U.S. patent application number 12/202664 was filed with the patent office on 2009-01-29 for arteriovenous access valve system and process.
This patent application is currently assigned to CreatiVasc Medical. Invention is credited to David L. Cull.
Application Number | 20090030498 12/202664 |
Document ID | / |
Family ID | 41797455 |
Filed Date | 2009-01-29 |
United States Patent
Application |
20090030498 |
Kind Code |
A1 |
Cull; David L. |
January 29, 2009 |
Arteriovenous Access Valve System and Process
Abstract
An arteriovenous graft system is described. The arteriovenous
graft system includes an arteriovenous graft that is well suited
for use during hemodialysis. In order to minimize or prevent
arterial steal, at least one valve device is positioned at the
arterial end of the arteriovenous graft. In one embodiment, a
subcutaneous arteriovenous graft system is described. The system
includes an arteriovenous graft having an arterial end and an
opposite venous end with a first valve device positioned at the
arterial end of the arteriovenous graft and a second valve device
positioned at the venous end of the arteriovenous graft. The system
also includes an actuator having an accumulator. The actuator is in
communication with both the first valve device and the second valve
device and is configured to cause each valve device to open or
close simultaneously. The accumulator assists in maintaining a
generally constant pressure when the actuator causes each valve
device to close.
Inventors: |
Cull; David L.; (Greenville,
SC) |
Correspondence
Address: |
DORITY & MANNING, P.A.
POST OFFICE BOX 1449
GREENVILLE
SC
29602-1449
US
|
Assignee: |
CreatiVasc Medical
Greenville
SC
|
Family ID: |
41797455 |
Appl. No.: |
12/202664 |
Filed: |
September 2, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11807479 |
May 29, 2007 |
|
|
|
12202664 |
|
|
|
|
Current U.S.
Class: |
623/1.13 ;
623/1.27; 623/2.1 |
Current CPC
Class: |
A61F 2/2475 20130101;
A61M 1/3655 20130101; A61M 2205/04 20130101; A61M 39/0247 20130101;
A61M 1/14 20130101; A61M 2039/0258 20130101; A61M 39/227 20130101;
A61M 2039/0211 20130101; A61F 2/06 20130101; A61M 39/228 20130101;
A61M 39/0208 20130101; A61M 2039/0276 20130101 |
Class at
Publication: |
623/1.13 ;
623/1.27; 623/2.1 |
International
Class: |
A61F 2/06 20060101
A61F002/06; A61F 2/24 20060101 A61F002/24 |
Claims
1. A subcutaneous arteriovenous graft system comprising: an
arteriovenous graft having an arterial end and an opposite venous
end; a first valve device positioned at the arterial end of the
arteriovenous graft and a second valve device positioned at the
venous end of the arteriovenous graft; and an actuator comprising
an accumulator, the actuator being in communication with both the
first valve device and the second valve device, the actuator being
configured to cause each valve device to open or close
simultaneously, the accumulator assisting in maintaining a
generally constant pressure when the actuator causes each valve
device to close.
2. A system as defined in claim 1, wherein each valve device
comprises an inner sleeve positioned within an outer sleeve, the
inner sleeve being attached to the outer sleeve so as to define a
discrete area, the discrete area being in fluid communication with
the actuator wherein, when fluid is fed into the discrete area, the
discrete area inflates to form a balloon and causes the restriction
of blood flow through the arteriovenous graft, the accumulator
assisting in maintaining the discrete area in an inflated state
until the fluid is removed from the discrete are.
3. A system as defined in claim 1, wherein the actuator comprises a
fluid injection port that is in fluid communication with the first
valve device and the second valve device.
4. A system as defined in claim 2, wherein the actuator comprises a
fluid injection port that is in fluid communication with the first
valve device and the second valve device, the fluid injection port
being positioned adjacent to the accumulator.
5. A system as defined in claim 3, wherein the fluid injection port
comprises a diaphragm, the diaphragm being of sufficient thickness
to resist pressure from the accumulator and prevent fluid from
unintentionally leaking from the diaphragm.
6. A system as defined in claim 1, wherein the accumulator
comprises a spring.
7. A system as defined in claim 2, wherein, when inflated, the
balloons of each valve device have a spherical or substantially
spherical shape.
8. A system as defined in claim 2, wherein the outer sleeve of each
valve device is more rigid than the inner sleeve and wherein the
outer sleeve maintains its shape when the respective balloon is
inflated.
9. A system as defined in claim 2, wherein the arteriovenous graft
is positioned within the inner sleeve of the balloon of the first
valve device and the balloon of the second valve device.
10. A system as defined in claim 1, wherein the actuator is
configured to deliver a fluid to each valve device for opening and
closing the valve devices.
11. A system as defined in claim 10, wherein the fluid comprises a
liquid.
12. A system as defined in claim 10, wherein the fluid comprises a
gas.
13. A hemodialysis method comprising: subcutaneously implanting an
arteriovenous graft system in a patient, the arteriovenous graft
system including an arteriovenous graft having a first end that is
connected to an artery and a second end that is connected to a
vein, the arteriovenous graft system further including a first
valve device positioned at the arterial end of the arteriovenous
graft and a second valve device positioned at the venous end of the
arteriovenous graft, the arteriovenous graft system further
including an actuator in communication with both the first valve
device and the second valve device, the actuator comprising an
accumulator; opening the first and second valve devices
simultaneously using the actuator causing blood to flow through the
arteriovenous graft; inserting first and second hypodermic needles
into the arteriovenous graft, the hypodermic needles being in fluid
communication with a hemodialysis machine; circulating blood
through the hemodialysis machine; and after a sufficient amount of
blood has been circulated through the hemodialysis machine, closing
the first and second valve devices using the actuator, the
accumulator assisting in maintaining a generally constant pressure
when the first and second valve devices are closed.
14. A method as defined in claim 13, further comprising the step of
flushing the arteriovenous graft after the first and second valve
devices have been closed.
15. A method as defined in claim 14, wherein the arteriovenous
graft is flushed by injecting a cleaning fluid into the
arteriovenous graft and then removing the fluid.
16. A method as defined in claim 13, wherein each valve device
comprises an inner sleeve positioned within an outer sleeve, the
inner sleeve being attached to the outer sleeve so as to define a
discrete area, the discrete area being in fluid communication with
the actuator wherein, when fluid is fed into the discrete area, the
discrete area inflates to form a balloon and causes the restriction
of blood flow through the arteriovenous graft, the accumulator
assisting in maintaining the discrete area in an inflated state
until the fluid is removed from the discrete are.
17. A method as defined in claim 13, wherein the actuator comprises
a fluid injection port that is in fluid communication with the
first valve device and the second valve device.
19. A method as defined in claim 16, wherein the actuator comprises
a piston that pumps a fluid to the discrete area of each valve
device.
18. A method as defined in claim 16, wherein the actuator comprises
a fluid injection port that is in fluid communication with the
first valve device and the second valve device, the fluid injection
port being positioned adjacent to the accumulator.
19. A method as defined in claim 17, wherein the fluid injection
port comprises a diaphragm, the diaphragm being of sufficient
thickness to resist pressure from the accumulator and prevent fluid
from unintentionally leaking from the diaphragm.
