DK163338B - HEART VALVE PROSTHESIS - Google Patents

Description

in

DK 163338 B

The present invention relates to a mechanical type heart valve prosthesis comprising an annular housing having an inner side defining a flow opening and having an outer surface intended to support an acidification and three flaps pivotally mounted about 5 each axis dividing each of the flaps into a peripheral and a central portion and arranged in the annular housing flow opening for a symmetrical and synchronous oscillation movement between an opening position and a position for closing the flow opening, respectively.

10

Cardiovascular prostheses of this type, so-called triple heart palpitations, can typically be inserted both into the aorta and the mitral annulus (that is, between the left ventricle and the aorta, respectively, between the left atrium and left ventricle). It has been known for many years to have various types of heart valves to replace diseased / damaged heart valves. However, none of the types used have proved ideal as they are associated with several drawbacks. Among the major drawbacks are side effects such as thrombus formation (blood clot formation) as well as hemolysis (an abnormal wear or damage of the red blood cells). Thrombus formation and hemolysis are primarily thought to be caused by flow disturbances / turbulence caused by the implanted prosthesis and by mechanical crushing of blood cells. Other side effects are medical follow-up treatment, which especially carriers of mechanical heart palpitations must live with for the rest of their lives.

25

A heart valve prosthesis of the type mentioned initially is known, for example, from the specification of US Patent No. 4,820,299 as well as from the specification to German Publication No. 3,409,005. The heart valve prostheses described in these two patents are provided with three pivotally mounted flaps. These can, as a result of heart contractions, oscillate between the open position where they allow the blood flow to a closed position where they prevent the flow of blood in the opposite direction. Each of the flaps is mounted so that, in their open position, they expose a peripheral flow opening and a central flow opening. These flow openings will be covered in a closed position of the flap by a peripheral portion and a central portion of the flap respectively. By heart contractions, the blood will press against the flaps from the inlet side of the house, thereby swinging them to their open position, where each flap's central

DK 163338B

Part 2 is directed with the flow of blood through the orifice. In the subsequent resting phase, the flaps should close and prevent the blood flow back, which is because the blood now exerts a greater pressure in the opposite direction on the central part of the flaps, causing them to return to the closed position.

Many of the known heart valve prostheses, in the closed state, will exhibit sealing problems along the perimeter of the flow opening, which can cause jet jets at high flow rates. The 10 jet jets produced are undesirable and harmful, giving rise to large shear stresses that increase the risk of thrombocyte and erythrocytes destruction and thus an increased risk of thrombus formation and hemolysis.

15 Furthermore, the clinically used mechanical heart valves give rise to large velocity gradients. As a result of the very small peripheral portions of the flow opening, the velocity profile of the blood flow rate as a function of the distance from them. The boundaries of the peripheral divide are a steeply increasing and rapidly decreasing curve, that is, a curve with large slope coefficients (velocity gradients). In general, however, it is advantageous to have as "soft" velocity profile as possible without large velocity gradients. The large velocity gradients give rise to the production of turbulence and, consequently, increased risk of thrombus formation and high molysis.

With the known three-fold mechanical heart valve prosthesis, the desire for a fairly large central flow through the heart valve prosthesis is fulfilled, as found in biological heart valves. However, between the housing and each of the flaps, a small peripheral opening will be formed, where a jet of jet occurs with large velocity gradients. Furthermore, these flap prostheses will not give rise to an outwardly directed peripheral current directed at the three exposures of the aortic root. Such a peripheral flow could advantageously cause the flaps to close at decelerated flow, as is the case with a normally functioning natural aortic valve. This results in an advantageous tendency for closure before the blood flows back through the flap. Thus, the known flap prostheses are also disadvantageous in allowing a relatively large ble odti1 baking flow before closing.

DK 163338 B

3 In the known heart valve prostheses, the position of the pivot axis will produce a relatively high profile of the prosthesis, with the flaps in the open position swinging relatively far out from the annular housing. It is particularly disadvantageous for implantation in the mitral annulus of a heart with a small left 5 heart chamber due to the risk of interference between the valve valves and the left heart chamber wall, as well as, during implantation, the risk of interference with sutures.

