U.S. patent application number 10/295323 was filed with the patent office on 2004-05-20 for valve annulus constriction apparatus and method.
Invention is credited to Callas, Peter L., Saunders, Richard J..
Application Number | 20040098116 10/295323 |
Document ID | / |
Family ID | 32297167 |
Filed Date | 2004-05-20 |
United States Patent
Application |
20040098116 |
Kind Code |
A1 |
Callas, Peter L. ; et
al. |
May 20, 2004 |
Valve annulus constriction apparatus and method
Abstract
An apparatus is described for supporting and/or constricting a
surface of a valve annulus. The apparatus includes a tubular member
of dimensions suitable for insertion into a body vessel. The
tubular member includes at least two first segments attachable to
an interior wall of the body vessel. The tubular member further
includes at least one second segment which is capable of decreasing
its axial length to draw one of the first segments towards the
other first segment.
Inventors: |
Callas, Peter L.; (Redwood
City, CA) ; Saunders, Richard J.; (Redwood City,
CA) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD, SEVENTH FLOOR
LOS ANGELES
CA
90025
US
|
Family ID: |
32297167 |
Appl. No.: |
10/295323 |
Filed: |
November 15, 2002 |
Current U.S.
Class: |
623/1.36 ;
623/1.15; 623/1.17 |
Current CPC
Class: |
A61F 2250/0048 20130101;
A61F 2/2451 20130101; A61F 2220/0008 20130101; A61F 2/86
20130101 |
Class at
Publication: |
623/001.36 ;
623/001.15; 623/001.17 |
International
Class: |
A61F 002/06 |
Claims
What is claimed is:
1. An apparatus comprising: a tubular member of dimensions suitable
for insertion into a body vessel, the tubular member having at
least two first segments attachable to an interior wall of the body
vessel, and at least one second segment disposed between the first
segments, wherein said at least one second segment is capable of
decreasing its axial length to draw one of the first segments
towards the other first segment, wherein the tubular member is
capable of reducing a longitudinal length of a portion of the body
vessel by drawing one of the first segments attached to a first
portion of the body vessel towards the other first segment attached
to a second portion of the body vessel.
2. The apparatus of claim 1, wherein the tubular member serves to
inhibit a portion of the body vessel from lengthening.
3. The apparatus of claim 1, wherein the second segment decreases
its axial length as the second segment is expanded in a radial
direction.
4. The apparatus of claim 1, wherein each of the first segments is
configured to maintain its axial length substantially constant as
the corresponding first segment is expanded in a radial
direction.
5. The apparatus of claim 1, wherein the second segment is
configured such that an amount of reduction in the axial length of
the second segment is greater than an amount of increase in the
diameter of the second segment.
6. The apparatus of claim 1, wherein the first segments comprises a
plurality of radially expandable cells, each of said radially
expandable cells configured such that, as the respective cell is
expanded in a radial direction, its axial length remains
substantially constant.
7. The apparatus of claim 1, wherein the second segment comprises a
plurality of radially expandable cells, each of said radially
expandable cells configured such that, as the respective cell is
expanded in a radial direction, its axial length decreases.
8. The apparatus of claim 1, wherein the second segment comprises a
plurality of radially expandable cells, each of said radially
expandable cells comprises a plurality of slanted struts configured
such that, as each cell is expanded in a radial direction, a bias
angle between the slanted struts and a longitudinal axis increases
to cause a longitudinal length of each cell to decrease.
9. The apparatus of claim 3, wherein the longitudinal length of the
second segment is selectively adjustable over a range of
longitudinal length by controlling the amount of expansion in the
radial direction.
10. The apparatus of claim 1, wherein the second segment is capable
of shrinking greater than 10% in the longitudinal direction.
11. The apparatus of claim 1, wherein the second segment is capable
of shrinking greater than 25% in the longitudinal direction.
12. The apparatus of claim 1, wherein the second segment is capable
of shrinking greater than 2 mm in the longitudinal direction.
13. The apparatus of claim 1, wherein the second segment is
configured to provide radial support so as to prevent the tubular
member from buckling inward.
14. The apparatus of claim 1, wherein said first segments includes
a plurality of hooks capable of attaching to the interior wall of
the body vessel as the corresponding first segment is expanded in a
radial direction.
15. The apparatus of claim 1, wherein each segment of the tubular
member is expandable independent of other segments.
16. The apparatus of claim 1, wherein the tubular member is coated
with a drug to treat valve regurgitation.
17. The apparatus of claim 1, wherein the tubular member is
provided with a medicinal coating to increase compatibility with a
blood vessel.
18. The apparatus of claim 1, wherein the tubular member is of
dimensions suitable to be inserted into at least one of coronary
arteries and coronary veins.
19. The apparatus of claim 18, wherein the tubular member is of
dimensions suitable to be inserted into to one of a coronary sinus,
a right coronary artery and circumflex coronary arteries.
20. The apparatus of claim 1, wherein the tubular member is a
stent.
21. The apparatus of claim 1, wherein the tubular member is
self-expanding.
22. The apparatus of claim 1, wherein the tubular member comprises
one of a shaped-memory alloy, nickel titanium, stainless steel
alloys, cobalt chrome alloys, nickel alloys and platinum
alloys.
23. The apparatus of claim 1, wherein the tubular member is
provided with visualization markers.
24. A catheter balloon comprising: a plurality of inflatable
segments, wherein a set of inflatable segments is capable of being
inflated independent of other set of inflatable segments.
25. The catheter balloon of claim 24, further comprising a
plurality of lumens, each lumen configured to inflate one or more
inflatable segments.
26. The catheter balloon of claim 24, further comprising at least
one segment capable of being partially inflated to varying degrees,
wherein when the segment is partially inflated, the segment exerts
a force on a corresponding stent segment to cause the corresponding
stent segment to partially expand.
27. A method comprising: inserting a tubular member into a body
vessel, said tubular member having at least two attachable
portions; and attaching the attachable portions of the tubular
member to an interior wall of the body vessel.
