U.S. patent application number 15/595825 was filed with the patent office on 2017-11-02 for protective sheath assembly for a polymer scaffold.
The applicant listed for this patent is Abbott Cardiovascular Systems Inc.. Invention is credited to Mark C. Johnson, Annie P. Liu, Stephen D. Pacetti.
Application Number | 20170312110 15/595825 |
Document ID | / |
Family ID | 51177148 |
Filed Date | 2017-11-02 |
United States Patent
Application |
20170312110 |
Kind Code |
A1 |
Pacetti; Stephen D. ; et
al. |
November 2, 2017 |
PROTECTIVE SHEATH ASSEMBLY FOR A POLYMER SCAFFOLD
Abstract
A medical device includes a polymer scaffold crimped to a
catheter having an expansion balloon. A sheath is placed over the
crimped scaffold after crimping to reduce recoil of the crimped
polymer scaffold and maintain scaffold-balloon engagement relied on
to hold the scaffold to the balloon when the scaffold is being
delivered to a target in a body. The sheath is removed by a health
professional either by removing the sheath directly or using a tube
containing the catheter.
Inventors: |
Pacetti; Stephen D.; (San
Jose, CA) ; Liu; Annie P.; (Cupertino, CA) ;
Johnson; Mark C.; (Murrieta, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Abbott Cardiovascular Systems Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
51177148 |
Appl. No.: |
15/595825 |
Filed: |
May 15, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13924421 |
Jun 21, 2013 |
9675483 |
|
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15595825 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61L 31/14 20130101;
A61F 2250/0059 20130101; A61F 2/0095 20130101; A61F 2002/9583
20130101; A61F 2210/0004 20130101; A61F 2/82 20130101; A61L 31/06
20130101; A61F 2/97 20130101; A61L 31/048 20130101; A61F 2/962
20130101; A61F 2/966 20130101; A61L 31/148 20130101; A61F 2/958
20130101; A61F 2/95 20130101 |
International
Class: |
A61F 2/958 20130101
A61F002/958; A61L 31/14 20060101 A61L031/14; A61F 2/962 20130101
A61F002/962; A61L 31/14 20060101 A61L031/14; A61L 31/06 20060101
A61L031/06; A61F 2/82 20130101 A61F002/82; A61L 31/04 20060101
A61L031/04 |
Claims
1-15. (canceled)
16. A method, comprising: providing a tube having a lumen, and
contained within the lumen a catheter including a scaffold crimped
to a balloon, wherein a sheath constrains the scaffold; and
removing the sheath from the catheter by removing the catheter from
the tube.
17. The method of claim 16, wherein the tube extends from at least
a catheter distal end comprising the balloon to a catheter proximal
end comprising a hub.
18. The method of claim 16, wherein the scaffold and catheter are
configured for implantation within a body only after the catheter
is removed from the tube and the sheath is removed from the
scaffold.
19. The method of claim 16, wherein the tube is rigid compared to
the sheath.
20. The method of claim 16, wherein the removing the sheath step
includes engaging a first member of the tube with a second member
of the catheter, and the first member moves the second member
towards the catheter distal end when the catheter is removed from
the tube.
21. A method, comprising: using a catheter having a hub located at
a proximal end thereof and, at a distal end thereof, a scaffold
crimped to a balloon and a sheath covers the scaffold, wherein the
sheath includes a portion having an outer diameter (d1); using a
tube having a lumen, the lumen forming an inner diameter defining a
second clearance (d2) that is greater than d1, and a member
defining a third clearance (d3) that is less than d1; wherein a
substantial portion of the catheter including the distal end is
contained within the lumen; and removing the catheter from the
tube, comprising: engaging the sheath portion with the member and
then moving the member towards the catheter distal end, whereupon
the sheath is removed from the scaffold.
22. The method of claim 21, wherein the tube distal end is
separable from the tube proximal end and the proximal end comprises
the member.
23. The method of claim 21, wherein the scaffold and catheter are
configured for implantation within a body only after the catheter
is removed from the tube and the sheath is removed from the
scaffold.
24. The method of claim 21, wherein a substantial portion of the
tube lumen forms the second clearance.
25. The method of claim 21, wherein the third clearance of the tube
is between the balloon and the hub.
26. The method of claim 21, wherein the third clearance of the tube
is adjacent the hub.
27. A method, comprising: using a catheter having a proximal end
comprising a hub and a distal end comprising a balloon, wherein a
catheter portion extending from the proximal end to the distal end
is contained within a first tube; placing the catheter distal end
into a second tube; and connecting the first tube to the second
tube; wherein a scaffold is crimped to the balloon and a sheath
covers the scaffold; and wherein the first tube comprises a neck at
a proximal end adjacent the catheter hub, the neck being configured
to remove a sheath from the scaffold when the catheter distal end
is pulled through the neck.
28. The method of claim 27, further comprising crimping the
scaffold to the balloon while the catheter portion is within the
first tube lumen and before the catheter distal end is placed
within the second tube.
29. The method of claim 27, wherein the scaffold and catheter are
configured for implantation within a body only after the catheter
is removed from the tube and the sheath is removed from the
scaffold.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to drug-eluting medical
devices; more particularly, the invention relates to protective
sheaths for scaffolds and stents crimped to a delivery balloon.
BACKGROUND OF THE INVENTION
[0002] A variety of non-surgical interventional procedures have
been developed over the years for opening stenosed or occluded
blood vessels in a patient caused by the build up of plaque or
other substances in the walls of the blood vessel. Such procedures
usually involve the percutaneous introduction of an interventional
device into the lumen of the artery. In one procedure the stenosis
can be treated by placing an expandable interventional device such
as an expandable stent into the stenosed region to expand and hold
open the segment of blood vessel or other arterial lumen. Metal or
metal alloy stents have been found useful in the treatment or
repair of blood vessels after a stenosis has been compressed by
percutaneous transluminal coronary angioplasty (PTCA), percutaneous
transluminal angioplasty (PTA) or removal by other means. Metal
stents are typically delivered in a compressed condition to the
target site, then deployed at the target into an expanded condition
or deployed state to support the vessel.
[0003] The following terminology is used. When reference is made to
a "stent", this term will refer to a permanent structure, usually
comprised of a metal or metal alloy, generally speaking, while a
scaffold will refer to a structure comprising a bioresorbable
polymer and capable of radially supporting a vessel for a limited
period of time, e.g., 3, 6 or 12 months following implantation. It
is understood, however, that the art sometimes uses the term
"stent" when referring to either type of structure.
[0004] Scaffolds and stents traditionally fall into two general
categories--balloon expanded and self-expanding. The later type
expands to a deployed or expanded state within a vessel when a
radial restraint is removed, while the former relies on an
externally-applied force to configure it from a crimped or stowed
state to the deployed or expanded state.
[0005] Self-expanding stents formed from, for example, shape memory
metals or super-elastic alloys such as nickel-titanum (NiTi) which
are designed to automatically expand from a compressed state when
the radial restraint is withdrawn or removed at the distal end of a
delivery catheter into the body lumen, i.e. when the radial
restraint is withdrawn or removed. Typically, these stents are
delivered within a radially restraining polymer sheath. The sheath
maintains the low profile needed to navigate the stent towards the
target site. Once at the target site, the sheath is then removed or
withdrawn in a controlled manner to facilitate deployment or
placement at the desired site. Examples of self-expanding stents
constrained within a sheath when delivered to a target site within
a body are found in U.S. Pat. No. 6,254,609, US 20030004561 and US
20020052640.
[0006] Balloon expanded stents, as the name implies, are expanded
upon application of an external force through inflation of a
balloon, upon which the stent is crimped. The expanding balloon
applies a radial outward force on the luminal surfaces of the
stent. During the expansion from a crimped or stowed, to deployed
or expanded state the stent undergoes a plastic or irreversible
deformation in the sense that the stent will essentially maintain
its deformed, deployed state after balloon pressure is
withdrawn.
[0007] Balloon expanded stents may also be stored within a sheath,
either during a transluminal delivery to a target site or during
the assembly or in the packaging of the stent-balloon catheter
delivery system. The balloon expanded stent may be contained within
a sheath when delivered to a target site to minimize dislodgment of
the stent from the balloon while en route to the target vessel.
Sheaths may also be used to protect a drug eluting stent during a
crimping process, which presses or crimps the stent to the balloon
catheter. When an iris-type crimping mechanism, for example, is
used to crimp a stent to balloon, the blades of the crimper, often
hardened metal, can form gouges in a drug-polymer coating or even
strip off coating through interaction similar to forces at play
when the blades and/or stent struts are misaligned during the
diameter reduction. Examples of stents that utilize a sheath to
protect the stent during a crimping process are found in U.S. Pat.
No. 6,783,542 and U.S. Pat. No. 6,805,703.