20. A method as defined in claim 13, wherein the accumulator
comprises a spring.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of U.S.
patent application Ser. No. 11/807,479, filed May 29, 2007.
BACKGROUND
[0002] The function of kidneys, which are glandular organs located
in the upper abdominal cavity of vertebrates, is to filter blood
and remove waste products. Specifically, kidneys separate water and
waste products of metabolism from blood and excrete them as urine
through the bladder. Chronic renal failure is a disease of the
kidney in which the kidney function breaks down and is no longer
able to filter blood and remove waste substances. Should certain
toxic waste substances not be removed from the blood, the toxic
substances may increase to lethal concentrations within the
body.
[0003] Hemodialysis is a life-sustaining treatment for patients who
have renal failure. Hemodialysis is a process whereby the patient's
blood is filtered and toxins are removed using an extracorporeal
dialysis machine. For hemodialysis to be effective, large volumes
of blood must be removed rapidly from the patient's body, passed
through the dialysis machine, and returned to the patient. A number
of operations have been developed to provide access to the
circulation system of a patient such that patients may be connected
to the dialysis machine.
[0004] For example, the most commonly performed hemodialysis access
operation is a subcutaneous placement of an arteriovenous graft,
which is made from a biocompatible tube. The biocompatible tube can
be made of, for instance, a fluoropolymer such as
polytetrafluoroethylene. One end of the tube is connected to an
artery while the other end is connected to a vein. The
arteriovenous graft is typically placed either in the leg or arm of
a patient.
[0005] Blood flows from the artery, through the graft and into the
vein. To connect the patient to a dialysis machine, two large
hypodermic needles are inserted through the skin and into the
graft. Blood is removed from the patient through one needle,
circulated through the dialysis machine, and returned to the
patient through the second needle. Typically, patients undergo
hemodialysis approximately four hours a day, three days a week.
[0006] Various problems, however, have been experienced with the
use of an arteriovenous graft. For example, arterial steal occurs
when excessive blood flow through the arteriovenous graft "steals"
blood from the distal arterial bed. Arterial steal can prevent the
proper supply of blood from reaching the extremity of a
patient.
[0007] Various other complications can also occur. For instance,
the blood flowing through the arteriovenous graft can often reach
turbulent flow rates. This stream of fast moving blood then exits
the arteriovenous graft and contacts the vein connected to the
graft. This collision between the flow of blood and the vein may
cause the development of myointimal hyperplasia which leads to the
thickening of the vein walls and a narrowing of the vessel. As the
vein narrows, flow through the arteriovenous graft decreases and
blood within the graft may ultimately clot.
[0008] The cessation of blood flow through the graft caused by clot
formation is known as graft thrombosis. Numerous techniques and
medications have been studied in attempts to block the development
of the scar tissue. Graft thrombosis, however, continues to remain
a reoccurring complication associated with the use of arteriovenous
grafts.
[0009] In view of the above drawbacks, a need currently exists in
the art for an arteriovenous graft that can prevent and minimize
arterial steal and graft thrombosis. A process for using an
arteriovenous graft in minimizing arterial steal and graft
thrombosis is also needed.
SUMMARY OF THE INVENTION
[0010] In general, the present invention is directed to
subcutaneous arteriovenous graft systems and to processes for using
the arteriovenous graft systems in a manner that eliminates or at
least reduces arterial steal and graft thrombosis. In one
embodiment, for instance, the system includes an arteriovenous
graft having an arterial end and an opposite venous end. The
arterial end is configured to be connected to an artery to form an
arterial anastomosis, while the venous end is configured to be
connected to a vein to form a venous anastomosis.
[0011] In accordance with the present invention, the system
includes at least one valve device positioned at the arterial end
of the arteriovenous graft. In one embodiment, for instance, the
valve device comprises an inflatable balloon. The inflatable
balloon is positioned so as to restrict blood flow through the
arteriovenous graft when inflated. In general, the valve device
should be positioned at the arterial end of the arteriovenous graft
as close as possible to the intersection of the graft with an
artery. For example, the valve device may be positioned so as to
restrict blood flow through the arteriovenous graft at a location
that is less than about 10 mm from the intersection of the
arteriovenous graft and an artery.
[0012] The inflatable balloon of the valve device may have an
annular shape that surrounds the arteriovenous graft. The
inflatable balloon may also be a separate structure or may be
integral with the arteriovenous graft. When integral with the
arteriovenous graft, the arteriovenous graft may include a
multi-layered segment located at the arterial end. The
multi-layered segment may comprise an inner layer and an outer
layer. The inner layer constricts the graft when a fluid is fed in
between the inner layer and the outer layer. When having an annular
shape, the balloon may be surrounded by a rigid collar that serves
to assist the balloon in constricting the graft.
[0013] In an alternative embodiment, the valve device may include
an inner sleeve and an outer sleeve. The inner sleeve may be
attached to the outer sleeve except for over a discrete area. The
discrete area can be in fluid communication with a fluid delivery
device. When a fluid is fed to the discrete area, fluid is fed in
between the inner sleeve and the outer sleeve causing the discrete
area of the inner sleeve to inflate. In this embodiment, the
discrete area, instead of surrounding the arteriovenous graft, can
be circular or substantially circular in shape. When inflated, the
discrete area forms a spherically shaped or a substantially
spherically shaped balloon. In one embodiment, for instance, the
outer sleeve may be more rigid than the inner sleeve. Thus, when
the inner sleeve is inflated, the outer sleeve maintains its shape.
In this embodiment, the balloon may be integral with the
arteriovenous graft. Alternatively, the arteriovenous graft may be
positioned within the inner sleeve.
[0014] In order to inflate and deflate the balloon, in one
embodiment, the valve device can further include an injection port
in fluid communication with the inflatable balloon. The injection
port defines a diaphragm configured to receive a hypodermic needle
for injecting fluid into or withdrawing fluid from the balloon. Of
particular advantage, the injection port may also be subcutaneously
implanted.
[0015] In an alternative embodiment, the inflatable balloon may be
positioned in operative association with a piston. In this
embodiment, when the balloon is inflated, the balloon forces the
piston either towards or away from the arteriovenous graft for
opening or closing the valve device.
[0016] When the valve device contains a piston, the valve device
can include various configurations. Further, the piston can be used
to inflate a balloon as described above or can be used to activate
any other suitable structure configured to open and close the
arteriovenous graft. In fact, in one embodiment, the piston itself
may be used to open and close the graft.
[0017] In one embodiment, for example, the valve device may
comprise a magnetically activated piston. In this embodiment, when
a magnetic field is placed in close proximity to the valve device,
the piston is moved for either opening or closing the valve device.
For example, in one embodiment, placing a magnetic field in close
proximity to the valve device opens the device which normally
remains closed.
[0018] In one particular embodiment, the magnetically activated
piston may be activated when exposed to a changing magnetic field,
such as a pulsing magnetic field. In this embodiment, the valve
device may include a coil member configured to convert a changing
magnetic field into an electric current. The coil member is in
communication with a solenoid. The solenoid is configured to move
the piston and open or close the valve device when electric current
is received from the coil member.
