MXPA98006761A - System of activation of a cardiac valve and cardiac valve activ - Google Patents

Abstract

The invention relates to a cultivation system for a cardiac valve comprising a seat (1) and at least one flapper (2a, 2b) rotating mounted on the seat (1) characterized in that it comprises at least one mobile magnetic element ( 4), formed by shower flap (2a, 2b) and possibly at least one fixed magnetic element (3) solicary with the seat (1), said magnetic elements (3,4) create a force that is exerted on said flapper (2a) , 2b) during its opening and / or closing movements

Description

SYSTEM OF ACTIVATION OF A CARDIAC VALVE AND VALVE CARDIACA ACTIVATED.

The present invention relates to a system for activating a heart valve as well as an activated heart valve.

Artificial cardiac valves, also called valvular, mitral or aortic prostheses, are specially constituted by one or two mobile flaps mounted on a seat by means of one or several joints, said seat being on the outside, sutured on the natural pathways of the patient.

In this work cycle of the valves, the phases of opening and closing of the fins have a very short life compared to those corresponding to blood flow or sealing, however these phases of opening and closing, and at the precise moment where they intervene in the cardiac cycle largely determine the quality of the valve.

The opening and closing mechanisms of a traditional artificial valve is as follows: When an artificial valve is closed, and that the pressure difference of each side of the valve orifice is REF .: 28182 reverses, the force of pressure that kept the fins closed changes direction and tends to open them. This force and then the pressure difference that generates it must reach a sufficient level to initiate the opening of one or the fins and the same initialize the blood flow through the prosthesis. Closing an open mechanical valve and letting blood flow pass develops as follows. The pressure difference of each side of the valve orifice is reversed and grows, then produces an inversion of blood flow at the end, this reflux closes the valve after dragging its fins or flaps.

In summary, a traditional mechanical valve operates with a lag time compared to pressure fluctuations since a significant pressure difference must be established before a movement starts. In addition, the opening and closing mechanisms of traditional artificial valves are identical, even if they are implanted in the aortic or mitral position, which is not the case with natural valves.

The opening and closing mechanisms of the natural valves are described below.

The natural aortic valve opens simultaneously to the reversal of the ventricular, aortic pressure difference, since without inertia, it opens under a pressure difference null, contrary to a mechanical valvular prosthesis. It closes progressively, but quickly and without reflux, at the end of the systole under the action of local pressure differences on the leaves that are the equivalent of the fins. These local pressure differences on the sheets precede the overall inversion of the pressure difference between the aorta and the ventricle, a necessary inversion to the initialization of a reflux. This happens because the aortic valve becomes superior to the ventricular pressure, whereas it is the reflux that closes a mechanical valvular prosthesis.

The natural mitral valve opens actively under the effect of the tension of strings linked from one part to the rebound of its leaves and from the other side to the internal walls of the ventricle. It is the dilation of the ventricle after the diastole that simultaneously causes the fall of the ventricular pressure (then the inversion of the atrio-ventricular pressure difference) and the opening of the mitral valve by pulling on its cords. The opening of the natural mitral valve is then tightly synchronized to the atrio-ventricular pressure inverse, whereas a mechanical valvular prosthesis needs the intervention of a pressure difference to open, and then opens with delay. The closure of the leaves of the natural mitral valve is simultaneously made of several events: the ropes that keep the leaves relax, the leaves progressively close under the action of local pressure differences (preceding the global inversion of the difference of pressure between the atrium and the ventricle), and the mitral valve orifice shrinks (bringing the leaves closer). As well as the aortic valve, the mitral valve closes at reflux, as opposed to an artificial valve whose flaps are dragged along the closure by reflux.