[0008] A polymer scaffold, such as that described in US 20100004735
may be made from a biodegradable, bioabsorbable, bioresorbable, or
bioerodable polymer. The terms biodegradable, bioabsorbable,
bioresorbable, biosoluble or bioerodable refer to the property of a
material or stent to degrade, absorb, resorb, or erode away after
the scaffold has been implanted at the target vessel. The polymer
scaffold described in US 2010/0004735, as opposed to a metal stent,
is intended to remain in the body for only a limited period of
time. In many treatment applications, the presence of a stent in a
body may be necessary for a limited period of time until its
intended function of, for example, maintaining vascular patency
and/or drug delivery is accomplished. Moreover, it is believed that
biodegradable scaffolds, as opposed to a metal stent, allow for
improved healing of the anatomical lumen and reduced incidence of
late stent thrombosis. For these reasons, there is a desire to
treat a vessel using a polymer scaffold, in particular a
bioresorbable polymer scaffold, as opposed to a metal stent, so
that the prosthesis's presence in the vessel is for a limited
duration. However, there are numerous challenges to overcome when
developing a delivery system having a polymer scaffold.
[0009] Polymeric materials considered for use as a polymeric
scaffold, e.g. poly(L-lactide) ("PLLA"),
poly(L-lactide-co-glycolide) ("PLGA"), poly(D-lactide-co-glycolide)
or poly(L-lactide-co-D-lactide) ("PLLA-co-PDLA") with less than 10%
D-lactide, and PLLD/PDLA stereo complex, may be described, through
comparison with a metallic material used to form a stent, in some
of the following ways. Suitable polymers have a low strength to
volume ratio, which means more material is needed to provide an
equivalent mechanical property to that of a metal. Therefore,
struts must be made thicker and wider to have the required strength
for a stent to support lumen walls at a desired radius. The
scaffold made from such polymers also tends to be brittle or have
limited fracture toughness. The anisotropic and rate-dependant
inelastic properties (i.e., strength/stiffness of the material
varies depending upon the rate at which the material is deformed)
inherent in the material only compound this complexity in working
with a polymer, particularly abioresorbable polymer such as PLLA or
PLGA. Challenges faced when securing a polymer scaffold to a
delivery balloon are discussed in U.S. patent application Ser. No.
12/861,719 (Attorney docket 62571.448).
[0010] When using a polymer scaffold, several of the accepted
processes for metal stent handling can no longer be used. A metal
stent may be crimped to a balloon in such a manner as to minimize,
if not eliminate recoil in the metal structure after removal from
the crimp head. Metal materials used for stents are generally
capable of being worked more during the crimping process than
polymer materials. This desirable property of the metal can mean
less concern over the metal stent--balloon engagement changing over
time when the stent-catheter is packaged and awaiting use in a
medical procedure. Due to the material's ability to be worked
during the crimping process, e.g., successively crimped and
released at high temperatures within the crimp mechanism, any
propensity for elastic recoil in the material following crimping
can be significantly reduced, if not eliminated, without affecting
the stent's radial strength when later expanded by the balloon. As
such, following a crimping process the stent-catheter assembly
often does not need packaging or treatment to maintain the desired
stent-balloon engagement and delivery profile. If the stent were to
recoil to a larger diameter, meaning elastically expand to a larger
diameter after the crimping forces are withdrawn, then significant
dislodgment force could be lost and the stent-balloon profile not
maintained at the desired diameter needed to deliver the stent to
the target site. Consequently, sheaths for metallic stents are
often solely protective, preventing contamination or mechanical
damage to the stent and coating. They do not need to be closely
fitted to prevent stent recoil on aging and storage.
[0011] While a polymer scaffold may be formed so that it is capable
of being crimped in such a manner as to reduce inherent elastic
recoil tendencies in the material when crimped, e.g., by
maintaining crimping blades on the scaffold surface for an
appreciable dwell period, the effectiveness of these methods are
limited. Significantly, the material generally is incapable of
being worked to the degree that a metal stent may be worked without
introducing deployed strength problems, such as excessive cracking
in the material. Recoil of the crimped structure, therefore, is a
problem that needs to be addressed.
[0012] In view of the foregoing, there is a need to address the
challenges associated with securing a polymer scaffold to a
delivery balloon and maintaining the integrity of a
scaffold-balloon catheter delivery system up until the time when
the scaffold and balloon are delivered to a target site within a
body. Related to these objectives, there is a need to improve the
design and handling of a sheath assembly that is removable (prior
to implantation) without causing damage or dislodgment of the
crimped scaffold underneath. There is also a need to improve upon
sheaths for, or removal of sheaths from stents.
SUMMARY OF THE INVENTION
[0013] The invention is directed to sheaths and/or sheath
assemblies used to maintain a polymer scaffold balloon engagement
and delivery system profile as well as methods for assembly of a
medical device including a balloon expandable polymer scaffold
contained within a sheath. The invention is also directed to a
sheath and methods for applying a sheath and sheath assembly that
enables the sheath to be easily removed by a medical professional,
e.g., a doctor, so as to minimize disruption to a crimped
scaffold-balloon engagement or damage to the crimped scaffold.
Sheaths and sheath assemblies according to the invention are
removed before the medical device is introduced into a mammalian
body. The invention is further directed to sheaths and their use
with stents.
[0014] Sheaths according to the invention are particularly useful
for maintaining scaffold-balloon engagement and desired delivery
profile following a crimping process where the scaffold is crimped
down to achieve a smaller crossing-profile, or crimped diameter. A
scaffold formed at a larger diameter, near to or greater than the
intended deployed diameter, can exhibit enhanced radial strength
when supporting a vessel, as compared to a scaffold formed nearer
to a crimped diameter. A scaffold formed near to a deployed
diameter, however, increases the propensity for elastic recoil in
the scaffold following the crimping process, due to the shape
memory in the material. The shape memory relied on for enhancing
radial strength at deployment, therefore, also introduces greater
elastic recoil tendencies for the crimped scaffold. Recoil both
increases the crossing profile and reduces the scaffold-balloon
engagement needed to hold the scaffold on the balloon. In one
aspect, the invention is directed to maintaining the crossing
profile and/or maintaining balloon-scaffold engagement for
scaffolds formed near to a deployed diameter.
[0015] In another aspect, the invention is directed to a method of
assembly of a catheter that includes crimping a polymer scaffold to
a balloon of the catheter and within a short period of removal of
the scaffold from the crimper placing a restraining sheath over the
scaffold. The steps may further include applying an extended dwell
time following a final crimping of the scaffold, followed by
applying the restraining sheath. Both the crimping dwell time and
applied restraining sheath are intended to reduce recoil in the
crimped scaffold. The restraining sheath may include both a
protecting sheath and a constraining sheath.
[0016] In another aspect, the invention is directed to a sterilized
medical device, e.g., by E-beam radiation, contained within a
sterile package, the package containing a scaffold crimped to a
balloon catheter and a sheath disposed over the crimped scaffold to
minimize recoil of the crimped scaffold. The sheath covers the
crimped scaffold and may extend beyond the distal end of the
catheter to facilitate removal from the scaffold. The sheath may
extend at least the length of the scaffold beyond the distal end of
the catheter. At the distal end of the sheath there is a portion
configured for being manually grabbed and pulled distally of the
catheter to remove the sheath from the catheter.
[0017] In another aspect, a medical device is contained within a
protecting tube or coil that has a member forming a reduced
clearance within the tube lumen. The reduced clearance interferes
with a sheath disposed over the scaffold when the tube is pushed
away from a proximal catheter end or the catheter drawn out from a
proximal end of the tube. In a preferred embodiment the sheath is a
two-piece sheath including a constraining sheath and protecting
sheath portion.
[0018] In another aspect, the invention is directed to an apparatus
and methods for removing a sheath pair from a scaffold in a safe,
intuitive manner by a health professional. According to this aspect
of the invention, the sheath pair may be removed by a medical
specialist such as a doctor without risk of the scaffold becoming
dislodged from the balloon or damaged, such as when the sheath pair
is accidentally removed in an improper manner by a health
professional.
[0019] Sheaths arranged according to the invention provide an
effective radial constraint for preventing recoil in a crimped
scaffold, yet are comparatively easy to manually remove from the
scaffold. A sheath that applies a radial constraint can be
difficult to remove manually without damaging the crimped scaffold,
dislodging or shifting it on the balloon. In these cases it is
desirable to arrange the sheaths in a manner to apply an effective
radial constraint yet make the sheaths capable of manual removal in
a safe and intuitive manner. By making the sheath removal process
easy to follow and intuitive, the possibility that a health
professional will damage the medical device when removing the
sheath is reduced.
[0020] In accordance with the foregoing, there is a scaffold,
medical device, method for making such a scaffold, or method for
assembly of a medical device (such as a scaffold-balloon catheter
assembly) comprising such a scaffold having one or more, or any
combination of the following things (1)-(37): [0021] (1) A one or
two piece sheath assembly disposed over a scaffold. A sheath or
sheath portion applies a radial constraint to reduce recoil of the
scaffold. A one-piece sheath applying a radial constraint is
described in FIGS. 5 and 6A-6D of US2012/0324696. [0022] (2) Ratio
of crimped diameter to balloon nominal inflation diameter or
expanded diameter is greater than about 2, 2.5 or greater than
about 3 or 4; and/or the ratio of pre-crimp diameter to balloon
nominal diameter is about 0.9 to 1.5. [0023] (3) The catheter and
scaffold are configured as a medical device suitable for being
implanted within a body only after both a sheath disposed over the
scaffold and a tube are removed. The catheter is not configured for
being introduced into the patient until the sheath pair and/or tube
are removed. [0024] (4) A scaffold crimped to a balloon and a
sheath disposed over the scaffold. The scaffold is configured for
being introduced into a mammalian body only after the sheath is
removed from the scaffold. And means for removing the sheath from
the scaffold. The scaffold may be at least partially contained
within a tube when the sheath is being removed. The means may
include a member on the tube and/or a sheath configured for being
partially or fully removed before a protecting sheath is removed.
