Bubble Study During an Echocardiogram

A Test Done to Detect Blood Flow Problems Inside the Heart

A bubble study is a noninvasive test that lets healthcare providers look at the flow of blood through the heart. It is done as part of a medical imaging study called an echocardiogram (echo) that shows the heart's structure. A bubble study is also known as an agitated saline contrast study.

A bubble study is often done to help diagnose patent foramen ovale (PFO), which is a hole between the upper chambers of the heart. During the bubble study test, saline mixed with air is put into a vein. Overall, it takes about 30 minutes to do a bubbly study test. 

This article goes over what a bubble study is used for, how it’s done, and what risks you should know about before you have the test. 

Heart rate monitor, patient and doctors in background in intensive care unit
Caiaimage / Sam Edwards / Getty Images

How a Bubble Study Is Done

A bubble study works because sound waves bounce around and create “echo waves” when they are near physical substances like gas or liquid. The echo waves show up on an echocardiogram as increased density.

How to Prepare

Usually, there is no preparation needed before a bubble study. Check with your healthcare provider about what you need to do to get ready for the test.

In a typical bubble study, a salty (saline) solution is shaken to make tiny bubbles and is injected into a vein. As the bubbles travel through the vein and into the right side of the heart, the increased density they produce on the echocardiography image allows a provider to watch the bubbles move through the heart chambers.

If the heart is working normally, the bubbles will be seen going into the right atrium, then the right ventricle. Then, they go out of the pulmonary artery and into the lungs. Once in the lungs, they can be filtered out through circulation.

If the bubbles enter the left side of the heart, it indicates that there is an abnormal opening between the two sides of the heart (intracardiac shunt). An intracardiac shunt can be caused by a PFO, an atrial septal defect, or a ventricular septal defect.

Commercial forms of “bubbles” are available to be used during bubble studies. These new agents usually are made of tiny protein or phospholipid casings with gas in them. They are safe in most cases and may provide better echo imaging. However, they are much more expensive than a shaken saline solution.

Are There Risks With a Bubble Study?

The bubble study test is considered safe. While your provider will want you to be aware of any serious complications, these are not common. 

The more serious risks of a bubble study include reduced blood flow and an air microembolism, which is when air enters a vein and causes a blockage. Research has shown that if a bubble study causes a microembolism, it could trigger a stroke.

A less serious but more common risk of having a bubble study is that you’ll have some discomfort in the part of your arm where the cannula is put in.

Bubble Study for Patent Foramen Ovale

The most common reason for needing a bubble study is to look for a PFO. While the bubbles are being injected into the vein, the patient is asked to bear down like they are trying to have a bowel movement (the Valsalva maneuver).

Doing this temporarily raises the pressures inside the right side of the heart. If there is a PFO, the bubbles can often be seen going into the left atrium. Bubbles appearing in the left atrium during the test confirm there is a PFO.

Why Are PFOs a Problem?

The main reason healthcare providers worry about PFOs is that they could allow blood clots to cross into the left side of the heart, where they could enter the circulation of the brain and lead to an embolic stroke.

While PFOs are common (occurring in up to 25% of adults), they only rarely lead to a stroke. While a positive bubble study might confirm you have a PFO, it does not tell your healthcare provider very much about your risk of having a stroke.

Most experts think that a better way to assess whether a PFO is likely to produce a stroke is to do a transcranial Doppler study (TCD) with a bubble study.

For this test, echo techniques are used to look at the bubbles traveling through the blood vessels of the brain. The TCD study can show whether the bubbles that were injected into a vein are actually getting into the brain circulation. 

If they are, having a PFO could be more likely to increase a person’s risk of stroke. Therefore, a provider will be more likely to recommend anticoagulation therapy, or if a stroke has already happened, possibly the surgical closure of the PFO.

Summary

A bubble study can be done to see how the blood flows through the heart. It is done as part of an echocardiogram. You may need a bubble study to diagnose a heart problem like a patent foramen ovale (PFO). 

A bubble study usually does not take long. A bubble study is safe but there are risks involved with any test. Your provider will talk to you about the risks of having a bubble study done and explain why they think the risk is worth the benefit for your condition. 

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
Richard N. Fogoros, MD

By Richard N. Fogoros, MD
Richard N. Fogoros, MD, is a retired professor of medicine and board-certified in internal medicine, clinical cardiology, and clinical electrophysiology.