Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/24—Heart valves ; Vascular valves, e.g. venous valves; Heart implants, e.g. passive devices for improving the function of the native valve or the heart muscle; Transmyocardial revascularisation [TMR] devices; Valves implantable in the body
  • A61F2/2403—Heart valves ; Vascular valves, e.g. venous valves; Heart implants, e.g. passive devices for improving the function of the native valve or the heart muscle; Transmyocardial revascularisation [TMR] devices; Valves implantable in the body with pivoting rigid closure members

Definitions

• the present invention relates to a heart valve prosthesis of mechani ⁇ cal type comprising an annular housing having an inside which defines a passage, and an outside which is intended to support a sewing ring and three valves which are pivotally mounted about each their respec ⁇ tive axis which axes are arranged in the passage of the annular hous ⁇ ing for a symmetrical and synchronous oscillation between positions for opening and for closing the passage, respectively.
• Heart valve prostheses of this type may typically both be placed in aorta and in mitral annu- lus (i.e. between the left ventricle and aorta and between the left atrium and the left ventricle, respectively).
• mitral annu- lus i.e. between the left ventricle and aorta and between the left atrium and the left ventricle, respectively.
• mitral annu- lus i.e. between the left ventricle and aorta and between the left atrium and the left ventricle, respectively.
• mitral annu- lus i.e. between the left ventricle and aorta and between the left atrium and the left ventricle, respectively.
• the for ⁇ mation of thrombi and hemolyses is primarily considered to be caused by flow disturbances/turbulence produced by the implanted prosthesis and by mechanical crushing of blood cells.
• Other side effects may be the subsequent medical treatment which, in particular, wearers of me- chanicai heart valve prostheses have to live with for the rest of their lives.
• a heart valve prosthesis of the type mentioned by way of introduction is known e.g. from the description of US Patent No. 4,820,299 and from the description of German publication No. 3,409,005.
• the heart valve prostheses described in these two patent publications are provided with three pivotally mounted valves. Due to the contractions of the heart these valves may pivot between the open position thus permitting the flow of the blood and the closed position thus preventing the flow of the blood in the opposite direction.
• Each of the valves is mounted in such a way that it clears a peripheral passage and a central passa ⁇ ge in its open position. In the closed position of the valve these passages will be covered by a peripheral part and a central part of the valve, respectively.
• the blood will press against the valves from the inlet side of the housing and thereby pivot said valves to their open position where each cen ⁇ tral part of the valve is directed in the direction opposite to the direction of flow of the blood through the passage.
• the valves are to close and prevent the reflux of the blood that is brought about by the blood exerting now a higher pres ⁇ sure on the central part of the valves in the opposite direction which causes said valves to return to the closed position.
• the desir- able rather large flow through the heart valve prosthesis is obtained analogously with biological heart valves.
• a small peripheral opening is provided between the housing and each of the valves where a jet with large gradients of velocity is provided.
• these val ⁇ ve prostheses will not cause an outwardly extending peripheral flow directed towards the three bags in the root of aorta.
• a peripheral flow could cause the valves to close by decelerating flow as it is the case with a normally working natural aorta valve.
• an advantageous tendency for closing is obtained before the blood refluxes through the valve.
• the known valve prostheses are disadvantageous in that they permit a relatively large blood reflux before they close.
• a heart valve prosthesis which is characterized in that the axes divide each of the valves into a peripheral and a central part and that the peripheral parts of the valves cover in combination an area of the passage which is greater than the area covered by the central parts.
• valves work according to a surprising principle, as they will pivot in the opposi- te direction as compared to the traditional valves.
• the central part of each valve is directed in the direction opposite to the direction of flow through the passage.
• this may trigger onset of closing by decelerating flow due to turbulent flows which are generated in the bags in the root of aorta.
• the relatively slow turbulent flow reduces the risk of thrombi formation.
• the central part of the passage may provide a sub ⁇ stantially laminar central main flow.
• the greater area of the peripheral parts in comparison with the area of the central part of the passage permits a small gradient of velocity by the flow of the blood and accordingly the risk of turbulence and accordingly the risk of thrombi formation is reduced.
• a suitable dimensioning of the mutual ratio of these two areas it is considered possible to obtain advantageous flow conditions with characteristics comparable with the characteristics of the flow conditions which occur with a normally working natural heart valve.
• the heart valve prosthesis according to the invention makes it possible to avoid the damaging jets which the known heart valve prostheses exhibit due to the intended peripheral leak.