28. The method of claim 27, wherein the tubular member attached to
the body vessel prevents a portion of the body vessel from
increasing in length.
29. The method of claim 27, further comprising drawing one of the
attachable portions towards the other attachable portions to reduce
the length of a portion of the body vessel.
30. The method of claim 27, further comprising coating the tubular
member with a drug to treat valve regurgitation.
31. The method of claim 27, wherein the tubular member is placed in
a coronary sinus.
32. The method of claim 27, wherein the tubular member is placed in
a circumflex artery.
33. The method of claim 27, wherein the tubular member is placed in
a right coronary artery.
34. The method of claim 27, further comprising tightening an
annulus surrounding a mitral heart valve by reducing a longitudinal
length of the attached tubular member.
35. The method of claim 27, further comprising tightening an
annulus surrounding a tricuspid heart valve by reducing a
longitudinal length of the attached tubular member.
36. The method of claim 27, wherein the tubular member comprises at
least two traction segments having a plurality of hooks, said
traction segments expandable to seat the plurality of hooks in the
body vessel.
37. The method of claim 36, wherein the tubular member further
comprises at least one shrink segment coupled between the traction
segments, said at least one shrink segment capable of decreasing in
longitudinal length to draw one of the traction segments towards
the other traction segment.
38. The method of claim 36, wherein the drawing one of the traction
segment towards the other traction segment comprises expanding the
shrink segment in a radial direction.
39. The method of claim 27, wherein the tubular member comprises a
plurality of expandable segments.
40. The method of claim 39, further comprising selectively
expanding at least one segment of the tubular member without
expanding other segments of the tubular member.
41. The method of claim 40, further comprising adjusting a
longitudinal length of the tubular member by selectively expanding
the shrink segment in a radial direction
Description
BACKGROUND
[0001] 1. Field
[0002] Stent like structures for insertion into body vessels, and
the treatment of valve insufficiency.
[0003] 2. Background
[0004] Generally speaking, oxygenated blood travels from the lungs
to the left atrium by way of the pulmonary veins. The veins from
the systemic circuit, the venae cavae and coronary sinus carry
blood deficient in oxygen into the right atrium. The right
ventricle takes blood received from the right atrium and sends it
to the lungs, while the left ventricle takes blood received from
the left atrium and sends it to the aorta.
[0005] The atrioventricular valves between respective ones of the
atria and ventricles play important roles in the transport of blood
through the body. The atrioventricular valves open during diastole,
when the heart muscle relaxes, to allow blood to flow from the
atria into the ventricles. The atrioventricular valves close during
systole, when the heart muscle contracts, preventing the back flow
of blood into the atria and allowing blood from the ventricles to
be efficiently pumped into the lungs via the pulmonary tract and to
the rest of the body via the aorta.
[0006] The mitral valve is the atrioventricular valve that controls
blood flow from the left atrium into the left ventricle. The mitral
valve is a bicuspid valve, describing the two cusps or leaflets
that open and close the valve. The cusps or leaflets are attached
to a muscular and fibrous ring around the orifice (mitral valve
annulus) and their apices hang down into the left ventricle. When
the ventricle fills with blood and begins to contract, the valve
cusps or leaflets flow into position in the atrioventricular
opening and are forced shut (coaptate) by the increasing pressure.
To prevent the valve cusps or leaflets from turning into the left
atrium and regurgitating blood, tendinous cords, the chordae
tendineae, are attached to the free margins and ventricular
surfaces of the cusps or leaflets. At the other ends, these cords
attached to one of a respective pair of papillary muscles
projecting from the ventricular wall. By contracting, these muscles
maintain the integrity of the valve during ventricular contraction
or systole.
[0007] When the two cusps or leaflets of the mitral valve do not
completely close, there is backflow, or regurgitation of blood. The
backflow increases the pressure in the left atrium which leads to
pulmonary hypertension and dilation of the heart which are common
symptoms of congestive heart failure. A heart then has to work
harder pumping blood for the body which can lead to heart damage.
Incomplete closing of the mitral valve cusps or leaflets is common,
occurring generally in about seven percent of the population.
Conditions contributing to incomplete closure of the mitral valve
cusps or leaflets include genetic defects, infections, coronary
artery disease, myocardial infarction, or congestive heart failure.
These conditions contribute to mitral valve regurgitation resulting
from enlargement of the mitral valve annulus and/or movement of the
papillary muscles away from the valve as a result of ventricular
enlargement. When the annulus enlarges, the cusps or leaflets of
the valve are no longer able to close (coaptate), because the
distance between the two cusps or leaflets has increased too much
for the cusps or leaflets to touch each other and thus close off
blood flow to the left atrium during, for example, systole. Mitral
valve regurgitation can also result as a secondary etiology due to
the remodeling of a distorted left ventricle in ischemic heart
disease. It is known that as the ventricle is remodeled, the
papillary muscles can be displaced away from their natural
position. This displacement alters the natural tethering of the
cusps or leaflets and restricts the ability of the cusps or
leaflets to close properly at the level of the annulus.
[0008] In general, most cases of mitral valve regurgitation are
mild and the symptoms may be controlled with drugs. In more serious
cases, the mitral valve can be repaired through a procedure known
as annuloplasty, a surgical procedure in which a synthetic ring is
placed around the valve annulus. Annuloplasty encourages aptation
of the mitral valve cusps or leaflets by shrinking the size of the
valve opening. In other instances, a faulty mitral valve must be
surgically replaced with a new valve. These surgical repairs
require the opening of the chest by sternotomy or at best through
small incisions in the chest wall, heart lung bypass and stopping
the heart beat. In general, annuloplasty is an extremely invasive
procedure, and, as such, a less invasive treatment for annular
dilation is desirable.
