.
`
`Ulllted States Patent [19]
`Vince
`
`lllllillllllllllllllllllIlllllllllllillIllllllllllIIIlllllllll
`[11] Patent Number:
`5,163,953
`[45] Date of Patent:
`Nov. 17, 1992
`
`US005163953A
`
`[54] TOROIDAL ARTIFICIAL HEART VALVE
`,
`STENT
`[76] Inventor; Dennis J_ Vince, 10-943 west
`Broadway, Vancouver, BC,
`Canada, V5Z 1K3
`
`[21] APPl- NO-I 833,543
`[22] Filed.
`Feb_ 10’ 1992
`
`i
`Int. Cl.“ .............................................. ..
`U:S. Cl. ................................ ..
`623/2;
`[58] Field of Search .................................. .. 623/2, 900
`[56]
`References Cited
`us‘ PATENT DOCUMENTS
`
`4,106,129 8/1978 Carpentier et all ................... .. 623/2
`Primary Examiner~—Randy C. Shay
`Attorney. Agent, or Firm——Townsend and Townsend
`[57]
`ABSTRACT
`
`A stent for a heart valve. The valve has a flap valve of
`biological material. The stem has a generally toroidal
`body formed of a ?exible coil of wire. A plurality of
`posts extend upwardly from the body to mount the flap
`-va1ves' The Stent in combination
`a percutaneous
`balloon dilatable Catheter is also describéd. The Catheter
`is positioned intraluminal of the valve and dilation of
`the balloon exerts stress to overcome the elastic limit of
`the stent to increase stent circumference.
`
`4,038,703 8/1977 Bokros .................................. ., 623/2
`
`5 Claims, 2 Drawing Sheets
`
`NORRED EXHIBIT 2104 - Page 1
`Medtronic, Inc., Medtronic Vascular, Inc.,
`& Medtronic Corevalve, LLC
`v. Troy R. Norred, M.D.
`Case IPR2014-00110
`
`

`
`US. Patent
`
`Nov. 17, 1992
`
`Sheet10f2
`
`-
`
`5,163,953
`
`~
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`NORRED EXHIBIT 2104 - Page 2
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`

`
`US. Patent
`
`Nov. 17, 1992
`
`Sheet 2 0f 2
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`5,163,953
`
`20
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`IO
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`NORRED EXHIBIT 2104 - Page 3
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`

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`1
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`5,163,953
`
`TOROIDAL ARTIFICIAL HEART VALVE STENT
`
`FIELD OF THE INVENTION
`
`This invention relates to a stent for an arti?cial heart
`valve.
`
`DESCRIPTION OF THE PRIOR ART
`Although heart replacement operations receive con
`siderable publicity by far the more common operation
`in heart surgery is replacement of one or more of the
`valves controlling blood ?ow in the heart. The valves
`are the tricuspid, the mitral, the pulmonic and the aortic
`valves.
`The heart may be considered as a simple pump con
`sisting of fours chambers, the left and right atria and the
`left and right ventricles with the valves located between
`the chambers and controlling blood ?ow.
`The valves used to replace natural heart valves are of
`two general types, bioprosthetic valves and mechanical
`valves. The former are valves that resemble normal
`heart valves and use valve lea?ets (or ?aps) of tissue or
`similar biological material. Mechanical valves usually
`employ disc valves manufactured of synthetic biocom
`patible material. Ball and cage valves have been used
`but use of these is decreasing.
`Early heart valve replacement used aortic valves
`unsupported by a frame or stent. However, the replace
`ment operation was dif?cult to perform. It was found
`that the operation was easier to perform and the valve
`functioned better if the valve was supported by a stent.
`The valve is sutured to the stent. Animal materials are
`now used, such as bovine or porcine pericardium. Early
`sterilization problems of the valves have been overcome
`but calci?cation and deterioration of arti?cial valve
`le?ets remains a signi?cant problem. Fatigue fracture of
`the stents and dif?culty in insertion of circular stents in
`non-circular sites also remains a problem.
`During cardiac systolic contraction, extremely high
`forces are applied at the point where the valve is at
`tached to the stent. In the prior art the preffered stent
`material is titanium and the stent is rigid.
`Thus the current, most common, prior art comprises
`a circular component or stent that forms the base of the
`valve with three posts, called commissural posts, ex
`tending from the stent and receiving the lea?et tissue
`that forms the ?ap valve of the arti?cial heart valve.