• the materials for producing the heart valve prosthesis may be chosen from the bio-compatible and wear-resisting materials which are tradi- tionally chosen for this kind of prostheses. However, it is to be en ⁇ sured that the materials have a very smooth surface so as to reduce the flow disturbances and accordingly reduce the risk of thrombi and hemolysis formation.
• Fig. 1 is a view illustrating two typical positionings for a heart valve prosthesis according to the invention
• FIG. 2 a plan view of an embodiment for a heart valve prosthesis according to the invention
• Fig. 3 a sectional view through the heart valve prosthesis shown in
• Fig. 2, and Fig. 4 a curve illustrating an estimated velocity profile for the flow through the heart valve prosthesis shown in Figs. 2 and 3.
• a heart 1 is shown, partially in section.
• Two typical posi- tionings for a heart valve prosthesis 2 according to the invention is shown in this figure.
• the one of the valve prostheses 2 is shown moun ⁇ ted in mitral annulus 3 as a mitral valve prosthesis between the left atrium 4 and the left ventricle 5.
• the other of the valve prostheses 2 is shown mounted in aorta position at the root 6 of aorta as an aorta valve prosthesis between the left ventricle 5 and aorta ascendens 7.
• the right atrium 8, the right ventricle 9, vena cava 10, and arcus aorta 11 are shown.
• the two valve prostheses 2 illustrated are implanted for an opening movement in each their direction.
• a sewing ring 12 is schematically illustrated mounted firmly relative to the housing 13 of the valve prosthesis 2 (See Figs. 2 and 3).
• the sewing ring 12 is used in the firm mounting of the valve prosthesis 2 in the heart 1, and may per se be produced in a well-known way from woven dacron.
• Figs. 2 and 3 illustrate an embodiment of a valve prosthesis 2 accord- ing to the invention.
• the valve prosthesis 2 is of a mechanical type and comprises an annular housing 13 where three valves 14 are pivotally mounted about each their respective axis 15.
• the annular housing 13 has an inside 16 which delimits a passage 17 for the flow of the blood through the valve prosthesis 2. Likewise the housing 13 has an outside 18 which in a manner well known per see is provided with two grooves 19 for fixing the sewing ring 12 (not shown) onto the outside 18 of the housing.
• each of the pivot axes 15 are provi- ded within the passage 17 of the' annular housing 13, which means that the housing 13 advantageously has a low profile which makes it easier to implant the ;alve prosthesis 2 to substitute a natural heart valve.
• the three valves 14 are arranged for a symmetrical and synchronous oscillation about the pivot axes 15 between a position for opening and for closing the passage 17, respectively.
• 14' illustrates a valve in a closed position
• 14" illustrates the valve in an open position.
• the axes 15 divide each of the valves 14 into a peripheral part 20 and a central part 21.
• the peripheral parts 20 of the valves 14 cover in combination an area of the passage 17 which is greater than the area covered by the central parts 21.
• the ratio between the peri- pheral area and the central area is approximately 1.5, but this ratio may vary within the interval of from approximately 1.2 to 1.8.
• the valve 14 of the valve prosthesis 2 pivots in the opposite direction relative to traditional valves as the central parts 21 of the valves pivot in a direction opposite the flow 22 of the blood through the valve prosthesis 2.
• the flow of the blood runs from below and upwards through the valve pro ⁇ sthesis shown as indicated with the arrow 22.
• the outlet side 23 of the housing 13 is directed upwards while the inlet side 24 of said housing is directed downwards.
• valve 14 in its closed position 14' the valve 14 abuts the external edge 25 of the inside 16 at the outlet side of the housing.
• the three valves 14 provide a three- sided pyramid the base of which levels with the outlet side 23 of the housing and the apex 26 of which faces the inlet side 24 of the hous ⁇ ing 13.
• the greater part of the valves 14 is within the annular housing 13.
• the open position 14" of the valves 14 the maximum travelling distance and accordingly the open position of the valves are defined by the co-operation of the valves 14 with a stop 27.
• the stop 27 ensures botft a correct functioning and a high degree of open ⁇ ing of the valves 14 thereby reducing the disturbing influence of the valve on the flow of blood.
• the stop 27 is provided in such a way that in their open position the valves 14 form an angle of approximately 80° relative to a cross-sectional area through the housing 13.
• a correct functioning is ensured for the valves 14 as they are unable to pivot past a position parallel with the direction of flow 22 of the blood. This could make the peripheral part 20 of the valve 14 pivot inwards against the central part of the passage 17 which may cause an incorrect closing.
• the annular housing 13 consists of an internal ring part 29 and an external ring part 30.
• the internal ring part 29 is deformable and comprises inwardly extending projections 31 which are provided with bearings 32 for pivot pins 33 on the valves 14.
• the external ring part 30 encircles, supports and secures the internal ring part 29.
• the construction of the annular housing 13 makes it possible to produce the valve prosthe ⁇ sis easily and at relatively low mounting costs.
• the construction of the bearings 32 and the pivot pins 33 is not critical to the present invention. Thus it is possible to use bearings well-known for a person skilled in the art. However, it is preferred to use a spherically shaped pivot pin mounted in a recess which allows the blood to flow by. Hereby the risk of forming areas with stagnant blood is avoided and so is the risk of thrombi formation.