[0025] (5) A catheter including a sheath over a scaffold. The
catheter is within a tube. And a means for removing the sheath from
the scaffold while the scaffold is at least partially within the
tube. [0026] (6) A method of maintaining a low crossing profile or
retention between a scaffold and balloon, comprising: crimping;
dwelling to reduce recoil; placing a first sheath over the
scaffold; removing the first sheath; placing a second sheath;
wherein prior to implantation second sheath is removed [0027] (7) A
tube having a member that interferes with a sheath when the sheath
is removed from the tube. [0028] (8) The protecting sheath is a one
or two piece sheath. [0029] (9) The tube has a proximal and distal
section; the distal section can be removed from the proximal
section to facilitate crimping or inspection while the catheter
remains within the proximal section. [0030] (10) A protecting
sheath, when protecting a crimped scaffold, covers at least the
entire length of the scaffold and balloon, and may extend beyond a
distal tip of the catheter by at least a scaffold length. [0031]
(11) The protecting sheath has one or two flared, stepped or
notched ends, or no stepped or notched ends. [0032] (12) A
constraining sheath length that is less, equal to, or greater than
the protecting sheath length. [0033] (13) A method for making a
sheath includes placing a protecting sheath within a constraining
sheath, and then raising the ends of the protecting sheath when the
protecting sheath is within the constraining sheath, where the
raised ends resist removal of the constraining sheath from the
protecting sheath. The method may further include attaching a tube
to the constraining sheath to from a two-piece constraining sheath.
The constraining sheath may be longer, the same length or shorter
than the protecting sheath. [0034] (14) The sheath may comprise
PTFE, PVDF, fluoropolymer, polyethylene, polypropylene, nylon,
nylon copolymers, Pebax, polyacetal, or polyimide. [0035] (15) The
polymer comprising the scaffold is bioresorbable, or the stent
comprises a durable, non-bioresorbable, or non-bioerodible polymer.
[0036] (16) A constraining sheath has at least a first and second
portion distinguished by their outer diameters--a first outer
diameter corresponding to the first sheath portion that can apply a
radial constraining force on the scaffold, and a second outer
diameter, greater than the first outer diameter, corresponding to
the second sheath portion that is located distal and/or proximal of
the first sheath portion when the first sheath portion is disposed
over the scaffold. [0037] (17) A catheter having a sheath wherein
the sheath has a diameter greater than any other part of the
catheter, wherein the catheter when removed from a tube causes the
sheath to be removed while at least part of the catheter remains
inside the tube. [0038] (18) A tube includes a member that
interferes with a sheath constraining a scaffold when a catheter
supporting the scaffold is being removed from the tube. [0039] (19)
The member can be releasably attached to the tube, or attached to
the tube before or after the catheter is inserted into the tube.
[0040] (20) Any of the embodiments of structure forming the member
and/or tube 140 having a portion defining the diameter d3 for
interfering with constraining sheath described in connection with
FIGS. 5A-5D and 6A-6B. [0041] (21) A member is fitted to, formed
in, or attached to a tube after crimping and sheath placement;
and/or the tube has a separable distal end for access to the
balloon during crimping a sheath placement. [0042] (22) A one or
two piece tube and catheter with the tube. For the one-piece tube a
member is disposed on the tube after the catheter (with sheath over
scaffold) is within the tube. For the two piece tube the member may
be pre-disposed on the tube before the catheter including a sheath
disposed over a scaffold is placed within the tube. [0043] (23) The
member may be disposed at either the proximal or distal end of the
tube. [0044] (24) The member interferes with only a sheath disposed
over the scaffold. No other portions of the scaffold, catheter or
balloon are interfered with by the member. They may be freely
removed from the tube without obstruction. [0045] (25) An apparatus
including a sheath disposed over a crimped scaffold, the sheath and
catheter being disposed within a rigid tube, the tube's bore
defining a clearance that is substantially less than a diameter of
the sheath. [0046] (26) The scaffold may be crimped to a balloon
catheter, the catheter may be contained within a tube and the
catheter (with or without the tube) may be contained within an
E-beam sterilized package. [0047] (27) Crimping of the scaffold to
the balloon includes placing a one-piece sheath over the scaffold
and/or a two-piece sheath after crimping to reduce recoil. [0048]
(28) A method of maintaining a low crossing profile or retention
between a scaffold and balloon, comprising: crimping; dwelling to
reduce recoil; placing a first sheath over the scaffold; removing
the first sheath; placing a second sheath; wherein prior to
implantation the second sheath is removed. [0049] (29) A method of
assembly including placing a catheter within a first tube wherein
only the distal end of the catheter is outside the tube, crimping;
and attaching a second tube to the first tube to cover the distal
end. The tube may include a clearance at either distal or proximal
end. [0050] (30) A one or two piece sheath in combination with a
stent or scaffold. [0051] (31) A method for maintaining a low
crossing profile and/or retention for a polymer includes crimping a
scaffold to a balloon, placing a first sheath over the crimped
scaffold; and replacing the first sheath with a second sheath;
wherein the crimped scaffold is adapted for being passed through a
mammalian body only after the second sheath is removed. Before or
after replacing the first sheath the scaffold may be placed in a
tube adapted to remove the second sheath. [0052] (32) An apparatus
including a catheter, the catheter including including a scaffold
comprising a polymer (or a stent comprising a durable polymer or a
metal or metal alloy), the scaffold being crimped to a balloon; a
sheath disposed over the scaffold; a tube containing at least a
portion of the catheter; and a member disposed within the tube,
wherein the member partially or fully removes the sheath from the
scaffold when the tube is separated from the catheter; and wherein
the catheter is configured for being introduced into a mammalian
body only after the sheath is removed from the scaffold. [0053]
(33) The apparatus of (32) or (34) or method of (36), in
combination with one of, more than one of, or any combination in
any order of the following list of things: wherein the scaffold is
formed from a radially expanded tube having a pre-crimp diameter
that is at least about 1.5, 2, 3, or 4 times the crimped diameter
of the scaffold; wherein the member is disposed at an end of the
catheter or the tube; wherein the tube is rigid compared to the
sheath; wherein the tube extends substantially the entire length of
a shaft of the catheter; wherein the sheath includes a constraining
portion and a protecting portion, the constraining portion applying
a radial inward force on the crimped scaffold to limit recoil of
the scaffold; wherein the sheath is a two piece sheath; wherein the
sheath includes a second member that exceeds the clearance, so that
the sheath is partially or fully pulled or pushed off the scaffold
when the second member encounters the clearance; and/or wherein the
member is a clip, rim, flange or portion of the tube. [0054] (34)
An apparatus for delivery of a medical device, including a balloon
catheter including a balloon having a nominal inflation diameter; a
scaffold formed form a radially expanded tube comprising a polymer;
the scaffold being crimped to the balloon and having a crimped
diameter, wherein the balloon nominal inflation diameter is about
2, 3 or 4 times greater than the crimped diameter of the scaffold;
a constraining sheath disposed over the scaffold, the sheath being
configured for minimizing recoil of the scaffold so as to maintain
the crimped diameter; and a rigid tube containing the catheter;
wherein the catheter is adapted for being passed through a
mammalian body only after the catheter is removed from the tube.
[0055] (35) The apparatus of (32) or (34) or method of (36), in
combination with one of, more than one of, or any combination in
any order of the following list of things: wherein the scaffold has
a morphology characterized by (1) substantially radially aligned
polymer chains resulting from a biaxial expansion of the scaffold
in the radial direction by between about 200 to 400% of a
pre-expansion tube diameter, and (2) the scaffold is crimped from
the tube or pre-crimp diameter to the crimped diameter that is at
least 2-3 times reduced from the tube diameter; wherein the
scaffold is made from a polymer composition comprising PLLA;
wherein the polymer chains of the crimped scaffold are aligned
substantially in a radial direction resulting from a radial
expansion of between about 400% and 450% and axial expansion of
between 150% and 200%, or 10% and 50%; wherein the tube is
configured to partially or fully remove the sheath from the
scaffold, or partially or fully remove a sheath constraining
portion from the catheter when the catheter is withdrawn from a
proximal end the tube; and/or wherein the catheter comprises a
shaft and a hub and wherein the entire shaft is contained within
the tube. [0056] (36) A method, including the steps of providing a
tube having a lumen, and contained within the lumen a catheter
including a scaffold crimped to a balloon, wherein a sheath
constrains the scaffold; and removing the sheath from the catheter
by removing the catheter from the tube. [0057] (37) The apparatus
of (32) or (34) or method of (36), in combination with one of, more
than one of, or any combination in any order of the following list
of things: wherein the tube extends from at least a catheter distal
end to a catheter proximal end; wherein the scaffold and catheter
are configured for implantation within a body only after both the
sheath and tube are removed; wherein the tube is rigid compared to
the sheath; and/or wherein the removing the sheath step includes
engaging a first member of the tube with a second member of the
catheter.