SUMMARY
[0009] In one embodiment, an apparatus is provided for supporting
and/or constricting a surface of a valve annulus. The apparatus
includes a tubular member of dimensions suitable for insertion into
a body vessel. The tubular member includes at least two first
segments attachable to an interior wall of the body vessel. The
tubular member further includes at least one second segment which
is capable of decreasing its axial length to draw one of the first
segments towards the other first segment.
[0010] In one embodiment, the tubular member may be used to
stabilize or modify a length of a blood vessel. Representatively,
when placed, for example, in coronary arteries and/or veins, the
tubular member may be used to constrict a surface of an
atrioventricular valve annulus, such as the mitral valve annulus
that is in close proximity to the coronary arteries and/or veins.
The apparatus may also be used to constrict the tricuspid valve
annulus. The apparatus and method are useful for treating mitral
valve dilation and regurgitation, among other problems. The
apparatus may also be used to support and/or constrict other valves
or structures in a human or animal body.
[0011] In a further embodiment, a method is described. The method
includes inserting a tubular member into a body vessel and securing
attachable portions of the tubular member to an interior wall of
the body vessel. In one implementation, the tubular member secured
to the body vessel serves to prevent a portion of the body vessel
from increasing in length. In another implementation, the tubular
member secured to the body vessel serves to constrict a portion of
the body vessel by causing a length of the tubular member between
the attachable portions to be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The features, aspects, and advantages of the disclosed
subject matter will become more fully apparent from the following
detailed description and appended claims when taken in conjunction
with accompanying illustrations in which:
[0013] FIG. 1 is an illustration of an embodiment of a segmented
stent;
[0014] FIG. 2 is a close up illustration of an embodiment of
unexpanded shrink segment;
[0015] FIG. 3 is a close up illustration of expanded shrink
segment;
[0016] FIG. 4 is an illustration of an embodiment of a segmented
balloon;
[0017] FIG. 5 is an illustration of an embodiment of a segmented
balloon having segments inflated to correspond with a first group
of segments of a stent;
[0018] FIG. 5A is an illustration of a cross-sectional view of the
segmented balloon taken along line A-A' of FIG. 5.
[0019] FIG. 5B is an illustration of a cross-sectional view of the
segmented balloon taken along line B-B' of FIG. 5.
[0020] FIG. 6 is an illustration of an embodiment of a segmented
stent having a first group of segments expanded and a second group
of unexpanded segments;
[0021] FIG. 7 is an illustration of an embodiment of a segmented
balloon having segments inflated to correspond with a first group
and a second group of segments of a stent;
[0022] FIG. 8 is an illustration of an embodiment of a segmented
stent having segments of a first group and segments of a second
group expanded;
[0023] FIG. 9 is an illustration of an embodiment of a segmented
stent having a group of segments with struts angled at a 30-degree
angle;
[0024] FIG. 10 is an illustration of an embodiment of a segmented
stent having a first group of segments with struts angled at a 30
degree angle, wherein the segments are expanded;
[0025] FIGS. 11-14 are illustrations of various embodiments of a
radial traction segment;
[0026] FIG. 15 is an illustration of an embodiment of a segmented
balloon having a first group of segments inflated, and one segment
from a second group inflated;
[0027] FIG. 16 is an illustration of an embodiment of a segmented
stent having a first group of segments expanded, and one segment
from a second group expanded;
[0028] FIG. 17 is an illustration of an embodiment of a segmented
balloon having a first group of segments inflated, and one segment
from a second group partially inflated;
[0029] FIG. 18 is an illustration of an embodiment of a segmented
stent having a first group of segments expanded, and one segment
from a second group partially expanded;
[0030] FIG. 19 is an illustration of an embodiment of a segmented
balloon having a first group of segments inflated, and one segment
from a second group fully inflated after being partially
inflated;
[0031] FIGS. 20 and 21 are illustrations of balloon segments having
a range of expandability;
[0032] FIG. 22 is an illustration of an embodiment of a segmented
stent having a first group of segments expanded, and one segment
from a second group fully expanded after being partially
expanded;
[0033] FIG. 23 is an illustration of an embodiment of a human
heart;
[0034] FIG. 24 is an illustration of an embodiment of an unexpanded
segmented stent placed in the circumflex branch of the heart;
[0035] FIG. 25 is an illustration of an embodiment of a segmented
stent placed in the circumflex branch of the heart with a first
group of segments expanded;
[0036] FIG. 26 is an illustration of an embodiment of the stent
illustrated in FIG. 25 after shrink segments have been radially
expanded;
[0037] FIGS. 27A-27D are illustrations of various embodiments of a
shrink segment; and
[0038] FIGS. 28A-28C are illustrations of various embodiments of a
hooks connected to a traction segment.
DETAILED DESCRIPTION
[0039] In the following description, for purposes of explanation
and not limitation, specific details are set forth in order to
provide an understanding of the disclosed subject matter. However,
it will be apparent to one skilled in the art that the disclosed
subject matter may be practiced in other embodiments that depart
from these specific details. In some instances, detailed
descriptions of well-known methods and devices are omitted so as
not to obscure the description of the disclosed subject matter with
unnecessary detail.
[0040] In an embodiment, the apparatus and method relate to stent
100, which is illustrated in FIG. 1. In an embodiment, stent 100
includes a cylindrical body made up of a number of radial traction
segments 110 (e.g., radial traction segments 111, 112 and 113), and
one or more shrink segments 140 (e.g., shrink segments 141 and
142). Each radial traction segment contains a pattern of struts
115. In an embodiment, struts 115 may connect directly to one
another, or may be connected by links 117. Struts 115 may be
configured in a number of strut patterns, such as multi-link, duet,
pentagonal, or others. FIG. 1 shows an embodiment with zig-zag
patterned struts 115 and link 117. Stent 100 may be made of a
material suitable for residence within a blood vessel. Suitable
materials include, but are not limited to, a shaped-memory alloy,
nickel titanium, stainless steel alloys, cobalt chrome alloys,
nickel alloys and platinum alloys. Stent 100 may include one or
more therapeutic or medicinal coatings to improve its compatibility
with a blood vessel. Individual segments of stent 100 may also
include visualization markers coated thereon or embedded therein
(e.g., radiographic, magnetic resonance, etc.).