It is the object of the present invention to alleviate the above-mentioned shortcomings and disadvantages of the known heart valve prostheses of the type mentioned initially by providing such a heart valve prosthesis which enables both a large central stream and a reasonably large outward peripheral flow to be obtained, simultaneously with small velocity gradients occurring in the flow of blood through the orifice, and which also has a very low profile heart valve prosthesis.

According to the invention, this is achieved with a heart valve prosthesis, which is characterized in that the peripheral parts of the valves together cover an area of the flow opening which is larger than the area covered by the central parts.

With such a heart valve prosthesis, the flaps will work according to a surprising principle, as they will swing the opposite way compared to the traditional flaps. Thus, the central portion of each open flap will be directed toward the flow through the flow opening. This not only results in a large central flow through the central part, but also a large outward flow through the peripheral parts of the flow opening. This, with a heart valve prosthesis, as mentioned, may give rise to a beginning closure by decelerating flow due to eddy currents formed in the aortic root exposures. Furthermore, due to its "leaching effect", the relatively slow eddy flow will reduce the risk of thrombus formation. The central portion of the flow opening can, by using an appropriate degree of opening for the flaps, produce a substantially laminar central main flow. In addition, the larger area of the peripheral area, compared to the area of the central portion of the flow opening, will allow a small velocity gradient at the blood flow, thus reducing the risk of turbulence and thus the risk of thrombus formation. By a suitable di-

DK 163338 B

In terms of dimensioning the interrelationship between these areas, it is considered possible to obtain advantageous flow conditions with characteristics comparable to those of the flow conditions occurring with a normally functioning natural heart valve! In the closed state, the heart valve prosthesis of the invention will make it possible to avoid the harmful jet jets that the known heart valve prostheses exhibit as a result of the intended peripheral leakage.

Due to the position of the pivot axes relatively close to the center of the annular housing, the outer parts of the flaps, in the open position, may be located symmetrically, projecting relative to the annular housing. This results in a very low profile heart valve prosthesis, thereby reducing the risk of the protruding flaps caramboling with the vessel wall.

15

Materials for making the heart valve prosthesis can be selected from the biocompatible and durable materials traditionally selected for such prostheses. It just needs to be ensured that the materials have a very smooth surface, thereby reducing flow disturbances and thus reducing the risk of thrombus formation and hemolysis.

The invention will now be explained in more detail with reference to the accompanying drawing, in which: FIG. 1 is a view illustrating two typical locations for a heart valve prosthesis of the invention; FIG. 2 is a plan view of an embodiment of a heart valve prosthesis according to the invention; FIG. 3 is a sectional view of the one shown in FIG. 2, a heart valve prosthesis, and FIG. 4 is a graph illustrating an estimated velocity profile of the flow through the FIG. 2 and 3.

In FIG. 1 shows a heart 1, partly in section. This figure shows 35 typical locations for a heart valve prosthesis 2 according to the invention.

One of the flap prostheses 2 is shown mounted in the mitral annulus 3 as a central flap prosthesis between the left atrium 4 and the left ventricle 5. The other flap prosthesis 2 is shown mounted in the aortic position at the aortic root 6 as an aortic flap prosthesis between the left ventricle 5 and the aortic ascendence.

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5. In FIG. 1, the right atrium 8, right ventricle 9, vena cava 10 and arcus aorta 11 are also seen.

As the blood flows from the left atrium 4 downwards (as seen in Figure 5) through the mitral valve prosthesis 2 to the left ventricle 5 and then upwards through the aortic valve prosthesis 2 to the aortic ascendence 7, the two valve prostheses 2 illustrated in FIG. 1, be implanted for an opening movement in each direction.

It should be noted that the diameter of the two illustrated flap prostheses 2 must be adjusted individually for each patient. Furthermore, there is a schematic illustration of a liner 12 which is mounted in relation to the housing 13 of the flap prosthesis 2 (see Figures 2 and 3). The acidification 12, which in a well-known manner may be made of woven dacron, is used in the fixed mounting of the flap prosthesis 2 in the heart 1.

