WO2018150392A1

WO2018150392A1 - Atrio-ventricular prosthesis with asymmetric flow

Info

Publication number: WO2018150392A1
Application number: PCT/IB2018/051026
Authority: WO
Inventors: Enrico Pasquino; Marcio Scorsin; Andrea Marchisio; Lorenzo VALERIO
Original assignee: Epygon
Priority date: 2017-02-20
Filing date: 2018-02-20
Publication date: 2018-08-23

Abstract

Multileaflet atrio-ventricular prosthesis characterized by the fact that it is designed to induce an asymmetric blood flow.

Description

Atrio-ventricular Prosthesis with Asymmetric Flow

FIELD OF INVENTION

The present invention relates to heart valve prostheses and more precisely to multileaflet atrio-ventricular prostheses.

STATE OF THE ART

Valve-replacement surgery has dramatically altered the natural history of valvular heart disease, affecting the lives of millions of patients. Bench engineering, investigations in animals, and clinical studies emphasized the importance of hemodynamics in valve design. Limitations of the current technology will continue to drive the field toward new, minimally invasive and endovascular approaches for valve delivery. Therefore, with the introduction of transcatheter prosthesis, new designed valves are now being developed and it is a great opportunity to rethink shape, material, structure and physiology. This is of major importance, regarding the atrio-ventricular valves because they are intimately connected with the ventricles.

The left ventricle (LV) is the strongest chamber in the human heart that pumps blood to provide oxygen and nutrients to tissues and in the whole body. The intraventricular circulation is a consequence of the asymmetry of the mitral orifice with respect to the ventricular chamber, where the eccentric inflow gives rise to an asymmetric rotatory motion that accompanies the redirection of the rapid flow entering from the mitral valve toward the opposite facing outflow tract. Therefore, the fluid dynamics trough the native mitral valve is characterized by the presence of intraventricular vortex which plays a central role in the global synchronicity of the beating heart. Although strongly connected with the theme of energy and system efficiency, fluid dynamics inside the LV is little or no use in clinical and are not taken into account for the design of prosthetic valves. Currently, all heart valve prosthesis bears the same characteristic: central flow. As far as aortic or pulmonary valves are concerned, central flow prosthesis is in accordance with the native ones. However, the same in not true when the atrio-ventricular valves are concerned because the flow through these valves (mainly the mitral) is not central but asymmetric directed towards the posterior wall. The energy required to open and close a prosthetic valve must be as little as possible to minimize resistance to forward flow, decrease turbulence, limit regions of stagnation, and reduce shear stress.

It has been demonstrated (Pedrizzetti G, et al. On the Left Ventricular Vortex Reversal after Mitral Valve Replacement. Annals of Biomedical Engineering, 2010;38:769-773) in patients subjected to mitral valve replacement that energy loss can be as high as 30% compared to healthy subjects. Moreover, energy dissipation was particularly higher in patients with altered left ventricular geometry. This is a very important finding because patients with mitral regurgitation have frequently an impaired LV function due to underlined disease as myocardial infarction or cardiomyopathy, characterized by remodeling or distortion of LV geometry that ultimately results in papillary-muscle displacement, leaflet tethering, impaired coaptation. Patients who may benefit more from a more physiologic valve are those with the most critical situation in terms of the LV function. In fact, the left ventricular remodeling is a common problem in the follow-up after the replacement of the mitral valve. Although artificial heart valves have evolved to a level of general acceptance in terms of durability and performance, it never achieved a comparable level of performance to that of the natural mitral valve and lead to many complications. Many of these problems are directly related to fluid mechanics associated with non-physiological tri-leaflet bioprosthesis or mechanical central flow valves.

Currently, all existing prosthesis are designed to obtain a central flow. This is due to the almost equidistant placement of the distal end of commissures and also from the similar angle between the valvular plane and the degree of inclination of the commissures.

DESCRIPTION OF THE INVENTION

The present invention concerns an atrio-ventricular bioprosthetic valve designed to reproduce the physiologic asymmetric flow necessary to preserve the normal energy consumption and ventricular efficiency.

