U.S. patent application number 12/703535 was filed with the patent office on 2010-06-10 for delivery system for medical devices.
This patent application is currently assigned to ABBOTT VASCULAR SOLUTIONS INC.. Invention is credited to Keif Fitzgerald, Michael Green, Patrick P. Wu, August Yambao.
Application Number | 20100145431 12/703535 |
Document ID | / |
Family ID | 34273870 |
Filed Date | 2010-06-10 |
United States Patent
Application |
20100145431 |
Kind Code |
A1 |
Wu; Patrick P. ; et
al. |
June 10, 2010 |
DELIVERY SYSTEM FOR MEDICAL DEVICES
Abstract
The invention is directed a delivery system for implantation a
self-expanding medical device in a body which includes a control
handle and a catheter portion. The catheter portion includes an
outer restraining member which covers the collapsed, medical
device, an inner catheter member having a distal end including a
region upon which the medical device is mounted, and an outer
sheath which is removably attached to the control handle. The outer
sheath creates a conduit for the catheter portion to prevent the
inner catheter member from moving axially when the outer
restraining member is retracted. The control handle has a rotatable
thumbwheel to actuate a retraction mechanism attached to the
proximal end of the outer restraining member which moves the
restraining member in a proximal direction to deploy the medical
device.
Inventors: |
Wu; Patrick P.; (Mountain
View, CA) ; Fitzgerald; Keif; (San Jose, CA) ;
Yambao; August; (Temecula, CA) ; Green; Michael;
(Pleasanton, CA) |
Correspondence
Address: |
FULWIDER PATTON, LLP (ABBOTT)
6060 CENTER DRIVE, 10TH FLOOR
LOS ANGELES
CA
90045
US
|
Assignee: |
ABBOTT VASCULAR SOLUTIONS
INC.
Santa Clara
CA
|
Family ID: |
34273870 |
Appl. No.: |
12/703535 |
Filed: |
February 10, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11635341 |
Dec 7, 2006 |
7674282 |
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12703535 |
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10661406 |
Sep 12, 2003 |
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11635341 |
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Current U.S.
Class: |
623/1.11 |
Current CPC
Class: |
A61M 2025/0098 20130101;
A61F 2/95 20130101; A61F 2/9517 20200501; A61F 2/966 20130101 |
Class at
Publication: |
623/1.11 |
International
Class: |
A61F 2/84 20060101
A61F002/84 |
Claims
1. A system for delivering and deploying a medical device within a
patient, the system comprising: a delivery catheter including an
inner catheter member having a region for mounting the medical
device thereon and an outer restraining member co-axially disposed
over inner catheter member and the medical device, the outer
restraining member being adapted for axial movement with respect to
said inner tubular member; and a control handle having a rotatable
thumbwheel connected to a retraction mechanism, the inner catheter
member having a proximal end attached to the control handle and the
outer restraining member having a proximal end attached to the
retraction mechanism, wherein rotation of the thumbwheel causes
linear movement of the retraction mechanism to proximally retract
the outer restraining member sheath to uncover the medical device
while the inner catheter member remains stationary.
2. The delivery system of claim 1, wherein the inner catheter
member includes a guide wire lumen extending from the proximal end
of the inner catheter member to the distal end of the inner
catheter member.
3. The delivery system of claim 1, further including a lock
mechanism for preventing the retraction mechanism from moving
proximally until the medical device is ready to be deployed.
4. The delivery system of claim 1, further including means for
evacuating air from the delivery catheter.
5. The delivery system of claim 1, wherein the delivery catheter
further includes an outer sheath which extends co-axially over a
portion of the outer restraining member and is attached to the
control handle, the outer sheath being attachable to the entry
point of the patient to provide a conduit for the delivery catheter
to prevent the distal end of the inner catheter member from moving
distally when the outer restraining member is being retracted via
the control handle.
6. The delivery system of claim 5, wherein the outer sheath is
removably attached to the control handle.
7. The delivery system of claim 5, wherein the proximal end of the
outer sheath is attached to a strain relief member which is
removably attached to the control handle.
8. The delivery system of claim 7, wherein the strain relief member
has a proximal end which includes a channel formed therein and the
control handle has a distal recess formed therein and a tab-like
member extending into the distal recess, the channel being adapted
to receive the tab-like member to allow the strain relief member to
be threadingly engaged with the control handle.
9. The delivery system of claim 8, further including a projection
extending into the channel formed on the strain relief member which
forms an abutting surface that prevents the tab-like member from
moving past it until a rotational force is placed on the strain
relief member.
10. The delivery system of claim 1, wherein the retraction
mechanism includes a gear rack which is slideable within a channel
formed in the control handle and a spur gear attached to the gears
of the gear rack, the thumbwheel having an actuating gear attached
thereto which mates with the spur gear to cause the gear rack to
move linearly within the channel when the thumbwheel is
rotated.
11. The delivery system of claim 10, further including stop means
for preventing unintentional movement of the gear rack.
12. The delivery system of claim 11, further including means for
allowing motion of the gear rack in only one direction within the
channel.
13. The delivery system of claim 12, wherein the means for allowing
motion of the gear rack in only one direction is a spring having an
edge which contacts the distal surface of the gears forming the
gear rack to prevent distal movement of the gear rack.