[0019] In an alternative embodiment, the valve device may include a
piston that is biased towards a closed position. For example, a
spring or other structure may apply a biasing force against the
piston that maintains the piston in the closed position. In order
to move the piston, the piston can be in operative association with
a lever arm. When a magnetic field is placed in close proximity to
the valve device, the lever arm may be configured to move causing
the piston to move and open the valve device. In this embodiment,
for instance, the piston may be in fluid communication with an
inflatable balloon as described above. When the piston is moved
into an open position, a fluid flows out of the balloon for
deflating the balloon. When the piston is placed in the closed
position, on the other hand, the fluid can be forced into the
balloon for inflating the balloon.
[0020] In one embodiment, the arteriovenous graft system further
includes a second valve device positioned at the venous end of the
arteriovenous graft. The second valve device may be any suitable
valve device as described above. The second valve device, for
instance, may be identical to the first valve device or,
alternatively, may be different.
[0021] The second valve device may be actuated using any suitable
actuator. For instance, as described above, in one embodiment, the
second valve device may include an inflatable balloon that is in
fluid communication with an injection port. Alternatively, the
second valve device may comprise an inflatable balloon that is in
communication with a piston as described above.
[0022] In still another embodiment of the present disclosure, the
subcutaneous arteriovenous graft system includes a first valve
device positioned at the arterial end of the arteriovenous graft, a
second valve device positioned at the venous end of the
arteriovenous graft and a single actuator in communication with
both the first valve device and the second valve device. The
actuator is configured to open and close the valve devices
simultaneously. The actuator may comprise, for instance, a fluid
injection port, a piston as described above or any other suitable
device. For instance, the injection port or the piston may be
configured to deliver a fluid to each of the valve devices for
inflating and deflating a balloon that closes and opens the valves
respectively.
[0023] The second valve device may not be exposed or subjected to
the same fluid pressures that are exerted on the first valve
device. In this regard, the first valve device is designed to
restrict or stop fluid flow at relatively high pressures. The
second valve device, however, may be a low pressure valve device.
In one embodiment, for instance, the second valve device may be a
check valve positioned at the venous end of the arteriovenous
graft. For example, the second valve device may be formed integral
with the arteriovenous graft and may be formed from a membrane that
allows fluid flow from the arteriovenous graft and into an
adjoining vein but prevents fluid flow from the vein into the
arteriovenous graft.
[0024] In an alternative embodiment, the check valve may comprise a
pair of opposing and overlapping flaps positioned within the
arteriovenous graft. The flaps can be integral with the graft or
can be attached to the arteriovenous graft on opposing sides. For
instance, the flaps can be attached to the graft using sutures or
through a welding process. In order to prevent leakage, the check
valve can further include edge seals that are positioned on
opposing sides of each flap. The edge seals can create a seal with
the radial wall of the arteriovenous graft.
[0025] The arteriovenous graft of the present invention is used for
hemodialysis. During hemodialysis, two hypodermic needles are
inserted into the arteriovenous graft. Blood is removed from the
graft using one needle, circulated through a dialysis machine, and
returned to the arteriovenous graft through the second needle. When
hemodialysis is not being conducted, however, the valve devices of
the present invention may be activated in order to minimize
arterial steal and prevent thrombosis of the graft.
[0026] For example, in one embodiment of the present invention,
when the arteriovenous graft system only includes a single valve
device at the arterial end, after hemodialysis has ended, the valve
device is closed thus preventing blood flow through the graft.
After the valve device is closed, a blood compatible fluid may be
injected into the graft using a hypodermic needle. As used herein,
a blood compatible fluid refers to any fluid that is biocompatible
with the circulation system. For example, in one embodiment, the
blood compatible fluid is a heparinized saline solution. The saline
solution is used to flush the graft after the valve device is
closed in order to remove blood from the graft.
[0027] In another embodiment, after hemodialysis, the valve device
is partially closed to a first position thereby constricting the
arteriovenous graft and reducing blood flow through the graft. The
patient is then monitored over a period of time, such as days or
weeks, and the valve device may be selectively opened or closed
from the first position until arterial steal is minimized. In this
embodiment, the valve device is closed an amount sufficient to
reduce blood flow through the graft without slowing the blood flow
to a point where blood clots may form.
[0028] As described above, in another embodiment of the present
invention, the arteriovenous graft system includes a first valve
device at the arterial end and a second valve device at the venous
end. In this embodiment, after hemodialysis has ended, the first
valve device at the arterial end is closed thereby preventing blood
flow through the graft. A hypodermic needle then flushes the graft
with a blood compatible fluid evacuating all blood from the graft.
After the graft has been flushed with the blood compatible fluid,
the second valve device is then closed and the hypodermic needle is
removed from the graft.
[0029] When the arteriovenous graft system contains first and
second valve devices that are controlled by a single actuator, in
one embodiment, the valve devices are opened so that there is blood
flow through the graft. Two hypodermic needles are inserted into
the graft and the blood is circulated through a dialysis machine.
After hemodialysis has ended, the actuator is used to close both
valve devices simultaneously. The arteriovenous graft can then be
flushed. For instance, a fluid can be injected and removed from the
graft using one or more hypodermic needles.
[0030] In still another embodiment of the present disclosure, a
subcutaneous arteriovenous graft system is described. The system
includes an arteriovenous graft having an arterial end and an
opposite venous end with a first valve device positioned at the
arterial end of the arteriovenous graft and a second valve device
positioned at the venous end of the arteriovenous graft. The system
also includes an actuator having an accumulator. The actuator is in
communication with both the first valve device and the second valve
device and is configured to cause each valve device to open or
close simultaneously. The accumulator assists in maintaining a
generally constant pressure when the actuator causes each valve
device to close.
[0031] Other features and aspects of the present invention are
discussed in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] A full and enabling disclosure of the present invention is
set forth in the specification with reference to the following
figures.
[0033] FIG. 1 is a side view with cut away portions of a human arm
illustrating the placement of an arteriovenous graft;
[0034] FIGS. 2A, 2B and 2C are perspective views of embodiments of
arteriovenous graft systems made in accordance with the present
invention;
[0035] FIG. 3 is a perspective view of one embodiment of a valve
device that may be used in the arteriovenous graft system of the
present invention;
[0036] FIG. 4 is a perspective view of another embodiment of a
valve device that may be used in the arteriovenous graft system of
the present invention;
[0037] FIG. 5 is a perspective view of still another embodiment of
an arteriovenous graft system made in accordance with the present
invention;
[0038] FIG. 6 is an unassembled perspective view of one embodiment
of a balloon valve that may be used in accordance with the present
disclosure;
[0039] FIG. 7 is a cross-sectional view of the valve device
illustrated in FIG. 6;
[0040] FIG. 8 is a cross-sectional view taken along line A-A of the
valve device shown in FIG. 7;
[0041] FIG. 9 is a cross-sectional view of the valve device
illustrated in FIG. 6 showing the balloon inflated;
[0042] FIG. 10 is a perspective view with cut away portions showing
another embodiment of a valve device that may be used in accordance
with the present disclosure;
[0043] FIG. 11 is a cross-sectional view of the valve device
illustrated in FIG. 10;
[0044] FIG. 12 is a side view with cut away portions illustrating
the valve device shown in FIG. 10 in association with a
balloon;
[0045] FIG. 13 is a cross-sectional view of the valve device
illustrated in FIG. 12 illustrating the balloon being deflated;
[0046] FIG. 14 is an unassembled perspective view of one embodiment
of a check valve that may be used in accordance with the present
disclosure;
[0047] FIG. 15 is a perspective view with cut away portions of the
check valve illustrated in FIG. 14;
[0048] FIG. 16 is a cross-sectional view of the check valve
illustrated in FIG. 14;
[0049] FIG. 17 is a cross-sectional view taken along line A-A of
the check valve illustrated in FIG. 16;
[0050] FIG. 18 is an alternative embodiment of a check valve that
may be used in accordance with the present disclosure;
[0051] FIG. 19 is a perspective view of yet another alternative
embodiment of an arteriovenous graft system in accordance with the
present disclosure;
[0052] FIG. 20 is a perspective view of yet another alternative
embodiment of an arteriovenous graft system in accordance with the
present disclosure; and
[0053] FIG. 21A is an exploded view of the actuator illustrated in
FIG. 20; and
[0054] FIGS. 21B and 21C are cross-sectional views of the actuator
illustrated in FIG. 21A.