The fins or flaps of the artificial valves then have a closed inertia and both opening and closing need an energetic wear taken on the energy of the blood flows. It is clear that this energy produced by the heart, then communicated to the blood flow, should be as important or more important that the loss of transvalvular load is great and that the blood reflux, through the valve, at closure, is important. The increased cardiac effort thus generated is penalized by the patient, particularly in the case of mitral valves where the debits and then the energies of the already weak blood flows naturally are more so in the presence of cardiac pathologies. If we want to reduce the transvalvular load loss, we can give the fins a maximum opening capacity for large displacement amplitudes, but this then generates an increase in reflux in the necessarily elongated closing phase. Conversely, in order to reduce reflux by decreasing the opening and closing stroke of the fins, the transvalvular load loss is increased.

At high heart rate, some valvular prostheses see the volume performance reflowing over the atrial debulking volume in a rehibitory manner (because the duration of the reflux necessary for the closure of the fins tends to occupy an important place in the cycle).

In the case of valvular prostheses of several fins, one of these may not open, which causes thrombosis. This can happen when the patient has a low cardiac pathological heart rate and / or adopts a sensibly horizontal position.

As the blood flows at the level of the cardiac orifice are not necessarily symmetrical, classical valve prostheses may have a dysmetric functioning. Such an operation mode can be detrimental to the integrity of the valvular prosthesis due to the poor distribution of the constriction that suffers then.

In addition, in the previous artificial valves, the fins pass directly from a fully open position to a closed position, which is translated by important and abrupt displacements of the fins, sometimes causing a rupture or premature wear of the valve as well as the appearance of noise and cavitation.

In the particular case of the so-called "active opening" valve described in US-A-4 605408 where, the excess, the copy exerted on the fins force them to close later still and then more brutally.

All these drawbacks linked to the very nature of all existing mechanical valvular prostheses largely explain the complications found in patients who carry a valvular prosthesis: excessive load loss, and thromboembolic accidents. These latter are particularly frequent in the mitral position when replacing the natural mitral valve with active opening by a passive opening valvular prosthesis. Indeed, provided with two fins, the prosthesis can open asymmetrically, particularly when the patient is under debit, a condition in which the risk of thrombosis is greater.

The invention has the goal of solving the preceding problems or at least of diminishing them satisfactorily.

This goal is achieved according to the invention by means of an activation system for heart valve having a seat and at least one wing mounted on the seat, characterized in that it has at least one mobile magnetic element, formed by said wing and possibly at least one fixed magnetic element, integral with the seat, said magnetic elements create a force that exerts on said fin during its opening and / or closing movements.

According to a particular embodiment, said mobile magnetic element produces a first magnetic field and said fixed element produces a second magnetic field.

Preferably, the first and second magnetic fields are determined in such a way that their reciprocal influence makes, when the blood pressure is identical of part and another of the valve, a position of equilibrium, towards which the fin is called at any time by the force that varies depending on the position of said fin in a way that minimizes blood reflux without increasing the loss of transvalvular load.

This equilibrium position corresponds preferably to an intermediate opening position of the fin. According to an advantageous characteristic, the variations d said force, as a function of the position of the fin are independent of each side of the equilibrium position.

According to another characteristic, the force produces a magnetic copy that exerts on the fin, whose maximum value is understood between 10- ^ and 10 ~ - > N.m. This torque is lower than the blood pressure forces exerted on the fin in its fully open and closed positions.

According to other advantageous features, the first and second magnetic fields are determined such that the fin rotates in the seat with the minimum friction.

Preferably, the equilibrium position is located between the full opening and closing positions.

The reciprocal influence of the first and second magnetic fields produces repulsive magnetic forces between the moving magnetic element and the fixed magnetic element.

These repulsive magnetic forces have an intensity of more than 10-IN.

According to a first embodiment, said fixed magnetic element is integrated into the thickness of the seat, for example, close to a joint. This arrangement allows to avoid all contact with the blood. In parallel, said mobile magnetic element is integrated in the thickness of the fin and enclosed in a hermetic manner, which also allows to avoid any contact with the blood. These arrangements allow the activation system of the invention to be biocompatible and above all hemocompatible.

In general, the fin is made in the mass with a hemocompatible material allowing the incorporation of magnets without modifying their magnetic characteristics.

