Feasibility evaluation of the transapical saddle-shaped valved stent for transcatheter mitral valve implantation

Abstract

Background and aims of study: Transcatheter mitral valve implantation (TMVI) is a promising and minimally invasive treatment for high-risk mitral regurgitation. We aimed to investigate the feasibility of a novel self-expanding valved stent for TMVI via apical access.

Methods: We designed a novel self-expanding mitral valve stent system consisting of an atrial flange and saddle-shaped ventricular body connected by two opposing anchors and two opposing extensions. During valve deployment, each anchor was controlled by a recurrent string. TMVI was performed in 10 pigs using the valve prosthesis through apical access to verify technical feasibility. Echocardiography and ventricular angiography were used to assess hemodynamic data and valve function. Surviving pigs were killed 4 weeks later to confirm stent deployment.

Results: Ten animals underwent TMVI using the novel mitral valve stent. Optimal valve deployment and accurate anatomical adjustments were obtained in nine animals. Implantation failed in one case, and the animal died 1 day later due to stent mismatch. After stent implantation, the hemodynamic parameters of the other animals were stable, and valve function was normal. The mean pressure across the mitral valve and left ventricular outflow tract were 2.98 ± 0.91 mmHg and 3.42 ± 0.66 mmHg, respectively. Macroscopic evaluation confirmed the stable and secure positioning of the stents. No obvious valve displacement, embolism, or paravalvular leakage was observed 4 weeks postvalve implantation.

Conclusions: This study demonstrated that the novel mitral valve is technically feasible in animals. However, the long-term feasibility and durability of this valved stent must be improved and verified.

Keywords: mitral regurgitation; transcatheter mitral valve implantation; valve prosthesis.

Figure 1

Novel mitral valved stent for transcatheter implantation. (A) Atrial side view of the valve prosthesis. (B) Ventricular side view of the valve prosthesis. (C,D) Lateral side view of the valve prosthesis. The main structure of the valve prosthesis was mainly divided into four parts, including the atrial flange and the ventricular portion, which are attached to two opposing extensions (star marker) and two opposing anchors (rectangular dotted lines). (E) The valve prosthesis is compressed within a delivery system, with recurrent strings (red arrow) hanging from each pair of anchors. Anchor (red triangle) is abducted at an angle by the string for grasping.

Figure 2

Preoperative echocardiography evaluation before the animal experiment. (A) The native mitral valve opening during the left ventricular diastole. (B) The native mitral valve closed during the left ventricular systole without valve regurgitation. LA, left atrium; LV, left ventricle

Figure 3

Representative echocardiography images after valve deployment. (A) The valve prosthesis was closed during the left ventricular systole. (B) The valve prosthesis is opened during left ventricular diastole. LA, left atrium; LV, left ventricle

Figure 4

Representative fluoroscopy images after valved stent deployment. (A) The valve prosthesis was successfully deployed in the heart (asterisk labeled prosthesis), and the delivery system was removed and the ventricular angiography was performed with a pigtail catheter (arrow pointing to the pigtail catheter). (B) Ventricular angiography showed that the valve prosthesis was closed normally in diastole. There is trace paravalvular leakage in this case. No obvious LVOT obstruction was observed. Ao, Aorta; LA, left atrium; LV, left ventricle; LVOT, left ventricular outflow tract; MV, mitral valve

Figure 5

Representative images of necropsy. (A) The pig heart atrium was removed to expose the valve prosthesis. The atrial flange of the valved stent is located on the mitral annulus. (B) The left ventricle tissue was dissected to reveal the valve prosthesis and subvalvular structure. Both anchors successfully clamped the native leaflet (green arrow) and the valve prosthesis was stable in the mitral position. There was no LVOT obstruction, valve displacement, rupture of chordae tendineae or papillary muscle ischemia, or other subvalvular structural injury. The native mitral leaflets are sandwiched between anchors and the ventricular body of the stent. (C) Careful examination of the valve prosthesis revealed no embolism or nitinol fracture. No leaflets rupture or dislocating was observed. LVOT, left ventricular outflow tract