[0055] Repeat use of reference characters in the present
specification and drawings is intended to represent the same or
analogous features of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0056] Reference now will be made to the embodiments of the
invention, one or more examples of which are set forth below. Each
example is provided by way of explanation of the invention, not as
a limitation of the invention. In fact, it will be apparent to
those skilled in the art that various modifications and variations
may be made in the invention without departing from the scope or
spirit of the invention. For instance, features illustrated or
described as part of one embodiment may be used in another
embodiment to yield a still further embodiment. For example, an
arteriovenous graft system may include combinations of the valve
devices described below. Thus, it is intended that the present
invention cover such modifications and variations as come within
the scope of the appended claims and their equivalents. It is to be
understood by one of ordinary skill in the art that the present
discussion is a description of exemplary embodiments only, and is
not intended as limiting the broader aspects of the present
invention, which broader aspects are embodied in the exemplary
construction.
[0057] In general, the present invention is directed to an
implantable arteriovenous graft system that may be used in carrying
out hemodialysis treatments. Although the following description
will refer to the arteriovenous graft system being implanted into
an arm, it should be understood that the system may be implanted in
any suitable location of the body. For example, in other
embodiments, the arteriovenous graft system may be implanted into a
leg.
[0058] In addition to being well suited for carrying out
hemodialysis, the arteriovenous graft system of the present
invention also prevents or minimizes arterial steal and graft
thrombosis. In particular, the arteriovenous graft system is
designed to prevent or minimize blood flow through the graft when
hemodialysis is not occurring.
[0059] Referring to FIG. 1, for purposes of explanation, a right
arm 10 of a patient is shown. Selected arteries (shown as dotted
pathways) are illustrated in conjunction with selected veins (shown
as dark pathways). An arteriovenous graft 12 is shown connected at
one end to an artery and at an opposite end to a vein. In
particular, the arteriovenous graft 12 is connected to the brachial
artery 14 and to the cephalic vein 16.
[0060] The arteriovenous graft 12 is made from any suitable
biocompatible material. For example, in one embodiment, the graft
is made from a fluoropolymer, such as polytetrafluoroethylene,
which is commercially available as GORTEX.TM. from the W. L. Gore
Company.
[0061] Referring to FIGS. 2A and 2B, one embodiment of an
arteriovenous graft system made in accordance with the present
invention is shown including an arteriovenous graft 12. As
illustrated, the arteriovenous graft 12 is connected to an artery
14 and to a vein 16. In order to carry out hemodialysis, a first
hypodermic needle 18 is inserted through the skin and into the
arteriovenous graft 12. Blood is removed from the arteriovenous
graft 12 through the needle and into a dialysis machine 20. In the
dialysis machine, waste materials are removed from the blood. After
circulating through the dialysis machine 20, the blood is then fed
back into the arteriovenous graft 12 through a second hypodermic
needle 22.
[0062] In accordance with the present invention, the arteriovenous
graft system as shown in FIGS. 2A and 2B further includes at least
a first valve device generally 24 positioned at the arterial end of
the arteriovenous graft 12. Optionally, the arteriovenous graft
system can further include a second valve device generally 26
positioned at the venous end of the arteriovenous graft. The valve
devices 24 and 26 are in an open position during normal
hemodialysis as shown in FIG. 2A. When hemodialysis has ended,
however, the valve devices 24 and 26 are moved to a closed position
in order to prevent blood flow through the arteriovenous graft. In
this manner, arterial steal is either eliminated or reduced.
Further, by reducing turbulent blood flow through the arteriovenous
graft, graft thrombosis is also prevented.
[0063] In addition to minimizing arterial steal and preventing
graft thrombosis, the system and the process of the present
invention also offer various other advantages. For example,
reducing or stopping blood flow through the arteriovenous graft
when hemodialysis is not occurring also prevents the graft from
bleeding when the hypodermic needles used to carry out hemodialysis
are removed from the graft. Hypodermic needles as shown in FIG. 2B,
for instance, usually have a relatively large diameter or gauge.
Thus, when the needles are removed from a graft, bleeding can occur
where the needles have previously been. Needle hole bleeding
through the graft can result in the formation of scar tissue and
graft pseudoaneurisms. These complications, however, may be
prevented through the use of the system of the present
invention.
[0064] In the embodiment shown in FIG. 2A, the valve devices 26 and
24 each include an inflatable balloon 28 and 30. When inflated, the
balloons 28 and 30 constrict the arteriovenous graft 12 for
reducing or eliminating blood flow through the graft.
[0065] As shown in FIG. 2A, the inflatable balloons 28 and 30, in
this embodiment, have an annular shape that surround the
arteriovenous graft 12. As shown, each of the inflatable balloons
28 and 30 are also surrounded by a rigid collar 32 and 34. Each
collar 32 and 34 may be included in the system in order to maintain
each of the balloons 28 and 30 in the proper position. Further, the
collars 32 and 34 also serve to bias the balloon towards the
arteriovenous graft 12 when inflated. Each collar 32 and 34 may be
made from any rigid biocompatible material. For example, the
collars 32 and 34 may be made from a metal, such as titanium, or a
plastic material.
[0066] Each annular balloon 28 and 30 may be a separate structure
from the arteriovenous graft 12 or may be integral with the graft.
When integral with the graft, for instance, the graft may include a
multi-layered segment where each of the valve devices is to be
located. For example, within the multi-layered segment, the
arteriovenous graft 12 may include an outer rigid layer and an
inner luminal layer. The balloon 28 and 30 may be formed in between
the outer layer and the inner layer. In particular, when a fluid is
injected in between the inner and outer layers, the inner layer may
expand and constrict the lumen. See FIG. 2C.
[0067] In addition to having an annular shape, it should be
understood that each balloon 28 and 30 may have any shape
sufficient to constrict the arteriovenous graft when inflated. For
instance, in another embodiment, each balloon 28 and 30 may be
located on one side of the graft 12. When inflated, the balloons 28
and 30 force opposite sides of the graft together.
