U.S. patent application number 11/585483 was filed with the patent office on 2007-05-03 for saddle-shaped mitral valve annuloplasty prostheses with asymmetry, and related methods.
This patent application is currently assigned to St. Jude Medical, Inc.. Invention is credited to Melinda Kaye Kovach, Irving L. Kron, Timothy John McGill, Nathaniel Zacharias Zenz--Olson.
Application Number | 20070100441 11/585483 |
Document ID | / |
Family ID | 37745955 |
Filed Date | 2007-05-03 |
United States Patent
Application |
20070100441 |
Kind Code |
A1 |
Kron; Irving L. ; et
al. |
May 3, 2007 |
Saddle-shaped mitral valve annuloplasty prostheses with asymmetry,
and related methods
Abstract
A mitral valve annuloplasty prosthesis (ring or C) has a
generally saddle shape, i.e., portions of the prosthesis that are
or will be adjacent the anterior and posterior commissures of the
valve are relatively low as compared to at least some other
portions of the prosthesis that are or will be between the
commissures. However, the saddle shape is asymmetrical, in that the
portion that is or will be adjacent the posterior commissure is
lower than the portion that is or will be adjacent the anterior
commissure.
Inventors: |
Kron; Irving L.;
(Charlottesville, VA) ; Kovach; Melinda Kaye;
(Plymouth, MN) ; McGill; Timothy John;
(Minneapolis, MN) ; Zenz--Olson; Nathaniel Zacharias;
(Blaine, MN) |
Correspondence
Address: |
FISH & NEAVE IP GROUP;ROPES & GRAY LLP
1211 AVENUE OF THE AMERICAS
NEW YORK
NY
10036-8704
US
|
Assignee: |
St. Jude Medical, Inc.
|
Family ID: |
37745955 |
Appl. No.: |
11/585483 |
Filed: |
October 24, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60730297 |
Oct 26, 2005 |
|
|
|
Current U.S.
Class: |
623/2.36 |
Current CPC
Class: |
A61F 2/2448
20130101 |
Class at
Publication: |
623/002.36 |
International
Class: |
A61F 2/24 20060101
A61F002/24 |
Claims
1. A mitral valve annuloplasty ring having an anterior portion
including A1, A2, and A3 segments, and a posterior portion
including P1, P2, and P3 segments, the segments being connected in
a closed loop series in the order A1, A2, A3, P3, P2, and P1, the
ring having an AP axis that extends from the anterior portion to
the posterior portion, a first reference point located on the
anterior portion to one side of the AP axis, a second reference
point located on the anterior portion to the other side of the AP
axis, and a third reference point located on the posterior portion
to one side of the AP axis, the AP axis being perpendicular to a
line between the first and second reference points, and the first
and second reference points and the AP axis being located so that
the AP axis bisects a greatest width dimension of the ring that is
measured perpendicular to the AP axis, each of the first through
third reference points being spaced from the AP axis by 0.5 mm, and
the first through third reference points lying in and thereby
defining a reference plane, the ring further having a fourth
reference point where the A1 and P1 segments meet, and a fifth
reference point where the A3 and P3 segments meet, the fourth and
fifth reference points being spaced from the reference plane to one
side of that plane, and spacing of the fifth reference point from
the reference plane being greater than spacing of the fourth
reference point from the reference plane.
2. The ring defined in claim 1 wherein the first and third
reference points are both on the side of the AP axis that is closer
to the fourth reference point.
3. The ring defined in claim 1 wherein at least a portion of the P3
segment is spaced from the reference plane to the one side of the
reference plane by an amount greater than the spacing of the fifth
reference point from the reference plane.
4. The ring defined in claim 3 wherein at least a portion of the P1
segment is spaced from the reference plane to the one side of the
reference plane by an amount greater than the spacing of the fourth
reference point from the reference plane.
5. The ring defined in claim 4 wherein the spacing of the fifth
reference point from the reference plane is greater than spacing of
any portion of the P1 segment from the reference plane.
