Atrial fibrillation is the most frequent cardiac arrhythmia. Recently, an ultrasound-guided transesophageal high-intensity focused ultrasound (HIFU) device has been designed to perform minimally invasive pulmonary vein isolation. It was made with a 3MHz 8-ring HIFU transducer including in its center a 5MHz 64-element imaging transducer. The HIFU transducer could focus the ultrasound beam over a broad range of depths from 17 to 55mm to perform lesions in various locations, while preserving intervening tissues. Those characteristics having been demonstrated in vitro, the aim of this study was to perform deep cardiac lesions in pig model under ultrasound guidance. A first ex vivo/in situ experiment gave promising results. Indeed, wide linear lesions were obtained in depth at desired locations. In vivo investigations are ongoing to confirm those preliminary results.