`Because of its rigidity, the stent has no dynamic func
`tion in the action of valve lea?ets; it is merely a frame.
`Similarly the commissural post are rigid and ?xed in
`their position of attachment to the circular base.
`
`35
`
`45
`
`BRIEF SUMMARY OF THE INVENTION
`The present invention seek to improve on the prior
`art by providing a stent that assists in the operation of
`the arti?cial valve rather than merely acting as a frame.
`Accordingly, and in a ?rst aspect, the present inven
`tion is a stent for a heart valve, the valve having ?ap
`valves of biological material, the stent comprising, a
`generally toroidal body formed of a ?exible coil of wire
`and a plurality of posts extending upwardly from the
`toroidal body to mount the flap valves.
`Preferably, the stent is of unitary construction with
`the plurality of posts formed by the wire of the gener
`ally toroidal body.
`Preferably there are three posts dividing the gener
`ally toroidal body into three segments.
`
`55
`
`65
`
`2
`The generally toroidal body of the stent is desirably
`ensheathed in a Silastic tube. (Silastic is a trademark of
`Dow Corning for a silicone polymer). Such a material is
`biologically compatible. It prevents tissue ingrowth into
`the stent. Preferably the Silastic sheath is covered with
`a suitable biocompatible material selected to promote
`tissue endothelialization. The latter forms a sewing ring
`to enable surgical installation of the valve as with con
`ventional bioprosthetic valves. The sewing ring tech
`nique is well known in the art.
`‘
`In a further aspect, the invention is a stent as de?ned
`above in combination with a percutaneous balloon dilat
`able catheter, intraluminal of the valve, dilation of the
`balloon exerting stress to overcome the elastic limit of
`the stent, resulting in permanent extension of the helix
`and thus permanently increasing stent circumference.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The invention is illustrated, by way of example, in the
`accompanying drawings in wich: FIG. 1 is a plan view
`of a stent according to the present invention; FIG. 2 is
`a side elevation of the stent of FIG. 1; FIG. 3 shows the
`stent of FIG. 1 in position in a heart valve; FIG. 4
`shows a detail of the stent; FIG. 5 illustrates the use of
`a balloon catheter with the stent of the present inven
`tion; and FIG. 6 illustrates further the use of a balloon
`catheter with the stent of FIG. 1.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`FIGS. 1 and 2 show a stent 10 for a heart valve. FIG.
`3 shows the stent 10 in place in a valve. The valve has
`?aps 11 of a biological material acting as valves in re
`placement of the natural valves. The stent 10 comprises
`a generally toroidal body 12 formed of a ?exible coil of
`wire. In the illustrated embodiment a plurality of com
`missural posts 14 extend upwardly from the body 12 to
`mount the ?aps 11. The stent 10 has a unitary structure.
`The body 12 is made of a coil of wire and the same wire
`is extended upwardly from the body 12 to form the
`commissural posts 14. The illustrated embodiment
`shows three posts 14 dividing the body 12 into three
`segments.
`The body 12 of the stent 10 is covered in a Silastic
`material 16, as shown in FIG. 4. There is also a sewing
`ring 18, as shown in FIGS. 3 and 4, to allow stitching of
`the stent 10 in place in the heart.
`A heart valve supported by a stent 10 according to
`the present invention functions as follows.
`During ventricular systole, as the intraluminal pres
`sure increases, circumferentisl stress (hoop stress) de
`velops on the circumference of the stent 10. This stress
`is transmitted as axial stress to the body 12. The body 12
`expands and the energy is stored all along the body 12
`as torsional stress. The circumference thus increases.
`This in turn increases the valve ori?ce and reduces ?ow
`resistance from the ventricle through the valve during
`ventricular ejection.
`During ventricular diastole, as the intraluminal pres
`sure falls, the fall in hoop stress allows the stored energy
`in the body 12 to decrease the circumference of the
`stent 10 in an elastic recovery. The ori?ce in the valve
`reduces and resistance to backward ?ow of the valve
`(regurgitation) is thus increased.
`Thus, the present invention provides a variable ori
`?ce valve. The ori?cie varies in a direction to encour
`age forward ?ow, reduced regurgitation and comple
`ment the ?ap valve action. In addition, as the ori?ce is
`
`NORRED EXHIBIT 2104 - Page 4
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`

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`5,163,953
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`10
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`20
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`4
`Thus, the present invention provides an arti?cial
`heart valve stent having new and valuable properties,
`including:
`The ?exible circular body 12 allows insertion into a
`non-circular anatomic site.
