Assessment of the stentless mitral valve and operation using bioengineering method

We report the results of assessment of the Normo valve and the Normo operation using bioengineering methods.

The Normo valve, made from bovine pericardium using a specially designed template and the flexible ring (27-mm Duran; Medtronic Inc), was installed into the pulsatile circulatory simulator. A 27-mm bioprosthetic valve (Mosaic; Medtronic Inc) was used as a control. The hydrodynamic performance of the Normo valve and bioprosthesis was investigated and compared. To assess the original template design, we created modified templates with slight alterations for both leaflets. The 4 types of valve made using these modified templates were tested to evaluate their hydrodynamic performance relative to the original design. In addition, finite element analysis was conducted to evaluate the relationship between leaflet stress and the distance between 2 major papillary muscles with the distances set at 18 mm, 24 mm, 30 mm, and 36 mm.

The waveforms of the Normo valve and bioprosthesis showed a similar pattern. As for the large leaflet, the Normo valve made from original design template revealed lowest pressure gradient compared to other 2 types. As for the small leaflet, the Normo valve made from original design template showed lowest pressure gradient with greatest forward flow. The stress on the leaflet increased for the distance between 2 papillary muscles at 18 mm and 36 mm.

The data obtained from the bioengineering method confirm the validity of the Normo valve's design. Furthermore, the results show preferable positioning for the fixation of the leg to 2 papillary muscles.