FIG. 2 and 3 illustrate an embodiment of a flap prosthesis 2 according to the invention. As can be seen from this, the flap prosthesis 2 is of mechanical type and comprises an annular housing 13 in which three flaps 14 are pivotally spaced about each axis 15. The annular housing 13 has an inner surface 16 defining a flow opening 17 for the flow of blood. through the flap prosthesis 2. The housing 13 also has an outer surface 18 which, in a manner known per se, is provided with two beads 19 for retaining the acid 12 (not shown here) on the outer surface 18 of the housing.

25

Each of the pivot axes 15 is thus, as most clearly shown in FIG.

3, located within the flow opening 17 of the annular housing 13, which means that the housing 13 advantageously has a low profile which makes it easier to implant the flap prosthesis 2 as a replacement for a natural heart valve. The three flaps 14 are arranged for a symmetrical and synchronous vibration movement about the pivot axes 15 between a position for opening and a position for closing the flow opening 17. In FIG. 3, 14 'illustrates a flap in a closed position and 14 "illustrates the flap in an open position.

35 In FIG. 2 it is seen that the axes 15 divide each of the flaps 14 into a peripheral portion 20 and a central portion 21. Furthermore, it can be seen that the peripheral portions 20 of the flaps 14, with a peripheral edge 28, together cover an area of the flow opening 17 which is larger. than the area covered

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6 of the central parts 21. In the embodiment shown, the ratio of the peripheral area to the central area is approx. 1.5, but this ratio may vary within a range of approx. 1.2 to 1.8. With this area ratio, the flap 14 of the flap prosthesis 2 will swing the opposite way relative to traditional flaps, with the central parts 21 of the flaps swinging in the direction opposite to the flow of blood 22 through the flap prosthesis 2. The flow of blood through the flap prosthesis shown will refer to FIG. 3, running downward and upward, as indicated by arrow 22. Thus, the outlet side 23 of the housing 13 is directed upwards, while its inlet side 24 is directed downwards.

From FIG. 3 it appears that the flap 14 in the closed position 14 'abuts the outer edge 25 of the inner surface 16 at the outlet side of the housing. Thus, in the closed state, the three flaps 14 will form a three-sided pyramid, 15 whose baseline lies flush with the outlet side 23 of the housing, and the tip 26 of which faces the inlet side of the housing 13. Thus, the majority of the flaps 14 are within the annular housing 13. the open position 14 of the flaps 14 "is the maximum travel and thus the open position of the flaps is defined by the cooperation of the flaps 14 with a stop stop 20 27. The stop stop 27 ensures partly a correct operation and a large opening angle for the flaps 14, which reduces the disturbing influence of the flaps on the flow of blood. The stop stop 27 is positioned so that the flaps 14 in their open position form an angle of about 80 ° with respect to a cross-sectional plane through the valve housing 13. This ensures a correct operation of the flaps 14, since they cannot swing past a position parallel to the direction of blood flow 22. This could cause the peripheral portion 20 of flap 14 to swing inward toward the central portion of the seam opening 17, which would cause an incorrect closure.

In FIG. 2, it is suggested that the annular housing 13 is made up of an inner ring portion 29 and an outer ring portion 30. The inner ring portion 29 is deformable and includes inwardly projecting projections 31 provided with bearings 32 for bearing pins 33 on the flaps 14. The outer ring portion 30 will, as shown, enclose, stiffen and retain the inner ring portion 29.

Thus, by assembling the flap prosthesis 2, it is possible to deform the inner ring portion 29 to such an extent that the flaps 14 can be mounted therein. Then, the inner ring portion 29 is mounted in the outer ring portion 30, after which the flap prosthesis 2 is ready for use. It just needs to be ensured that they

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7 two ring members 29.30 are mounted in a fixed mutual fit. This structure of the annular valve housing 13 makes it possible to manufacture the flap prosthesis easily and with relatively low mounting costs. The design of the bearings 32 and the bearing pins 33 is not critical to the present invention. It is thus possible to use well-known bearings in the art. However, it is preferred to use a spherical bearing pin which is housed in a recess which allows the blood to flush by. This avoids the risk of forming stagnant blood areas and thus the risk of thrombus formation.