14. The delivery system of claim 1, wherein the control handle
further includes means for allowing motion of the outer restraining
member in only one direction.
15. The delivery system of claim 1, further including an
anti-clotting agent placed between the outer restraining member and
the inner catheter member.
16. The delivery system of claim 5, further including an
anti-clotting agent placed between the outer restraining member and
the outer sheath.
17. The delivery system of claim 5, wherein the outer sheath has
distal portion which has a smaller inner diameter than the proximal
portion of the sheath.
18. The delivery system of claim 1, wherein the medical device is a
self-expanding medical device.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to delivery systems
for delivering and deploying medical devices, such as stents, which
are adapted to be implanted into a patient's body, such as a blood
vessel and, more particularly, to a delivery system for more
accurately deploying a self-expanding medical device into an area
of treatment.
[0002] Stents are generally cylindrically shaped devices which
function to hold open and sometimes expand a segment of a blood
vessel or other arterial lumen, such as coronary artery. Stents are
usually delivered in a compressed condition to the target site and
then deployed at that location into an expanded condition to
support the vessel and help maintain it in an open position. They
are particularly suitable for use to support and hold back a
dissected arterial lining which can occlude the fluid passageway
there through. Stents are particularly useful in the treatment and
repair of blood vessels after a stenosis has been compressed by
percutaneous transluminal coronary angioplasty (PTCA), percutaneous
transluminal angioplasty (PTA), or removed by atherectomy or other
means, to help improve the results of the procedure and reduce the
possibility of restenosis. Stents, or stent-like devices, are often
used as the support and mounting structure for implantable vascular
grafts which can be used to create an artificial conduit to bypass
the diseased portion of the vasculature, such as an abdominal
aortic aneurism.
[0003] A variety of devices are known in the art for use as stents
and have included coiled wires in a variety of patterns that are
expanded after being placed intraluminally on a balloon catheter;
helically wound coiled springs manufactured from an expandable heat
sensitive metal; and self-expanding stents inserted into a
compressed state for deployment into a body lumen. One of the
difficulties encountered in using prior art stents involve
maintaining the radial rigidity needed to hold open a body lumen
while at the same time maintaining the longitudinal flexibility of
the stent to facilitate its delivery and accommodate the often
tortuous path of the body lumen.
[0004] Prior art stents typically fall into two general categories
of construction. The first type of stent is expandable upon
application of a controlled force, often through the inflation of
the balloon portion of a dilatation catheter which, upon inflation
of the balloon or other expansion means, expands the compressed
stent to a larger diameter to be left in place within the artery at
the target site. The second type of stent is a self-expanding stent
formed from shape memory metals or superelastic nickel-titanium
(NiTi) alloys, which will automatically expand from a compressed
state when the stent is advanced out of the distal end of the
delivery, or when a restraining sheath which holds the compressed
stent in its delivery position is retracted to expose the
stent.
[0005] Some prior art stent delivery systems for delivery and
implanting self-expanding stents include an member lumen upon which
the compressed or collapsed stent is mounted and an outer
restraining sheath which is initially placed over the compressed
stent prior to deployment. When the stent is to be deployed in the
body vessel, the outer sheath is moved in relation to the inner
member to "uncover" the compressed stent, allowing the stent to
move to its expanded condition. Some delivery systems utilize a
"push-pull" type technique in which the outer sheath is retracted
while the inner member is pushed forward. Another common delivery
system utilizes a simple pull-back delivery system in which the
self-expanding stent is maintained in its compressed position by an
outer sheath. Once the mounted stent has been moved at the desired
treatment location, the outer sheath is pulled back via a
deployment handle located at a remote position outside of the
patient, which uncovers the stent to allow it to self-expand within
the patient. Still other delivery systems use an actuating wire
attached to the outer sheath. When the actuating wire is pulled to
retract the outer sheath and deploy the stent, the inner member
must remain stationary, preventing the stent from moving axially
within the body vessel.
[0006] However, problems have been associated with such prior art
delivery systems. For example, systems which rely on a "push-pull
design" or "push-back design" can experience unwanted movement of
the collapsed stent within the body vessel when the inner member is
pushed forward which can lead to inaccurate stent positioning.
Systems which utilize a "pull back" system or an actuating wire
design will tend to move to follow the radius of curvature when
placed in curved anatomy of the patient. As the outer sheath member
is actuated, tension in the delivery system can cause the system to
straighten. As the system straightens, the position of the stent
changes because the length of the catheter no longer conforms to
the curvature of the anatomy. This change of the geometry of the
system within the anatomy can lead to inaccurate stent
positioning.
