Pulmonary embolism can be difficult to diagnose, especially in people who have underlying heart or lung disease. For that reason, your doctor will likely discuss your medical history, do a physical exam, and order one or more of the following tests.
Your doctor may order a blood test for the clot-dissolving substance D dimer. High levels may suggest an increased likelihood of blood clots, although many other factors can also cause high D dimer levels.
Blood tests also can measure the amount of oxygen and carbon dioxide in your blood. A clot in a blood vessel in your lungs may lower the level of oxygen in your blood.
In addition, blood tests may be done to determine whether you have an inherited clotting disorder.
This noninvasive test shows images of your heart and lungs on film. Although X-rays can't diagnose pulmonary embolism and may even appear normal when pulmonary embolism exists, they can rule out conditions that mimic the disease.
A noninvasive test known as duplex ultrasonography (sometimes called duplex scan or compression ultrasonography) uses sound waves to scan the veins in your thigh, knee and calf, and sometimes in your arms, to check for deep vein blood clots.
A wand-shaped device called a transducer is moved over the skin, directing the sound waves to the veins being tested. These waves are then reflected back to the transducer to create a moving image on a computer. The absence of clots reduces the likelihood of deep vein thrombosis. If clots are present, treatment likely will be started immediately.
CT pulmonary angiography
CT scanning generates X-rays to produce cross-sectional images of your body. CT pulmonary angiography ― also called CT pulmonary embolism study ― creates 3D images that can detect abnormalities such as pulmonary embolism within the arteries in your lungs. In some cases, contrast material is given intravenously during the CT scan to outline the pulmonary arteries.
Ventilation-perfusion scan (V/Q scan)
When there is a need to avoid radiation exposure or contrast from a CT scan due to a medical condition, a V/Q scan may be performed. In this test, a tracer is injected into a vein in your arm. The tracer maps blood flow (perfusion) and compares it with the airflow to your lungs (ventilation) and can be used to determine whether blood clots are causing symptoms of pulmonary hypertension.
This test provides a clear picture of the blood flow in the arteries of your lungs. It's the most accurate way to diagnose pulmonary embolism, but because it requires a high degree of skill to administer and has potentially serious risks, it's usually performed when other tests fail to provide a definitive diagnosis.
In a pulmonary angiogram, a flexible tube (catheter) is inserted into a large vein — usually in your groin — and threaded through your heart and into the pulmonary arteries. A special dye is then injected into the catheter, and X-rays are taken as the dye travels along the arteries in your lungs.
In some people, this procedure may cause a temporary change in heart rhythm. In addition, the dye may cause increased risk of kidney damage in people with reduced kidney function.
MRI is a medical imaging technique that uses a magnetic field and computer-generated radio waves to create detailed images of the organs and tissues in your body. MRI is usually reserved for pregnant women (to avoid radiation to the fetus) and people whose kidneys may be harmed by dyes used in other tests.
Treatment of pulmonary embolism is aimed at keeping the blood clot from getting bigger and preventing new clots from forming. Prompt treatment is essential to prevent serious complications or death.
Medications include different types of blood thinners and clot dissolvers.
Blood thinners (anticoagulants). These drugs prevent existing clots from enlarging and new clots from forming while your body works to break up the clots. Heparin is a frequently used anticoagulant that can be given through the vein or injected under the skin. It acts quickly and is often overlapped for several days with an oral anticoagulant, such as warfarin, until it becomes effective, which can take days.
Newer oral anticoagulants work more quickly and have fewer interactions with other medications. Some have the advantage of being given by mouth, without the need for overlap with heparin. However, all anticoagulants have side effects, and bleeding is the most common.
- Clot dissolvers (thrombolytics). While clots usually dissolve on their own, sometimes thrombolytics given through the vein can dissolve clots quickly. Because these clot-busting drugs can cause sudden and severe bleeding, they usually are reserved for life-threatening situations.
Surgical and other procedures
- Clot removal. If you have a very large, life-threatening clot in your lung, your doctor may suggest removing it via a thin, flexible tube (catheter) threaded through your blood vessels.
- Vein filter. A catheter can also be used to position a filter in the body's main vein (inferior vena cava) that leads from your legs to the right side of your heart. This filter can help keep clots from going to your lungs. This procedure is typically reserved for people who can't take anticoagulant drugs or when they have had recurrent clots despite use of anticoagulants. Some filters can be removed when no longer needed.
Because you may be at risk of another deep vein thrombosis or pulmonary embolism, it's important to continue treatment, such as remaining on blood thinners, and be monitored as often as suggested by your doctor. Also, keep regular doctor visits to prevent or treat complications.
Preparing for your appointment
Pulmonary embolism is often initially evaluated in hospitals, emergency rooms or urgent care centers. If you think you might have a pulmonary embolism, seek immediate medical attention.
What you can do
You may want to prepare a list that includes:
- Detailed descriptions of your symptoms
- Information about your past medical problems, especially any recent surgeries or illnesses that kept you bedridden for several days
- Details on any recent journeys that involved long car or plane rides
- All medications you're taking, including vitamins, herbal products and any other supplements, and the dosages
- Information about the medical problems of parents or siblings
- Questions you want to ask the doctor
What to expect from your doctor
During the physical exam, your doctor will likely inspect your legs for evidence of a deep vein clot — an area that's swollen, tender, red and warm. He or she will also listen to your heart and lungs and check your blood pressure, and will likely order one or more tests.