[0041] In one embodiment, stent 100 placed near a mitral valve
region may be used to deliver or release a drug or therapeutic
agent to treat mitral valve regurgitation. Various drugs are known
in the art for treating mitral valve regurgitation. For example,
administering nitroprusside (a vascular smooth muscle relaxant) may
effectively diminish the amount of mitral regurgitation, thereby
increasing forward output by the left ventricle and reducing
pulmonary congestion. Inotropic agents such as dobutamine may also
be administered to increase the force of contraction of the
myocardium. In one embodiment, the stent 100 may be coated with
these exemplary drugs for delivery near the mitral valve region.
The drugs may have timed-release features to be released slowly
over a certain period of time. The drug eluting support annulus or
other devices may also have the drug or agent dispersed on the
surface of the support annulus or other devices, or co-dissolved in
a matrix solution to be dispersed on the support annulus. Methods
to coat the support annulus with a therapeutic drug include dip
coating, spin coating, spray coating, or other coating methods
commonly practiced in the art.
[0042] In some cases, patients with defective heart valves may have
concomitant coronary artery disease (CAD). As such, it may be
advantageous for stent 100 to deliver a drug to treat occlusions in
the artery or other related CAD such as vulnerable plaque. The drug
to treat CAD may be delivered alone or in combination with drugs to
treat mitral valve regurgitation. Drugs to treat CAD include, but
are not limited to, statins, lipid lowering agents, antioxidants,
extracellular matrix synthesis promoters, inhibitors of plaque
inflammation and extracellular degradation, estradiol drug classes
and its derivatives.
[0043] In one embodiment, the drugs to treat CAD may be coated on a
stent 100 using methods such as dip coating, spin coating, spray
coating or other coating methods known in the art. The drug may
alternatively be encapsulated in microparticles or nanoparticles
and dispersed in a coating on the support annulus or other device.
A diffusion limiting top-coat may optionally be applied to the
above coatings. The active agents may optionally be loaded on a
support annulus or other device together either by adding them
together to the solution of the matrix polymer before coating, or
by coating different layers, each containing a different agent or
combination of agents. The drug eluting the stent may alternatively
have an active agent or a combination of agents dispersed in a
bioerodable annulus forming polymer.
[0044] Stent 100 is of dimensions suitable to be inserted into a
body lumen, such as the coronary arteries or coronary veins. In one
implementation, the stent 100 is of dimensions suitable to be
inserted into a right coronary artery or the circumflex branch.
After insertion, each radial traction segment 110 may be expanded
by a balloon or other known method. Upon expansion, struts 115 may
make radial contact with the inner surfaces of the body lumen so as
to maintain stent 100 in a fixed position in the body lumen.
[0045] In an embodiment, stent 100 may also include hooks 105,
which may be coupled to radial traction segments 110. The hooks 105
may be embodied in various shapes and forms. FIGS. 28A-28C
represent various hook members 105 that may be used with the stent
100. In the illustrated embodiments, the hook members 105 include
one or more sharp sections 106 provided at one end thereof. The
sharp sections 106 formed on the hook members permit the stent to
firmly attach to an interior wall of a body vessel, as the radial
traction segments are radially expanded. As shown in FIG. 28A, the
hook member 105 may also include an arm section 107 extending
between traction segment 110 and the sharp sections 106.
[0046] In an embodiment, hooks 105 are only connected to radial
traction segments 110 located at either horizontal ends of stent
100 (e.g., radial traction segment 111 and 113, respectively, in
the embodiment shown in FIG. 1). In other embodiments, hooks 105
may also be coupled to radial traction segments 110 that lie in the
interior of stent 100. Upon expansion of radial traction segments
110, hooks 105 will be seated in an inner surface(s) of the body
lumen to provide further radial traction. It is appreciated that
hooks 105 may also be coupled to segments 140 in other embodiments,
or may be attached to any structures placed at either horizontal
end of stent 100 or any structures placed between radial traction
segments 110 and/or 140.
[0047] As stated above, in an embodiment, stent 100 also includes
one or more shrink segments 140 (e.g., linear shrink segments).
Shrink segments 140 may include struts 145. Struts 145 are biased
at angles so that as shrink segment 140 is expanded, shrink segment
140 decreases in longitudinal length. When one or more shrink
segments decrease in length, the overall length of stent 100
decreases, thus constituting an inner surface of the body lumen in
which stent 100 is seated.
[0048] Various patterns may be used to construct a shrink segment.
FIGS. 27A-27D represent a number of patterns that may be used in
shrink segments 140. The shrinks segments shown in FIGS. 27A-27D
include a number of radially expandable cells. In one embodiment,
each radially expandable cell is configured such that, as the cell
is expanded in a radial direction, its axial length will decrease.
FIG. 27A is an illustration of an embodiment of the shrink segment
140, in which each radially expandable cell 172 has a square
configuration with struts disposed in slanted orientation with
respect to a longitudinal axis of the shrink segment. FIG. 27B is
an illustration of an embodiment of the shrink segment 140, in
which each radially expandable cell 174 has a diamond
configuration. FIG. 27C is an illustration of an embodiment of the
shrink segment 140 having an alternating slots pattern 176. It is
to be appreciated that the slot pattern 176 formed in the shrink
segment shown in FIG. 27C will deform as the shrink segment is
radially expanded, causing its longitudinal length to decrease.
FIG. 27D is an illustration of an embodiment of the shrink segment
140 having an alternating axial/radial slots pattern 178.