According to another embodiment, the system includes a mobile magnetic element and two or three fixed magnetic elements, for each joint of the fin. Preferably, the fixed magnetic elements are then arranged in a ring around an axis of articulation of the fin or flap.

According to another embodiment, the magnetic elements are permanent magnets denominated as rare earth, based on samarium and cobalt, or based on neodymium iron and boron.

Another object of the invention is a heart valve equipped with an activation system described above.

A particular embodiment of such valve consists in manufacturing a fin made in the mass in a hemocompatible titanium alloy to form a housing, placing this mobile magnetic element in this housing, closing this housing with a cover of the same titanium alliance, in order to tightly weld this cap to the fin.

Obviously, an alternative may be to make the fin in any material, then fully dress the said fin with a hemocompatible material.

A first variation of embodiment of the valve of the invention consists in providing it with two fins activated by the single reciprocal influence of the mobile magnetic elements of each fin.

A second variation consists in carrying out at least one of the two fins or one of the two seats with a ferromagnetic material, in order to form at least one mobile or fixed magnetic element that does not produce magnetic fields but that is influenced by the or the magnetic fields produced by the other mobile or fixed magnetic elements.

Another variation consists in providing only magnetic mobile elements on the valve; the seat does not then have any magnetic element.

A further variation consists of foreseeing the presence of interactive magnetic elements and the presence on the seat of inactive fixed magnetic elements, whose influence is negligible.

The activation system of the invention allows, thanks to the intermediate opening position of the vane, obtained with the balance of the pressures of each side of the valve, an active opening of the valve, particularly in the mitral position, guaranteeing a symmetrical opening of all the fins, even in case of very weak blood debit, and to decrease reflux at closing. The guarantee of the opening of all the fins reduces the risk of thrombus formation.

The valves equipped with the evacuation systems are commanded by the variations of blood pressure, and not by the debits as is the case with the passive valves, that is to say not activated according to the principle of the invention. In fact the debit is itself generated by pressure variations, it is impossible to have early opening phase in relation to the operating sequences of the artificial and traditional valves not activated. It turns out that the fins of the activated valves appear as being without inertia for blood flows which thus retain all their acquired energy.

The activation system of the invention allows to improve the performance of the valves reducing blood reflux, and effect, the magnetic assistance causes the anticipated closure of the flap, while the velocity of the blood reflux is still almost nil. The jets that occur at the moment of closure when it is effected in the presence of a significant reflux velocity (as is the case with non-activated valves) generally carry risks of cavitation and hemolysis that are limited by the use of the invention. .

It is admitted that the transitory phases of the blood runoff are accompanied by abrupt pressure variations causing the opening or closing. The anticipation of the opening and closing movements in relation to the debit investments at the level of the valve orifice then allows the fin to perform its movement under weak loads, unlike the passive valves whose fins, especially at the end of the stroke , they support high loads. The stroke portion of the flap that is made under high pressure difference is shorter - that with the valves not activated, which limits the shocks and therefore the wear. This same anticipation symmetrizes the movements of the fins because they are identical magnetic pairs that f initiate the movements of the fins. Consequently, the movements of the fins are symmetrical, the distribution of the symmetric constrictions, which is favorable to the good resistance of the fatigue of the active valvular prosthesis.

The opening and closing movements have a first phase which is carried out under the impulse of magnetic forces and a second phase which is under the influence of the hydraulic forces. Thus, the automatic return of the fins in the intermediate opening position of equilibrium allows to decompose the movements and reduce the speeds of opening and closing purposes, which suppresses violent collisions on the seat, thus decreasing the risks of noise rupture , of hemolysis cavitation.

The activation system of the invention allows a greater opening of the fin to reduce the loss of transvalvular load and without increasing the reflux thanks to the anticipation of the closing movement.