[0007] Delivery systems which utilize the "pull-back" type
technique usually require removal of "slack" developed between the
outer sheath and the inner catheter member upon which the stent is
mounted. Generally, the exposed catheter, i.e. the portion of the
outer member which remains outside of the patient, must usually be
kept straight or relatively straight during deployment. Failure to
do so may result in deploying the stent beyond the target area and
can cause the stent to bunch up. This phenomenon occurs because the
inner catheter member tends to move forward when the outer sheath
is retracted. The reason why this happens is because the inner
catheter member and outer catheter member are typically the same
length prior to stent deployment. The length of the exposed
catheter, again, the portion of the outer catheter which extends
between the deployment handle and the insertion point in the
patient, however, is usually fixed. When the outer sheath is
retracted proximally into the deployment handle during deployment,
the length of the exposed outer sheath tends to shorten. The inner
catheter member, however, remains the same length as it is held
fixed in the deployment handle. However, the outer sheath tends to
shorten during deployment, thus changing the shape of the exposed
portion of the catheter. This shape change occurs because the outer
sheath wants to straighten out once it's being retracted. Since the
inner catheter member is fixed proximally within the deployment
handle, it will move distally as the outer sheath is retracted. As
a result, the movement of the inner catheter member caused by the
retraction of the outer sheath can cause the stent to deploy
prematurely and at a location beyond the targeted site. As a
result, less than accurate deployment of the stent can occur.
[0008] This problem usually does not exist when the delivery system
is kept straight during deployment as the outer sheath is allowed
to slide proximally relative to the inner catheter member. However,
if the delivery system is not kept straight during deployment, then
the inner catheter member has this tendency to move distally during
deployment. This change in the shape of the exposed catheter forces
the inner catheter member to change shape as well in order for the
inner catheter member to maintain the same length as the outer
sheath. Since the inner catheter member is fixed within the
deployment handle, it can only move distally. Consequently, the
inner catheter member moves distally along with the mounted stent,
causing the stent to be deployed beyond the targeted site in the
patient's anatomy.
[0009] The above-described stent delivery systems also can be
somewhat difficult to operate with just one hand, unless a
mechanical advantage system (such as a gear mechanism) is utilized.
Often, deployment with one hand is desirable since it allows the
physician to use his/her other hand to support a guiding catheter
which may be utilized during the procedure. The above-described
stent delivery systems should not be susceptible to any axial
movement of the catheters during stent deployment. Even a slight
axial movement of the catheter assembly during deployment can cause
some inaccurate placement of the stent in the body lumen. Some
stent delivery systems employ a control handle which utilizes a
pistol grip actuator that requires the physician to repeatedly pull
back a trigger mechanism to cause the outer sheath to retract. In
doing so, the physician usually creates a backwards force on the
delivery system which also can cause the catheter portion of the
delivery system to move within the patient's vasculature, resulting
in less than accurate placement of the stent within the patient.
Also, some of these stent delivery systems have a limited range of
retraction of the outer sheath which can limit the use of the
delivery system to smaller medical devices which require only a
small amount of retraction in order to expand the device. Larger
medical devices, such as vasculature grafts, cannot be deployed
because the control handle of the system cannot retract the outer
sheath a sufficient length in order to expose the entire graft.
[0010] Thus, there is a need for a delivery system for delivering
and deploying a self-expanding medical device, such a stent, which
prevents the axial movement of the inner catheter member relative
to the outer sheath to prevent the inner catheter member from
moving forward during deployment. Such a delivery system also
should also compensate for any slack that may be present in the
delivery system and should prevent the inner catheter member from
moving forward within the patient's vasculature as the outer
restraining sheath is being retracted from the self-expanding
medical device. Such a delivery system would be beneficial if it
allowed the physician to actuate the system with only one hand,
thus allowing the physician to use his/her other hand during the
procedure. The present invention disclosed herein satisfies these
and other needs.
SUMMARY OF THE INVENTION
[0011] The present invention is directed to a delivery system for
delivering and more accurately deploying a medical device, such as
a stent, to the target site in a body lumen. The delivery system in
accordance with the present invention incorporates unique features
which facilitates minimal movement during device deployment,
accurate placement, and single-handed system operation. While the
delivery system can be used to deploy any self-expanding stent, it
also can be used to deploy other self-expanding medical devices,
including medical devices which are not self-expanding as well.
[0012] In one aspect of the present invention, the delivery system
include a control handle and a catheter portion which is designed
for advancement to a target area in a patient's body lumen over a
deployed guide wire using "over the wire" techniques known in the
art. The catheter portion includes an inner catheter member having
a proximal portion attached within the control handle and a distal
portion upon which the medical device is mounted in a collapsed
position. An outer restraining member extends over the inner
catheter member in a coaxial arrangement. The outer restraining
member holds the medical device in the collapsed position until the
device is to be deployed. If the medical device is not
self-expanding, the outer restraining member does not necessarily
restrain the device, but provides a protective cover for the
device. The outer restraining member is retractable to release the
medical device by a retraction mechanism housed in the control
handle. The control handle includes a rotatable thumbwheel which is
easily moveable to provide a manual mechanism for retracting the
restraining sheath. The control handle immobilizes the inner
catheter member, preventing it from moving relative to the outer
restraining member during deployment. The control handle allows the
delivery system to be operated by just one hand, freeing the
physician's other hand for other purposes, such as stabilizing the
guiding catheter during deployment of the medical device.
[0013] In one aspect of the present invention, the catheter portion
includes an outer sheath which is utilized to stiffen the catheter
portion of the delivery system so that the inner catheter member
will not change shape outside the body when the outer restraining
member is retracted to deploy the medical device. The outer sheath
extends at least partially over the length of the outer restraining
member in a coaxial relationship in order to create a conduit
between the control handle and the point of insertion into the
patient. This outer sheath helps to reduce frictional forces which
may be created with the medical device that is inserted into the
patient to obtain entry for the catheter portion, such as a
rotating hemostatic valve (RHV), or other similar device, and helps
to prevent the inner catheter member from moving distally as the
outer restraining sheath is being retracted via the control
handle.