• valve 14 is arranged in such a way that said valve pivots the same distance to either side of the annular housing 13.
• a very small total height is obtained (with open valve) and accordingly, there is a small risk of interference with the vascular wall.
• the left ventricle will contract violently thereby leaving very little space for a prosthesis.
• This construction may be desirable for a prosthesis to replace a mitral valve (at 3) and where minimum projection into the left ventricle 5 is desired.
• the valves shown are plane, but it is also possible to provide the valves with a slightly outwardly extending curvature. Only it is to be ensured that the curvature of such valves is not too large as it may cause severe disturbances in the flow of blood and a subsequently a risk of side effects like for instance the formation of thrombi and hemolysis.
• Fig. 2 shows that the pivot axes 15 of the valves 14 form an isosceles triangle which is inscribed in a circle formed by the inside 16 of the housing.
• valve pro ⁇ sthesis makes it possible to obtain a large outwardly extending peri ⁇ pheral flow simultaneously with small gradients of velocity appearing when the blood flows through the passage 17.
• Fig. 4 illustrates an estimated profile of velocity 34 for the flow of the blood through the valve prosthesis 13 shown in Figs. 2 and 3 with the valves 14 in the completely open position 14".
• the profile of velocity 34 shows the velocity of flow measured over the passage 17 (expressed by a measure distance r).
• the profile of velocity 34 illu- strates that an approximately laminar flow appears through the central part of the passage 17 and through the peripheral parts of the passage 17.
• the profile of velocity 34 has a maximum 35 which illustrates the maximum velocity of flow through the central part and a maximum 36 which illustrates the maximum velocity of flow through the peripheral parts.
• a regional minimum 37 indicates that the velocity is lowered in the shaded area behind a valve 14.
• the profile of velocity is conside ⁇ red to be measured immediately downstream of the housing 13.
• valve prosthesis 2 where the central parts 21 of the valves is turned against the direction to the flow 22 of the blood through the valve prosthesis the valves will cause a peripheral flow in their com ⁇ pletely open positions which are slightly outwardly orientated.
• This peripheral flow is advantageous as it may contribute to an onset of closing of the valves at decelerated flow due to those turbulent flows which are provided in the bags in the root of aorta.
• the relatively large flow in the peripheral parts may contribute to avoid ⁇ ing areas with stagnant blood and areas with high shear-tensions.
• valve prosthesis according to the invention is able to pro ⁇ quiz flow conditions which are comparable with the flow conditions obtained with a normally working natural heart valve.
• the valve pro ⁇ sthesis provides the peripheral outwardly orientated flow which con- tributes an onset of closing already at decelerated flow thereby redu ⁇ cing the quantity of the refluxed blood before closing.
• a flow is obtained where very little disturbance of flow is induced which reduces the risk of side effects.
• This anticoagulation treatment is carried out to reduce the ability of the blood to coagulate.
• the treatment is traditional as it is a well-known fact that by mechanical valves there is a risk of activating the coagulation system presumably due to the destruction of the blood cells. It will be of great value to avoid the anticoagulation treatment due to the inconveniences caus ⁇ ed by the treatment and the control and due to the risk of fatal bleeding complications.
• valves When the heart valve prosthesis is implanted in the aorta position the valves may have a slightly outwardly extending curvature as mentioned previously to increase the closing effect at decelerated flow. How- ever, an opening angle of a plane valve 14 is expected to be approxi ⁇ mately 80° relative to a cross section through the housing (the posi ⁇ tion illustrated at 14" in Fig. 3) to produce more or less the desi ⁇ red outwardly extending flow.
• valves 14 In their closed position the illustrated valves 14 form a three-sided pyramid.
• the angle where a valve pivots between open and closed positions becomes small thereby reducing the wear and triggering a prompt reaction.
• Such prompt reaction is advantageous as hereby the reflux of the quantity of blood at closing may be reduced.
• the illu ⁇ strated valves 14 pivot through an angle of approximately 50°, viz. from an angle of approximately 30° to an angle of approximately 80° relative to a cross-section through the housing 13.
• a very low profile for the prosthesis is advantageously obtained.

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• Health & Medical Sciences (AREA)
• Cardiology (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Transplantation (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Vascular Medicine (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Prostheses (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8144545

Family Applications (1)

Country Status (3)

Cited By (2)

Citations (4)

• 1989
  • 1989-11-14 DK DK569489A patent/DK163338C/da not_active IP Right Cessation
• 1990
  • 1990-11-08 AU AU67353/90A patent/AU6735390A/en not_active Abandoned
  • 1990-11-08 WO PCT/DK1990/000287 patent/WO1991007148A1/en unknown

Patent Citations (4)

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