INCORPORATION BY REFERENCE
[0058] All publications and patent applications mentioned in the
present specification are herein incorporated by reference to the
same extent as if each individual publication or patent application
was specifically and individually indicated to be incorporated by
reference. To the extent there are any inconsistent usages of words
and/or phrases between an incorporated publication or patent and
the present specification, these words and/or phrases will have a
meaning that is consistent with the manner in which they are used
in the present specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0059] FIG. 1 is a side view of a polymer scaffold-balloon catheter
assembly with a first pair of sheaths placed over the crimped
scaffold. The sheaths may be removed when the catheter assembly is
withdrawn from a protecting tube.
[0060] FIG. 1A shows a side view cross-section of a portion of the
device of FIG. 1 at a proximal end thereof, but with a first
constraining sheath replaced by a constraining sheath as shown in
FIGS. 7A-7D.
[0061] FIG. 2A is a perspective view of the sheath pair of FIG.
1.
[0062] FIGS. 2B-2D show a side view, and first and perspective
views of a protecting sheath of the sheath pair of FIG. 2A.
[0063] FIGS. 3A-3D illustrate a method of securing the sheath pair
of FIG. 2A to a distal end of the catheter assembly of FIG. 1.
[0064] FIGS. 4A-4C illustrate a method of removing a sheath of FIG.
1 from the distal end of the catheter assembly of FIG. 1. The
catheter assembly is within a tube.
[0065] FIGS. 5A-5B shows a clip before and after being attached to
the tube of FIG. 1.
[0066] FIG. 5C shows a sleeve having a flange. The sleeve is
attached to an end of a tube.
[0067] FIG. 5D shows a rim formed in a tube.
[0068] FIGS. 6A-6B depict a two-piece tube or coil having a neck
formed near a proximal end of the tube.
[0069] FIGS. 7A-7D depict aspects of a second and third pair of
sheaths for constraining and protecting a scaffold.
[0070] FIGS. 8A-8C show a sequence for removal of the sheath pairs
of FIGS. 7A-7D.
DETAILED DESCRIPTION OF EMBODIMENTS
[0071] For purposes of this disclosure, the following terms and
definitions apply:
[0072] The term "about" means 20%, 10%, 5%, 2% or 1% less or more
than a stated value, a range or each endpoint of a stated range, or
a one-sigma variation from a stated mean value. The term
"substantially" refers to at least a 30%, 20%, 10%, 5%, 2% or 1%
deviation from a value or range. For example, d1 substantially less
than d2 means d1 is at least 30%, 20%, 10%, 5%, 2% or 1% less than
d2.
[0073] The term "rigid" is a relative term used to describe
something that is substantially stiffer than some other thing. For
example, a first sheath or tube that is radially rigid, rigid in
the radial direction, or simply rigid as compared to a second
sheath or tube means that the first sheath/tube is incompressible
compared to the second sheath, or essentially does not deform when
an external, radially compressive force or pinching force is
applied as compared to the second sheath, for the same applied
load.
[0074] "Inflated diameter" or "expanded diameter" refers to the
diameter the scaffold attains when its supporting balloon is
inflated to expand the scaffold from its crimped configuration to
implant the scaffold within a vessel. The inflated diameter may
refer to a post-dilation balloon diameter which is beyond the
nominal balloon diameter, e.g., a 6.5 mm balloon has about a 7.4 mm
post-dilation diameter, or a 6.0 mm balloon has about a 6.5 mm
post-dilation diameter. The nominal to post dilation ratios for a
balloon may range from 1.05 to 1.15 (i.e., a post-dilation diameter
may be 5% to 15% greater than a nominal inflated balloon diameter).
The scaffold diameter, after attaining an inflated diameter by
balloon pressure, will to some degree decrease in diameter due to
recoil effects related primarily to, any or all of, the manner in
which the scaffold was fabricated and processed, the scaffold
material and the scaffold design.
[0075] "Post-dilation diameter" (PDD) of a scaffold refers to the
diameter of the scaffold after being increased to its expanded
diameter and the balloon removed from the patient's vasculature.
The PDD accounts for the effects of recoil. For example, an acute
PDD refers to the scaffold diameter that accounts for an acute
recoil in the scaffold.
[0076] A "pre-crimp diameter" means an OD of a tube, or the
scaffold before it is crimped to a balloon. Similarly, a "final
crimped diameter" means the OD of the scaffold when crimped to a
balloon and removed from a crimping mechanism just prior to sheath
placement. The "pre-crimp diameter" can be 2, 2.5, 3.0 times
greater than the crimped diameter and about 0.9, 1.0, 1.1, 1.3 and
about 1-1.5 times higher than an expanded diameter or post-dilation
diameter. A "partial crimp" diameter is a diameter attained after a
scaffold or segment is crimped to a diameter less than a pre-crimp
diameter and greater than the final crimp diameter. A partial crimp
diameter can be an intermediate diameter after crimping from a
pre-crimp diameter to about the nominal or over inflated diameter
of the balloon to which the scaffold will be crimped. An example of
a partial crimping diameter is described by the scaffold diameter
following "Stage II" in FIGS. 3A and 4A, and described in U.S.
application Ser. No. 13/644,347 (docket no. 62571.675). A crimping
mechanism or crimper may correspond to a linkage/mechanism
including cooperating blades or teeth configured to apply an
approximately uniform radial pressure on a scaffold to reduce its
diameter to a final crimp diameter. The crimping performed by the
crimping mechanism may include a polymer material disposed between
the teeth and surface of a scaffold; as example of such arrangement
being found in US 2012/0042501 (attorney docket 62571.448).
[0077] "Recoil" means the response of a material following the
plastic/inelastic deformation of the material and in the absence of
externally applied forces, e.g., vessel contraction. When the
scaffold is radially deformed well beyond its elastic range and the
external pressure (e.g., a balloon pressure on the luminal surface)
is removed the scaffold diameter will tend to revert back to its
earlier state before the external pressure was applied. Thus, when
a scaffold is radially expanded by applied balloon pressure and the
balloon removed, the scaffold will tend to return towards the
smaller diameter it had, i.e., crimped diameter, before balloon
pressure was applied. A scaffold that has recoil of 10% within 1/2
hour following implantation and an expanded diameter of 6 mm has an
acute post-dilation diameter of 5.4 mm. The recoil effect for
balloon-expanded scaffolds can occur over a long period of time.
Post-implant inspection of scaffolds shows that recoil can increase
over a period of about one week following implantation. Unless
stated otherwise, when reference is made to "recoil" it is meant to
mean recoil along a radial direction (as opposed to axial or along
longitudinal direction) of the scaffold.
[0078] "Acute Recoil" is defined as the percentage decrease in
scaffold diameter within the first about 1/2 hour following
implantation within a vessel.
[0079] "Axial" and "longitudinal" are used interchangeably and
refer to a direction, orientation, or line that is parallel or
substantially parallel to the central axis of a stent or the
central axis of a tubular construct. The term "circumferential"
refers to the direction along a circumference of the stent or
tubular construct. Thus, a link spaced 180 degrees from another
link means 180 degrees as measured about the circumference of the
tubular construct.
[0080] "Radial" refers to a direction, orientation, or line that is
perpendicular or substantially perpendicular to the central axis of
the stent or the central axis of a tubular construct and is
sometimes used to describe a circumferential property, i.e. radial
strength.
[0081] A polymer scaffold according to a preferred embodiment is
formed from a radially expanded or biaxially expanded extruded PLLA
tube. The degree of radial expansion (RE) and axial expansion (AE)
that the polymer tube undergoes can characterize the degree of
induced circumferential molecular and crystal orientation as well
as strength in a circumferential direction. In some embodiments the
RE is about 400% and the AE is 40-50%. Other embodiments of
processing parameters, RE and AE expansions considered within the
scope of the disclosure are found in U.S. application Ser. No.
13/840,257 filed Mar. 15, 2013 (Attorney Docket 104584.47).
[0082] The scaffold is laser cut from the expanded tube. The
diameter of the tube is preferably selected to be about the same,
or larger than the intended deployed diameter for the scaffold to
provided desirable radial strength characteristics, as explained
earlier. The scaffold is then crimped onto the balloon of the
balloon catheter. Preferably, an iris-type crimping mechanism is
used to crimp the scaffold to the balloon. The desired crimped
profile for the scaffold is 1/2 or less than 1/2 of the starting
(pre crimp) diameter of the expanded tube and scaffold. In the
embodiments, the ratio of the starting diameter or pre-crimp
diameter to the final crimp diameter may be 2:1, 2.5:1, 3:1, or
higher and the pre-crimp diameter may be about 0.9 to about 1.5
higher than the balloon nominal inflation diameter. The ratio of
pre-crimp or intermediate crimp diameter to final crimped diameter
may be greater than a ratio of expanded or post-dilation diameter
to the final crimped diameter of the scaffold.
[0083] The pre-crimp memory in the scaffold material following
crimping will induce some recoil when the scaffold is removed from
the crimper. While a dwell period within the crimper can reduce
this recoil tendency, there is residual recoil to restrain while
the scaffold awaits use. This is done by placing a restraining
sheath over the scaffold after the crimper blades are released and
the scaffold removed from the crimper head. This need to reduce
recoil is particularly evident when the diameter reduction during
crimping is high, e.g., as in above examples, since for a larger
starting diameter compared to the crimped diameter the crimped
material can have higher recoil tendencies. Examples of polymers
that may be used to construct sheaths described herein are Pebax,
PTFE, polyethylene, polycarbonate, polyimide and nylon. Examples of
restraining sheaths for polymer scaffold, and methods for attaching
and removing restraining sheaths for polymer scaffold are described
in US20120109281, US20120324696 and U.S. Pat. No. 8,414,528, and
U.S. application Ser. No. 13/708,638 (docket no. 62571.676).