6. A mitral valve annuloplasty prosthesis having a posterior
portion including P1, P2, and P3 segments, and an anterior portion
including A1 and A3 segments and a gap intermediate the A1 and A3
segments, the segments being connected in a series in the order A1,
P1, P2, P3, and A3, the prosthesis having an AP axis that extends
from the anterior portion to the posterior portion, a first
reference point located to one side of the AP axis on a trajectory
that includes a smooth continuation, across the gap, of both the A1
and A3 segments and that follows a path through the gap that would
be occupied by material of the prosthesis if the prosthesis were a
complete prosthetic ring, a second reference point located on the
trajectory to the other side of the AP axis, and a third reference
point located on the posterior portion to one side of the AP axis,
the AP axis being perpendicular to a line between the first and
second reference points, and the first and second reference points
and the AP axis being located so that the AP axis bisects a
greatest width dimension of the ring that is measured perpendicular
to the AP axis, each of the first through third reference points
being spaced from the AP axis by 0.5 mm, and the first through
third reference points lying in and thereby defining a reference
plane, the prosthesis further having a fourth reference point where
the A1 and P1 segments meet, and a fifth reference point where the
A3 and P3 segments meet, the fourth and fifth reference points
being spaced from the reference plane to one side of that plane,
and spacing of the fifth reference point from the reference plane
being greater than spacing of the fourth reference point from the
reference plane.
7. The prosthesis defined in claim 6 wherein the first through
third reference points are all located in material of the
prosthesis.
8. The prosthesis defined in claim 6 wherein the third reference
point is located in material of the prosthesis and the first and
second reference points are located in the gap.
9. The prosthesis defined in claim 6 wherein the gap is located
approximately centrally in the anterior portion.
10. The prosthesis defined in claim 6 wherein the first and third
reference points are both on the side of the AP axis that is closer
to the fourth reference point.
11. The prosthesis defined in claim 6 wherein at least a portion of
the P3 segment is spaced from the reference plane to the one side
of the reference plane by an amount greater than the spacing of the
fifth reference point from the reference plane.
12. The prosthesis defined in claim 11 wherein at least a portion
of the P1 segment is spaced from the reference plane to the one
side of the reference plan by an amount greater than the spacing of
the fourth reference point from the reference plane.
13. The prosthesis defined in claim 12 wherein the spacing of the
fifth reference point from the reference plane is greater than
spacing of any portion of the P1 segment from the reference
plane.
14. A method of treating a patient's mitral valve comprising:
applying an annuloplasty prosthesis to the mitral valve adjacent
the annulus of the mitral valve, the annuloplasty prosthesis
dipping down adjacent the anterior and posterior valve commissures
relative to at least some other portions of the annulus between the
commissures, the prosthesis pushing down the portion of the annulus
that is adjacent to the posterior commissure farther than the
prosthesis dips down adjacent the anterior commissure.
15. The method defined in claim 14 wherein the prosthesis comprises
a ring.
16. The method defined in claim 14 wherein the prosthesis is a
C-shaped prosthesis having a gap adjacent at least a portion of the
A2 segment of the valve leaflets.
17. The method defined in claim 14 wherein the other portions of
the annulus include at least a portion of the annulus that is
adjacent the A2 segment of the valve leaflets and at least a
portion of the annulus that is adjacent the P2 segment of the valve
leaflets.
18. The method defined in claim 15 wherein the ring also dips down
adjacent at least a portion of each of the A1, A3, P1, and P3
segments of the valve leaflets relative to said portion of the
annulus that is adjacent the A2 segment of the valve leaflets and
said portion of the annulus that is adjacent the P2 segment of the
valve leaflets.
Description
[0001] This application claims the benefit of U.S. provisional
patent application No. 60/730,297, filed Oct. 26, 2005, which is
hereby incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates generally to medical devices, and in
particular, to annuloplasty rings and other similar prostheses for
reshaping the mitral valve annulus of a patient's heart. The
invention also relates to methods of using such prostheses.
BACKGROUND OF THE INVENTION
[0003] The mitral annulus represents the junction of the fibrous
and muscular tissue that joins the left atrium and the left
ventricle. The mitral valve is a bicuspid valve having a relatively
large anterior leaflet that coapts or meets with a smaller
posterior leaflet.
[0004] FIG. 1 illustrates a normal mitral heart valve 14 from the
left atrium from a surgical view of the heart. The anterior portion
A of the mitral annulus 15 forms a part of the "cardiac skeleton"
and is bounded by anterior and posterior commissures 16, 17. The
anterior commissure 16 and posterior commissure 17 are generally at
the junction points of the anterior leaflet 18 and the posterior
leaflet 19. The junction points are also known as the anterolateral
commissure 16 and posteromedial commissure 17. The posterior
portion P of the mitral annulus 15 consists mainly of muscular
tissue of the outer wall of the heart.