[0014] In another aspect of the present invention, the outer sheath
is attached to a strain relief member which is threadingly engaged
with the control handle. In this particular aspect of the
invention, the proximal end of the strain relief has a channel
formed in it which is designed to receive a tab-like projection
formed in a recess of the control housing in order to allow the
strain relief member to be threaded onto the control handle.
Depending upon physician preference, the outer sheath can either
remain or be removed from the control handle during use.
[0015] In another aspect of the present invention, the retraction
mechanism of the control handle allows the outer restraining member
to be retracted in a proximal direction only and includes a stop
mechanism which prevents the retraction mechanism from prematurely
deploying. The control handle allows the physician to actuate the
retraction mechanism using a simple thumb motion on the thumbwheel
which helps to prevent unwanted forces from acting on the control
handle which can typically be developed when a pistol-like actuated
control handle is utilized. As a result, a more accurate placement
of the medical device may be achieved.
[0016] The inner catheter member has a guide wire lumen which
extends from the distal end of the inner catheter member to the
proximal end to allow a guide wire to be used to advance the
catheter portion to the target area in the body lumen in an "over
the wire" technique. In this regard, the catheter/medical device
can be introduced within the patient's vasculature in a
conventional Seldinger technique through a guiding catheter. The
distal end of the inner catheter member includes a soft, low
profile tip assembly with a radiopaque marker.
[0017] These and other advantages of the present invention become
apparent from the following detailed description and the
accompanying exemplary drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a perspective view showing a control handle which
forms part of the delivery system of the present invention.
[0019] FIG. 2 is an elevational view, partially in section, showing
a schematic representation of the catheter portion of the delivery
system which attaches to the control handle.
[0020] FIG. 3 is a perspective view of a delivery system showing
the flattening of the arc during deployment in silhouette.
[0021] FIG. 4 is a cross sectional view of the control handle of
FIG. 1.
[0022] FIG. 5 is an enlarged cross-sectional view of the retraction
mechanism of the control handle of FIG. 4.
[0023] FIG. 6 is a cross-sectional view of the control handle of
FIG. 4 in which the rack and pinion portion of the control handle
has been partially retracted.
[0024] FIG. 7 is a perspective view showing the proximal end of the
strain relief portion of the catheter system which is attached to
the outer sheath utilized in conjunction with the present delivery
system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] The present invention relates to a delivery system for
delivering and deploying a medical device into a target site in a
patient's body, such as a body lumen. For sake of illustration, the
following exemplary embodiments are directed to a delivery system
for delivering and deploying a self-expanding stent, although it is
understood that the present invention is applicable to other
medical devices which are implantable in a body lumen as well as
other parts of the body. Additionally, the medical device can be
either a self-expanding device or a non self-expanding device.
[0026] Referring now to FIGS. 1 and 2, in one particular embodiment
of the present invention, the delivery system 10 incorporating
features of the present invention includes a control handle 12 and
a catheter portion 14. As can best be seen in FIG. 1, the control
handle includes a hand portion 16 which allows the physician to
hold the control handle utilizing one hand. The control handle 12
also includes a rotatable thumbwheel 18 which allows the physician
to retract the restraining sheath utilized to maintain the
self-expanding medical device in its collapsed, delivery position
near the distal end of the catheter portion 14 of the system. The
hand portion 16 can be easily grasped by the physician and the
thumbwheel 18 can be easily rotated by the physician to actuate the
mechanism which pulls back the restraining sheath to expose the
self-expanding stent to achieve deployment of the device within the
patient. A lock mechanism 20 is utilized to maintain the catheter
portion 14 of the device in a securely locked condition until the
physician is ready to manipulate the thumbwheel 18 to deploy the
medical device. The design of the control handle allows the
physician to hold the hand portion 16 in either his/her right or
left hand and easily manipulate the thumbwheel 18. Alternatively,
the physician can grasp the portion of the control handle distal to
the thumbwheel 18 if desired, and still be capable of easily
rotating the thumbwheel 18 in order to retract the restraining
sheath. This sleek design of the control handle allows added
versatility when handling and deploying the delivery system made in
accordance with the present invention.
[0027] Referring now specifically to FIG. 2, the catheter portion
14 is shown schematically as including an inner catheter member 22
which is adapted to carry the medical device, such as a
self-expanding stent 24, near the distal end of the inner catheter
member 22. An outer restraining member extends generally coaxially
over the inner catheter member 22 and is designed to maintain the
stent 24 in its collapsed delivery configuration until the stent is
to be deployed by the physician. This outer restraining member 26
can be retracted via the control handle 12 in accordance with the
present invention. A third catheter member forms the outermost
catheter portion 14 of the system and is shown as an outer sheath
28 which is removably attached to the control handle 12. In this
regard, the outer sheath 28 is coaxially disposed over the outer
restraining member 26 and can be removably attached to the control
handle 12 or attached to a strain relief 30 which is removably
attached to a nose cone 32 forming part of the control handle 12.
Further details on the construction of the removable strain relief
30 and its attachment to the nose cone 32 are described in greater
detail below.