[0084] FIG. 1 shows a side view of a distal portion of a
scaffold-balloon catheter assembly 2. The catheter assembly 2
includes a catheter shaft 4 and a scaffold 10 crimped to a delivery
balloon 12. As shown there are two separate sheaths 20, 30 disposed
over the scaffold 10. The scaffold 10 is contained within a
protecting sheath 20 and a constraining sheath 30, which is slid
over the outer surface of the protecting sheath 20 to position it
over the scaffold 10. Before inserting the catheter assembly 2
distal end within a patient, both the constraining sheath 30 and
protecting sheath 20 are removed by a health professional.
[0085] The sheaths 20, 30 provide an effective radial constraint
for reducing recoil in the crimped scaffold 10. Yet the sheaths 20,
30 are also easily removed by a health professional at the time of
a medical procedure by pulling or pushing the outer sheath 30
towards the distal end of the scaffold 10 and balloon 12 using a
tube, within which is the catheter assembly 2. This aspect of the
disclosure (involving a tube) is described in more detail later.
The removal technique for sheaths 20, 30 includes a similar motion
to the removal technique required for other coronary device
products, where a single, non-constraining sheath is used to cover
and protect the stent. In those cases the sheath is grasped by the
doctor or technician's gloved hands and pulled off towards the
distal end of the device. But, as described herein, a sheath that
applies a radial constraint can be difficult to manually remove
without adversely affecting the structural integrity of the medical
device. In these cases, it is desirable to arrange the sheaths so
that special handling is not required by the health professional
when the sheath is manually removed. By making the sheath removal
process easy to follow or intuitive, the possibility that a health
professional will damage the medical device by improperly removing
the sheath is reduced.
[0086] The constraint imposed by the sheaths 20, 30 maintain the
scaffold 10 at essentially the same, or close to the same diameter
it had when removed from the crimping mechanism. The sheath 30 is
tightly fit over the sheath 20 and scaffold 10 so that the radial
inward force applied on the scaffold 10 can prevent or reduce
recoil in the scaffold 10. The health professional may then remove
both sheaths at the time of the medical procedure. As such, any
potential recoil in the scaffold 10 prior to using the medical
device is minimized.
[0087] The sheath 30, although imposing a tight fit on the scaffold
10 (through sheath 20), can be easily removed by a health
professional without risk of the scaffold 10 being accidentally
pulled off of the balloon 12. This may be done in a number of ways
according to the disclosure; at least one of the ways based on the
manner in which the sheath 20 is positioned and removed from the
scaffold 10. If there are excessive pulling forces on the scaffold
10 when sheaths are removed, the catheter shaft 4 may be damaged,
the scaffold 10 may dislodge from a balloon 12, or shift on the
balloon 12; thereby reducing scaffold-balloon engagement relied on
to hold the scaffold 10 to the balloon 12.
[0088] When the scaffold 10 is constrained by sheath 30, as in FIG.
1, the constraining sheath 30 is located over the section of the
protecting sheath 20 where the crimped scaffold 10 is found. This
sheath 30 is made from a polymer tube material having a thickness
and pre-stressed inner diameter size suitably chosen to cause the
sheath 30 to apply a radially inward directed force on the scaffold
10. The thicker the tube and the smaller the pre-stressed inner
diameter size for the sheath 30 the higher this constraint will be
on the scaffold 10. However, the sheath 30 thickness should not be
too thick, nor its inner diameter too small as this will make it
difficult to slide the sheath 30 over, or remove the sheath 30 from
the scaffold 10. If excessive force is needed to reposition the
sheath 30, the scaffold 10 can dislodge from the balloon 12 or the
scaffold 10 and catheter shaft 4 can become damaged when the sheath
30 is moved.
[0089] If only sheath 30 were applied, i.e., the sheath 20 is not
present, the amount of preload that the sheath 30 could apply to
the scaffold 10 without affecting scaffold-balloon engagement would
be limited. However, by introducing the protecting sheath 20
between the scaffold-balloon surface and sheath 30 the sheath 30
can impose a higher preload on the scaffold 10 without risk to the
integrity of the scaffold-balloon engagement when the sheath 30 is
applied to and/or removed from the scaffold 10. The protecting
sheath 20 therefore serves to protect the integrity of the
scaffold-balloon structure as the sheath 30 is repositioned
relative to the scaffold 10. An example of a one-piece sheath that
is capable of performing in a similar manner is found in
US2012/0324696 at FIGS. 5 and 6A-6D.
[0090] The protecting sheath 20 extends over the entire length of
the scaffold (as shown) and beyond the distal tip of the catheter
assembly 2 (as can be seen in FIG. 3B) may the sheath 20 extend.
The protecting sheath 20 is preferably formed from a unitary piece
of polymer material, which is shaped to form differently sized
portions 22, 24 and 25 for protecting the scaffold/balloon
10/12.
[0091] At the distal end 20b of sheath 20 there is a raised end 22
in the form of a cylinder section having a larger diameter than the
body portion 21 of the sheath 20 to the right of end 22 which
covers the scaffold 10 in FIG. 1. Raised end 22 provides an
abutting surface with respect to distal movement of sheath 30,
i.e., end 30b of sheath 30 abuts end 22 when sheath 30 is moved to
the left in FIG. 1. End 22 may alternatively take the shape of a
cone with the largest diameter end of the cone being the most
distal end of the sheath 20. The raised end 22 may function to
remove the sheaths 20, 30, as explained below.
[0092] The protecting sheath 20 has a cut 26, extending from the
proximal end 20a to a location about at the distal the tip of the
catheter assembly 2 (or sheath 20). The cut 26 forms an upper and
lower separable halve 28, 29 of the sheath 20 (FIG. 2D). These
halves 29, 28 are configured to freely move apart when the sheath
30 is positioned towards the distal end 20b. The location 26a may
be thought of as a living hinge 26a about which the upper half 29
and lower half 28 of the sheath 20 can rotate, or deflect away from
the scaffold 10. When sheath 30 is moved distally of the scaffold
10 in FIG. 1, the halves 28, 29 will tend to open up naturally, due
to the preload applied by sheath 30 near hinge 26a (the separable
halves 28, 29 can be more clearly seen in FIGS. 2A-2D). This
arrangement for halves 29, 28 provides easy removal of sheath 20
from the scaffold 10, with minimal disruption to scaffold-balloon
structural integrity, after sheath 30 is moved towards distal end
20b. When sheath 30 is being fitted over the scaffold 10 or removed
from the scaffold 10, the presence of the halves 28, 29 prevent
direct contact between the sliding sheath 30 and the surface of the
scaffold 10.
[0093] Sheath 20 may alternatively be formed as two completely
separable halves, e.g., as halves 145a and 140a illustrated in FIG.
11C of US2012/0324696 or as the same two halves shown in FIG. 2 but
with the cut 26 running the length of, or substantially the entire
length of the sheath 20. In the case of the former sheath 20
embodiment, sheath 150 of FIG. 11C of US2012/0324696 is replaced by
the sheath 30 illustrated in FIG. 1 or other suitable embodiments
thereof, discussed more fully below.
[0094] FIG. 1A shows a proximal end 20a of sheath 20 with another
embodiment of a constraining sheath--an outer sheath 230 (see FIGS.
7A-7C)--disposed over the sheath 20. Referring to FIG. 1A, at the
proximal end 20a there are portions 24 and 25 formed when the
combined proximal ends of halves 28, 29 are brought together as in
FIG. 1. When the halves 28, 29 are brought together notch portion
25 and raised (or stepped) portion 24, similar to end 22, are
formed. The notched portion 25 has an outer diameter less than the
inner diameter of the portion 21 of the sheath 30/230 that covers
the scaffold 10, as well as the outer diameter of the
scaffold/balloon 10/12. The raised portion 24 has a diameter
greater than the body portion 21, which refers to the inner
diameter of the sheath 30 or sheath 230 in FIG. 1A and the diameter
for end 24 may be the same as the diameter for end 22. The raised
portion 24 provides an abutment or stop 24a preventing a proximal
end 30a of the sheath 30/230 from moving to the right in FIG. 1.
The portion 24 may prevent the sheath 30/230 from sliding off of
the scaffold 10 and/or locate the portion of end 30a of sheath
30/230 relative to sheath 20 proximal end 20a so that sheath 30/230
applies a uniform compressive force over the entire length of the
scaffold. A compressive portion of the sheath 30/230 (discussed
below) has a length about equal to the length of the portion 25
plus the scaffold/balloon length so that when end 30a abuts end 24
the sheath 30 will properly cover the entire scaffold/balloon 10/12
length.
[0095] Portion 25 discourages removal of the sheath 20 prior to
removal of sheath 30 from the scaffold 10. Referring again to FIG.
1A, there is a close-up of the proximal end 20a with the sheath 230
(shown in phantom) replaced by the inwardly directed preload F30 it
applies to sheath portion 21 when positioned over the scaffold 10.