`The body 12 expands and contracts with variations in
`the intracavitational pressure increasing the effective
`valve ori?ce in systole and decreasing the effective
`valve ori?ce in diastole
`Dynamic movement of the commissural posts 14 is
`induced by blood ?ow acting on the valve lea?ets 11
`attached to the commissural posts 14. During systole
`the commissural posts rotate outwardly and increase
`the effective valve ori?ce size. During diastole the com
`missural posts 14 are rotated inwardly and reduce the
`effective valve ori?ce size. At the same time the valve
`lea?ets are opposed and the appositional surfaces are
`increased. This dynamic movement is enabled by the
`commissural posts 14 being an integral part of the stent
`10.
`The body 12 of the stent 10 can be permanently di
`lated with an intraluminal balloon dilator by exceeding
`the elastic limits of the helix and introducing plastic
`onset in the body 12.
`The commissural posts 14, being an integral part of
`the stent 10, permit ?exing stresses to be distributed
`along the body 12. This reduces the risk of stress frac
`ture of the commissural posts 14 at their attachment to
`the body 12.
`I claim:
`1. A stent for a heart valve, the valve having ?ap
`valves of biological material, the stent comprising:
`a generally toroidal body formed of a ?exible coil of
`wire; and
`a plurality of posts extending substantially parallel to
`the axis of the toroidal body to mount the ?ap
`valves.
`2. A stent as claimed in claim 1 having a unitary
`structure with the plurality of posts formed by the wire
`of the generally toroidal body.
`3. A stent as claimed in claim 2 in which there are
`three posts dividing the toroidal body into three seg
`ments.
`4. A stent as claimed in claim 1 covered in a ?exible
`silicone sheath.
`5. A stent as claimed in clim 1 in combination with a
`percutaneous balloon dilatable catheter, intraluminal of
`the valve, dilation of the balloon exerting stress to over
`come the elastic limit of the stent to increase stent cir
`cumference.
`
`3
`reduced. the commissural posts 14 are moved towards
`the centre ofthe ori?ce, as shown by the arrows in FIG.
`2. Thus the valve cusp’s free edges will move closer
`together and the coaptational surfaces are increased.
`This improves diastolic function by limiting regurgita
`tion.
`During ventricular systole, with ventricular ejection
`through the valve ori?ce, the ejected stream will dis
`place the valve cusps outwardly. The valve cusps,
`which are attached to the commissural posts 14, are
`rotated outwardly by the forces. The posts 14 are an
`integral part of the stent 10 and thus have ?exibility.
`This outward rotation of the commissural posts 14 will
`take place as a result of torsional forces all around the
`circumference of the body 12. All three posts 14 and
`their attached valves 11 are rotated outwardly uni
`formly. This increases the ori?ce size, reducing resis
`tance to flow.
`In contrast, in the prior art valve, with a non-?exible
`stent, the commissural posts are held in their resting
`position at systole and diastole. This results in a reduc
`tion of the valve ori?ce.
`During ventricular diastole the reverse dynamics
`occur. The torsional energy stored in the body 12 ro
`tates the commissural posts 14 toward the centre of the
`ori?ce. The pressure distal to the valve forces the cusps
`and the attached commissural posts 14 inwardly and the
`valve closes. The distribution of these forces by the
`body 12 to all three commissural posts 14 ensures uni
`form positioning of the commissural posts 14 and their
`attached valve lea?ets 11. The commissural posts 14
`abut and prevent prolapse during valve closure.
`A very useful aspect of the invention is illustrated in
`FIGS. 3 and 4. The elasticity of the stent 10 permits
`enlarging of the circumference of the valve and perma
`nently increasing the ori?ce. A percutaneous balloon
`dilation catheter 20 can be inserted intraluminal to the
`valve. Dilation of the balloon 20 exerts suf?cient stress
`to overcome the elastic limit of the body 12 of the stent
`10 and permanently expands the circumference of the
`stent by exceeding the plastic onset of the helix. The
`45
`balloon catheter 20 is then de?ated and removed, leav
`ing a permanently increased valve ori?ce. The addi
`tional coaptational surface of the valve, which results
`from the special properties of the ?exible stent, provides
`adequate appositional surfaces to ensure diastolic com
`petence of the enlarged valve.
`
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`NORRED EXHIBIT 2104 - Page 5