[0049] FIG. 2 is a close up illustration of an embodiment of
unexpanded shrink segment 142. FIG. 3 is a close up illustration of
shrink segment 142 following expansion (designated expanded shrink
segment 142'). Shrink segment 142 may be expanded in a radial
direction by various means, including with a balloon. In an
unexpanded state, shrink segment 142 has a longitudinal length of
SL.sub.1 and a radial height SH.sub.1. Following expansion from
SH.sub.1 to SH.sub.2 (FIG. 3), shrink segment 142' has a
longitudinal length SL.sub.2, which is less than SL.sub.1.
Accordingly, when hooks 105 have been seated, and shrink segments
140, including shrink segment 141 and shrink segment 142, are
expanded, the length of shrink segments 140 will each decrease from
SL.sub.1 to SL.sub.2. The reduction in the length of segments 140
will cause radial traction segments 110 to be pulled toward one
another, thereby reducing an overall length of stent 100. Referring
again to FIG. 2 and FIG. 3, when the radial height of shrink
segment 142 is increased by .DELTA..sub.SH (i.e., SH.sub.2 to
SH.sub.1), the longitudinal length of shrink segment 142 is
decreased by .DELTA..sub.SL (i.e., SL.sub.1 to SL.sub.2). In
embodiments, the ratio of .DELTA..sub.SL:.DELTA..sub.SH may be
varied by modifying the pattern of struts 115. As described below,
struts 115 may be designed such that the
.DELTA..sub.SL:.DELTA..sub.SH ratio is 2:1, 1:1, 1:2 or other
ratios.
[0050] Referring again to FIG. 1, in an unexpanded state, stent 100
has a total length defined as TSL.sub.1. Stent 100 can be
manufactured with a length that is suitable for insertion into a
coronary sinus or circumflex branch of the left coronary artery.
The coronary sinus and circumflex branch are positioned, in a
typical heart, exterior to the left atrium and left ventricle
approximate portions of the mitral valve annulus. Stent 100 can be
placed in one or both of the coronary sinus and circumflex branch
to inhibit the mitral valve annulus from lengthening (e.g., getting
larger in diameter). By constricting a portion of the coronary
sinus and/or circumflex branch in this area, an atrioventricular
valve annulus (e.g., mitral valve annulus) can also be constricted
to an appropriate degree. Representatively, in terms of the mitral
valve, by constricting the mitral valve annulus, cusps or leaflets
can be brought closer together to improve aptation (coaptation) and
reduce regurgitation. Additionally, the height and length of the
various segments 110 and 140 may vary so as to construct stent 100
in a shape that is tapered to conform with the particular blood
vessel or body lumen into which it is inserted.
[0051] Stent 100 may include various combinations of radial
traction segments 110 (segment 111, segment 112, and segment 113)
and shrink segments 140 (segment 141 and segment 142). For example,
in the embodiment illustrated in FIG. 1, stent 100 includes
alternating radial traction segments 110 with one shrink segment
140 disposed between each of radial traction segments 110. In other
embodiments, stent 100 could include a number of radial traction
segments 110 placed adjacent to one another, or a number of shrink
segments 140 placed adjacent to one another. It is also appreciated
that stent 100 may include various quantities of shrink segments
140. The embodiment of stent 100 illustrated in FIG. 1 includes
three radial traction segments 110 and two shrink segments 140.
However, in other embodiments, stent 100 may include only one
shrink segment 140, or more than two shrink segments 140. Stent 100
may include any number of radial traction segments 110.
Additionally, the quantity of radial traction segments 110 may be
even or odd, and the quantity of shrink segments 140 may also be
even or odd.
[0052] FIG. 4 is an illustration of an embodiment of segmented
balloon 200. In an embodiment, balloon 200 includes a number of
segments that correspond to segments of stent 100 (FIG. 1).
Representatively, in FIG. 2, balloon segments 211, 212 and 213
correspond to radial traction stent segments 111, 112 and 113 of
stent 100. Balloon segment 241 corresponds to shrink stent segment
141 and balloon segment 242 corresponds to shrink stent segment 142
of stent 100. Balloon segments 211, 212, 213, 241 and 242 may be
inflated individually, in groups, or all at once. Additionally,
balloon segments 211, 212, 213, 241 and 242 may be either partially
inflated to varying degrees or may be completely inflated. If
balloon segments 211, 212, 213, 241 and 242 are fully inflated, the
corresponding stent segments will be expanded to a first degree. In
an embodiment, if balloon segments 211, 212, 213, 241 and 242 are
partially inflated, they will exert a force on the corresponding
stent segments that will cause the corresponding stent segments to
expand to a degree that is less than the first degree.
[0053] FIG. 5 is an illustration of an embodiment of segmented
balloon 200 in which only a group of balloon segments corresponding
to radial traction segments 110 have been inflated. A suitable
balloon material is similar to dilation catheter balloons or stent
placing balloons. Balloons 200 may be inflated according to
conventional techniques, for example, suitable liquid delivered at
a proximal end of a catheter. Segments 211, 212 and 213, which
correspond to radial traction segments 110 of stent 100, may be
expanded individually, all at once, or in groups. Upon expansion,
balloon segments 211, 212 and 213 will exert force on the
respective corresponding stent segments (i.e., stent segments 111,
112 and 113), therefore causing these stent segments to expand. The
embodiment of segmented balloon 200 illustrated in FIG. 5 includes
five inflatable segments corresponding to radial traction segments
and shrink segments of the stent 100. However, in other
embodiments, segmented balloon may include any number of inflatable
segments (e.g., 1, 2, 3, 4, etc). For example, the same inflatable
segment of the balloon may be used to expand more than one segment
of the stent by deflating the inflated segment, realigning the
inflatable segment to align with another segment of the stent and
reinflating the balloon segment.
