Transapical mitral valved stent implantation: a survival series in swine

Abstract

Objective: To assess short-term survival after transcatheter mitral valve replacement using a unique mitral valved stent design and anchoring system.

Methods: The new nitinol self-expandable valved stent houses a trileaflet glutaraldehyde-preserved bioprosthesis and contains atrial and ventricular fixation systems. Eight pigs underwent transesophageal echocardiogram-guided transapical mitral valved stent implantation through a lower mini-sternotomy. Intracardiac pressure gradients were estimated by transesophageal echocardiogram.

Results: The mean mitral annulus size was 24.6 +/- 1.4 mm, and the valved stent size was 26.0 +/- 2.6 mm. The average mean transvalvular gradient across the valved stent immediately after deployment, at 6 hours, and after 1 week remained low. The gradient across the neighboring left ventricular outflow tract was not affected. Average animal survival was 7.3 days (8 hours to 29 days). Animals that died before 1 week (n = 4) were found at necropsy to have valved stent malpositioning. Animals that survived 1 week or more had accurate deployment and only trace post-deployment paravalvular leak. The causes of death in this latter group were endocarditis (n = 1), failure of atrial fixation (n = 2), and failure of ventricular fixation (n = 1). There was no valved stent embolization in any of the animals.

Conclusion: Adequate function and effective anchoring of the new mitral valved stent allowed for short-term animal survival after transapical mitral valved stent implantation.