The goal of this clinical trial is to learn how well the SONAS ultrasound device can detect right-to-left shunts of adults with hereditary hemorrhagic telangiectasia (HHT) who are already scheduled for a contrast bubble echocardiogram (TTCE). The main questions it aims to answer are:

1. How accurately does SONAS detect right-to-left shunts compared to the standard TTCE test?
2. Can SONAS results help tell the difference between shunts in the heart and shunts in the lungs?

Participants will wear a headband with the SONAS device on the head while they undergo their routine TTCE bubble test. They will receive the usual contrast (agitated saline) through a vein, and both SONAS and TTCE signals will be recorded at the same time. There will be one examination in rest, and one during a breathing exercise (the Valsalva manoeuvre).

This study is being done to find out whether a new ultrasound device called SONAS can safely and reliably detect "right-to-left shunts" in people with hereditary hemorrhagic telangiectasia (HHT). Right-to-left shunts are abnormal connections between blood vessels that allow blood to bypass the lungs and go directly from the right side of the heart to the left side. This can increase the risk of problems such as stroke or brain abscess. Today, these shunts are usually found with a "bubble heart ultrasound" (TTCE), which needs experienced staff and can be time-consuming. SONAS is a small, portable device that detects blood flow signals in the brain after a bubble injection and may offer a simpler way to detect these shunts.

In this study, all participants are are already scheduled to have a bubble heart ultrasound as part of their regular care. The study adds the SONAS device on top of this routine test. During the procedure, a soft headband with small ultrasound sensors is placed in frond of the ears on both sides of the head. At the same time, the standard bubble test is done: normal saline mixed with a small amount of the participant's blood and some air is injected into a vein, and the heart is imaged with ultrasound. Participants will be asked to perform a straining manoeuvre (called a Valsalva) to see if this makes a shunt more visible. While this is happening, SONAS continuously records signals from the brain that show when the bubbles pass through.

There will be a comparison between what SONAS shows with what the standard heart ultrasound shows. By comparing these results, the researchers want to see how closely the SONAS score matches the standard test and whether certain SONAS outcomes indicate a clinically important shunt. They will also look at the timing and pattern of the bubble signals to explore whether SONAS can help tell the difference between shunts that come from the heart and those that come from the lungs. The study does not change any decisions about diagnosis or treatment: all medical decisions remain based on the usual heart ultrasound and other standard tests.

Throughout the procedure, the safety and comfort of participants are closely monitored. SONAS does not deliver any contrast or radiation. All problems or unusual events that occur during or shortly after the combined test are recorded. The information collected in this study will help determine whether SONAS is a practical, safe, and useful tool to support or simplify screening for right-to-left shunts.

Inclusion Criteria:

• Age 18 years or older.
• Suspected or confirmed hereditary hemorrhagic telangiectasia (HHT).
• Incidentally: Patients who have experienced cryptogenic stroke

Exclusion Criteria:

• Pregnancy or breastfeeding.
• Known or suspected fracture(s) of the temporal / parietal skull bones, or with open skin injuries in the anatomical area of the temporal / parietal lobes.
• Patients with known metal skull implants in the anatomical area of the temporal / parietal bones, or with anatomical formation of the head or ear tha may interfere with proper headset placement.
• Patients with known allergies or reactions to parabens, which are present in the gel pad material of the applied part.

All anonymized Individual Patient Data that underlie results in the publication.

Beginning 3 months and ending 2 years after the publication of results.

Fellow researchers interested in doing a meta-analysis of data will be able to access the IPD and supporting information. There will be access to the Study Protocol and anonymized individual patient data. Access is possible by contacting the Central Contact Person or Principal Investigator of the study.