A distal end of portion 25 forms a ledge 25a. When sheath 30 is
positioned over the scaffold 10 the inwardly directed preload F30
applied to sheath portion 21 urges the halves 29, 28 together. With
the halves 28, 29 urged together, the scaffold/balloon proximal end
14a blocks movement of the sheath 20 to the left in FIG. 1A by
interfering with the movement of the ledge 25a to the left. Thus,
if a user attempts to pull the sheath 20 off prior to removing the
sheath 230/30 from the scaffold 10 area (which can damage the
scaffold/balloon integrity or catheter shaft 4), there will be
resistance to this movement due to the ledges 25a abutting the
balloon proximal end 14a (the ledge 25a thus may be thought of as
an interference or interfering ledge part of the sheath 20). This
resistance should indicate to the user that the sheaths 20, 30/230
are being removed in an improper manner. When the sheaths 20,
30/230 are removed properly, the first sheath 30 is moved to the
distal end 20b of the sheath 20 (thereby removing the preload F30)
so that the halves 28, 29 freely open up to allow the ledge 25a to
easily pass over the scaffold 10 so that sheath 20 is removed
without resistance. The user is thereby informed that the sheath 20
is removed properly when there is no resistance to removing the
sheath 20 from the balloon-catheter assembly 2.
[0096] Thus, scaffold-balloon integrity is protected by the
presence of the halves 28, 29 and the notched portion 25, as
discussed above. The extended length of sheath 20, beyond the tip
of the catheter assembly 2, e.g., is about equal to a length of the
scaffold 10, the length of the sheath 30 or greater than both. This
length beyond the distal tip facilitates an intuitive sliding
removal or attachment of the sheath 30 from/to the scaffold 10 by
respectively sliding the sheath 30 along the sheath 20 extension
that is beyond the distal tip of the catheter assembly 2. The
length of the sheath 20 that extends beyond the distal end of the
catheter assembly 2 (length L21 in FIG. 4A of US2012/0324696) may
depend on the choice of sheaths used. For example, from the
perspective of the health professional removal process, if the
sheath 20 is more stiff (e.g., higher wall thickness and/or
modulus) relative to the sheath 30 then the length beyond distal
end 4 for sheath 20 may be longer so that the halves 28, 29 of
sheath 20 can be more safely displaced from the scaffold 10 by
clearing the sheath 30 more distally of the scaffold 10. If the
sheath 30 wall thickness and/or modulus is higher relative to
sheath 20 than the length may be shorter since the sheath 30 will
tend to naturally open up the halves 28, 29 as it is moved distally
of the distal tip of the catheter assembly 2. Also, a thicker or
higher modulus sheath 20 and/or sheath 30 may be desirable to
increase the resistance to improper removal of sheath 20, e.g., as
when a user attempts to remove sheath 20 with, or before removing
sheath 30 from the scaffold 10 (as discussed earlier).
[0097] In a preferred embodiment the constraining sheath is made
with a portion having a diameter greater than the diameter of other
portions of the constraining sheath. When sheath 30 is positioned
on a scaffold, as in FIG. 1, member 130 may define a diameter
substantially greater than any other diameter along the length of
the catheter portion received within a protecting tube or coil.
[0098] In one example, adjacent to, or at proximal end 30a of
sheath 30 in FIG. 1 there is a raised portion 130 having a diameter
d1. The diameter d1 is selected so that the sheath 30 is engaged
by, or makes contact with a member disposed on a tube (or coil)
when the catheter assembly 2 is being removed from the tube, as
illustrated in FIGS. 4A-4C (discussed in more detail below). The
portion 130 may be formed from the same material as sheath 30,
e.g., start with a tube of diameter d1 and reduce or step-down to
the diameter of the constraining portion of sheath 30 (FIG. 1)
while leaving portion 130 at the original diameter d1. The portion
130 may be raised, flared out, or frusto-conical in shape, or a
separate piece attached to the sheath 30 to form 130. The length of
portion 130 may be such that when end 30a is abutting portion 24
the entire scaffold is receiving a uniform compressive force. In
this regard, for a portion 130 formed by a flared out or raised
in/out portion of the same tube used to form sheath 30, the portion
130 is proximal of the sheath 30 so that a uniform compressive
force is applied over the entire length of the scaffold 10. In
other embodiments--e.g., a welded annular piece forming the
diameter d1, or 2, 3, 6, circumferentially-spaced tabs each forming
an extent for sheath 30 equal to d1 when attached to the outer
surface of sheath 30--the portion 130 may be located over the
scaffold when sheath 30 is constraining the scaffold without
affecting the radial compressive force anywhere over the scaffold
length.
[0099] Referring to FIGS. 2B-2D, there are shown various views of
the sheath 20. FIG. 2A shows the sheath 20 with the sheath 30. The
constraining portion of sheath 30 referred to earlier, may have the
length L30 such that sheath 30 applies a sufficiently uniform
radial inward force or preload on the scaffold 10 when end 30a
abuts end 24a (FIG. 1A). The length L30 is slightly greater than
the length of the scaffold-balloon structure. The sheath 30 can be
slid towards or away from the scaffold location (i.e., its location
in FIG. 2A or FIG. 1) over the sheath outer surface 20. As noted
earlier, the sheath 20 has separable upper and lower halves 29, 28
formed by a cut 26 made across the tube forming sheath 20. FIG. 2D
is a perspective view of the upper and lower halves 28, 29
separated from each other. As can be appreciated from this view,
the halves 28, 29 rotate about the hinge 26a when they separate.
FIGS. 2B and 2C show an additional side and perspective view,
respectively, of the sheath 20 showing the aforementioned
structure, including the portions of notched or stepped portion 25
and end 24 (FIG. 1A) discussed earlier.
[0100] The length L20 in FIG. 2C may extend over the scaffold 10
length as well as a sufficient distance beyond the scaffold 10 so
that the sheath 30 can be pushed onto the scaffold 10, and removed
from the scaffold 10 while the halves 28, 29 are disposed over the
scaffold 10. The length L20 may be at least twice the length of
sheath 30, i.e., L20=2*L30, to achieve this purpose. This length
should be sufficient to allow the upper and lower halves 28, 29 to
peel or rotate about the living hinge 26a and freely away from the
scaffold surface (as in FIG. 2D) without interference from the
sheath 30 when sheath 30 abuts end 22.
[0101] As mentioned earlier, a thicker tube and smaller inner
diameter for sheath 30 will cause the sheath 30 to apply a greater
pre-load on the scaffold 10. The sheath 30 thickness and/or inner
diameter size is selected with the sheath 20 in mind. That is, the
sizing of one can determine what sizing to use for the other, based
on achieving an appropriate balance among the amount of pre-load
desired, the ease in which the sheath 30 can be placed over or
removed from the scaffold 10 location, increasing resistance to
improper removal of sheath 20 (ledge 25a abutting proximal end 14a,
as discussed above) and avoiding disruption to the integrity of the
scaffold-balloon structure, e.g., pulling the scaffold 10 off the
balloon when the sheath 30 is being removed. For example, if a
relatively thin and/or low modulus tube is used for sheath 20 (as
compared to sheath 30), the sheath 30 will impose a higher
localized pre-load on the scaffold 10. And the scaffold 10 is more
likely to be affected by sheath 30 movement because the sheath 20
easily deforms under the movement of the sheath 30. If the sheath
20 is made thick and/or a higher modulus tube material is used for
sheath 20 (compared to sheath 30) the scaffold 10 will not be as
affected by movement of the sheath 30. And local changes in
pre-load on the scaffold 10 will tend to be lower since the sheath
20 does not deform as easily under the movement of the sheath
30.
[0102] Referring to FIGS. 3A-3D, methods of assembly of a medical
device according to some aspects of the disclosure are now
described. The medical device, in its assembled state according to
some aspects of the disclosure, includes the scaffold crimped to a
balloon catheter, the two piece sheath disposed over the scaffold
as in FIG. 1, and the catheter being contained within a protecting
tube. The aspects of the protecting tube (or coil) are discussed in
greater detail below in connection with FIGS. 4A-4C, 5A-5D and
6A-6B.
[0103] The catheter assembly 2 with sheaths arranged as in FIG. 1
and contained within a protecting tube is packaged and sterilized.
At the time when the catheter assembly is to be used in a medical
procedure the package is opened and the tube and sheath pair
removed. According to another aspect of the disclosure the catheter
assembly 2 is not configured for being introduced into the patient
until a sheath or sheath pair, e.g., sheath 30/230, is removed.
Examples follow.
[0104] After (or before) placing the catheter within the tube, and
before the sheaths 20/30 are placed, the scaffold 10 is crimped to
the balloon 12 of the catheter assembly 2 using a crimping
mechanism. As noted above, for a polymer scaffold the diameter
reduction during crimping may be 2:1, 2.5:1, 3:1, 4:1 or higher.
The scaffold may be placed on a balloon having a nominal, expanded
or post-dilation diameter that is about 2, 2.5., or 3 times the
diameter of the scaffold when the scaffold has a final crimp
diameter on the balloon.
[0105] The diameter reduction (from a pre-crimp size to the final
crimp diameter) introduces high stresses in the scaffold structure.