[0068] For example, referring to FIGS. 6 through 8, an alternative
embodiment of a valve device containing an inflatable balloon is
shown. As illustrated in FIG. 6, the valve device includes an inner
sleeve 110 positioned within an outer sleeve 112. The inner sleeve
can be attached or bonded to the outer sleeve at all locations
except over a discrete area 114. As shown in FIGS. 7 and 8, the
discrete area 114 is positioned opposite a fluid passageway 116.
The fluid passageway 116 is placed in communication with a fluid
delivery device. When fluid is forced through the fluid passageway
116, the fluid causes the discrete area 114 to inflate and form a
balloon as shown in FIG. 9.
[0069] The inner and outer sleeves can be made from various
materials and can be formed using various techniques. In one
embodiment, for instance, the inner and outer sleeves can be
injection molded and bonded together. For example, both the inner
sleeve and the outer sleeve may be made from a suitable elastomer,
such as a silicone elastomer. The outer sleeve 112 can be made more
rigid than the inner sleeve 110 so that the outer sleeve preserves
its shape when the discrete area 114 is inflated. The outer sleeve
112 can be made more rigid by having a greater thickness or by
being made from a stiffer material, such as a material that has a
higher durometer in comparison to the material used to form the
inner sleeve.
[0070] In order to attach the inner sleeve 110 to the outer sleeve
112, any suitable technique may be used. For example, in one
embodiment, an adhesive material, such as an adhesive material
containing a silicone elastomer may be used to bond the two layers
together. In other embodiments, the two layers may bond together
during the molding process.
[0071] As shown in FIG. 8, in one embodiment, the discrete area 114
may have a thickness that is less than the thickness of the
remainder of the inner sleeve 110. For instance, the discrete area
114 may have a thickness of less than about 0.015 inches. As shown
in FIG. 6, in one embodiment, the discrete area 114 may have a
circular or a substantially circular shape. By having a
substantially circular shape, the discrete area expands uniformly
and inflates evenly across its plane during inflation, thus
minimizing stress on the material. Once inflated as shown in FIG.
9, the discrete area 114 can have a spherical or substantially
spherical shape. The inflated shape can compress the arteriovenous
graft and prevent leakage. The substantially spherical shape also
allows the balloon to be inflated to a size and pressure which can
assure constriction and sealing of a 200 mmHg pressure gradient
across the graft. The balloon can also be designed to be
overpressurized by greater than about 30% thus serving as a safety
factor. Ultimately, the design is free of bulk, pinch points which
minimizes patient discomfort.
[0072] The valve device as shown in FIGS. 6 through 9 can be
integral with the arteriovenous graft or the arteriovenous graft
can fit inside the inner sleeve 110. In one embodiment, the inner
and outer sleeves can be slit along the length in order to
facilitate installation over a graft. Once installed over a graft,
the slit formed in the valve device can be connected together
through thermal bonding, clips or sutures.
[0073] In order to inflate the balloons as shown in the figures, in
one embodiment as shown in FIGS. 2A and 2B, each valve device may
further include an injection port 36 and 38. For example, as shown
in FIG. 2A, injection port 36 may be in fluid communication with
the balloon 28 via a tubing 40. Similarly, injection port 38 may be
in fluid communication with the balloon 30 via a tubing 42. Each
injection port 36 and 38 may be configured to be subcutaneously
implanted in a patient.
[0074] In the embodiment illustrated in FIG. 2A, injection ports 36
and 38 each include a diaphragm 44 and 46 positioned on one side of
a housing 48 and 50. The housings 48 and 50 may be made from any
suitable rigid and biocompatible material. For example, each
housing may be made from a metal, such as titanium. Each diaphragm
44 and 46, on the other hand, may be made from a material capable
of receiving the tip of a hypodermic needle. For example, each
diaphragm 44 and 46 may be made from an elastomeric film, such as a
silicone membrane.
[0075] As shown particularly in FIG. 2B, in order to inflate or
deflate the balloons 28 and 30, hypodermic needles 52 and 54 may
inject a fluid into each of the injection ports 36 and 38 through
the diaphragms 44 and 46. The fluid travels from the injection
ports 36 and 38 through the tubing 40 and 42 and into each
respective balloon 28 and 30. Similarly, the hypodermic needles 52
and 54 may also be used to withdraw fluid from the balloons 28 and
30.
[0076] As shown in FIG. 2B, once inflated, the balloons 28 and 30
constrict the arteriovenous graft 12 at the arterial end and at the
venous end. The fluid used to inflate the balloons 28 and 30 may
vary depending upon the particular application. The fluid may be,
for instance, a gas or liquid. In one embodiment, for instance, a
saline solution may be injected into the injection ports 36 and 38
for inflating the balloons. In one embodiment, it may take from
about 2 ccs to about 6 ccs of fluid to transition each balloon
valve 28 and 30 from an open position to a closed position.
[0077] When closed, each valve device should be capable of
maintaining its position when exposed to systolic pressure. For
example, systolic pressures in arteries may be greater than about
250 mmHg, such as from about 170 mmHg to about 270 mmHg.
[0078] In addition to withstanding relatively high fluid pressures,
each of the valve devices 24 and 26 should also be constructed so
that the valve devices can constrict the arteriovenous graft as
close as possible to the intersection of the graft with the artery
14 and the vein 16. For example, the first valve device 24, in one
embodiment, constricts the arteriovenous graft at a distance of
from about 5 mm from the arterial anastomosis, such as no greater
than about 20 mm from the arterial anastomosis. The position of the
second valve device 26 in relation to the venous anastomosis may
also be within the above defined limits.
[0079] The methods for using the arteriovenous graft system of the
present invention will now be discussed in relation to a system
that contains a single valve device positioned at the arterial end
of the graft and a system that contains two valve devices as shown
in FIGS. 2A and 2B.
[0080] When the arteriovenous graft system of the present invention
contains a single valve device positioned at the arterial end, in
one embodiment, the valve device may be positioned so as to
constrict blood flow through the graft when hemodialysis is not
occurring. In this embodiment, arterial steal is not being
completely prevented but is being minimized. In particular, the
single valve device constricts the graft so that blood flow through
the graft continues without clotting but is at a reduced flow
rate.
[0081] In this embodiment, the patient's condition may need to be
monitored over a period of time, such as days or weeks, and the
valve device may be adjusted in order to minimize arterial steal
without causing a complete blood stoppage. For instance, over
several days or weeks, the arteriovenous graft of the patient may
be monitored and the valve device may be adjusted so as to
gradually increase or decrease the narrowing of the arteriovenous
graft. The ultimate position of the valve will vary depending upon
the patient and the location of the arteriovenous graft.
[0082] In an alternative embodiment, the single valve device may be
used to completely close off the arteriovenous graft 12 at the
arterial end. In this embodiment, during hemodialysis, the valve
device 24 is in the open position and the arteriovenous graft 12 is
cannulated with the two dialysis needles 18 and 22 as shown in FIG.
2A. Upon completion of dialysis, a fluid is injected into the
injection port 36 of the first valve device causing the balloon 28
to inflate thereby closing the valve device and eliminating
arterial blood flow through the graft.