[0005] Referring to FIGS. 1 and 2, posterior leaflet 19 is divided
into three scallops indicated as P1, P2, and P3 in sequence from
the anterior commissure 16 counterclockwise to the posterior
commissure 17. Anterior leaflet 18 is also divided into three areas
indicated as A1, A2, and A3 in sequence from the anterior
commissure 16 clockwise to the posterior commissure 17.
[0006] Ischemic heart disease can cause a mitral valve to become
incompetent. In patients who suffer from cardiomyopathy due to
ischemia, regions of the left ventricle lose their contractility
and dilate. As the disease progresses, the left ventricle enlarges
and becomes more round in shape, going from a conical shape to more
of a spherical shape. Referring to FIG. 2, papillary muscles 23, 25
are displaced down (inferiorly) and away from each other. The
change in the location of the papillary muscles increases the
distance between the papillary muscles and the mitral valve
annulus. This creates tension on the chordae tendonae 21 that
connect the posterior papillary muscle 23 to the mitral valve
leaflets in the A2, A3, P2, and P3 regions of the annulus. Since
the chordae tendonae 21 do not change their length significantly,
the chordae 21 tend to pull or "tether" the mitral leaflets. In
severe cases of left ventricle dilation, the tethering of the
chordae prevents the leaflets from coming together or coapting
correctly, resulting in mitral valve regurgitation. In addition to
remodeling of the left ventricle, the mitral valve tends to flatten
during ventricular systole instead of achieving its natural saddle
shape. This also disrupts the natural coaptation of the mitral
leaflets and the natural distribution of stresses over the leaflets
and chordae tendonae.
[0007] In ischemic mitral regurgitation (IMR), the entire
circumference of the mitral annulus may dilate. The posterior
portion of the annulus may dilate more than the anterior portion
because the anterior portion has more support from the heart's
fibrous skeleton. In cases where IMR is caused by posteromedial
myocardial infarction, there may be an asymmetric dilation of the
posteromedial annulus, which is indicated at A2, A3, P2, and P3. In
this case, the IMR may be caused by tethering of leaflet segments
connected to the posteromedial papillary muscle. This is often in
the A2, A3, P2, and P3 segments of the mitral valve.
[0008] Often, this type of mitral valve regurgitation is surgically
repaired with an annuloplasty ring (which may be either a complete
ring or a C-shaped "ring" with an opening along the anterior side).
The repair restores proper leaflet coaptation by decreasing the
diameter of the mitral valve annulus, thereby mitigating the effect
of the tethering of the chordae and the effects of dilation of the
annulus. One surgical correction for IMR is to tether the
posteromedial annulus of the mitral valve to the posteromedial
papillary muscle. This papillary muscle relocation procedure
reduces the chordal tension and allows the leaflets to coapt more
effectively.
SUMMARY OF THE INVENTION
[0009] In accordance with the present invention, patient conditions
like those described above are treated by applying an annuloplasty
prosthesis (ring or C) that is shaped to push down the mitral valve
annulus in the vicinity of the posterior commissure relative to
other portions of the annulus. The prosthesis also dips down
adjacent the anterior commissure, but it pushes down the portion of
the annulus that is adjacent the posterior commissure farther than
it dips down adjacent the anterior commissure. The effect of the
prosthesis on the two commissure regions of the annulus is
therefore asymmetrical.
[0010] A mitral valve annuloplasty ring in accordance with the
invention includes A1, A2, A3, P3, P2, and P1 segments connected to
one another in a closed loop series in the order just mentioned.
Each of these ring segments is configured for placement adjacent
the portion of a mitral valve annulus that is adjacent the
corresponding A1, A2, A3, P3, P2, or P1 segment of the mitral valve
leaflets. The ring has an anterior-to-posterior ("AP") axis that
extends across the ring from its anterior (A1/A2/A3) side to its
posterior (P1/P2/P3) side. The AP axis is perpendicular to a line
between two reference points that are spaced from one another along
the anterior side of the ring. The AP axis also bisects this line.
