosis and pulmonary embolism. As many as 900,000 Americans are affected each year by venous thromboembolism, and an estimated 100,000 people die as a result. 

Risk Factors

Certain factors and lifestyle behaviors may put people at higher risk of developing pulmonary embolism due to deep vein thrombosis. These include prolonged immobility, such as when bedridden or a passenger on a long flight. In addition, remaining in the same position for hours at a time, such as in a car or even at a desk, slows blood flow and increases the risk of these conditions.

Similarly, people who have had any type of surgery are at higher risk of developing blood clots. Remaining immobile while recovering slows blood flow and causes blood to pool in the legs.

If you have an inherited blood clotting disorder, such as hypercoagulable states or thrombophilia, you are at higher risk of developing blood clots and pulmonary embolism. Several genetic disorders can increase the risk as well. People older than 60 years old may be at higher risk because of rising blood pressure levels and decreased activity.

People who smoke are at risk because the toxic chemicals in cigarettes damage blood cells and blood vessels. Those who are overweight or who take oral contraceptives, or birth control pills, are at an even higher risk of developing blood clots and pulmonary embolism.

People with certain types of cancer, including lung cancer, ovarian cancer, or pancreatic cancer, have a greater chance of developing blood clots that may lead to pulmonary embolism. In addition, chemotherapy used to treat cancers of all kinds increases this risk. It’s not fully understood why chemotherapy may increase the risk of blood clots forming. This treatment may damage blood vessels and reduce the production of proteins that protect people from developing clots.

Pregnancy may increase risk for women, as the weight of an unborn child puts additional pressure on the pelvis and the veins in the legs, which can affect blood flow. If you are pregnant and concerned about blood clots, speak to your obstetrician.

Signs and Symptoms

Pulmonary embolism may rarely occur without any warning symptoms, but most people with this condition first experience noticeable swelling and pain in the leg. This is because when a vein in the leg is blocked due to deep vein thrombosis, the blood can’t travel back to the heart.

When clots travel to the lungs and lodge in the arteries, people experience sudden additional symptoms, including shortness of breath, lightheadedness, fainting, chest pain, and a rapid pulse and heartbeat. They may also cough up blood.

Pulmonary embolism can also lead to pulmonary hypertension, a related condition in which blood pressure in the lungs is too high. The right side of the heart must then work harder to promote blood flow through obstructed arteries. If you are diagnosed with pulmonary hypertension, your doctor works with you to create a treatment plan based on your symptoms and health history.

Diagnostic Tests

During an exam, your doctor may order tests to help determine if you have a pulmonary embolism. After your NYU Langone physician reviews your test results, he or she discusses them with you and explains in detail all treatment options.

Chest X-rays

In a chest X-ray, light beams produce pictures of structures inside the chest. For pulmonary embolism, a chest X-ray may reveal a blockage in the arteries in the lungs.

CT Angiogram

Your doctor may use a CT angiogram—an X-ray scan of the blood vessels—to look for evidence of pulmonary embolism. This type of CT scan uses X-rays to take multiple views of the chest. At NYU Langone, doctors regularly use CT scans with the least amount of radiation possible. These provide images of arterial blockage in the lungs.

Depending on the type of scan, you may be given an intravenous (IV) dose of a saline solution and contrast material during the test. This material enhances the image, so that your doctor can see inside the arteries to the lungs. This enables the doctor to determine whether there is a blockage.

The test typically takes 10 to 15 minutes. It doesn’t hurt, but you may experience a sensation of warmth if contrast material is injected into a vein.

MRI Scans

MRI scans use magnetic waves and computers to create two- and three-dimensional pictures of the inside of the body. It is an important tool for diagnosing pulmonary embolism.

Before the test begins, you receive an injection of contrast dye, which allows your doctor to see the arteries in the lungs clearly on the magnetic image.

A technician takes the pictures while you lie very still. The test takes 40 to 90 minutes.

Venous Duplex Ultrasound

This test combines conventional ultrasound, which uses sound waves to create images of parts of the body, with Doppler ultrasound, which shows the motion of fluid in blood vessels. Doctors may use this on the leg to determine if you have deep vein thrombosis, which may be the source of pulmonary embolism.

The test takes about 30 minutes to 1 hour and does not cause discomfort.


If your doctor suspects you have a pulmonary embolism, which can also affect your heart function, he or she may order an echocardiogram. This sonogram of the heart uses high-frequency sound waves to create images of the heart beating and pumping blood.

If your doctor finds evidence of your heart pumping too hard this may indicate pulmonary embolism.

Pulmonary Angiogram

NYU Langone doctors may sometimes use a pulmonary angiogram, which is more conventional than CT angiogram, to view the arteries of the lungs. During this procedure, the doctor also uses contrast dye to make it easier to see the arteries on an X-ray. This enables our vascular specialists to identify narrow, enlarged, and blocked blood vessels.

Using local anesthesia, a doctor makes a small incision in the skin near the groin and inserts a thin tube called a catheter, which is fed into an artery. The doctor then guides the catheter through the arteries to the lung. The contrast dye is injected through the catheter, and the doctor watches the procedure on a nearby monitor as several sets of X-rays are taken.

The full procedure takes from less than an hour to several hours, depending on what your interventional vascular specialist finds.

Although a pulmonary angiogram is not painful, you may feel some pressure when the catheter is inserted and a warm sensation throughout your body due to the contrast material.


The doctor may also want to look at the blood vessels of the extremities to locate a blood clot that may be the source of a pulmonary embolism.

During a venogram, the doctor inserts a thin, flexible tube called a catheter, usually from the groin and then into a vein near where a blood clot is suspected. A contrast dye is slowly injected into the catheter. The dye helps to illuminate the movement of blood through the vessel, which is captured in X-ray images in a technique called fluoroscopy.

After the test, the catheter is removed. A venogram takes about 30 minutes.

Ventilation–Perfusion Scan 

A ventilation–perfusion scan uses tiny amounts of radioactive material to assess air flow and blood flow through the lungs. It also measures the blood supply in the lungs. These allow the doctor to find evidence of any blood clots in the lungs.

Generally, a ventilation–perfusion scan is not as accurate as a CT angiogram. However, it can be used in people who are allergic to contrast dye, have renal insufficiency, or are unable to have a CT scan for any reason.

Our Research and Education in Pulmonary Embolism

Learn more about our research and professional education opportunities.