10

In FIG. 3, it appears that the flap 14 is arranged so that it pivots equally far on each side of the annular vent Thus 13. This results in a very small total height (with open flap), and thus a small risk of interference with the vessel wall. Especially in diseases where the 15 heart has to work hard, the left ventricle will contract sharply, leaving very little room for a prosthesis. However, in certain situations, it may be desirable to move the pivot axis 15 of the flaps 14 in the direction toward the inlet side 24 of the housing so that the peripheral portions 20 of the flaps are not substantially projecting beyond the confines of the annular housing 13. This configuration may be desirable for a prosthesis to replace a central flap (at 3), and where minimum ventricular retraction is desired.

The flaps shown are planar, but it is also possible to design the flaps 25 with a slight outward curvature. It should only be ensured that such flaps do not have excessive curvature, as this can cause severe blood flow disturbances and a consequent risk of side effects such as thrombus formation and hemolysis.

In FIG. 2 it is seen that the pivot axes 15 of the flaps 14 form a straight-legged triangle inscribed in a circle formed by the inside of the housing 16. With this design of the pivot axes an advantageous relationship is obtained between the central parts 21 of the flaps 14 and the peripheral parts 20, viz. the previously mentioned ratio of approx. 1: 1.5.

35 In the following, it is explained how the above-mentioned flap prosthesis makes it possible to achieve a large outwardly directed peripheral flow, while at the same time small velocity gradients occur at the flow of blood through the flow opening 17.

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8 In FIG. 4, an estimated velocity profile 34 of the blood flow through the one shown in FIG. 2 and 3, flap prosthesis 13 with flaps 14 in fully open position 14 ''. The velocity profile 34 shows the flow velocity measured over the flow opening 17 (printed at a gauge stand r). The velocity profile 34 illustrates that there is an approximately laminar flow through the central portion of the flow opening 17 and through the peripheral portions of the flow opening 17. The velocity profile 34 has an apex 35 illustrating the maximum flow velocity through the central portion and 10, which illustrates the maximum flow rate through the peripheral portions. A local minimum point 37 indicates that the velocity is lowered in the shadow area behind a flap 14. The velocity profile is assumed to be measured immediately downstream of the housing 13.

15 As can be seen from FIG. 4, relatively small velocity changes occur over the measurement distance. This means that the slope dv / dr indicating the velocity gradient is relatively small, which is an expression of less turbulence formation. As mentioned earlier, turbulence can induce thrombus formation and hemolysis.

20

It is noted that the appearance of the velocity profile will vary throughout the heart cycle, synchronously with the flap opening and closing, as will also vary if it is measured closer or further away from the housing 13.

In the flap prosthesis 2, where the central parts 21 of the flaps swing in the direction of blood flow 22 through the flap prosthesis, the flaps in their fully open positions 14 "give rise to a peripheral flow having a slightly outward orientation. This peripheral flow is advantageous since it may be instrumental in the initial closure of the flaps by decelerating flow due to eddy currents formed in the aortic root exposures, and the relatively large peripheral flow will help avoid stagnant blood and high blood flow areas. shear stresses.

Thus, the flap prosthesis of the invention will be capable of producing flow conditions comparable to the flow conditions obtained with a normally functioning natural heart valve. The flap prosthesis provides the peripheral outward flow which contributes to a beginning closure already by decelerating flow, 9

DK 163338 B

which reduces the amount of flowing blood before closure. Furthermore, a flow is obtained where a very small degree of flow disturbance is induced, which reduces the risk of side effects.