[0054] In one embodiment, the segmented balloon 200 includes a
number of lumens with separate lumens for inflating separate
balloon segments (e.g., by delivering liquid to separate segments
of the balloon). For example, as seen by referring to FIG. 5A, a
cross-sectional view of the segmented balloon taken along line A-A'
of FIG. 5 shows multiple-lumens. In the embodiment illustrated in
FIG. 5A, there are three lumens 250-252. One lumen 250 is provided
in the segmented balloon to inflated all segments 211, 212 and 213,
which correspond to radial traction segments 110 of stent 100. The
other lumens 251 and 252 are provided to inflate individual
segments 241 and 242, which correspond to shrink segments 140 of
stent 100. By providing individual lumens 251 and 252 for the
segments 241 and 242, one segment of the segmented balloon 200 may
be inflated independent of other segments of the balloon 200. FIG.
5B shows cross-sectional view of a distal end of the segmented
balloon taken along line B-B' of FIG. 5. As shown in FIG. 5B, only
one lumen 250 corresponding to the last remaining segment 213 is
provided at the distal end of the segmented balloon. In the
illustrated embodiment, three lumens 250-252 are shown; however any
number of lumens may be provided in a segmented balloon to allow
one or more segments to be inflated independent of other inflatable
segments.
[0055] FIG. 6 is an illustration of an embodiment of stent 100
after balloon 200 has been inflated in the manner illustrated in
FIG. 5. As shown in FIG. 6, upon inflation of balloon 200 in this
manner, segments 111, 112 and 113 of stent 100 will be expanded,
but segments 141 and 142 of stent 100 will not be significantly
expanded. In an embodiment, the expansion of stent segments 110
will seat hooks 105 into an inner surface of a body lumen such as
the interior wall of the coronary sinus surrounding the mitral
valve annulus to provide radial traction between stent 100 and an
inner surface of a body lumen.
[0056] FIG. 7 is an illustration of an embodiment of segmented
balloon 200 having balloon segments 241 and 242, which correspond
to linear shrink segments 141 and 142, respectively, inflated, in
addition to segments 211, 212 and 213 (See FIG. 3). As balloon
segments 241 and 242 are inflated, force is applied to linear
shrink segments 141 and 142, thus causing expansion of segments 141
and 142. FIG. 8 is an illustration of an embodiment of stent 100
after expansion of linear shrink segments 141 and 142. As discussed
above, the longitudinal length of linear shrink segments 140
reduces from a length SL.sub.1 (prior to expansion) to a length of
SL.sub.2 upon expansion. As such, upon expansion, the total length
of stent 100 is reduced by a length of R.times.(SL.sub.1-SL.sub.2)-
, where R is the total number of segments 140 that are expanded.
The total length of stent 100 following expansion of segments 140
is defined as TSL.sub.2.
[0057] In one embodiment, the linear shrink segments 141 and 142
are radially expanded one at a time. For example, after one segment
of the balloon has been inflated to radially expand one of the
linear shrink segments 141 and 142, the inflated segment of the
balloon may be deflated prior to adjustment of a different shrink
segment. It should be noted that once the catheter balloon has been
used to reduce a length of one of the linear shrink segments,
realignment of the balloon with respect to the stent (e.g., by
using visualization markers such as radiopaque markers) may be
necessary prior to adjustment of different shrink segment.
[0058] In another embodiment, two or more linear shrink segments
(e.g., segments 141 and 142) may be radially expanded at the same
time. In this embodiment, the segmented balloon may be configured
so that, as each linear shrink segment reduces in its longitudinal
length, the individual inflatable segments of the balloon will
maintain proper alignment with the individual segments of the
stent.
[0059] Referring to FIGS. 1 and 27A-27D, a shrink segment may
includes a number of radially expandable cells, in which each cell
is configured such that, as the cell is expanded in a radial
direction, its axial length will decrease. In embodiments shown in
FIGS. 1, 27A and 27B, each radially expandable cell is formed with
a number of slated struts configured such that, as each cell is
expanded in a radial direction, a bias angle between the slated
struts and a longitudinal axis increases to cause its axial length
to decrease. It is to be appreciated that, the angles between
struts 145 in linear shrink segments 140 may be biased at different
angle so as to control the degree of reduction in length of each
linear shrink segment 140 upon expansion.
[0060] Representatively, FIG. 1 illustrates an embodiment in which
the struts of each unit cell 151 are biased at 45.degree. angles
(angled .alpha.). As each unit cell 151 is expanded in the radial
direction, the bias angle between the diagonally disposed elements
and the longitudinal axis will increase, causing the longitudinal
length (L) of each unit cell 151 to decrease. Upon expansion, at a
45.degree. strut bias, the longitudinal length shrinkage: vertical
height expansion ratio for each unit cell 151 is 1:1. Specifically,
upon expansion, the reduction in longitudinal length (L) of the
individual unit cell 151 is substantially equal to the increase in
vertical height (H) of the cell 151. It should be understood that
the amount of linear shrinkage of a shrink segment is function of
the number of unit cells around the circumference of the shrink
segment and the number of unit cells in the longitudinal
direction.
[0061] In one embodiment, a shrink segment is capable of shrinking
greater than 10% in the longitudinal direction. In another
embodiment, a shrink segment is capable of shrinking greater than
25% in the longitudinal direction. For example, in one
implementation, for a shrink segment having struts biased at
45.degree. angles, a longitudinal length of 6.8 mm and a diameter
of 2 mm, an increase in the diameter of 0.5 mm will cause a 2.66 mm
reduction in the longitudinal length.
[0062] In another embodiment, illustrated by FIG. 9, struts 145 are
biased at a 30.degree. angle (angled .alpha.). Upon expansion, at a
30.degree. strut bias, the longitudinal length shrinkage: vertical
height expansion ratio for each unit cell 152 is 2:1. As such, upon
expansion, the reduction in longitudinal length (L) of the
individual cell 152 may be approximately twice the increase in
vertical height (H) of the cell 152. Accordingly, when a 30.degree.
strut bias is employed, the total length of stent 100 will be
reduced to length TSL.sub.3 that is shorter than the total length
TSL.sub.2 of stent 100 when it is shrunk with struts 140 at a
45.degree. strut bias. The bias angle is measured relative to a
longitudinal axis of the stent. It is appreciated that struts 145
may be biased at various different angles as one means of
regulating the degree of longitudinal shrinkage of stent 100.
