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Microbubble testing

Microbubble testing is a specialised medical scanning procedure that our consultants use when diagnosing various heart conditions. The test itself involves the use of tiny gas-filled bubbles, called microbubbles, to improve the clarity of ultrasound imaging.

The procedure is particularly useful in detecting issues related to the heart's structure and function, especially in cases where traditional imaging methods may not provide sufficient detail.

Microbubble testing uses tiny, gas-filled bubbles to enhance ultrasound images, usually of the heart and surrounding blood vessels.

The microbubbles are injected into your bloodstream, and when the ultrasound is performed, the microbubbles create a clear contrast between the blood and surrounding tissues, allowing our consultants to observe the flow of blood through the heart and other blood vessels more accurately.

This test is particularly useful in visualising the upper chambers of the heart (the atria) and identifying abnormal connections or blood flow patterns that might not be visible with standard ultrasound imaging.

Microbubble testing is primarily used to diagnose heart-related conditions, particularly those that involve abnormal blood flow or structural defects in the heart. One of the most common uses of microbubble testing is to detect a condition known as Patent Foramen Ovale (PFO).

PFO is a small, flap-like opening between the upper chambers of the heart (the left and right atria). This opening is normal before birth, allowing blood to bypass the lungs while the foetus develops, and typically closes soon after birth.

However, in some people, the PFO remains open, which can allow blood clots or other particles to pass from the right side to the left side of the heart, potentially leading to a stroke or other complications.

As well as detecting PFO, microbubble testing can also diagnose a range of different heart conditions, including atrial septal defects (ASD), which are similar to PFO but involve a larger hole between the heart's upper chambers.

The test can also help identify abnormal blood flow patterns, evaluate the function of heart valves, and assess the presence of blood clots within the heart.

Microbubble testing begins with the injection into a vein (usually one on your arm) of something called a ‘contrast agent’, a special medical liquid containing microbubbles. These microbubbles are extremely small, often less than a micrometre in diameter.

Once injected, the microbubbles travel through the bloodstream and reach your heart within seconds.

As the ultrasound probe is placed on the chest, it emits high-frequency sound waves that bounce off the microbubbles and are detected by the probe. These reflected sound waves create an image on the ultrasound screen, allowing your consultant to visualise the heart's structure and blood flow in real-time.

The cost of a microbubble test depends on your individual circumstances. At the time of your appointment your consultant will discuss all options with you and ensure all your questions are answered.

Our fixed-price packages include the cost of your surgery and all appropriate aftercare appointments. However, any pre-surgery diagnostic tests and your consultant's outpatient appointment consultation fee are charged separately.

Our flexible payment options help you spread the cost of your payment across a time period that suits you.

Microbubble tests are usually recommended for people who have experienced unexplained strokes or Transient Ischemic Attacks (TIAs), often referred to as ‘mini-strokes.’ These events can sometimes be caused by blood clots that pass through a PFO or other abnormal heart structures and travel to the brain.

Patients with certain heart conditions, such as atrial septal defects or valve disorders, may also benefit from microbubble testing. The test is useful for anyone who has symptoms or a medical history that includes any suspicion of heart abnormality or blood flow that might not be detectable through other imaging techniques.

Microbubble testing is one of the safest, most effective ways of assessing your heart and circulatory system. The main benefit is its ability to create detailed images of the heart's structure and function in real-time. This allows consultants to make more accurate diagnoses and develop more precise treatment plans.

Another benefit is that microbubble testing is not very invasive. There’s only a small injection followed by a straightforward ultrasound scan, making it safer and less uncomfortable for patients compared to more invasive procedures.

Microbubble testing is also very effective at detecting conditions like PFO, which can be tricky to diagnose with standard ultrasound techniques. Early detection of these kinds of conditions can be crucial in preventing strokes and other complications.

Before undergoing microbubble testing, you’ll discuss the process with your consultant to go through your medical history, current symptoms, and any previous tests or treatments. Your consultant will explain the procedure in detail and answer any questions you may have.