These two reference points are located along the anterior side of
the ring so that the AP axis also bisects a greatest width
dimension of the ring, which greatest width dimension is measured
perpendicular to the AP axis. A third reference point is located
along the posterior side of the ring to one side of the AP axis
(e.g., the side that is toward or closer to the anterior
commissure). Each of the above-mentioned three reference points is
spaced from the AP axis by 0.5 mm. These three reference points lie
in and thereby define a reference plane. A point on the ring
between the A1 and P1 segments, and another point on the ring
between the A3 and P3 segments are both displaced from the
reference plane to the same side of that plane. The amount of
displacement from the reference plane to the point between the A3
and P3 segments is greater than the amount of displacement from the
reference plane to the point between the A1 and P1 segments.
[0011] Instead of being a complete ring as described above, an
annuloplasty prosthesis in accordance with the invention may have a
C shape. This C shape can be similar to a complete ring in
accordance with the invention, but with a portion of the anterior
side of the ring omitted. The gap in the C that results from this
omission is generally located approximately centrally on the
anterior side of the C structure. The anterior side of the C may be
thought of as defining a trajectory that includes both the anterior
structure (i.e., comparable to at least portions of the A1 and A3
segments of a comparable ring) and a smooth continuation, across
the gap, of both of those anterior structural segments. This
trajectory follows a path through the gap that would be occupied by
material of the prosthesis if the C were instead a complete ring in
accordance with the invention. The summary description provided
above for the various reference points and the reference plane of a
complete ring applies again to such a C, with the exception that
the first and second reference points need to be described as being
on the above-mentioned trajectory because they may lie either in
anterior material of the prosthesis (if the gap is relatively
small) or in the gap (if the gap is relatively large).
[0012] Further features of the invention, its nature and various
advantages, will be more apparent from the accompanying drawings
and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a simplified or schematic view of a normal mitral
heart valve as viewed from the left atrium during surgery.
[0014] FIG. 2 is a simplified or schematic view of mitral heart
valve structures that have been dissected vertically at the
anterolateral commissure and splayed open.
[0015] FIG. 3 is a simplified "plan" view of an illustrative
embodiment of a mitral valve annuloplasty ring in accordance with
the invention. FIG. 3 shows the ring having the same orientation as
FIG. 1 shows a mitral valve with which the ring may be used, but
the scale of FIG. 3 is larger than the scale of FIG. 1.
[0016] FIG. 4 is a simplified elevational view taken along the line
4-4 in FIG. 3.
[0017] FIG. 5 is a simplified elevational view taken along the line
5-5 in FIG. 3. The scale of FIG. 5 is larger than the scale of FIG.
3.
[0018] FIG. 6 is similar to FIG. 3, but shows an illustrative
embodiment of a C-shaped mitral valve annuloplasty prosthesis in
accordance with the invention.
[0019] FIG. 7 is similar to FIG. 6, but shows another illustrative
embodiment of a C-shaped mitral valve annuloplasty prosthesis in
accordance with the invention.
[0020] FIG. 8 is a view taken along the line 8-8 in FIG. 7.
DETAILED DESCRIPTION
[0021] An illustrative embodiment of a mitral valve annuloplasty
ring 100, in accordance with the invention, that is better suited
to treating patient conditions like those described in the
background section of this specification is shown in FIGS. 3-5.
FIG. 3 shows ring 100 in the same orientation as FIG. 1 shows a
mitral valve to which ring 100 may be applied. FIG. 3 shows that
ring 100 has a generally D shape. The relatively straight side of
the D (toward the top in FIG. 3) is the anterior side of the ring
in use. The curved side of the D (toward the bottom in FIG. 3) is
the posterior side of the ring in use.
[0022] As shown in FIG. 3, ring 100 includes anterior segments A1,
A2, and A3, and posterior segments P1, P2, and P3. Each of these
segments is radially adjacent but beyond or outside the
corresponding portion of the mitral valve leaflets when the ring is
in use (i.e., implanted in a patient adjacent the annulus of the
patient's mitral valve). Thus, for example, anterior ring segment
A1 will be adjacent the base of the A1 segment of anterior leaflet
18 when ring 100 is in use. Similarly, posterior ring segment P1
will be adjacent the base of the P1 segment of posterior leaflet 19
when ring 100 is in use. The same correspondence between ring
segments and leaflet segments applies to all ring segments all the
way around ring 100. Thus it will be seen that ring 100 includes a
closed loop series of segments A1, A2, A3, P3, P2, and P1, in that
order.
