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Pulmonary Embolism: Diagnosis

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This information was reviewed and approved by Chhaya Patel, MD (3/1/2021).

An evaluation for pulmonary embolism (PE) includes questions about your health history and a physical exam of your legs, arms, heart and lungs.

Diagnostic testing for PE can include:

Pulse Oximetry

If you have PE, your blood oxygen level will be lower than normal. A pulse oximeter device is usually clipped onto your finger and measures the blood oxygen saturation level using red and infrared light through the tissue in your finger. A blood oxygen saturation level less than 90 percent is abnormal.

Arterial Blood Gas

An arterial blood gas is a blood sample test ordered by your physician to evaluate measurements of oxygen, carbon dioxide, and several other parameters. Your physician will order this test to evaluate the effectiveness of oxygenation in the body. The blood sample is drawn at the pulse site on the wrist.

Chest X-Ray

Blood clots do not show up on an X-ray, but it can see other things such as fluid or pneumonia on the lungs that can explain your symptoms. A normal chest X-ray with unexplained low blood oxygen level, increases the suspicion that you have a pulmonary embolism.

Ventilation-Perfusion Scan (VQ Scan)

A VQ lung scan is a test that shows how the air goes into and circulates in the lungs. Your doctor will use this information to determine if you have PE. During this scan, you lie very still on an imaging table and breathe in a radioactive gas mixed with oxygen. During the VQ scan, the radioisotope shows the air going into the lungs. About eight images are taken during this test. Poor air flow can indicate PE.

Computed Tomography (CT) of the Chest with Contrast

A CT (CAT) scan takes pictures in cross sections or slices of the chest area including your lungs, heart and the bones around these areas. This test provides detailed images of the tissues and can help make an early a diagnosis. You will lie still on the CT scanner’s table while the table moves you through a doughnut shaped ring. You will be asked to hold your breath while pictures are taken. The pictures will be taken before, during and after a contrast media is injected into an IV in your arm. This media shows blood and airflow.

Pulmonary Angiogram

If the VQ scan interpretation is not able to diagnosis PE or if the CT scan is normal and symptoms are still present, a pulmonary angiogram may be ordered to reveal blockages or other problems in your veins or arteries. This test uses contrast dye so that the blood vessels are visible on an X-ray.


An echocardiogram is an ultrasound of the heart that shows the structures and functions of the heart muscle and heart valves from different angles. This test does not diagnose PE, but it identifies the strain the right side of the heart that is caused by PE and other heart problems that can have the same symptoms as PE.

Electrocardiogram (EKG)

An electrocardiogram test measures the rate and consistency of your heartbeat and can indicate other problems such as atrial fibrillation.

Magnetic Resonance Imaging (MRI)

An MRI is an advanced medical imaging technique that does not use x-ray or radiation. Instead it uses a strong magnetic field, radio waves and a computer to create detailed images of internal body structures. A cardiac MRI is performed to help evaluate the structure and function of the heart.

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