The magnetic activation of the valve has particularly important effects especially in the phases of the cardiac cycle where the hydraulic forces are weak, that is to say between the diastole and the systole and the inverse between the systole and the diastole. The intensities of the pairs and the magnetic forces in play may remain weak being effective. They are not, then, capable of disturbing the hydraulic functioning of the valve during the diastolic and systolic phases. Thus, the values of the pairs are not capable of training in any increase of the transvalvular load loss, when the valve is open, no more than a transvalvular leakage debit when the valve is closed.

The invention will be better understood with the reading of the description that follows, accompanied by the corresponding drawings: - the figures up to 1 represent schematic views in section of the heart in the different cardiac phases.

Figures 2a and 2b are graphs respectively representing pressure variations and ventricular volume variations in the course of the cardiac cycle for the left heart; Figures 3a, 3b, 3c are respective perspective views, in cross section and in top views of a valve equipped with an embodiment of the activation system of the invention, in the closed position.

Figures 4a, 4b, 4c are respective perspective views, in cross section, and in top view of the valve of Figures 3a, 3b, 3c in intermediate balancing position; Figures 5a, 5b, 5c are respective perspective views, in cross section and in top view of the valve of Figures 3a, 3b and 3c in full opening position.

Figures 6, 7 and 8 represent some of the different possible magnetic configurations for the activation system of the invention; Figures 9, 10 and 11 represent the graphs of variations of the magnetic pair of restitution corresponding, respectively, to the magnetic configurations of Figures 6, 7 and 8; The figures even represent the different phases of the cardiac cycle. The blood behaves like all fluids, it is always poured from a high pressure zone into a low pressure area thus generating a debit. The cardiac contraction puts the blood under pressure and the valves direct the debit of the blood thus generated. The variations in pressure and debit that appear in the cardiac cycle are represented, by the left heart, in figures 2a and 2b. The behavior of the right heart is qualitatively identical to that of the left heart. The systole corresponds to the period of ventricular contraction (figures le and ld) while the diastole corresponds to those of relaxation (figures la and lb).

The description that follows will allow to place in the cardiac cycle the opening and closing movements of the aortic and mitral valves previously described.

During the start of the diastole (figure) the left atrium A is relaxed and the left ventricle B begins to dilate. This dilation generates an early opening of the mitral valve Vl by pulling on the cords. Blood passes in atrium A in atrium B. While, aortic valves V2 is closed because the pressure in aorta C is higher than in ventricle B. But, aortic pressure falls slowly while ventricular pressure rises slightly . At the end of diastole (Figure lb), atrium A shrinks in a manner to inject a volume of supplementary blood into ventricle B.

Later, the phase of the systole begins and ventricle B begins to shrink by pressing the blood it contains. The ventricular pressure then increases very brutally almost immediately exceeding the atrial pressure, which causes the closure of the valve Vl, facilitated by the also brutal loosening of the tension on the cords (figure 1 and point f 'on figure 2a) . The blood reflux into atrium A is not then possible. The fact that for a short time the aortic pressure still exceeds the ventricular pressure, the aortic valve V2 remains closed. Then the ventricular pressure exceeds the aortic pressure, the valve V2 opens and the ventricular ejection occurs (figure ld and point O on figure 2A). As the blood drains into the aorta C, the aortic pressure increases but the B ventricle does not empty completely and the maximum aortic pressure is reached before the end of the ejection. The debit of the blood that leaves the ventricle B during the terminal phase of the systole is weak and inferior to the debit of the blood that is removed from the aorta. In parallel, the atrial pressure also increases, slowly, throughout the time of ejection. Then the ventricle B relaxes and the ventricular pressure falls below the aortic pressure, which causes the closing of the aortic valve V2 (point f, figure 2a).

While the decreasing ventricular pressure is still higher than the atrial pressure, so that the atrio-ventricular valve Vl remains closed (figure le). When the left ventricle begins to expand, simultaneously with the reversal of ventriculo-auricular pressure, valve Vl opens (point 0 ', figure 2a) and the ventricle begins to fill again as described above in relation to the beginning of the diastole (figure la).