With the flow conditions achieved through the flap prosthesis, which should have a very smooth surface of the parts that are in direct contact with the blood, it may be possible to completely avoid anticoagulation treatment normally performed in connection with the implantation of a mechanical heart valve prosthesis. . This anticoagulation treatment is given to reduce the blood's ability to coagulate. This is a traditional treatment since, in experience with mechanical flaps, there is a risk of activation of the coagulation system, which is probably due to blood cell or egg yolk. It will be valuable to avoid anticoagulation treatment due to the disadvantages of treatment and control and because of the risk of fatal bleeding complications.

When implanted in the aortic position, the valves may, as previously mentioned, have a slight outward curvature to increase the effect of closure by decelerating flow. However, an opening of a flat flap 14 is anticipated to an angle of approx. 80 ° relative to a 20 cross-sectional plane through the housing (the position illustrated at 14 "in FIG. 3) to be able to produce the desired outward flow.

The illustrated flaps 14, in closed condition, form a three-sided pyramid. In this way, the angle that a flap swings between open and closed position becomes small, which reduces wear and gives a quick reaction.

Such a quick reaction is advantageous as it can reduce the flow of blood upon closure. The illustrated flaps 14 swing through an angle of approx. 50 *, namely from an angle of approx.

30 30 "to an angle of about 80e relative to a cross-sectional plane through housing 13. If the baseline of the pyramid is in plane with the outlet side 23 of the housing and the tip faces the inlet side 24, a very low profile of the prosthesis is advantageously obtained.

35

Claims (10)

A mechanical-type cardiac prosthesis (2) comprising an annular housing (13) having an inner face (16) defining a flow opening (17) and having an outer face (18) intended to supporting a suture (12) and three flaps (14) pivotally spaced about each axis (15) dividing each of the flaps (14) into a peripheral (20) and a central portion (21), and being arranged in the annular housing (13) flow opening (17) for a symmetrical and synchronous oscillation movement between a position for opening and a position for closing the flow opening, respectively, characterized in that the peripheral parts (20) of the flaps cover an area of the flow opening ( 17) which is larger than the area covered by the central parts (21). 15 Heart valve prosthesis according to claim 1, characterized in that the size ratio of the two areas is from approx. 1.2 to 1.8, preferably from ca. 1.4 to 1.6 and in particular is about 1.5. Heart valve prosthesis according to any one of the preceding claims, characterized in that the three flaps (14) in closed condition form a three-sided pyramid with the tip (26) facing the inlet side (24) and with the baseline aligned with the housing. outlet side (23). 25 Heart valve prosthesis according to any one of the preceding claims, characterized in that the housing is made up of an inner ring part (29) and an outer ring part (30), the inner ring part being deformable and equipped with bearings (32) for bearing pins. on the flaps (14), and 30 where the outer ring portion (30) encloses, braces and retains the inner ring portion (29). Heart valve prosthesis according to any one of the preceding claims, characterized in that the flaps (14) are housed in the housing in the vicinity of its inlet side (24) and that the relationship between the peripheral part (20) and the central part ( 21) of each flap (14) is arranged so that these open-ended portions are projecting approximately equally on each side of the annular housing (13). 11 DK 163338 B A cardiac prosthesis according to any one of claims 1-4, characterized in that each flap (14) is mounted near the inlet side (24) of the housing and that the peripheral portion (20) and the central portion (21) are arranged so that the peripheral portion (20) is substantially not protruding outside the housing constraint. Cardiac prosthesis according to any one of claims 1-5, characterized in that each of the flaps (14) is formed with a slight outward curvature and is positioned near the outlet side 10 (23) of the housing (13). Cardiac prosthesis according to any one of claims 1-6, characterized in that the flaps (14) are planar and that they swing from an open to closed state from an angle of approx. 30 * to an angle of approx. 80e with respect to a cross-sectional plane through the housing (13). A cardiac prosthesis according to any one of the preceding claims, characterized in that stop stops (27) are arranged on the inside (16) of the annular housing (13) which cooperate with the flaps in order to limit their opening angle and define their open state (14 ”). A cardiac prosthesis according to any one of the preceding claims, characterized in that the pivot axes of the flaps (14) form a straight-legged triangle (Fig. 2) inscribed in the circle formed by the inside of the housing (13). 16). 30 35