Pulmonary embolism can be difficult to diagnose, especially in people who have underlying heart or lung disease. For that reason, your doctor will likely 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 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 check for blood clots in your thigh veins.
In this test, your doctor uses a wand-shaped device called a transducer to direct the sound waves to the veins being tested. These waves are then reflected back to the transducer and translated into a moving image by a computer. The absence of clots reduces the likelihood of DVT. If the upper thigh vessels are clear, the ultrasonography will also scan the veins behind the knee looking for residual clots. If clots are present, treatment likely will be started immediately.
Spiral CT scan
In a spiral (helical) CT scan, the scanner rotates around your body in a spiral — like the stripe on a candy cane — to create 3-D images. This type of CT can detect abnormalities within the arteries in your lungs with much greater precision than conventional CT scans. In some cases, contrast material is given intravenously during the CT scan to outline the pulmonary arteries.
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 into your heart and on 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.
One risk of this procedure is a temporary change in your heart rhythm. In addition, the dye may cause kidney damage in people with decreased kidney function.
MRI scans use radio waves and a powerful magnetic field to produce detailed images of internal structures. Because MRI is expensive, it's 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 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.
- Blood thinners (anticoagulants). These drugs prevent 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. A newer class of anticoagulants, referred to as novel oral anticoagulants (NOACs), has been tested and approved for treatment of venous thromboembolism, including pulmonary embolism. These medications work quickly and have fewer interactions with other medications. Some NOACs have the advantage of being given by mouth, without the need for overlap with heparin. However, all anticoagulants have side effects, with bleeding being the most common.
- Clot dissolvers (thrombolytics). While clots usually dissolve on their own, there are medications given through the vein that 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 — called the inferior vena cava — that leads from your legs to the right side of your heart. This filter can help keep clots from being carried into your lungs. This procedure is typically reserved for people who can't take anticoagulant drugs or when anticoagulant drugs don't work well enough or fast enough. Some filters can be removed when they are no longer needed.
Preparing for your appointment
Most cases of pulmonary embolism are 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 write 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
- Information about the medical problems of parents or siblings
- Medications you're taking
- Questions you want to ask the doctor
What to expect from your doctor
During the physical exam, your doctor might 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.