Figures 2a and 2b represent respectively the variations of ventricular pressure and volume in the course of the different bases described above and as reference to the figures to the as mentioned below figure 2b. It appears clearly in the study of the cardiac cycle that the natural valves are synchronized on the relative pressures reigning in the atrium, the ventricle and / or the aorta and not on the debits. These valves then have opening and closing modes anticipated in relation to the variations of the debits. In addition, the opening of the mitral valve is facilitated by ventricular dilation that is accompanied by traction on the chordae tendineae.

The activation system of the invention tends to operate artificial valves, according to opening and closing modes that are very close to those of natural valves.

The valve shown in Figures 3a, 3b and 3c and following is an artificial valve equipped with the activation system of the invention.

This valve comprises a seat 1, at least one flap or flap, and preferably two identical fins 2a, 2b, mounted on a seat 1 symmetrically, in relation to the diametrical axis XX '. Each of the fins 2a, 2b rotates about an axis YY ', parallel and adjacent to the axis XX' by means of two symmetrical joints, arranged on each part and each of the fins.

An articulation is, for example, constituted by a transverse finger 10 integral with the inner side flank of the seat 1 and intended to fit freely relative to the interior of a cylindrical cavity 20 created in the thickness of the lateral edge of the fin 2a, 2b or in an arranged protuberance 21.

In the illustrated embodiment of the valve, the two fins 2a and 2b come in the closed position (FIGS. 3a to 3c), butt against each other by their respective inner edge 22a, 22b have a chamfer so that in position of closure, the fins 2a, 2b make between them an angle 2ß comprised between 90 ° and 180 °. The opening position is here fixed at a = 85 ° (see figure 9), in relation to the base plane S of the seat 1.

The activation system itself comprises, by articulation, of a part, at least one and in the represented embodiment, three fixed magnetic elements 3, integral with the seat 1 and at least one moving magnetic element 4 held here by the wing 2a , 2b. The magnetic elements 3, 4 are adapted and intended to create a force exerted on the fin 2a, 2b during its opening and / or closing movements.

In the embodiment shown in the figures, the fixed magnetic elements 3 and mobile 4 produce respectively a first and a second magnetic field whose own characteristics are possibly different. These magnetic elements 3, 4 are preferably permanent magnets said of rare earths (for example based on samarium and cobalt or ~ on the basis of iron and boron neodymium) to strong magnetism and coercivity, then at high magnetic stability.

The fixed magnetic elements 3, few hindrances can be integrated into the thickness of the outer flank of the seat 1 and are not then able to come into contact with the blood. The fixed magnetic elements 3 can be arranged in a crown as illustrated in Figure 3b, but they can have another arrangement favorable to obtaining the magnetic fields sought. The first and second magnetic fields are determined so as to produce repulsive magnetic forces between the moving element 4 and the fixed element 3. These forces have an intensity between 0 and 10-1N. These repulsive forces allow both the control of the rotation of the fin 2a and 2b and the centering of the said fin in the feel, which ensures a minimum of friction. the moving magnetic element 4 is integrated in the thickness of the fin 2a, 2b.

In the embodiment shown in the breakdown of figure 3a, the movable magnetic element 4 is integrally fixed in a housing 24 created laterally in the protrusion 21. The housing 24 is itself sealed in a sealed manner by a welded cover ( not represented) thus enclosing element 4.

The fins 2a, 2b are at least as regards the protuberances 21, preferably made of a hemocompatible titanium alloy. This metal has the advantage of being light, resistant and allowing both the manufacture of the housings 24 and the welding of the lid. It also allows, because of its strength, finer fins than existing ones made with traditional materials (for example the pyrocarbonate), and thus allows to release a more important passage surface, then decrease the loss of transvalvular load. however, the activation system is compatible with all other hemocompatible materials (ceramics, metal alloys, pyrolytic carbonate ...).