[0023] In addition to defining ring segments as above, it is
convenient to refer to several reference points on ring 100. Each
of these reference points (A3/P3, A1/P1, R1, R2, and R3) is located
on an axis that runs annularly around the ring and that passes
coaxially through the center of the core material of the ring. The
point A3/P3 is the point at which ring segments A3 and P3 join or
meet one another. This point is adjacent the posterior commissure
17 (FIG. 1) of the mitral valve when ring 100 is in use. (The exact
location of point A3/P3 along the ring is not critical. FIG. 3 thus
tends to show the approximate locations of the various ring
segments and points like A3/P3 and A1/P1. The locations of these
features are, of course, generally as shown in FIG. 3.)
[0024] Another significant point on ring 100 is point A1/P1. This
is the point at which segments A1 and P1 join or meet one another.
When ring 100 is in use, point A1/P1 is adjacent the anterior
commissure 16 (FIG. 1) of the mitral valve.
[0025] Other points on ring 100 are reference points R1, R2, and
R3. These reference points are located as will now be described.
Ring 100 has a so-called anterior-posterior ("AP") axis, which
extends across the ring from its anterior side to its posterior
side. The AP axis is located so that it is perpendicular to and
bisects a line between reference points R1 and R2. Reference points
R1 and R2 are located along the anterior side of the ring so that
the AP axis bisects a greatest width dimension W of the ring, which
greatest width dimension is measured perpendicular to the AP axis.
Anterior-side reference point R1 is spaced to one side of the AP
axis by 0.5 mm. Anterior-side reference point R2 is spaced to the
other side of the AP axis by 0.5 mm. Reference point R3 is on the
posterior side of the ring and is spaced to one side (e.g., the R1
side) of the AP axis by 0.5 mm. Reference points R1-R3 lie in and
thereby define the location of a so-called reference plane.
[0026] (It should be noted that the "greatest width dimension" W is
the perpendicular distance between two tangents to the ring that
are both parallel to the AP axis and that are as far apart as
possible on opposite sides of the ring. It is possible that there
may be some distance across the ring, measured in some other way,
that is greater than W, but that is irrelevant to the present
invention and not what is meant by the "greatest width dimension"
as used herein.)
[0027] FIG. 4 shows that ring 100 is not planar. In the particular
embodiment shown in FIGS. 3-5, each of anterior ring segments A1,
A2, and A3 is substantially out of sight behind the corresponding
posterior ring segment P1, P2, and P3 in FIG. 4. This is not
necessarily exactly the case in all embodiments, but it simplifies
FIG. 4 and facilitates the present discussion. The reference plane
referred to in the preceding paragraph is identified in FIG. 4 (and
FIG. 5) by the reference number 110.
[0028] FIG. 4 shows ring segments A1 and P1 curving down and away
from reference plane 110 as one proceeds to the left from a medial
portion of what is visible in FIG. 4. FIG. 4 also shows ring
segments A3 and P3 curving down and away from plane 110 as one
proceeds to the right from the medial portion of FIG. 4.
[0029] Although points A1/P1 and A3/P3 are not per se visible in
FIG. 4, their approximate left-right locations are indicated with
arrows labeled A1/P1 and A3/P3, respectively. It will be apparent
from this depiction that point A3/P3 is lower relative to plane 110
than point A1/P1. Thus dimension D3 (the distance of point A3/P3
below plane 110) is greater than dimension D1 (the distance of
point A1/P1 below plane 110). Ring 100 is thus asymmetrical from
left to right (as viewed in FIG. 4) in this respect.
[0030] FIG. 5 shows another view of ring 100 on an even larger
scale than FIGS. 3 and 4 (see FIG. 3 for the orientation of FIG. 5
relative to FIGS. 3 and 4). FIG. 5 shows all the features of ring
100 that have been previously described. FIG. 5 again shows that
the side of ring 100 that includes point A3/P3 is displaced farther
from plane 110 than the side of the ring that includes point A1/P1.
This is again shown in FIG. 5 by the fact that dimension D3 is
greater than dimension D1.