[0028] The outer sheath 28 is utilized in order to stiffen the
catheter portion of the delivery system so that the arc of the
inner catheter member 22 will not change shape outside the body
when the outer restraining member 26 is pulled back to deploy the
stent. In this regard, the inner catheter member 22 can be
maintained in a stationary position relative to the control handle
12 and the outer restraining member 26 so that the inner catheter
member 22 will not move distally once retraction of the outer
restraining member 22 commences.
[0029] Referring specifically now to FIG. 3, the problem that
exists when a delivery system does not utilize an outer sheath 28,
such as the one made in accordance with the present invention, is
described in greater detail. FIG. 3 shows the delivery system as it
extends outside of the patient 34 (schematically represented in
FIG. 3). A rotating hemostatic valve 36 is shown schematically
inserted within the patient 34. In FIG. 3, the delivery system is
shown without the outer sheath 28 connected to the control handle
12 and merely represents an outer restraining member 26 coaxially
disposed over the inner catheter member 22. When the delivery
system is maintained at a curvature with respect to the entry
point, i.e. at the rotating hemostatic valve 36, the inner catheter
member has a tendency to move distally during the retraction of the
outer restraining member. FIG. 3 shows the presence of a curvature
in the exposed portion of the catheter portion prior to deployment.
In this state, the lengths of the inner and outer members are
substantially the same. However, the outer restraining member tends
to shorten during deployment, thus changing the shape of the
exposed portion of the catheter. This shape change occurs because
the outer restraining member wants to straighten out once it's
being retracted. This change in the shape of the outer restraining
member is shown in silhouette 38 in FIG. 3. Since the inner
catheter member is fixed proximally within the control handle, it
will move distally as the outer restraining member is retracted. As
a result, the movement of the inner catheter member caused by the
retraction of the outer restraining member can cause the stent to
deploy prematurely and at a location beyond the targeted site. As a
result, less than accurate deployment of the stent can occur.
[0030] The outer sheath 28 is designed to attach to the point of
entry in the patient, for example the rotating hemostatic valve 36
located at the insertion opening in the patient's vasculature, to
avoid the premature deployment of the stent since this outer sheath
28 creates a conduit that allows the outer restraining member 26 of
the catheter portion 14 to move without excessive friction. The
outer diameter of the outer sheath 28 can remain compatible to a
specified sheath sizing or it can include a necked-down distal
region 29 in which the inner and outer diameters of the outer
sheath 28 is less than the remainder of the outer sheath. This
necked-down region 29 helps to reduce the possibility of blood loss
through the annular space formed between outer sheath and the outer
restraining member. The outer sheath 28 ensures accurate deployment
without the need to remove slack from the exposed catheter portion,
i.e. the portion of the catheter which extends between the rotating
hemostatic valve and the control handle. As a result, a physician
utilizing the delivery system of the present invention may not be
required to keep the exposed catheter portion straight or
substantially straight in order to achieve accurate placement of
the stent.
[0031] Referring again specifically to FIG. 2, the various
components making up the catheter portion 14 of the delivery system
10 are described in greater detail herein. The inner catheter
member 22 extends from the control handle 12 to a distal portion
which includes a region for mounting the self-expanding stent 24.
In one particular embodiment of the present invention, the inner
catheter member 22 is a composite structure formed of two different
type of tubing, each tubing having a specific function. FIG. 2
shows the inner catheter member 22 including a proximal portion 40,
made from a hypotube, which extends within the control handle 12 as
is shown in FIGS. 4-6. The distal portion 41 of the inner catheter
member which is attached distal to the proximal portion 40 and can
be made from polymide material which is braided with stainless
steel which serves to provide a strong, but flexible, catheter
portion in order to provide good trackability and pushability over
a guide wire (not shown). The application of tensile force to the
shaft of the outer restraining member 26 and outer sheath 28 during
stent deployment can create an equal and opposite compressive force
on the inner catheter member 22. For the outer restraining member
26 to retract (via the movement of the control handle 12) without
causing the rest of the catheter portion 14 to buckle, the inner
catheter member 22 must possess sufficient column strength to
prevent buckling or deformation. Otherwise, buckling or deformation
to the inner catheter member 22 can cause the distal end of the
catheter portion 14 to move within the artery, causing inaccurate
deployment of the stent. Therefore, the tubing used to form the
distal portion 41 of the inner catheter member 22 should be
fabricated from a tubular element which possesses sufficient
rigidity to prevent unwanted buckling or deformation, yet is
flexible enough to track along the torturous anatomy to the target
site.
[0032] Alternative tubing includes a more flexible material such as
polyethereketone (PEEK) or similar material which possess excellent
compressive strength, yet is reasonably flexible. The proximal
portion 40 can be made from hypotube which provides maximum
strength, but is fairly rigid. However, this is not a concern since
this proximal portion 40 of the inner catheter member 22 remains
relatively straight within the control handle 12. The distal
portion of the inner catheter member 22 must exit the guiding
catheter and track through the torturous anatomy to reach the
target site. Therefore, this portion must possess sufficient
compressive strength, yet be fairly flexible.
[0033] As mentioned above, the inner catheter member 22 further
includes the distal portion which has the stent 24 mounted thereto.