[0083] After the valve device is closed, a blood compatible fluid
is then injected into the arteriovenous graft 12 through, for
instance, a dialysis needle to flush any residual blood out of the
graft. The blood compatible fluid can be, for instance, heparinized
saline. The residual blood is flushed out of the graft in order to
prevent any clotting.
[0084] In this embodiment, some residual saline remains in the
graft until hemodialysis is once again conducted on the patient.
This embodiment should only be used when it is determined that
substantially no blood from the vein 16 will flow into the graft
once valve device 24 is closed.
[0085] In order to prevent any blood flowing from the vein 16 back
into the arteriovenous graft 12 after the first valve device 24 has
been closed, in one embodiment of the present invention as shown
particularly in FIGS. 2A and 2B, the arteriovenous graft system can
include the second valve device 26. In this embodiment, the process
as described above is repeated. After the arteriovenous graft 12 is
flushed with a blood compatible fluid, however, a fluid is injected
into the injection port 38 of the second valve device 26 which
causes the second valve device to close.
[0086] In addition to the valve devices as illustrated in FIGS. 2A
and 2B, in other embodiments, other valve devices may also be
utilized in the system of the present invention. For example,
referring to FIG. 4, another embodiment of a valve device generally
60 is shown in communication with an arteriovenous graft 12. In
this embodiment, the valve device 60 includes a fluid chamber 62 in
communication with an injection port 64 similar to the injection
ports described above. As shown, injection port 64 includes a
diaphragm 68 configured to receive fluid from a hypodermic needle
70.
[0087] The valve device 60 further includes a piston 72 contained
within a housing 74. The piston 72 is positioned below the fluid
chamber 62.
[0088] In this embodiment, when a fluid is injected from the needle
70 into the injection port 64, the fluid is forced into the fluid
chamber 62 via a tube 66. The pressure of the fluid then forces the
piston 72 to lower closing the valve and constricting flow through
the arteriovenous graft 12.
[0089] Valve device 60 as shown in FIG. 4 may be used in a single
valve system of the present invention or in a double valve system
of the present invention as illustrated in FIG. 2A.
[0090] Referring to FIG. 3, another embodiment of a valve device
generally 80 that may be used in the arteriovenous graft system of
the present invention is illustrated. In this embodiment, the valve
device 80 includes a housing 82 containing a magnetically actuated
piston 84. Specifically, the valve device is configured such that
the piston 84 moves between an open and closed position when the
valve device is contacted with a magnetic field.
[0091] In this particular embodiment, the valve device 80 includes
a coil member 86. The coil member 86 is configured to convert a
pulsating magnetic field into an electric current. As shown, the
coil member 86 then supplies the electric current to a solenoid 88.
Solenoid 88 then moves the piston 84 to either open or close the
valve device.
[0092] In order to activate the valve device 80, a magnetic key 90
is placed close to the skin of a patient. In this embodiment, the
magnetic key 90 may be an electromagnet that creates a pulsating
magnetic field. As described above, the pulsating magnetic field is
then converted into an electric current by the coil member 86. The
magnetic key 90 may be configured either to open or to close the
valve device. In one embodiment, for instance, the valve device 80
may normally be found in a closed position blocking off the
arteriovenous graft 12. When the magnetic key 90, however, is
placed adjacent to the patient's skin, the valve device 80 then
opens allowing blood to circulate through the graft. In other
embodiments, however, it should be understood that the valve device
may be configured to close when placed adjacent to the magnetic key
90.
[0093] In addition to the valve device 80 as shown in FIG. 3, other
magnetically activated valves may be used in the system of the
present invention. For example, in another embodiment of the
present invention, the valve device may include a piston in
operative association with a permanent magnet. A ferrous plate may
be positioned on the opposite side of the arteriovenous graft.
Thus, the permanent magnet contained in the piston is attracted to
the ferrous surface for closing off the arteriovenous graft. When a
magnet with opposite polarity, however, is placed adjacent to the
valve device, the permanent magnet contained within the piston is
attracted to the reverse magnetic field causing the valve to
open.
[0094] Referring to FIGS. 10 through 13, still another embodiment
of a magnetically activated valve device that may be used in
accordance with the present disclosure is shown. In this
embodiment, the valve device includes a magnetically activated
piston 120 as shown in FIG. 10. As illustrated, the piston 120 is
contained within a housing 122. The piston is biased towards a
closed position by a spring 124. In particular, the spring 124
applies a biasing force to the piston 120.
[0095] As shown in FIGS. 10 and 11, the piston is also attached to
a lever arm 126. The lever arm 126 is attached to a magnet member
128 or a magnetically attractable member 128. In this embodiment,
when an external key comprising a magnet or an electromagnet is
placed adjacent to the member 128, the lever arm 126 moves which in
turn causes the piston to move and open or close the valve.
[0096] In the embodiment shown in the figures, the piston 120 is
normally biased in a closed position. When a magnetic key is placed
adjacent to the valve device, the lever arm causes the piston 120
to move and open the valve device. It should be understood,
however, that in other embodiments the lever arm may be used to
close the valve.
[0097] The piston 120 as shown in FIG. 10 can be placed in
association with an arteriovenous graft in order to open and close
the graft. In one particular embodiment as shown in FIG. 12, for
example, the piston 120 can be placed in communication with a
balloon valve such as the one illustrated in FIGS. 6 through 9. In
this embodiment, the piston 120 is used as a fluid delivery device
that delivers fluid to the balloon.
[0098] For instance, referring to FIG. 12, the piston 120 is shown
in a closed position caused by a biasing force being placed against
the piston by the spring 124. When in the closed position, the
piston 120 forces a fluid through the conduit 130 and in contact
against the discrete area 114, causing the discrete area to inflate
and form a substantially spherical shape. When inflated, the
discrete area 114 blocks flow through the arteriovenous graft.
[0099] When it is desired to open the arteriovenous graft for
dialysis treatment, for instance, a key comprising a magnet or an
electromagnet is placed adjacent to the valve device. Referring to
FIG. 13, for instance, the magnetic or electromagnetic key is
placed adjacent to the magnetic member or magnetically attractable
member 128 causing the lever arm 126 to pivot or move. The lever
arm 126 is attached to a linking member 132 that is in turn
connected to the piston 120. When the lever arm 126 is pivoted, the
linking member 132 causes the piston to retract as shown. Fluid
contained within the conduit 130 is thereby drawn out of the
discrete area 114 causing the balloon to deflate. In this manner,
the valve device is opened for allowing blood flow through the
arteriovenous graft. During the dialysis treatment, the external
magnetic key can be fixed into position to ensure that the valve
device stays open. For instance, the external key can be taped or
otherwise attached to the skin of the patient. When the dialysis
treatment is concluded, the external magnetic key is removed and
the valve device automatically returns to the closed position.
[0100] The fluid that is contained within the valve device may vary
depending upon the particular application and the desired results.
In one embodiment, for instance, a saline solution may be contained
within the valve device.
[0101] In the embodiment illustrated in the drawings, the lever arm
126 is moved based upon an attracting magnetic force. It should be
understood, however, that magnetic repulsion can also be used to
move the lever arm as well.