The respective magnetic fields of the fixed and moving elements 4 are determined in such a way that their reciprocal influence can ensure the control of the movements of the fin. More particularly, when the blood pressure is identical from one part of the valve to another, an equilibrium position E of the fins 2a, 2b is created. The fins are returned at any time to this position of stable equilibrium E with a force that produces a magnetic torque that varies depending on the angular position of said fins. The laws and graphs of the variations of the magnetic return torque are determined in a way that minimizes blood reflux without increasing the transvascular load loss. These graphs, represented in the figure (in relation to the described embodiment), are independent from part to part of the equilibrium position E.

The maximum copy is comprised between 10 -3 and 10-5N.m .. The equilibrium position E is shown in figures 4a, 4b and 4c. Corresponds to a null magnetic pair and offers an angular closing opening. { figures 3a to 3c) and full opening (figures 5a to 5c). This intermediate opening corresponds, in general, to an angle of 2ß between the fins 2a, 2b understood between 60 ° and 140 °, the positions of the fins are in any case symmetrical in relation to the diametrical plan D passing through the axis XX '. The equilibrium position E of the fins corresponds, here, to an angle a of 55 °, in relation to the base plane S of the settlement 1 (see figure 9).

In Figures 5a, 5b and 5c, the valve is shown with the fins 2a, 2b in full opening position. In this position, the two wings 2a, 2b are oriented according to planes parallel to each other and in relation to the diametral plan D.

In the closed position (figures 3a) and in the fully open position (figure 5a) the mobile magnetic element carried by the fin 2a, 2b is placed exactly parallel and facing one of the fixed magnetic elements 3 ends.

In the semi-opening position corresponding to the balance, the moving magnetic element 4 is oriented face-to-face but perpendicular to the fixed magnetic element 3 interleaved.

The first and second magnetic fields produced respectively by the mobile magnetic element 4 and by the magnetic elements 3 depend, of course, on the respective geometry and the relative positions of the elements 3, 4 as well as on their magnetization directions.

Figures 6, 7 and 8 represent only some of the various magnetic configurations of the activation system of the invention. Other configurations are possible allowing, as here, to obtain variations of the back copy that minimizes the blood reflux without increasing the transvalvular load loss.

The magnetic configuration of 3 fixed magnets 3 and a mobile magnet 4, per fin corresponding to the embodiment of figures 3a, 4a and 5a, is shown in figure 6, in the equilibrium position E.

In general, the magnet vector is always directed h.to the magnetic North of the magnet considered.

In the configuration shown, the magnetization vectors of the fixed magnets 31, 32, 33 are positively oriented along the axis of articulation YY ', that is to say from Y to Y'.

The magnetizing vector N 'of the mobile magnet 4 is also oriented parallel to the axis of articulation but in the opposite direction, ie from Y' to Y.

The intensity of the magnetic field, produced by the intercalary fixed magnet 32 (and then the value of its vector N), is lower than that of the other fixed magnets 31 and 33. As the rotation of the fin 2a does not change the orientation of the field magnetic field produced by the mobile magnet 4 (the magnet vector N 'remains, in this rotation, oriented according to X'X), then automatically creates a copy with tendency to align the mobile magnet 4 with the fixed interlayer magnet 32, bringing the fin 2a towards the equilibrium position E.

Figure 9 shows the graphs of variation of the magnetic pair as a function of the angle α of the fin relative to the base plane S of the seat 1 (see Figure 3b, 4b, 5b). The full opening position corresponds to an angle α of 85 °, the equilibrium position E to an angle α of 55 ° and the closing position to an angle α of 25 °.

The magnetic return torque, applied from the closed position to the magnetic equilibrium position E, gives the fin an impulse to open it when the pressure difference of part e of the valve is zero, and the guide to its equilibrium position magnetic E. Likewise, if the debit is very weak, the fins open symmetrically, during the phase of hearing? to haia down, at least 55 ° so that it offers the blood an important area of passage, which guarantees a Minimum load loss. The rest of the opening journey (from 55 ° to full opening) is done without significant energy loss for runoff, because the magnetic forces are very weak in front of the hydraulic forces.