The distal end of the inner catheter member 22 includes a stent
holder 43 which is formed between a proximal abutting shoulder 42
and a distal abutting shoulder 44. These shoulders create an area
for mounting the self-expanding stent 24 in its collapsed position.
These shoulders 42 and 44 also help to maintain the stent on the
stent holder of the inner catheter member 22 as the outer
restraining member 26 is retracted. The proximal shoulder 42
provides an abutting surface which contacts the end of the stent in
the event frictional forces act on the stent as the outer
restraining member 26 is being retracted. A distal marker 46 made
from a highly radiopaque material, such as tantalum or a platinum
iridium alloy (Pt/IR 90%/10%), provides a visual reference point
for the physician when utilizing fluoroscope or other imaging
equipment. The shoulder 42 also can be made from a highly
radiopaque material to serve as a visual marker as well. A soft tip
48 is attached to the inner catheter member 22 in order to create
an atraumatic tip to help prevent snow plowing of the catheter
portion as it is being delivered in an over-the-wire fashion along
a guide wire. For example, the soft tip 48 can be made from a
polymeric material such as polyether-block co-polyamide polymer
sold under the trademark PEBAX 25b-barium sulfate, a soft material
which includes a radiopaque element that provides an additional
visualization point for the physician during fluoroscopy.
[0034] A guide wire lumen 50 extends along the entire length of the
inner catheter member 22 and can be made from a tri-layer of
materials such as PEBAX 72D, primacore and HDPE. The guide wire
lumen 50 extends through the soft tip 48 and is attached to a luer
fitting 52 mounted within a recess formed in the control handle 12.
The luer fitting 52 permits the control handle to be attached to
syringes used to flush the system and also provides an opening for
the guide wire. The luer fitting 52 is attached at the proximal end
of the hypotube and fits within the recess formed in the control
handle to prevent the inner catheter member 22 from moving relative
to the outer restraining member 26 during stent deployment. The
luer fitting 52 can be attached to the hypotube 40 by gluing the
fitting and hypotube together using a suitable adhesive. It should
be appreciated that the mounting of the inner catheter member 22 to
the control handle 12 can be achieved in any number of ways without
departing from the spirit and scope of the present invention.
[0035] This guide wire lumen 50 can be made from other materials
which provide a low friction interface between the delivery
catheter and the guide wire which is used in the procedure to
advance the catheter portion to the target site using over-the-wire
techniques that are well known in the art. For example, the guide
wire lumen can be made from tubing which is compatible with a 0.014
inch guide wire for an over-the-wire configuration.
[0036] The guide wire lumen 50 extends from the distal end of the
inner catheter member 22 to the proximal end to allow a guide wire
to be used to advance the catheter portion 14 (with mounted stent
24) to the target area in the body lumen in an "over the wire"
technique. In this regard, the catheter portion 14 can be
introduced within the patient's vasculature using, for example, a
conventional Seldinger technique through a guiding catheter.
[0037] The outer surface of the inner catheter member can be coated
with a silicone lubricant such as Microgilde manufactured by
Advanced Cardiovascular Systems, Inc., Santa Clara, Calif., to
further reduce the amount of frictional buildup between the outer
restraining member and inner catheter member.
[0038] In one embodiment of the present invention, the outer
restraining member 26 is a composite structure formed from three
different sized tubing materials, each tubing material having a
specific function. The outer restraining member 26 is shown
including a proximal portion 54 which extends within the control
handle 12 and is attached to the mechanism which produces the
retraction force needed to retract the outer restraining member
from the stent. This proximal portion 54 of the outer restraining
member 26 is designed to move axially (along the longitudinal axis
of the control handle). This proximal portion 54 of the outer
member can be made from a material such as a polymide. The outer
restraining member 26 also includes a mid-portion 56 which can also
be made from a material such as a polymide or other similar
material which provide a low profile, yet is strong enough to
develop the pushability needed as the delivery system is moved
along the guide wire in an over-the-wire delivery. This mid-portion
56 can be made with tubing having a different wall thickness than
the proximal portion 54. The outer restraining member 26 also
includes a distal portion 58 which has a larger inner diameter than
the tubing forming the mid-portion 56 in order to obtain the
necessary diameter to maintain the collapsed self-expanding stent
24 in position on the system. This portion of the outer restraining
member 26 is designed to hold the stent 24 in its compressed or
collapsed state and is retracted by actuating the thumbwheel 18 of
the control handle 12 which proximally moves the restraining member
while maintaining the inner catheter member 22 stationary during
stent deployment. The distal portion 58 can be made from a material
such as polymide or other suitable materials which will provide the
necessary restraining force needed to keep the self-expanding stent
in place. Since it is usually desired to have a low profile at this
distal location of the catheter, a tubing having a thinner wall
thickness can be utilized.
[0039] Alternative material for forming the outer restraining
member 26 includes material such as cross-linked HDPE. Alternative
materials for the distal portion 58 include materials such as
polyolefin which can be bonded to the mid-portion 56 of the outer
restraining member 26. A material such as polyolefin is used since
it has sufficient strength to hold the compressed stent and has
relatively low frictional characteristics to minimize any friction
between the stent and the tubing. Friction can be further reduced
by applying a coat of silicone lubricant, such as Microgilde, to
the inside surface of the distal portion 58 before the stent is
loaded onto the stent holder.