[0063] As discussed above, in regard to radial traction segments
110, various strut designs are adequate and can be used to practice
the disclosed subject matter. In one embodiment, the traction
segments 110 are configured to maintain its axial length
substantially constant as the traction segments 110 are expanded in
a radial direction. FIGS. 11-14 represent a number of strut designs
that may be used in radial traction segments 110. FIG. 11 is an
illustration of an embodiment of radial traction segment having
struts 115 in a zig-zag pattern. In an embodiment, a radial
traction segment 100 also includes link 117. One or more struts may
be connected by link 117. FIG. 12 is an illustration of an
embodiment of radial traction segment 110 having struts in a
zig-zag pattern, and having an additional cross strut. The cross
struts tend to add to the tensile strength of the segment. FIG. 13
is an illustration of an embodiment of radial traction segment 110
having a loop pattern of struts. FIG. 14 is an illustration of an
embodiment of a stent segment having a loop pattern with an
additional cross strut. The cross struts tend to add to the tensile
strength of the segment.
[0064] In an embodiment, stent 100 and balloon 200 may be
configured to expand each linear segment 140 of stent 100
individually, in groups, or all at once. One way this may be
accomplished is through a multi-lumen balloon 200 (e.g., with
separate lumens corresponding to separate balloon segments). As
stated above, in an embodiment, segments 211, 212 and 213
corresponding to radial traction segments 110 (e.g., radial
traction segments 111, 112 and 113, respectively) are typically
first inflated to seat hooks 105. After hooks 105 have been seated,
in an embodiment, linear shrink segments 141 and 142 may be
expanded one at a time by expanding individual balloons
corresponding to each particular segment. In this regard, FIG. 15
is an illustration of an embodiment of balloon 200 in which, among
the balloon segments corresponding to linear shrink segments, only
segment 242 corresponding to a shrink segment 142 is inflated
(inflation illustrated by reference numeral 242'). Segment 241 is
not inflated and, as such, shrink segment 141 that corresponds to
balloon segment 241 will not expand. FIG. 16 is an illustration of
stent 100 following inflation of balloon 200 as illustrated in FIG.
15. Upon expansion of stent segment 142, the total length of stent
100 will be reduced from length TSL.sub.1 to length TSL.sub.4. In
an embodiment, length TSL.sub.4 will be greater than length
TSL.sub.2, which as described above, was obtained when all shrink
segments 140 were expanded at the same time, as illustrated in FIG.
8. As such, by inflating balloon segments 240 one at a time, or in
a group that does not include all balloon segments 240, the degree
of reduction in length of stent 100 will be reduced. Additionally,
in an embodiment, by inflating balloon segments 210 one at a time,
or in groups, stent 100 may be gradually reduced to size TSL.sub.1,
which is a length of stent 100 after all linear shrink segments 140
have been expanded. Balloon segments 240 may be expanded over
varying periods of time, as required by the person administering
stent 100. For example, one linear shrink segment 140 could be
expanded to introduce a first degree of reduction in the length of
stent 100. Then, a few months later (or whatever time frame is
determined to be appropriate), another balloon segment 240 may be
inflated to expand a different linear shrink 140, thereby further
reducing the total length of stent 100.
[0065] In an embodiment, balloon segments 240 may be partially
inflated so as to partially expand stent segments 140. FIGS. 17-18
are embodiments of balloon segment 242 partially inflated to a
height H.sub.1 (illustrated by reference numeral 242'). By
partially expanding stent segments 140, the degree of reduction in
the length of linear shrink segments 140 will be less than the
degree of reduction in length that is obtained when shrink segments
140 are completely expanded. In this regard, FIG. 19 illustrates
stent 100 following inflation of balloon 200 in the manner
illustrated in FIGS. 17-18. Shrink segment 142 is partially
expanded to reduce the length of shrink segment 142 to length
SL.sub.I. SL.sub.I is greater than SL.sub.2, which is the length of
shrink segment 142 upon full expansion. As a result of this
reduction in the length of linear shrink stent segment 142, the
total length of stent 110 is reduced to TSL.sub.5, which is greater
than the length of stent 110 if linear shrink stent segment 142 is
fully expanded.
[0066] As shown in FIGS. 20-21, in an embodiment, balloon segments
240 may be further inflated so as to further expand partially
expanded shrink segments 140. For example, balloon segment 242,
which, as shown in FIGS. 17-18, may be expanded to intermediate
height H.sub.1, may be further expanded to H.sub.2. Upon this
further expansion of segment 242, the corresponding linear shrink
segment will be further expanded and shrink longitudinally as shown
in FIG. 22 (illustrated by reference numeral 242"). In this manner,
the length of stent 110 may be gradually reduced. In such
embodiments, balloon segments 140 may be partially inflated, and
then further inflated any number of times so as to gradually reduce
the length of a shrink segment 140, and to gradually reduce the
overall length of stent 110. In an embodiment, balloon segments 240
may be further inflated until full expansion, thereby fully
expanding corresponding stent segments 110.
[0067] FIG. 23 is a diagram showing a top cross-section of human
heart 300 taken through the right and left atrium. Human heart 300
includes mitral valve 320 and tricuspid valve 360. Mitral valve 320
is substantially surrounded by mitral annulus 325. A portion of
circumflex branch 330 runs close (externally adjacent) to a portion
of mitral valve 320, exterior to the left atrium and left
ventricle. A portion of coronary sinus also extends close
(externally adjacent) to a portion of mitral valve 320.