The return torque, applied from the fully open position to the magnetic equilibrium position E, allows the movement to start, after guiding the fin towards its magnetic equilibrium position, at the moment where the transvalcular pressure difference is inverted. From this last position, the movement of the fin towards its closed position is very short because the fin offers an important surface of support to the fluid, which minimizes reflux. The fin is then closed, ensuring the hermetic level that a passive valve of the same profile, until the start of the next cycle.

This example of magnetic assistance also corresponds to the functional requirements of a mitral valve prosthesis.

It appears in Figure 9, that the graph of the closing torque of the fin for a corresponded between 55 ° and 85 °, is different from the graph of the opening torque for a comprised between 55 ° and 25 °. In effect, the symmetry of the graphs, part and other of the equilibrium position E, exists only for a between 35 ° and 75 °. Further, the curves differ, from the very fact that the laws that govern the variations of the pair for opening and closing, are independent of each other.

Figure 7 shows a magnetic configuration of two fixed magnets 31, 32 and a moving magnet 4.

The magnetization vectors N, of the fixed magnets 31, 32, are oriented along the axis of articulation Y'Y, ie in the direction of Y 'towards Y, in reverse with the configuration of figure 6.

The magnetic vector N ', of the mobile magnet 4, is oriented along the longitudinal axis AA' of the fin 2a, which makes an angle a with the base plane S of the seat 1 and towards the free edge of the end of said fin . When the flap 2a approaches its full opening position, the moving magnet 4 is rejected by the fixed magnet 32, which creates a return to the equilibrium position E, represented in figure 7 where the flap makes a angle a of 35 ° with the base plane 3.

The same phenomenon occurs when the area 2a approaches its closing position by interaction of the mobile magnet 4 with the fixed magnet 31. The magnetic return torque applied from the closed position towards the magnetic equilibrium position guarantees a minimum opening of the fin at 35 ° during the runoff phase river of the blood.

The return copy applied from the full opening position to the magnetic equilibrium position E, allows to initiate, and guide the fin to that position. At the moment when the difference of transvalvular pressure is reversed. From this last position, the movement of the fin towards its closed position is almost instantaneous, because the fin offers an important support surface for the fluid, and it has nothing left but an angular run of 10 ° to travel. The magnetic return torque to the magnetic equilibrium position still exists when the fin forms an angle of 90 ° with the base plan S of the seat, the profile of the valve can then authorize a 90 ° opening of the fins, in a manner to minimize the loss of transvalvular load in case of high debit, without having an increase of reflux.

This example of magnetic assistance corresponds well to the functional requirements of an aortic valve prosthesis.

Figure 10 shows the graph of the variations of the return torque as a function of the angular position of the fin for the magnetic configuration shown in Figure 7.

The equilibrium position E is found at a = 35 ° in relation to the plane S and does not correspond, here, to a semi-opening. It is clear, according to this graph, that there is no symmetry in the law of variation of the magnetic copy, of part and another of the equilibrium position E. This variation does not necessarily obey the same rules for the phase of opening and for the phase closure, but must not present in any way, brutal changes in slope.

Figure 8 represents a magnetic configuration to a fixed magnet 3 and a moving magnet 4. The magnet vector of the fixed magnet 3 is oriented according to a direction d, while the magnet vector of the moving magnet 4 is oriented according to the normal of the extracted of the fin 2a. Consequently, the mobile magnet 4 has a tendency to move, so that its magnetization vector N 'is parallel to the magnetization vector N of the fixed magnet 3 but with an opposite direction, in order to perform the closing of the lines of the magnetic field. That return in putting the fixed magnets 3 and mobile 4 face to face. This phenomenon creates a magnetic pair returning from the fin 2a to an equilibrium position E, materialized by the plane BB 'of figure 8. Here, the fin is in its magnetic equilibrium position E, when it forms a 45 ° angle with the base plane S of the seat. The magnetic return torque, applied from the closed position to the magnetic equilibrium position, guarantees a minimum opening of the fin at 45 ° during the downward dripping phase of the blood. The copy back, applied from the fully open position to the magnetic equilibrium position, allows the fin to be guided towards this position, at the moment where the transvalvular pressure difference is inverted and thus the reflux is minimized.