[0040] The outer sheath 28 extends along a portion of the length of
the outer restraining member 26 as is necessary to create the
conduit for the length of the catheter which remains outside the
patient. The length of this outer sheath 28 can be varied depending
upon the size of the medical device mounted on the distal end of
the inner catheter member 22. In this regard, the length of the
outer sheath 28 generally can be as long as, or longer than, the
guide catheter (not shown) utilized when the delivery system is
placed in the patient's vasculature.
[0041] In one aspect of the invention, the outer sheath 28 includes
the neck-down region 29 in which the inner diameter of the outer
sheath 28 is comparable to the outer diameter of the mid-portion 56
of the outer restraining member 26. In this fashion, a fairly tight
fit extends between these two catheter portions in order to
minimize blood loss between these catheter portions. Since the
distal portion 58 has a larger diameter than the tubing forming the
mid-portion 56, the distal end of the outer sheath 28 should
generally terminate a sufficient distance to allow the outer
restraining member 26 to be fully retracted by the control handle
12, while preventing the larger diameter distal portion 58 from
abutting the distal end of the outer sheath 28. In this regard, for
example, if a 40 mm stent is mounted on the inner catheter member
22, then the length of the retraction needed to properly release
the device would require that the distal end of the outer sheath 28
be at least 40 mm away from the transition portion where the
mid-portion 56 translates to the distal portion 58 to allow the
outer restraining member 26 to retract properly. If a longer length
medical device is mounted on the inner catheter member 22 then the
overall length of the outer sheath 28, of course, should be
adjusted. It is also possible for the inner diameter of the outer
sheath 28 to be at least as large as the outer diameter of the
distal portion 58 of the outer restraining sheath 26 to allow
proper retraction of the outer restraining sheath 26.
[0042] The outer sheath 28 can be made from materials such as
polymide and other suitable materials. Other materials include
polyetheretherketone (PEEK) and polyether-block co-polyamide
polymer sold under the trademark purple PEBAX SA2032476. The strain
relief 30 which is attached to the proximal end of the outer sheath
can be made from a material such as Pebex 70D. As will be described
in greater detail below, the strain relief 30 includes a proximal
end 60 which can be threaded into the nose cone 32 of the control
handle 12 to allow the physician to remove the outer sheath 28, if
not needed.
[0043] Referring now to FIG. 7, the proximal end 60 of the strain
relief 30 is shown in greater detail. As can be seen from this
figure, the proximal end 60 includes a continuous channel 62 which
creates a maze-like thread that allows the strain relief 30 to be
removably attached to the control handle 12. This maze-like channel
threads into the nose cone 32 and allows the outer sheath 28 to be
connected or detached based upon physician preference. Referring
specifically now to FIGS. 4 and 6, the channel 62 of the proximal
end 60 is adapted to be threaded along a tab-like projection 64
which extends into the recess of nose cone 32 of the control handle
12. This tab-like projection 64 can be sized or shaped to fit
within the channel 62. A projection stop element 66, which extends
within this channel 62, acts like a detent once the proximal end 60
of the strain relief 32 has been threaded into the nose cone. This
projecting stop 66 prevents the strain relief from being moved from
the nose cone until the physician desires to remove the outer
sheath from the control handle. In this manner, the area 68
adjacent to the projecting stop 66 is designed to contain the
tab-like projection 64 until the physician is ready to remove the
outer sheath. The physician can remove the outer sheath 28 by
simply twisting the strain relief 32 to allow the tab-like
projection 64 to move past the projecting stop element 66 and then
be moved along the channel 62 until the projection 64 disengages
from the channel. It should be appreciated that other coupling
means could be formed or attached to the control handle, besides a
tab-like projection 64, to receive the channel 62. Additionally,
the outer sheath 28 does not have to be attached to the strain
relief 30, but can be removably attached to the control handle
itself. In this regard, the proximal end of the outer sheath can
have a similar channel formed therein as is shown in FIG. 7.
[0044] The control handle 12 of the present delivery system 10 will
be described in greater detail herein. Referring now specifically
to FIGS. 4-6, a cross sectional view of the actuating mechanism
housed within the control handle 12 is shown. The thumbwheel 18 of
the control handle 12 is connected to the actuating mechanism which
is adapted to retract the outer restraining member 26 relative to
the inner catheter member 22 to allow the distal portion 58 of the
outer restraining member to retract from the stent and cause it to
self-expand into the target area. The actuator mechanism includes a
slideable gear rack 70 which is disposed within a channel 72 formed
along the length of the control handle 12. The slideable gear rack
70 is in turn attached to a spur gear 74 which engages the gears 76
on the gear rack 70. The thumbwheel 18 is connected directly to an
actuating gear 78 which rotates as the thumbwheel is rotated by the
physician. In this regard, once the thumbwheel 18 is rotated, the
spur gear 74 is rotated by the actuating gear 78 causing the gear
rack 70 to move proximally within the channel 72 formed in the
control handle. FIG. 6 depicts the gear rack 70 in a position in
which the gear rack 70 has been somewhat retracted through the
rotation of the thumbwheel 18. Since the delivery system 10 can be
used with just one hand, the physician's other hand is free to
perform other tasks, such as stabilizing the guiding catheter used
during the procedure. By stabilizing the guiding catheter as well,
enhanced accuracy in deploying the stent can be obtained
[0045] A lock mechanism 20, as shown in FIGS. 4 and 5, extends into
the control handle to prevent the gear rack 70 from moving until
the physician is ready to deploy the stent. In this regard, the
lock mechanism 20 includes a locking arm 80 which is designed to
abut against a stop element 82 formed or attacked to the gear rack
70. As can be seen in FIG. 5, the locking arm 80 is shown in an
abutting relationship with the stop element 82 to prevent the gear
rack 70 from moving proximally in order to prevent retraction of
the outer restraining member 26. The lock mechanism 20 includes a
cam-like spring 84 designed to slide along a surface 86 formed into
the body of the control handle 12. When the lock mechanism 20 is
moved proximally by the physician, the locking arm 80 moves upward
and away from the stop element 82 to permit the stop element 82 to
move past it. It should be appreciated that this is just one
mechanism which can be utilized to prevent unwanted retraction of
the outer restraining member 26.