[0102] The valve device as shown in FIGS. 10 through 13 can be
designed to be relatively small for being implanted under the skin
of a patient. For instance, the housing 122 as shown in FIG. 10 can
have a diameter less than about 3 cm and can have a height of less
than about 1 cm.
[0103] Using a magnetically actuated valve device as shown in FIGS.
10 through 13 can provide various advantages. For instance, because
the valve device is magnetically actuated, the valve device
eliminates the need to use hypodermic needles for transferring
liquid into and out of a plenum or port.
[0104] In still another embodiment, the valve device as shown in
FIGS. 10 through 13 may be actuated other than through use of a
magnet. For instance, in one embodiment, the valve device may
include a pump in communication with a battery. The pump may be
turned on and off using wireless telemetry. In fact, wireless
telemetry may also deliver real time pressure measurements thereby
communicating the status of the valve device.
[0105] Another embodiment of an arteriovenous graft system in
accordance with the present disclosure is illustrated in FIG. 19.
Like reference numerals have been used to identify similar features
and elements of other embodiments. As shown, the system illustrated
in FIG. 19 is similar to the embodiment illustrated in FIG. 2A. As
shown, the system includes an arteriovenous graft 12 that is
connected to an artery 14 at one end and to a vein 16 at an
opposite end. In accordance with the present disclosure, the system
includes a first valve device 24 positioned at the arterial end and
a second valve device 26 positioned at the venous end of the graft.
The first valve device 24 and the second valve device 26 are
constructed similar to the valve devices illustrated in FIGS. 6-9.
It should be understood, however, that any suitable valve device
can be positioned at either end of the graft. Further, the first
valve device can be the same or can be different from the second
valve device.
[0106] In the embodiment illustrated in FIG. 19, the first valve
device 24 and the second valve device 26 are both connected to a
single actuator 36. The actuator 36 is configured to open and close
both valve devices simultaneously. For example, in the embodiment
illustrated, the actuator 36 comprises a fluid port that is in
communication with the first valve device 24 via tubing 40 and is
in communication with the second valve device 26 via tubing 42.
When a fluid is injected or withdrawn from the port 36, both valve
devices close or open respectively.
[0107] Various benefits and advantages may be realized by only
having a single actuator for both valve devices as shown in FIG.
19. For instance, only having a single actuator simplifies the
system and only requires that a single actuator be implanted within
a patient. Further, in some applications, there may be advantages
to having the valve devices open and close simultaneously.
[0108] The actuator 36 as shown in FIG. 19 comprises an injection
port. It should be understood, however, that any suitable valve
actuator may be installed within the system. For instance, in an
alternative embodiment, the actuator 36 may comprise a piston such
as shown in FIGS. 10-13 that may be configured to inflate and
deflate a balloon contained within the valve devices. In still
another embodiment, the actuator 36 may comprise a solenoid that is
configured to electrically open and close the valve devices.
[0109] In order to carry out hemodialysis, a first hypodermic
needle 18 and a second hypodermic needle 22 are shown inserted into
the arteriovenous graft 12. When the valve devices 24 and 26 are
open, blood can circulate from the graft into the first hypodermic
needle 18, through the dialysis machine 20 and back into the graft
through the hypodermic needle 22.
[0110] In one embodiment, the valve devices 24 and 26 are normally
configured to be in a closed position. In order to open the valve
devices and permit blood flow through the graft, fluid can be
removed through the actuator 36 causing the balloons in the valve
devices to deflate. Once both valve devices are open, the dialysis
process can be carried out.
[0111] Once a sufficient amount of blood has been circulated
through the dialysis machine, fluid can then be inserted into the
actuator 36 for simultaneously closing the valve devices 24 and 26.
Closing the valve devices stops blood flow through the graft. After
hemodialysis is complete, the graft 12 can be flushed. For
instance, a blood compatible fluid can be circulated through the
graft using a single hypodermic needle or through the use of two
hypodermic needles. In one particular embodiment, for instance, one
hypodermic needle can be used to insert a blood compatible fluid,
such as a saline solution, through the graft while a second needle
can be used to remove the fluid.
[0112] Referring to FIG. 5, another embodiment of an arteriovenous
graft system made in accordance with the present invention is
shown. Like reference numerals have been used in order to identify
similar features and elements of other embodiments. As shown, in
this embodiment, the arteriovenous graft system includes a first
valve device generally 24 at the arterial end of the graft similar
to the valve device shown in FIGS. 2A and 2B. In particular, the
first valve device 24 includes a balloon 28 that is inflated or
deflated using an injection port 36. The balloon 28 is for
constricting the arteriovenous graft when desired. As explained
above, the first valve device 24, for most applications, is capable
of maintaining a closed or constricted position on the graft even
when exposed to relatively high fluid pressures. In some
embodiments, however, these same pressures are not experienced at
the venous end of the graft.
[0113] In this regard, in this embodiment, the arteriovenous graft
12 includes a second valve device generally 100 that may be
described as a low pressure valve device when compared to the first
valve device 24.
[0114] For example, in one embodiment, the second valve device 100
may be a check valve that allows fluid flow from the graft 12 into
the vein 16 but does not permit flow from the vein 16 into the
graft 12. In general, any suitable check valve may be used in
accordance with the present invention.
[0115] In the embodiment shown in FIG. 5, the second valve device
100 includes a membrane 102 made from, for instance, a polymeric
film that is formed or is connected so as to be integral with the
arteriovenous graft 12. The membrane 102 may be, for instance, a
flap that allows fluid flow in one direction from the graft 12 into
the vein 16. The membrane 102 may be formed from a single piece of
film or may be formed from multiple segments. For example, in one
embodiment, the film can include one or more slits that permit
fluid flow in one direction.
[0116] The arteriovenous graft system in FIG. 5 provides various
advantages. For example, in the embodiment shown in FIG. 5, only
the first valve device 24 needs to be manually opened or
closed.
[0117] In the embodiment shown in FIG. 5, the first valve device is
represented as a balloon valve. It should be understood, however,
that the first valve device may be any of the other valve devices
shown and described above.
[0118] The second valve device 100 as shown in FIG. 5 represents
one embodiment of a check valve (a valve that allows flow in one
direction) that may be used in accordance with the present
disclosure. It should be understood, however, that various other
check valves may be used. For instance, referring to FIGS. 14
through 18, another embodiment of a check valve device 150 is
illustrated. As shown in FIGS. 14 and 15, for instance, the check
valve device 150 includes a pair of overlapping flaps 152 and 154.
The overlapping flaps allow fluid flow only in one direction. As
shown, the opposing flaps 152 and 154 are generally planar and
parallel. The flaps can be integral with the arteriovenous graft
156 or can be attached to the graft using any suitable technique.
For instance, as shown in FIG. 15, the arteriovenous graft 156 can
include a pair of opposing slits through which the flaps are
inserted. The flaps can then be attached to the graft 156 by being
welded in place or through the use of a biocompatible adhesive. In
an alternative embodiment as shown in FIG. 18, sutures 158 can be
used in order to attach the flaps to the arteriovenous graft
156.
