Prosthesis deterioration rate, years after a previous surgical valve replacement, is rising. Usually, the standard management is reoperation, but for very high risk patients an alternative has arisen: the valve-in-valve approach. We present an 84-year-old Caucasian woman with a mitral bioprosthesis (Mosaic II, number 29) since 1994. Over the last few months the patient displayed worsening heart failure symptoms, until her current admission in NYHA III-IV functional class, because of a severely degenerated mitral prosthesis (severe regurgitation, severe pulmonary hypertension). The transapical access, conventionally used for transcatheter aortic valve implantation (Edwards SAPIEN THV 23) was chosen, guided by transoesophageal echocardiography (TOE) with a new three-dimensional (3D) probe. After the procedure, the mitral regurgitation completely disappeared, an appropriate valve opening was achieved (valve area >2 cm(2)) and the patient was discharged 6 days later, remaining well in the outpatient follow-up. Only a restricted number of patients have been submitted to mitral transcatheter valve-in-valve implantation and to the best of our knowledge this is the first accurate description of the 3D TOE part, focusing on the surgeon requirements.