The memory in the material following crimping causes recoil of the
scaffold structure, as discussed earlier; one can incorporate
lengthy dwell times within the crimper, e.g., after the final crimp
step, to allow stress-relaxation to occur in the structure while
heated crimper blades are maintaining a fixed diameter and
temperature to facilitate stress relaxation. Both the dwell period
and the imposition of a constraining sheath over the crimped
scaffold after crimping helps to reduce recoil after crimping.
Crimping of the scaffold 10 to the balloon 12 including desirable
dwell times and temperatures that can affect stress relaxation and
recoil after crimping are disclosed in U.S. patent application Ser.
No. 12/861,719 (docket no. 62571.448), U.S. patent application Ser.
No. 13/089,225 (docket no. 62571.517) and U.S. patent application
Ser. No. 13/107,666 (docket no. 62571.522).
[0106] Following removal from a crimping mechanism the scaffold
will recoil unless subject to a radial constraint. According to one
aspect of the disclosure a temporary one-piece sheath is placed on
the scaffold immediately following crimping, then replaced by the
sheath of FIG. 1 after about 1/2 hour from removal from the
crimping mechanism. Examples of the one-piece sheath according to
the disclosure is one-piece sheath 23 described in U.S. application
Ser. No. 13/708,638 (docket no. 62571.676).
[0107] The sheath pair 20/30 may be attached as follows. The sheath
pair, shown in FIG. 3A, is placed on a mandrel 8 before being
attached to the catheter assembly 2. The mandrel 8 is passed
through the catheter shaft 4 guidewire lumen (not shown), and exits
at the distal end of the catheter assembly 2. The sheath pair is
then placed on the mandrel 8 distally of the catheter assembly 2.
The mandrel 8 may then be used to guide the sheath pair over the
scaffold-balloon 10/12 as illustrated in FIGS. 3B-3D.
[0108] Referring to FIG. 3B, the distal end 30b of the sheath 30 is
adjacent to the raised end 22 of the sheath 20. In this
configuration the halves 28, 29 can freely open or close. The
sheath pair is then brought towards the scaffold-balloon 10/12. The
halves 28, 29 easily deflect over the scaffold-balloon 10/12. The
sheath pair may be slid towards the scaffold-balloon 10/12 as
follows. Holding the catheter assembly 2 stationary, grasping the
mandrel 8 with one hand and the sheath pair with the other hand and
sliding the sheath pair over the mandrel 8 until the halves 28, 29
are located over the scaffold-balloon 10/12 as shown in FIG. 3C.
When properly positioned, the portions 24, 25 are positioned with
respect to proximal end 14a as shown in FIG. 1A.
[0109] Referring to FIGS. 3C-3D, once the halves 28, 29 are located
properly over the scaffold-balloon 10/12 to protect this structure,
the constraining sheath 30 can be pushed over the scaffold-balloon
10/12 (as indicated in FIGS. 3C-3D by P). The sheath 30 may be
pushed over the scaffold-balloon 10/12 in the following manner. The
raised end 22 and mandrel 8 are grasped with one hand to hold the
two stationary. Then, using the other hand the sheath 30 is pushed
over the scaffold-balloon 10/12 until the end 30a of sheath 30 is
disposed adjacent to, or abuts the raised end 24 of the sheath 20,
which indicates the proximate location of the proximal end 14a
(FIG. 1A) of the balloon-scaffold 10/12. Alternatively, the portion
24 and catheter shaft 4 may be simultaneously held with on hand,
while the sheath 30 is pushed towards the scaffold 10 with the
other hand. By grasping the portion 24 with the catheter shaft 4,
the halves 28, 29 are held in place relative to the scaffold 10
while the sheath 30 is being pushed over the scaffold 10.
[0110] With the sheath positioned over the scaffold as in FIG. 1,
the catheter is placed within a tube or coil. The tube or coil,
which may be rigid compared to the catheter shaft, protects the
catheter during shipment/delivery and storage. When the packaged
and sterile medical device is received by a health professional, it
may be enclosed within a rigid tube to protect the contents inside
from damage.
[0111] According to another aspect of the disclosure, the tube or
coil is fit with, or includes a member for removing a sheath or
sheaths from the scaffold as the catheter is removed from the tube
or coil. More generally, there is a structure including a tube and
a member that interferes with a sheath constraining a scaffold when
a catheter supporting the scaffold is being removed from the
tube.
[0112] Referring to the example of FIG. 4A-4C, there is shown a
sequence of events during removal of the catheter 2 from a tube
140. The tube has a clearance d2, which is larger than the diameter
d1 of the member 130. As such, for the tube 140 having a clearance
d2 everywhere long the tube's lumen, the catheter freely slides
along the tube without interference from the tube. According to
another aspect of the disclosure a member 152 interferes with the
catheter 2 removal from the tube 140, resulting in one or more
sheaths being removed from the scaffold 10 when the catheter 2 is
removed from the tube 140. The member 152 (described in greater
detail below) forms a reduced clearance d3, which is less than d1
and d2.
[0113] A member may be disposed near a proximal or distal end of a
tube or catheter. Preferably, the member 152 is located near the
catheter proximal end (i.e., adjacent the catheter hub) when the
catheter is within the tube 140. Referring again to FIGS. 4A-4C,
during its removal sequence the catheter 2 is withdrawn from the
tube 140 proximal end (not shown) or the tube 140 pushed towards
the catheter 2 distal end while the catheter proximal end is held.
In either case, the member 152 is eventually is brought near the
member 130 of sheath 30 and begins to push sheath 30 towards a
distal end of sheath 20 or the distal end of the catheter 2. FIG.
4C shows the sheath 30 displaced to the left and almost completely
removed from the scaffold 10. This action leaves only the inner
sheath 20 halves 28/29 remaining over the scaffold 10. After the
catheter 2 has been removed from the tube 140 the sheath 20 may be
easily removed from the scaffold 10 (since sheath 20 does not apply
a compressive force on the scaffold 10). In the case of a raised
end 22 for sheath 20, FIG. 1, the continued movement of sheath 30
to the left in FIG. 4C by member 152 may also remove sheath 20 from
scaffold 10 (as explained in greater detail in connection with
FIGS. 4A-4C of U.S. Pat. No. 8,414,528). Alternatively, the sheath
20 can be partially or fully maintained in its position over the
scaffold 10 after removal of the catheter from the tube 140. And
the sheath 30 may be partially retained on the sheath 20 and/or the
catheter after removal from the tube 140. Thus, after the catheter
is removed from the tube, the sheaths 20/30 may be fully or
partially removed from the scaffold 10 and/or catheter.
[0114] Embodiments of structure defining clearance d3 for
interfering with a sheath are now described in connection with
FIGS. 5A-5D and 6A-6B.
[0115] Referring to FIGS. 5A-5B, a clip 150 is placed near a
proximal end of the tube 140. The clip may be formed by two halves
150a, 150b connected to each other through a living hinge 153. Each
half 150a, 150b has a protrusion 152. The tube 140 is modified to
provide two opposite through-holes 143 for passage of protrusions
152 into the bore of the tube 140 when the clip halves 150a, 150b
are brought together, as illustrated in FIGS. 5A-5B. There is a
clearance d3 between the ends of the protrusions 152. The clip may
be held together by a fastener 156, such as adhesive, ultrasonic
welding, solvent bonding, tape, cable tie or tie wrap.
[0116] Referring to FIG. 5C there is a sleeve 150' that has an
inner flange 152'. The flange forms a reduced clearance d3. The
inner surface of the sleeve 150' is sized to snugly receive the
tube 140 so that the proximal end abuts the flange 152'. The sleeve
150' may be fastened to the proximal end of the tube 140 to provide
the member in the tube 140 for interfering with the removal of the
catheter 2 from the tube; that is, removing at least sheath 30 from
the scaffold 10. The catheter 2, prior to crimping or prior to
sheath placement, is fed into the end of sleeve 150' with tube 140
fitted at the opposite end of sleeve 150'.
[0117] Referring to FIG. 5D a rim 150'' forming an inner surface
152'' may be formed in the tube 140. The inner surface 152''
provides a decrease in clearance from d2 to d3 near the proximal
end of the tube 140. The rim 150'' is formed by re-shaping an end
of a tube having an inner diameter d2. Such reshaping may be
accomplished by swaging or applying a combination of heat and
pressure.
[0118] FIGS.6A-6B depict aspects of a tube 160 for receiving the
catheter 2 according to another aspect of the disclosure. In one
respect the tube 160 provides another embodiment of structure
forming the member for interfering with a sheath. Referring first
to FIG. 6B, which refers to the proximal end 165 of the tube 160,
the diameter is stepped down from d2 to d3. The d3 clearance may
extend over a length L (L can be about less than or equal to the
length of the sheath 30/230) to provide a narrowed passage or neck
150''' with clearance d3 between walls 152'''.
[0119] Referring to FIG. 6A the tube 160 is formed by a first tube
portion 160a, which includes the proximal end 165 of the tube 160,
and a second tube portion 160b, which includes the distal end 166
of the tube 160. The portions 160a and 160b are separate pieces of
the tube 160. A sleeve, tape or clip 168 may be used to fasten the
two pieces together. When the catheter and scaffold (radially
constrained by a sheath) are assembled the catheter shaft and
distal end portion are contained within the tube 160. The handle or
hub portion of the catheter (not shown) is external to the tube 160
and adjacent the tube 160 proximal end 165. As indicated in FIG. 6A
the neck 150''' is located near the proximal end 165. The catheter
is removed from the tube 160 by pulling the handle or hub portion
(e.g., the catheter portion having a steering and/or lumen pressure
control) away from the tube proximal end 165 or pushing the tube
towards the catheter distal end. In either case the neck 150'''
interferes with a sheath, constraining sheath or outer sheath,
e.g., sheath 30, but not any other portion of the catheter.
