Our research project at LabTau aims at developing a probe capable of delivering HIFU into the heart by a trans oesophageal approach for treating cardiac arrhythmia. Anatomical guidance is achieved with B-mode ultrasound imaging. The goal of the present study is to generate thermal lesion on beating heart of primate, where arrhythmia foci are present in humans, in order to prove the feasibility of the approach. Treatments will be monitored in real time with conventional and passive ultrafast elastography, and then with MRI. This original strategy for treating arrhythmia would avoid invasive insertion of catheter into the heart.