[0031] Note in connection with FIG. 5, especially, that the
displacement at point A1/P1 from reference plane 110 is not
necessarily the greatest displacement of that side of the ring from
that plane. Another point (like 120 in FIG. 5) along P1 may
actually have greater displacement from plane 110 than point A1/P1.
The same may be true on the other side of ring where point A3/P3
may not have that side's greatest displacement from plane 110.
Another point 130 along P3 may have even greater displacement from
plane 110. Nevertheless, it remains the case that point A3/P3 has
greater displacement (D3) from plane 110 than point A1/P1 has.
Local maximum displacement point 130 (if different from point
A3/P3, as it is in ring 100) also has greater displacement from
plane 110 than local maximum displacement point 120 (again assumed
to be different than point A1/P1, as in ring 100). A possible
embodiment is for point A3/P3 to have greater displacement from
plane 110 than any point (even point 120) on the other side of the
ring.
[0032] It will also be noted from what has been shown and described
about ring 100 that, at a minimum, at least some portions of ring
segments A3 and P3 curve, slope, or incline away from reference
plane 110 (in the direction away from ring segments A2 and P2) in
order for point A3/P3 to be displaced from that plane. Similarly,
at least some portions of ring segments A1 and P1 curve, slope, or
incline away from plane 110 (in the direction away from ring
segments A2 and P2) in order for point A1/P1 to be displaced from
that plane. Both the A1/P1 side of the ring and the A3/P3 side of
the ring are displaced to the same side of plane 110. Ring 100 is
thus saddle shaped. However, the displacement from plane 110 that
is reached on the A3/P3 side of the ring is greater than the
displacement that is reached on the A1/P1 side of the ring. The
above-mentioned saddle shape is thus somewhat asymmetrical, with
the A3/P3 side of the ring being more depressed than the A1/P1 side
of the ring.
[0033] The greater "downward" displacement of the side of ring 100
that includes point A3/P3 is of significant benefit in compensating
for patient conditions like those described in the background
section of this specification. Those conditions tend to downwardly
displace tissue structures 23 (and their associated structures 21)
more than tissue structures 25 (and their associated structures 21)
(see again FIG. 2). Extra downward depression of the mitral valve
annulus radially out from leaflet segments A3 and P3 (and including
posterior commissure 17) may beneficially compensate for this
problem. Such extra downward depression of this portion of the
valve annulus is provided by ring 100, which has greater
displacement from plane 110 on its side that includes segments A3
and P3 and point A3/P3 than on its other side (i.e., its side that
includes segments A1 and P1 and point A1/P1).
[0034] It is known that mitral valve annuloplasty prostheses are
not always complete rings like ring 100. For example, a portion of
the anterior side of what would otherwise be a complete ring can be
omitted to produce a C-shaped prosthesis. Examples of such Cs are
shown in FIGS. 6 and 7. The C 200 in FIG. 6 has a relatively small
gap 402 on the anterior side. The C 300 in FIG. 7 has a relatively
large gap 402 on the anterior side. The anterior gap in FIG. 7 is
approximately the maximum acceptable gap. Any amount of
anterior-side gap (up to the approximate amount shown in FIG. 7)
can be employed in C-shaped prostheses.
[0035] The present invention can be applied to C-shaped prostheses
like those exemplified by FIGS. 6 and 7. The portions of such a
C-shaped prosthesis that are present in the C are shaped and
disposed in three dimensions as though they were the corresponding
portions of a complete ring in accordance with the invention (see
also FIG. 8, which is another view of illustrative C shown in FIG.
7). In other words, a C-shaped prosthesis in accordance with the
invention is shaped as though made from a complete ring in
accordance with the invention, but with some of the anterior of the
complete ring omitted to produce the C.
[0036] Although some portion of the anterior of a C in accordance
with the invention has been omitted, it is possible to visualize a
"trajectory" of the anterior side. Chain-dotted line 400 indicates
such a trajectory in FIGS. 6-8. Note that trajectory 400 spans the
entire anterior side of each C. Where the anterior side has
structure or material (i.e., to the left and right of anterior gap
402), trajectory 400 passes coaxially and centrally along that
structure. In gap 402 (where each C has no actual structure or
material) trajectory 400 continues smoothly out of the material to
one side of the gap, across the gap, and into the material on the
other side of the gap. In other words, trajectory 402 follows the
same path that the anterior side of the prosthesis 200 or 300 would
have if it were a complete ring in accordance with the
invention.
