A right to left shunt (RLS) is a condition where blood bypasses the lungs and flows from the right side to the left side of the heart, which can increase the risk of stroke. A patent foramen ovale (PFO) is a specific type of RLS where an opening in the heart that should close after birth remains open, also raising stroke risk.

Diagnosing RLS and PFO can be done using several methods:

Transthoracic Echocardiography (TTE): Non-invasive but not very sensitive.
Transesophageal Echocardiography: More accurate but requires an invasive procedure.
Transcranial Doppler (TCD): Non-invasive and accurate but not widely available.

A study was conducted at six clinical sites to compare a new robot-assisted TCD (raTCD) with TTE for diagnosing RLS. The study included patients who had experienced an event suggesting an embolic stroke or transient ischemic attack between October 2020 and October 2021. The primary goal was to see which method detected RLS more effectively.

Study Results: raTCD vs. TTE for RLS Detection

Out of 154 enrolled patients, 129 were suitable for scanning, and 121 had complete data. The average age was 60 years, and 47% were women. All patients had ischemic strokes or transient ischemic attacks. The raTCD detected RLS in 64% of patients, while TTE only detected it in 20%. For larger RLS, raTCD found 27% of cases, compared to TTE’s 10%. There were no serious side effects from the tests.

The study concluded that raTCD is safe and about three times more effective in diagnosing RLS than TTE. TTE missed or underdiagnosed two-thirds of the large shunts that raTCD detected. Moreover, raTCD can be used by healthcare professionals without prior training in TCD, making this technology more accessible. Overall, TCD, especially with the robot-assisted method, appears to be a better screening tool for RLS and PFO than TTE.