The asymmetric flow can be obtained with different valvular designs, in particular:

1- Asymmetric functional component: Different number, shape and size of leaflets can be arranged so as to produce an asymmetric flow. This feature can be achieved by mounting a tissue valve with different leaflet sizes based on the unequal placement of the commissures. With at least two different sizes of tissue leaflets supported by a more posterior commissure, the opening can be modulated so as the flow can be directed towards the LV posterior wall i.e., modulating the angle between the annular attachment and the commissure may be different being the larger leaflet having a greater angle and the smaller leaflet a lesser angle. Alternatively, a bileaflet prosthesis may have the larger leaflet (that corresponds anatomically to the anterior mitral leaflet) covering more than 50% of the surface. Consequently, in this way, it is possible to achieve an asymmetric flow similar to the flow of the native valve.

The same concept is true also for tri or more leaflet valves that could also be built this way, i.e. with only one large main leaflet at the anterior side of the prosthesis, and two or more supporting posterior leaflets with different angles of attachment of the commissures.

- Different axis prosthesis/annulus: with such a configuration the valve is assembled as a standard multileaflet valvular prosthesis. The design, shape and size of the leaflets may be symmetric, what changes is the plane of closure of the leaflets regarding the inter-annular plan. All mitral bioprosthesis surgically implanted have the plane of closure of the leaflets at the same level of the interannular plane. By placing the posterior side of the prosthesis at a higher level than the anterior side, a not aligned axis is created between the plane of closure of the leaflets and the inter-annular plane. The central flow typical of this type of prosthesis is then directed to the posterior wall of the ventricle, consequently allowing the formation of an asymmetric (not central) intraventricular flow. This solution can be applied also for mechanical prosthesis.

Brief description of the figures

Figure 1 a : (prior art) Symmetric bileaflet prosthesis mounted in a stent frame S, anterior leaflet (AL) and posterior leaflet (PL). With this design, the leaflet's coaptation C occurs in the middle of the stent frame.

Figure 1 b : (prior art) The transvalvular flow F generate is central (non-physiologic) because the anterior leaflet (AL) is of the same size of the posterior leaflet (PL).

Figure 2 a : Example of an asymmetric bi-leaflet prosthesis according to the invention that is mounted in a stent frame S. The anterior leaflet (AL) is larger (more than 50%) than the posterior leaflet (PL). The leaflet's coaptation C occurs more posteriorly on the stent frame S. Figure 2b : Prosthesis of figure 2a in an active mode. The transvalvular flow is therefore asymmetric towards the left ventricle posterior wall, similar to the physiologic flow.

Figure 3 : Example of a trileaflet prosthesis according to the invention. The plane of closure of the trileaflets a-a is oblique to the interannular plane a-a'. Therefore, the transvalvular flow F generated is asymmetric similar to the native valve.

Claims

1- Multileaflet (AL,PL) atrio-ventricular prosthesis characterized by the fact that it is designed to induce an asymmetric blood flow.

2- Prosthesis according to claim 1 wherein at least two leaflets (AL,PL) have different shapes.

3- Prosthesis according to claim 2 wherein one leaflet (AL) corresponds to the anterior leaflet of the native mitral valve and is designed to cover more than 50% of the valvular area.

4- Prosthesis according to anyone of the previous claims wherein at least one leaflet has located in a plane that is different from the interannular plane.

5- Prosthesis according to claim 4 wherein one leaflet corresponds to the anterior leaflet of the native mitral valve and has an angle of inclination with respect to the interannular plane that is greater than the other(s) leaflet(s).

6- Prosthesis according to claim 4 or 5 wherein the plane of insertion and closure of the leaflets is different from the interannular plane.

7- Prosthesis according to anyone of the previous claims wherein the posterior portion of the prosthesis is higher than the anterior portion, in such a way as to produce an oblique flow towards the posterior wall of the left ventricle.