Objective: Percutaneous valve replacement was recently introduced, and reports of early clinical experience have already been published. To date, this technique is limited to the replacement of pulmonary and aortic valves in a strictly selected group of patients. The aim of this study was to analyse a self-expanding valved stent for minimally invasive replacement of the mitral valve in animals.
Methods: A newly designed nitinol stent was specially designed for this experimental acute study. It comprised of a left ventricular tubular stent with star shaped left atrial anchoring springs and carried a trileaflet bovine pericardial valve. A polytetrafluoroethylene membrane was sutured to envelop the atrial springs and the outside of the ventricular stent. The ventricular anchoring system was the same as in our previously reported results with a similar mitral valved stent. Seven pigs underwent minimally invasive off-pump mitral valved stent implantation. This was performed through a lower mini-sternotomy and a standard transapical approach under transoesophageal echocardiographic (TEE) guidance was used.
Results: The valved stent is fully retrievable and precise deployment and accurate adjustment of its intra-annular position is achievable to eliminate paravalvular leakage. The deployment time ranged from 127 to 255s and the blood loss from 70 to 220cc. One animal died of intractable ventricular fibrillation. Mitral regurgitation in all surviving animals was minimal (trace in 5/6 and mild in 1/6 during echo examination; on the contrast ventriculogram no mitral insufficiency was observed except in one documented as mild paravalvular regurgitation). These animals remained haemodynamically stable (6/6) and without TEE or ventriculographic changes for 1h.
Conclusion: Implantation of a tricuspid bovine pericardial valved stent in the mitral position is feasible in pigs through a transcatheter approach. This was possible through a smaller delivery system than previously reported. Additional studies are required to demonstrate long-term feasibility, durability, and heart function.