While there is no special preparation required for microbubble testing in most cases, the consultant may advise you to avoid eating or drinking for a few hours before the test, especially if the test is being performed as part of a larger cardiac evaluation.

If you’re taking any medications, let the medical team know, as some drugs may need to be temporarily paused before the test.

On the day of the test, you will be asked to lie down on an examination table. A technician or nurse will place an intravenous (IV) line into a vein in your arm. This IV line will be used to inject the microbubble contrast agent into your bloodstream.

Once the IV is in place, the ultrasound technician will apply a special gel to your chest. This gel helps the ultrasound probe make better contact with your skin, which makes images clearer. The probe will then be placed on your chest, and the technician will begin taking ultrasound images of your heart.

As the microbubbles are injected into your bloodstream, the technician will monitor the ultrasound screen to observe how the microbubbles move through your heart. During the test, you may be asked to perform certain breathing exercises, such as holding your breath or coughing, to help the consultant see how the bubbles move through the heart.

The whole test usually takes about 30 to 60 minutes. You will be awake and able to communicate with the medical staff throughout the test.

After the test is completed, the IV line will be removed, and you will be able to get up and move around. There’s no need for any special recovery period, and most people can go home and resume their normal activities straight away.

Your consultant will review the ultrasound images and discuss the results with you either on the day, or at a follow-up appointment. In some cases, additional tests may be needed if the microbubble test reveals any abnormalities that require further investigation.

Microbubble testing is particularly effective in diagnosing conditions that involve abnormal connections or blood flow patterns within the heart. Some of the most common conditions that can be investigated with this test include:

As well as PFAs and TIAs, microbubble tests can also find and assess:

Atrial Septal Defect (ASD)

A larger hole in the heart's upper chambers that can lead to heart failure or other complications if left untreated.

Heart valve disorders

Any conditions that affect the function of the heart's valves, leading to abnormal blood flow.

Intracardiac shunts

These are defined as abnormal connections between the heart chambers that allow blood to flow in the wrong direction.

Pulmonary Arteriovenous Malformations (PAVMs)

Any abnormal connections between blood vessels in the lungs can lead to low oxygen levels and other complications.

Preparing for microbubble testing is pretty straightforward. Follow any instructions from your consultant, such as fasting or avoiding certain medications before the test. It’s also important to wear comfortable clothing, as you will need to lie still during the procedure.

If you have any concerns or questions about the test, be sure to discuss them with your consultant beforehand. Understanding what to expect can help ease any anxiety you may have about the tests.

Microbubble testing is safe for most people, including children and adults. However, it may not be suitable for people with certain conditions, such as severe lung disease or allergies to contrast agents. Your consultant will assess your overall health and medical history to determine if microbubble testing is appropriate for you.

Recovering from microbubble testing is generally quick and easy. The test is minimally invasive, so most people experience no side effects and can return to their normal activities immediately afterwards.

In some cases, some individuals may experience mild discomfort at the injection site or a temporary rash. These symptoms usually resolve on their own without the need for any extra medical attention.

The results of microbubble testing are usually available shortly after the procedure. Your doctor will review the ultrasound images and look for any signs of abnormal blood flow or structural defects in the heart.

If the test reveals a PFO, ASD, or other condition, your doctor will discuss the findings with you and recommend appropriate treatment options. In some cases, additional tests may be needed to confirm the diagnosis or to plan for treatment.

For most people, microbubble testing provides valuable information that can help guide decisions about their heart health. Whether the results show a need for further treatment or simply provide reassurance, the test is an important tool to make sure any potential heart issues are identified and addressed promptly.

Content reviewed by Circle in-house team in January 2025. Next review due January 2027.

  1. Bubble contrast echocardiogram, NHS
  2. Stable microbubble test and click test to predict respiratory distress syndrome in preterm infants not requiring ventilation at birth, NIHWhat 
  3. What is a bubble study? Harvard Health Publishing

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