[0046] A spring 88 is mounted on a tab or protrusion 90 formed on
the body of the control handle 12. This spring 88 is designed to
contact the distal surface 91 of the gears 76 forming the gear rack
70 to prevent the gear rack 70 from moving distally at any time. As
a result, the control handle 12 of the present invention is capable
of moving the outer restraining member in one direction, namely
proximally. In this regard, the spring 88 allows the control handle
to store energy and prevents the physician from losing energy
during deployment. The spring 88 accomplishes this by creating an
abutting edge 89 which contacts the distal surface 91 of the gears
76, as is shown in FIG. 5, preventing the gears 76 from moving
distally, but allowing movement of the gear rack 70 in a proximal
direction. The spring 88 could alternatively be placed in an
abutting arrangement with one of the gears of the other moveable
components forming the retraction mechanism. For example, the
spring 88 could be placed near and in contact with the spur gear or
actuating gear in order to allow rotation in only one direction. It
should be appreciated to those skilled in the art that still other
ways of restricting movement of the gear rack and outer restraining
member could be implemented without departing from the spirit and
the scope of the present invention.
[0047] The delivery system of the present invention also includes a
flushing system used to evacuate air from the system. It is
important to evacuate air from the system when the delivery system
is being used in a patient's vasculature since air bubbles can
sometimes cause damage to vital organs. In other instances, it may
be desirable to have a fluid pre-placed into the system to prevent
the possible accumulation of blood between the outer restraining
member and the inner catheter member since stagnated blood has the
tendency to coagulate and cause thrombosis. An alternative flushing
fluid besides saline could be an anti-clotting agent which can be
placed in the annular space formed between the outer restraining
member and the inner catheter member to minimize blood clotting.
Such an anti-clotting agent includes heparin, which not only
provides an anti-clotting factor, but also includes smooth
deployment and reduces deployment forces. Additionally, if blood
clots in the annular space, it would lead to higher deployment
forces, non-deployments, and potentially partial deployments. An
anti-clotting agent, such as heparin, also can be placed in the
annular space formed between the outer sheath and the outer
restraining member to prevent clotting of blood within this space
as well. It should be appreciated other anti-clotting agents
besides heparin could be utilized in the same fashion. For these
reasons, it may be beneficial to pre-flush the system before
placing the delivery catheter in the patient.
[0048] Referring now to FIG. 2, the flushing system consists of an
opening 92 or several openings extending through the inner catheter
member 22 in the area of where the distal portion 58 meets the
mid-portion 56 of the outer restraining member 26. The openings are
drilled through to the guide wire lumen 50 to effectively open up a
passageway from the guide wire lumen to the annular space formed
between the inner catheter member 22 and the outer restraining
member 26. A syringe can be attached to the luer fitting 52 on the
catheter handle 12 and sterile fluid can be pumped into the guide
wire lumen 50 in order to flush air from the system. A mandrel (not
shown) can be placed in the guide wire lumen at the tip 48 to block
the flow of the sterile fluid through the distal tip. The sterile
fluid is thus forced to flow out of the small openings 92 into the
annular space formed between the inner catheter member and outer
restraining member. The fluid eventually flows past the collapsed
stent where the fluid and any air in the system will escape through
the distal opening of the outer restraining member 26. Once fluid
is observed dripping from the distal end of the outer restraining
member 26, the mandrel can be removed since air has been evacuated
from the system. Since the gap sizes are so small between the
various components, capillary force prevents air from infiltrating
the delivery system once the evacuation has been completed.
[0049] The components of the control handle can be made from
conventional materials well-known in the medical manufacturing art.
For example, the control handle can be made from a plastic or
plastic-like material such as ABS plastic, as can the various other
components including the locking mechanism, gears and gear
rack.
[0050] It is to be understood that even though numerous
characteristics and advantages of the present invention have been
set forth in specific description, together with details of the
structure and function of the invention, the disclosure is
illustrative only and changes may be made in detail, such as size,
shape and arrangement of the various components of the present
invention, without departing from the spirit and scope of the
present invention. It would be appreciated to those skilled in the
art that further modifications or improvement may additionally be
made to the delivery system disclosed herein without departing from
the scope of the invention. Accordingly, it is not intended that
the invention be limited, except as by the appended claims.
* * * * *