This example of magnetic assistance may also suit the functional requirements of an aortic or mitral valve prosthesis, but it will be a less optimal solution, because it is less specific.

Of course, it is possible, always according to the invention, to obtain the graphs of variations of figures 9, 10 and 11 with different configurations of these represented in figures 6, 7 and 8 or of other configurations, choosing geometries and / or relative positions and / or particular animations of the fixed 3 and mobile 4 magnets.

We can also think about creating a reciprocal influence between the activation system of the fin 2a and the activation system of the fin 2b.

According to this embodiment, the activation system operates under the sole influence of the mobile magnetic elements. in this case, the fixed magnetic elements of the seat are then non-existent or inactive or produce an influence that does not count in relation to those produced by the mobile magnetic elements.

Claims (20)

CLAIMS.

1. Activating system for heart valve composed of a seat and at least one wing rotating placed on the seat of at least one fixed magnetic element, integral with the seat and / or at least one mobile magnetic element formed by said wing; said magnetic elements creating, by reciprocal influence, a force exerted on said fin during its opening and / or closing movements. characterized in that said force fluctuates as a function of the position of said flap so as to minimize the blood reflux without increasing the transvalvular load loss and returns the flap at any time to an equilibrium position corresponding to an intermediate opening position.

2. System according to claim 1, characterized in that said mobile magnetic element produces a first magnetic field ~ and said fixed magnetic element produces a second magnetic field.

3. System according to one of the preceding claims, characterized in that the magnetic elements are arranged in such a way that the variations of said force, as a function of the position of the fin, are independent of part or the other of the equilibrium position.

4. System according to one of the preceding claims, characterized in that said force produces a magnetic copy being exerted on the fin, whose maximum value is comprised between 10"^ and 10 ~ 5 N.m.

5. System according to one of the preceding claims, characterized in that the magnetic elements are determined such that the fin rotates in the seat with the minimum friction.

6. System according to one of the preceding claims, characterized in that the equilibrium position is located between the full opening and closing positions.

7. System according to one of the preceding claims, characterized in that the reciprocal influence of the magnetic elements produces repulsive magnetic forces.

8. System according to claim 7, characterized in that said repulsive magnetic forces have an intensity of more than 10-1N.

9. Systems according to one of the preceding claims, characterized in that said fixed magnetic element is integrated in the thickness of the seat.

10. Systems according to one of the preceding claims, characterized in that said mobile magnetic element is hermetically integrated in the thickness of said fin.

11. System according to one of the preceding claims, characterized in that it has three fixed magnetic elements.

12. System according to one of claims 1 to 10, characterized in that it has two fixed magnetic elements.

13. System according to claim 12, characterized in that the two fixed magnetized elements are placed on the seat in order to respectively define the opening and closing positions of the fin.

14. System according to one of claims 11 to 13, characterized in that the fixed magnetic elements are arranged in a ring around an axis of articulation of the fin.

15. System according to one of the preceding claims, characterized in that at least one of said magnetic elements is a permanent magnet.

16. System according to one of the preceding claims, characterized by at least one of said magnetic elements is a permanent magnet called lowland based samarium and cobalt or based on neodymium, iron and boron.

17. System according to one of the preceding claims, characterized in that the fin is made in the mass or dressed with a hemocompatible material allowing the incorporation of magnets without modifying their magnetic characteristics.

18. Cardiac valve having an activation system according to one of the preceding claims.

19. Valve according to claim 18, characterized in that it comprises 2 fins activated by the only reciprocal influence of the mobile magnetic elements of each fin.

20. Valve according to claims 18 or 19, characterized in that the fin is made in the table in a hemocompatible titanium alloy