Transoesophageal HIFU for cardiac ablation: In-vivo experiments in non-human primates

Abstract

Transesophageal HIFU was proposed as an alternative to the current atrial fibrillation treatments. The present work described a feasibility study of transesophageal thermal ablation in the heart of non-human primates. An endoscope integrating a 5MHz 64-element commercial transesophageal echocardiography probe and a 8-element HIFU transducer was built. The transducer was cooled at 5°C and ultrasonic beam could be steered over a 15 to 55 mm range. The probe was tested in-vivo on three 30kg-baboons. Left atrium and ventricles were exposed to repeated continuous sonications (4-15 times during 16s) at a focal intensity of 3000 W/cm². B-mode, shear-wave and passive elastographies were performed before and after treatments in an attempt to monitor thermal lesions. T1 mapping and contrast MR imaging were realized the day after treatment. Clinical states of the subjects during and after the treatment were positive. One lesion in the left ventricle could be evidenced by elastography and confirmed by MRI. Experiments demonstrated the feasibility of a transoesophageal HIFU procedure to produce thermal lesions in beating hearts. Further developments will aim at improving the robustness of the technique. Work supported by the FUS Foundation. [Probe designed in collaboration with Vermon SA (Tours, France).]