[0120] Tube 160 has a separable piece 160b for purposes of
processing or assembly of the catheter distal end while the
remaining portion of the catheter is contained within the tube
portion 160a. The portion 160b of the tube 160 has a length at
least equal to the length of the catheter distal portion including
the balloon. With the portion 160b detached from the portion 160a
an operator may have free access to the balloon 12 for crimping,
inspection and/or affixing one or more sheaths to the crimped
scaffold without having to remove the remainder of the catheter
from the tube 160. As such, a majority of the catheter may remain
within the protective tubing configured to a remove a sheath,
thereby preventing inadvertent damages to the catheter shaft during
processing, while a distal end including a scaffold and balloon may
be inspected, a scaffold crimped to a balloon and a sheath placed
over the scaffold.
[0121] The operator may place the sheath, e.g., sheath 20/30,
having a member defining the d1 diameter on the crimped scaffold
while the catheter remains in the tube portion 160b. After
attaching the sheath, e.g., sheath 20/30 of FIGS. 1-2, to the
scaffold, the portion 160b may be affixed to the portion 160a using
the sleeve 168. If the detachable portion 160b were not provided,
then the catheter could not be placed within the tube 160 since the
neck 150''' defining clearance d3 would disrupt the constraining
sheath when the catheter is placed within the tube. For a one-piece
tube the structure 150, 150', 150'' or 150''' may be fitted to,
formed in, or attached, respectively, to the tube after crimping
and sheath placement (since the hub, handle or handle portion of
the catheter is fixed at the proximal end of the shaft, the
catheter shaft may only be placed within the tube from the tube
proximal end 165). According to the embodiment of FIG. 6A, the neck
150''' may be formed in the tube and catheter placed within the
tube 160 prior to crimping and sheath placement. After sheath
placement the portion 160b can be re-attached.
[0122] With reference to FIGS. 7A-7D and FIGS. 8A-8C, now described
are sheaths according to other aspects of the disclosure.
[0123] Referring to FIGS. 7A-7C, as an alternative to sheath 20/30
depicted in FIGS. 1-2 and described earlier, a modified sheath 230
replaces the sheath 30. Sheath 230 differs from sheath 30 in the
following manner. Sheath 230 does not include the member 130 and
sheath has an expanded portion that may be gripped by a user
without also pulling on the protecting sheath 20 during sheath
removal. The sheath 20/230 (FIGS. 7A-7B) facilitates a more safe
removal of the constraining sheath by preventing, prior to, or
current with, removal of the sheath 230 the protecting sheath 20.
Removing both sheaths at the same time can damage the scaffold or
catheter, as discussed above. The preferred removal is to remove
sheath 20 only after a constraining sheath 230 has cleared the
scaffold.
[0124] By providing the extension 240 having a length L240 (as
opposed to sheath 30 having a total length L30) a user is
discouraged from gripping the sheath 20, since the extension 240 is
disposed over about the entirety of sheath 20 (thereby making it
difficult to pull on sheath 20 directly). The sheath 230 includes a
portion 240 and 235. The portion 240 may have a larger outer
diameter than the portion 235. The sheath 230 may be formed from a
single tube with diameter of the portion 240. The portion 235 is
formed as stepped-down part of the tube 230 and has length L30. The
portion 235 applies the radially compressive force on the scaffold
10. The total length of the sheath 230 is L230, which is equal to
the sum of L30 and L240. The length L230 may be about or slightly
less than the length of sheath 20, such that both ends 24 and 22 of
sheath 20 are visible when sheath 230 is disposed over sheath
20.
[0125] A method of removal of the sheath 20/230 from the scaffold
10 is now described. At the time when the catheter assembly is to
be used in a medical procedure the package is opened and the sheath
pair removed from the distal end. The catheter assembly 2 is not
configured for being introduced into the patient until the sheath
pair is removed. FIG. 8A depicts the arrangement of the sheaths 20,
230 at the distal end of the catheter assembly 2 when the packaged
and sterile medical device is received by a health professional.
Examples of such sterile packaging is found in U.S. patent
publication no. US 2008-0010947 (docket no. 62571.60). The sheath
20 and portion 240 may extend well-beyond the distal end of the
catheter 2 assembly such that they overhang the catheter distal end
by about the length of the scaffold or length L30. These
overhanging portions are provided to facilitate an intuitive
removal of the sheath pair by a health professional, thereby
reducing the chances that the sheath pair are removed
improperly.
[0126] Referring to FIGS. 8A-8C, methods for removing the sheath
pair from the scaffold-balloon 10/12 by the health professional are
now described. These illustrations refer to moving the sheath pair
over the mandrel 8; however, a mandrel 8 is not necessary. The
sheath pair 30/230 may be safely removed from the catheter assembly
2 without using a mandrel 8.
[0127] A sterilized and packaged catheter assembly with sheaths 20,
230 positioned as shown in FIG. 8A typically includes the
stiffening or storage mandrel 8 in the catheter shaft 4 lumen to
provide bending stiffness for shaft 4. A distal end of the mandrel
8 has a curled end, or an extension/stop at the distal end (not
shown), which is used to manually withdraw the mandrel 8 from the
catheter shaft 4 lumen by pulling the mandrel 8 towards the distal
end 6 of the catheter assembly 2. In the following example the
sheaths 20, 230 are removed. The proscribed steps preferably also
include the act of removing the mandrel 8 from the catheter shaft
lumen by, e.g., simultaneously gripping the raised end 22, sheath
230 and mandrel 8.
[0128] First, the sheath 230 portion 240 is grabbed and pulled away
from the scaffold-balloon 10/12 structure, which removes the
constraining portion 235 from the scaffold-balloon 10/12 structure.
The sheath 230 may be withdrawn or pulled away from the
scaffold-balloon 10/12 in the following manner. One hand grasps the
portion 230; the other hand grasps the catheter shaft 4 proximal of
the scaffold 10 to hold the catheter 2 stationary. The sheath 230
is pulled in the direction P (FIG. 8B). When the ID junction 241
abuts the stepped end 22 of sheath 20, the constraining portion 235
has cleared the scaffold. At this point continued pulling of the
sheath 230 will also remove the sheath 20 from the scaffold and
eventually separate the sheath 20/230 from the catheter 2. The
raised end 22 therefore functions as an abutment for removing both
sheaths in a safe manner with minimal disruption to the crimped
scaffold.
[0129] As an alternative to the sheath 230 formed from a single
piece of tubing, in FIG. 7D there is a sheath 250 made from two
tubes of different diameter fastened together. A sheath 250 has a
first portion 252 that applies the radial constraint to the
scaffold and a second portion 255 for removal of the first portion
252 from the scaffold. The sheath 250 may be positioned and removed
from the sheath 20 in the same manner as described above for sheath
230. As with sheath 230 there is the ID junction 251 for abutment
with the end 22 when the sheath 250 is removed.
[0130] In a preferred method of making sheath 20, the raised ends
are made with the sheath 30 and 230 over the tube forming the
sheath 20. The raised ends retain the sheath 30 on the sheath 20.
Since the one-piece sheath 30/230 is disposed over the tube forming
the sheath 20 prior to forming the raised ends, the overall length
of the one-piece sheath 30/230 is preferably limited to less than
the overall length of the sheath 20 (so that for manufacturing
reasons the ends can be accessed to form the raised ends). However,
by using a two-piece sheath 250 the overall length L250 of the
finished sheath can be significantly longer than the sheath 20,
since the raised ends of sheath 20 can be formed with the portion
252 on sheath 20 but prior to the tube portion 255 attached at 254
(FIG. 7D). According to the embodiment of FIG. 7D the sheath 250
may preferably either have a longer length L250 than sheath 20
length, a length about the same as sheath 20 or shorter length.
[0131] According to a method of crimping, a crimping process at or
near to a glass transition temperature of the polymer of the
scaffold 10 is conducted as explained in U.S. application Ser. No.
13/644,347 (docket no. 62571.675) including FIGS. 3A and 4A. Before
placing a two-piece sheath as described above, a temporary sheath
may be formed with slits or weakened areas that will facilitate a
tearing away of the sheath when it is attached to the scaffold.
Examples of such a sheath is described in U.S. application Ser. No.
13/708,638 (docket no. 62571.676) as shown in FIGS. 2, 3A-3E and
4.
[0132] The above description of illustrated embodiments of the
invention, including what is described in the Abstract, is not
intended to be exhaustive or to limit the invention to the precise
forms disclosed. While specific embodiments of, and examples for,
the invention are described herein for illustrative purposes,
various modifications are possible within the scope of the
invention, as those skilled in the relevant art will recognize.
[0133] These modifications can be made to the invention in light of
the above detailed description. The terms used in the claims should
not be construed to limit the invention to the specific embodiments
disclosed in the specification. Rather, the scope of the invention
is to be determined entirely by the claims, which are to be
construed in accordance with established doctrines of claim
interpretation.
* * * * *