[0119] In addition to the flaps 152 and 154, the check valve device
150 can further include edge seals 160, 162, 164 and 166 as shown
in FIGS. 16 and 17. The edge seals 160, 162, 164 and 166 are
positioned on both sides of each flap and are designed to create a
seal with the radial wall of the graft 156. The edge seals are
generally located where the flaps are not connected to the graft
156.
[0120] The check valve device 150 can be made from any suitable
material. For instance, the flaps and the edge seals can be made
from expanded or unexpanded PTFE, polyurethane and/or silicone. The
blood contacting surfaces may be treated and/or textured to enhance
their formation of a pseudointima, optimize thrombocompatibility
and flow characteristics.
[0121] Referring to FIG. 20, another embodiment of an arteriovenous
graft system in accordance with the present disclosure is
illustrated. Again, like reference numerals have been used to
identify similar features and elements of other embodiments. The
system illustrated in FIG. 20 is similar to the system illustrated
in FIG. 19. The system includes an arteriovenous graft 12 that is
connected to an artery 14 at one end and to a vein 16 at an
opposite end. The system also includes a first valve device 24
positioned at the arterial end and second valve device 26
positioned at the venous end of the graft. It should be understood,
however, that any suitable valve device can be positioned at either
end of the graft. Further, the first valve device can be the same
or can be different from the second valve device.
[0122] As shown in FIG. 20, the first valve device 24 and second
valve device 26 are both connected to actuator 200. Actuator
includes housing 214. Housing 214 can be made from any suitable
rigid and biocompatible material. For example, housing can be made
from a metal, such as titanium. Actuator 200 is configured to open
or close both valve devices simultaneously. For example, in the
illustrated embodiment, actuator 200 is in fluid communication with
first valve device 24 via tubing 40 connected to first outlet
nozzle 218 and is in fluid communication with the second valve
device 26 via tubing 42 connected to second outlet nozzle 220.
Actuator 200 can be configured to be subcutaneously implanted in a
patient.
[0123] Referring to FIGS. 21 A-C, actuator 200 includes an
accumulator 204. While a preferred accumulator is described herein,
it should be understood that any suitable accumulator can be
utilized in connection with the present invention. Accumulator 204
is positioned within housing 214. Accumulator 204 is an energy
storage device which can exert pressure into the arteriovenous
graft system of the present invention.
[0124] Accumulator 204 can advantageously assist in maintaining a
generally constant pressure when the actuator 200 causes each valve
24, 26 (as illustrated in FIG. 20) to close. When closed, each
valve device should be capable of maintaining its position when
exposed to systolic pressure. For example, systolic pressures in
arteries may be greater than about 250 mmHg, such as from about 170
mmHg to about 270 mmHg. Accumulator 204 includes spring 206 which
exerts force against piston 208 which can maintain suitable
pressure in the arteriovenous graft system of the present
invention. Liquid is prevented from contacting spring 206 because
diaphragm 210 provides a barrier between spring 206 and fluid path
212. O-ring 226 can assist in ensuring sealing engagement between
the diaphragm 210 and housing 214 to prevent fluid from entering
fluid path 212. An accumulator top 222 can maintain the various
components in the housing 214.
[0125] Actuator 200 also includes fluid injection port 202. Fluid
injection port 202 can assist in opening and closing first valve
device 24 and second valve device 26. For example, as shown in FIG.
20, fluid injection port 202 can be in fluid communication with
first valve device 24 via tubing 40 and in communication with the
second valve device 26 via tubing 42.
[0126] Turning again to FIGS. 21 A-C, fluid injection port 202
includes a septum 216 positioned on one side of a housing 214.
Septum 216 can be made from a material capable of receiving the tip
of a hypodermic needle. For example, septum 216 can be made from an
elastomeric film, such as a silicone membrane. Septum 216 can be of
any suitable thickness. However, septum 216 should be of sufficient
thickness to resist pressure from the accumulator 204 and prevent
fluid from unintentionally leaking from septum 216. The septum 216
can be held in place in the housing 214 by port top 224.
[0127] When fluid is injected or withdrawn through septum 216, both
valve devices 24, 26 open or close respectively. In this regard,
accumulator 204, which can be positioned adjacent to injection port
202, can store energy in spring 206 as a result of the pressure
generated from the fluid that is injected. If any of the pressure
in the system is lost, spring 206 can release energy through piston
208 to maintain a generally constant pressure. As pressure
decreases in the system, the spring 206 is permitted to expand and
piston 208 extends into fluid path 212, maintaining a generally
constant pressure. For instance, referring to FIG. 21B, spring 206
is almost fully extended indicating the pressure in the system is
less than that being exerted by the spring 206. By contrast,
referring to FIG. 21C, the spring 206 is not fully extended
indicating pressure against the accumulator 204 and energy stored
in spring 206. Again, however, any suitable accumulator can be used
in connection with the present disclosure.
[0128] Various benefits and advantages can be realized by having an
actuator 200 which includes an accumulator 204 as shown in FIG. 20.
For example, air can diffuse through tubing 40, 42 causing a
decrease in pressure at valve devices 24, 26. A concern over such
loss in pressure is that valve devices 24, 26 could open allowing
blood to enter graft 12. However, it has been advantageously
discovered that accumulator 204 of the present disclosure can
prevent such loss in pressure. Because accumulator 204 is
incorporated into actuator 200, the system is greatly simplified by
requiring only actuator 200 to be implanted within a patient.
However, it should be understood that the accumulator described
herein can be utilized in connection with any of the other
embodiments of the present invention, including embodiments in
which more than one actuator is utilized.
[0129] Turning again to FIG. 20, in order to carry out
hemodialysis, a first hypodermic needle 18 and a second hypodermic
needle 22 are shown inserted into the arteriovenous graft 12. As
described previously, when the valve devices 24 and 26 are open,
blood can circulate from the graft into the first hypodermic needle
18, through the dialysis machine 20 and back into the graft through
the hypodermic needle 22.
[0130] In one embodiment, the valve devices 24 and 26 are normally
configured to be in a closed position. In this regard, accumulator
204 assists in maintaining a generally constant pressure when the
actuator causes each valve device to close. In order to open the
valve devices and permit blood flow through the graft, fluid can be
removed through the actuator 200 causing the balloons in the valve
devices to deflate. Once both valve devices are open, the dialysis
process can be carried out.
[0131] Once a sufficient amount of blood has been circulated
through the dialysis machine 20, fluid can then be inserted into
the actuator 200 for simultaneously closing the valve devices 24
and 26. Closing the valve devices stops blood flow through the
graft. Again, accumulator 204 assists in maintaining a generally
constant pressure when the actuator causes each valve device to
close. After hemodialysis is complete, the graft 12 can be
flushed.
[0132] These and other modifications and variations to the present
invention may be practiced by those of ordinary skill in the art,
without departing from the spirit and scope of the present
invention, which is more particularly set forth in the appended
claims. In addition, it should be understood that aspects of the
various embodiments may be interchanged both in whole or in part.
Furthermore, those of ordinary skill in the art will appreciate
that the foregoing description is by way of example only, and is
not intended to limit the invention so further described in such
appended claims.
* * * * *