What is a bubble study?

Ask the doctor

Published: October, 2016

Q. My cardiologist mentioned that he was going to do a "bubble study" during my echocardiogram. What is that?

bubble study echocardiogramA. During an echocardiogram, a technician uses a probe that emits high-frequency sound waves (ultrasound) that "echo" off the structures of your heart. The waves, which are translated into video images visible on a monitor, can reveal in-formation about your heart's structure and function. A bubble study gives added information, as it can identify potential blood flow issues inside your heart.

For the bubble study, you will get an intravenous (IV) line in a vein in your arm. A saltwater solution called saline is mixed with a small amount of air to create tiny bubbles and then injected into your vein. This fluid then circulates up to the right side of your heart and shows up on the echocardiogram image. You may be asked to cough, which briefly increases the pressure in the heart's right side.

Normally, your lungs will simply filter out the bubbles. But if you have a tiny opening between your heart's upper chambers (the right and left atria), some bubbles will move through that hole and appear on the left side of the heart. This opening is called a patent foramen ovale (PFO). About one in four people have this finding, which occurs when the hole—which is present in everyone before birth as a normal part of development—fails to close fully

Most people with a PFO remain healthy without any problems. But some evidence suggests that PFOs might be responsible for certain rare strokes when no other cause can be found. Normally, the network of blood vessels in your lungs trap any tiny blood clots before blood recirculates through the heart and body. But if a clot bypasses the lungs by taking a shortcut through a PFO, it can travel to the arteries that supply the entire body. If a clot lodges in a blood vessel to the brain, it can cause a stroke. A doctor may suspect a PFO if you're relatively young and had a stroke but don't have other obvious risk factors, such as high blood pressure or atrial fibrillation. But for the most part, carefully done studies show that there is no clear benefit to closing PFOs routinely, as it is very difficult to determine if a stroke is truly caused by a PFO. As a result, clot-preventing drugs are the main treatment for stroke prevention.

A bubble study may also show a different type of opening in the wall between the atria. Known as an atrial septal defect, these are usually discovered and repaired in childhood but may go unnoticed until later in life. Depending on the size of the hole, these defects may need to be closed to prevent strain on the heart and heart failure over time.

— Deepak Bhatt, M.D., M.PH.
Editor in Chief, Harvard Heart Letter

Image: sudok1 /Thinkstock

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