Routine revascularization of asymptomatic carotid stenosis is questionable as optimal medical therapy has significantly reduced the risk of stroke. Therefore, it is crucial to identify high-risk patients who may still benefit from carotid revascularization. In 2017, the ESC guidelines clarified the criteria associated with a high risk of stroke despite optimal treatment to consider a revascularization procedure, including altered cerebral vasoreactivity. However, cerebral vasoreactivity using transcranial Doppler ultrasound is reserved for qualified centers. It requires a technical platform and trained personnel, is time-consuming and generally not readily available. A simpler test is therefore necessary. The goal is to quickly and easily detect patients with normal vasoreactivity who do not benefit from the cerebral vasoreactivity test (reference standard) and to reserve the time-consuming cerebral vasoreactivity test for patients likely to have altered vasoreactivity. The hypothesis of the study is that on a routine measure in transcranial echo-Doppler, the resistance index (RI), can predict the response to the cerebral vasoreactivity test. With this new test, it will be possible to select patients who do not benefit from pharmacological cerebral vasoreactivity testing (true negatives). Thus, the time-consuming cerebral vasoreactivity test will be reserved only for patients with a possibility of impaired vasoreactivity.