[0037] FIGS. 6 and 7 show that the same reference points R1 through
R3 that are descried above in connection with ring 100 can be used
again to define a reference plane 410 (see FIG. 8) that is useful
in describing the shape of Cs in accordance with the invention. In
the case of such Cs, however, it is appropriate to say that
reference points R1 and R2 are on anterior trajectory 400. This is
so because, depending on the size of gap 402, reference points R1
and R2 may be either in anterior material of the C (e.g., as in the
case of FIG. 6) or in the anterior gap 402 (e.g., as in the case of
FIG. 7). The anterior trajectory concept makes it possible to
describe the locations of reference points R1 and R2 generically,
regardless of the size of gap 402.
[0038] It is thus now possible to describe Cs in accordance with
the invention (e.g., a C like 200 or 300) as including the
following features: A1, P1, P2, P3, and A3 segments connected in
series in that order; an anterior gap 402; an anterior trajectory
400 as described above; an anterior-to-posterior axis AP
perpendicular to and bisecting a line between reference points R1
and R2, both of which are located along anterior trajectory 400; a
greatest width dimension W measured perpendicular to the AP axis,
reference points R1 and R2 and the AP axis being located so that
the AP axis bisects the greatest width dimension; each of reference
points R1 and R2 being spaced from the AP axis by 0.5 mm; reference
point R3 on the posterior side of the C, spaced to one side of the
AP axis by 0.5 mm, and defining with reference points R1 and R2 a
reference plane 410; both of points A1/P1 (where the A1 and P1
segments meet) and A3/P3 (where the A3 and P3 segments meet) being
spaced from reference plane 410 to the same side of that plane; and
the spacing of point A3/P3 from reference plane 410 being greater
than the spacing of point A1/P1 from that plane. Other features
that are described above for complete rings in accordance with the
invention are again applicable to Cs in accordance with the
invention because the only significant difference between Cs and
rings in accordance with the invention is the omission of a portion
of the anterior side of a ring to produce a C. The therapeutic
effects of Cs in accordance with the invention are similar to the
therapeutic effects described above for rings in accordance with
the invention.
[0039] A wide range of materials are well known for making
annuloplasty prostheses, and any of the known materials that are
suitable for making prostheses in accordance with this invention
can be used. Examples of suitable materials include titanium, a
titanium alloy, Elgiloy (a cobalt-nickel alloy), Nitinol (a
nickel-titanium alloy), stainless steel, a cobalt-chromium alloy, a
ceramic, and a polymer (e.g., ultra-high-molecular weight
polyethylene, polyurethane, or the like). The prostheses of this
invention (like ring 100 or Cs 200 or 300) can have any desired
degree of rigidity, consistent with the objective of this invention
for the prosthesis to apply significant forces in particular ways
to various parts of the mitral valve annulus. For example, the
prostheses of this invention can be rigid or substantially rigid.
Alternatively, the prostheses of this invention may be capable of
some plastic deformation if the surgeon wants to modify the
prosthesis shape somewhat for a particular patient's anatomy. The
prosthesis should not be plastically deformable by the patient's
anatomy alone, but the prosthesis may be capable of some elastic
deformation in response to the patient's anatomy, including changes
in anatomical shapes as a result of body functions such as
heartbeats. Nevertheless, a prosthesis that is capable of such
flexibility should always be resiliently trying to return to an
unloaded shape like that shown in the FIGS. herein. In that way,
even a prosthesis that is capable of some flexibility is always
applying the kind of therapeutic force to the mitral valve annulus
that is desired in accordance with the invention.
[0040] Just as any of several materials are suitable for use as the
basic material of the prostheses of this invention, the prostheses
of this invention may also include other known annuloplasty
prosthesis features. For example, the prostheses of this invention
may be wrapped in or otherwise associated with fabric or other
materials through which sutures can be passed as part of the
process of implanting the prosthesis in a patient.
[0041] It will be understood that the foregoing is only
illustrative of the principles of the invention, and that various
modifications can be made by those skilled in the art. For example,
certain aspects of the prosthesis shapes shown herein can be
modified. As just one specific illustration of this, the ratio of
greatest width to greatest height of the prosthesis (e.g., the
horizontal and vertical dimensions, respectively, in FIG. 3) can be
larger or smaller than what has been specifically shown.
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