Transcatheter Mitral Valve Implantation Using The Mi-thos Valve: Preclinical Results
Jian Yang1, Jiayou Tang1, Yang Liu, `1, Lai Wei2.
1Xijing Hospital, Xi'an, China, 2Zhongshan Hospital, Shanghai, China.
Objectives This preclinical study in ovine sought to evaluate the safety and feasibility of transcatheter mitral valve implantation (TMVI) using a Mi-thos valve (NewMed Medical Co., Ltd., Shanghai, China) in preparation for first-in-man implantation. Background The Mi-thos valve is a self-expanding bioprosthesis with cross-linked bovine pericardial tissue tricuspid leaflets mounted inside a nitinol self-expanding frame, specifically designed for the transcatheter replacement of the complex mitral apparatus. Methods The Mi-thos valve was implanted in 26 sheep using a transapical approach for short-term and long-term evaluation. Technical feasibility, safety, durability, and function of the valve were evaluated during and 6 months after the procedure using intracardiac and transthoracic echocardiography; multisliced computed tomography; necropsy of explanted heart tissue; ventriculography; and histological and electron microscopy. Results The procedure was successful in 100% of cases. Five animals were euthanized within 90 minutes. Three animals died within 3 months due to left heart dysfunction and paravalvular leakage. Mild-to-moderate paravalvular leaks and mitral regurgitation occurred in 7 animals. Multimodality image studies of the remaining 18 animals showed excellent function and alignment of the valves, with no coronary artery obstruction, left ventricular outflow tract obstruction, severe transvalvular gradients, or paravalvular leak. Cardioscopic and macroscopic evaluation demonstrated stable, secure positioning of the valve, with full endothelialization of the valve leaflets and fabric coatings and without evidence of injury to the ventricular or atrial walls. Histological and electron microscopic examinations at 6 months showed no obvious macro- or microcalcification in the leaflets. Conclusions Preclinical studies indicate that transcatheter implantation of the Mi-thos valve is technically safe and feasible, resulting in a stable and well-functioning mitral bioprosthesis. The long-term durability, functionality, and lack of leaflet calcification were all verified in the animal experiments. The information from these preclinical studies will be applied to patient selection criteria and first-in-human studies.
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