[0068] FIG. 24 is an illustration of an embodiment of unexpanded
stent 100 disposed in a body lumen near a valve annulus (e.g.,
circumflex branch 330, coronary sinus, coronary artery). Unexpanded
stent 100 may be delivered to the body vessel by various delivery
methods. For example, the stent may be delivered to a desired
location within the patient's body by mounting the stent on an
expandable member, such as a balloon catheter, provided on a distal
end of an intravascular catheter and a sheath extending, for
example, from a proximal end of the catheter over the stent. A
guide catheter may be routed through a femoral artery into the
aorta and into, for example, the circumflex branch of the left main
coronary artery, possibly with the aid of a guide wire. The
intravascular catheter including the stent may then be advanced
through the guide catheter and positioned at a desired location
with, for example, a suitable visualization technique. The exterior
sheath may be retracted to expose the stent. FIG. 24 shows stent
100 mounted on intravascular catheter 350 and positioned within
circumflex branch 330.
[0069] To place a stent (such as stent 100) in the coronary sinus
from a femoral artery, a guide catheter and possibly a guide wire
may first be introduced through the inferior vena cava and into the
right atrium. One exemplary guide catheter for delivering a stent
to a desired location within, for example, a coronary sinus, is
described in a commonly-assigned U.S. patent application Ser. No.
XX/XXX,XXX, Attorney Docket No. 005618.P3546, filed Nov. 12, 2002
to Eric T. Johnson and Cindy Sherman, entitled "Guide Catheter,"
which is hereby incorporated by reference.
[0070] According to one aspect, the stent inserted into a body
lumen near a mitral valve annulus or tricuspid valve annulus serves
to support and/or constrict a surface of a valve annulus of an
antrioventricular valve. In one embodiment, the stent may be
inserted in the coronary sinus or the circumflex artery or both to
inhibit an annulus surrounding the mitral valve from lengthening.
In another embodiment, certain segments of the inserted stent are
capable of shrinking in length as they are radially expanded so
that the stent can be used to constrict a surface of a body lumen
near an antrioventricular valve annulus so as to reshape the valve
annulus. When an antrioventricular valve such as a mitral or
tricuspid valve fails to close completely, the segmented stent may
be used to constrict a surface of a body lumen near the valve
annulus so as to cause the heart valve to close properly and to
reduce the severity of regurgitation during ventricular
contraction.
[0071] FIG. 25 is an illustration of an embodiment of stent 100
after portions of the segmented stent are securely attached to an
interior wall of circumflex branch 330. In one embodiment, this is
accomplished by inflating certain segments of a catheter balloon
once the stent has been inserted into a desired location so as to
expand radial traction segments against the interior wall (see,
e.g., FIGS. 5-6 and the accompanying text). Alternatively, the
segments are secured one at a time with a balloon catheter having a
single balloon (e.g., by positioning the balloon within a radial
segment, inflating, deploying, then repositioning). When the radial
traction segments are expanded against the interior wall, hooks 105
on the radial traction segments will become securely seated to the
body lumen surface. As described above, when segments 140 are
unexpanded, stent 100 has a length TSL.sub.1. A second length
LM.sub.1 is defined as a length of a segment of surface 322 of
mitral valve 320 that is generally parallel to the portion of inner
surface 332 of circumflex branch 330 which defines TSL.sub.1. FIG.
25 shows catheter 35 retracted proximal to stent 100.
[0072] Once the stent has been securely implanted, certain segments
of the catheter balloon may be inflated so as to radially expand
one or more of the shrink segments (see, e.g., FIGS. 7-22 and the
accompanying text). By doing so, the shrink segments, which shrink
in length as they are radially expanded, will pull radial traction
segments toward one another. Certain ones of the radial traction
segments that are connected to the inner wall of the circumflex
branch 330 (for example, through seated hooks 105) will tend to
cause a length of circumflex branch 330 to constrict. The stent 100
illustrated in FIG. 25 after shrink segments 140 have been radially
expanded is shown in FIG. 26. Upon expansion of shrink segments
140, the length of shrink segments 140 collectively decrease the
length of stent 100 from TSL1 to TSL2. Seated hooks 105 constrict
inner surface 332 of circumflex branch 330, as traction segments
110 are pulled together by shrink segments 140. The constriction of
inner surface 322 of circumflex branch 320 causes vertical force,
F.sub.V, and horizontal force, F.sub.H, to be applied to surface
322 of mitral valve 330. Forces F.sub.V and F.sub.H result in
reinforcement of, and/or indirect constriction of surface 322 of
mitral valve annulus 325. According to one aspect, the constriction
of the surface of an atrioventricular valve annulus reshapes the
valve annulus so that the valve (e.g., mitral valve) closes
properly and reduces regurgitation. As such, regurgitation may be
reduced without annuloplasty.
[0073] In one embodiment, each shrink segment of the segmented
stent is configured to be reduced in length over a range of
longitudinal length, as it is radially expanded. This allows the
overall stent length to be selectively adjusted over a defined
ranged of longitudinal length. Accordingly, an operator (e.g.,
physician) may readjust the longitudinal length of the stent, after
the initial insertion, if additional constricting of an annulus
surrounding a heart valve is required. For example, a balloon
catheter (e.g., a multi-lumen balloon catheter) may be reinserted
into a patient and positioned within stent 100. Visualization
techniques may be used to properly position the balloon.
Representatively, visualization markers (e.g., radiopaque markers)
may be present on stent 100 or the balloon segments of a balloon
catheter or both. Once positioned, selected shrink segments may be
modified to constrict/expand a blood vessel (e.g., circumflex
branch 330) to reshape an antrioventricular valve annulus.
[0074] FIGS. 24 to 26 illustrate a stent structure (stent 100)
placed in a circumflex branch of the left coronary artery. It is
appreciated that a similar structure may alternatively or
additionally placed in the coronary sinus adjacent a portion of the
mitral valve annulus. It is also appreciated that the stent or
method described may be used in a variety of body lumens or
vessels, not just those adjacent atrioventricular valve annulus, to
support or constrict the body lumen or structures adjacent the body
lumen.
[0075] While the foregoing embodiments have been described and
shown, it is understood that variations and modifications, such as
those suggested and others within the spirit and scope of the
following claims, may occur to those skilled in the art to which
the invention pertains.
* * * * *