Transapical mitral valved stent implantation: comparison between circular and D-shaped design

Abstract

In this study two designs of a self-expanding valved stent were compared after off-pump implantation into the mitral valve to identify the superior one. Two designs of a mitral valved stent were tested. The first design is composed of a circular atrial element connected to a tube-shaped ventricular element. In the second design, the atrial element is D-shaped to achieve better anatomical alignment. Prior to in vivo testing, the area with the highest risk of PVL was identified in a hydrostatic in vitro set-up. Subsequently, eight pigs received stents (circular, n=5; D-shaped, n=3) via apical access in the beating heart. Positioning and haemodynamics were evaluated by TEE and invasive pressure measurement pre-implantation, after 1 hr, and at two and four weeks. In vitro testing showed less PVL in the anteromedial region in D-shaped design stents (p<0.001). All stents were successfully deployed in vivo and six animals maintained normal haemodynamics for two weeks or longer. Rotational reorientation of all stents with D-shaped elements was observed. Both groups indicated no clinically relevant gradients over the mitral valved stent. This study demonstrates that the circular design was superior to the D-shaped model after rotational reorientation of the latter occurred.