U.S. patent application number 10/775841 was filed with the patent office on 2004-08-19 for expandable vein ligator catheter and method of use.
This patent application is currently assigned to VNUS Medical Technologies, Inc.. Invention is credited to Farley, Brian E., Henderson, Dawn A., Jones, Christopher S., Parker, Mark P., Tartaglia, Joseph M..
Application Number | 20040162555 10/775841 |
Document ID | / |
Family ID | 27129940 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040162555 |
Kind Code |
A1 |
Farley, Brian E. ; et
al. |
August 19, 2004 |
Expandable vein ligator catheter and method of use
Abstract
A catheter includes a plurality of primary leads to deliver
energy for ligating a hollow anatomical structure. Each of the
primary leads includes an electrode located at the working end of
the catheter. Separation is maintained between the primary leads
such that each primary lead can individually receive power of
selected polarity. The primary leads are constructed to expand
outwardly to place the electrodes into apposition with a hollow
anatomical structure. High frequency energy can be applied from the
leads to create a heating effect in the surrounding tissue of the
anatomical structure. The diameter of the hollow anatomical
structure is reduced by the heating effect, and the electrodes of
the primary leads are moved closer to one another. Where the hollow
anatomical structure is a vein, energy is applied until the
diameter of the vein is reduced to the point where the vein is
occluded. In one embodiment, a balloon is inflated to occlude the
structure before the application of energy. Where the structure is
a vein, the inflated balloon obstructs blood flow and facilitates
the infusion of saline, medication, or a high-impedance fluid to
the vein in order to reduce the occurrence of coagulation and to
improve the heating of the vein by the catheter. The catheter can
include a lumen to accommodate a guide wire or to allow fluid
delivery.
Inventors: |
Farley, Brian E.; (Los
Altos, CA) ; Henderson, Dawn A.; (Palo Alto, CA)
; Jones, Christopher S.; (Sunnyvale, CA) ; Parker,
Mark P.; (San Jose, CA) ; Tartaglia, Joseph M.;
(Morgan Hill, CA) |
Correspondence
Address: |
FULWIDER PATTON LEE & UTECHT, LLP
HOWARD HUGHES CENTER
6060 CENTER DRIVE
TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Assignee: |
VNUS Medical Technologies,
Inc.
|
Family ID: |
27129940 |
Appl. No.: |
10/775841 |
Filed: |
February 9, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10775841 |
Feb 9, 2004 |
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09497278 |
Feb 3, 2000 |
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6689126 |
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09497278 |
Feb 3, 2000 |
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08958766 |
Oct 26, 1997 |
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6165172 |
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08958766 |
Oct 26, 1997 |
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08927251 |
Sep 11, 1997 |
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6200312 |
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Current U.S.
Class: |
606/45 |
Current CPC
Class: |
A61B 2017/22051
20130101; A61B 2018/00214 20130101; A61B 2018/0022 20130101; A61B
2018/00404 20130101; A61B 2017/22038 20130101; A61B 2018/00898
20130101; A61B 2018/1253 20130101; A61B 2218/002 20130101; A61B
2017/22067 20130101; A61B 2090/3782 20160201; A61B 2018/124
20130101; A61B 18/1492 20130101; A61B 2018/00488 20130101; A61B
2018/00589 20130101; A61B 2018/126 20130101 |
Class at
Publication: |
606/045 |
International
Class: |
A61B 018/14 |
Claims
What is claimed is:
1. An apparatus for ligating a hollow anatomical structure,
comprising: a catheter having a sheath and a working end, wherein a
tip, a port and an opening are located at the working end of the
catheter, and the port is in fluid communication with a lumen; a
balloon located at the working end of the catheter, wherein the
port is located between the balloon and the tip; an inner member
disposed within the sheath such that the inner member and the
sheath are capable of being moved relative to one another; a
plurality of leads, each lead having a distal end, the plurality of
leads being coupled with the inner member such that the distal ends
of the plurality of leads become extended out of the opening at the
working end of the catheter when the sheath is moved relative to
the inner member, each lead being formed to move the distal end
away from a longitudinal axis defined by the sheath when the
plurality of leads are extended out the opening; wherein the distal
end of each lead is capable of delivering energy to the anatomical
structure.
2. The apparatus of claim 1, wherein the anatomical structure is a
vein, and the formed leads have sufficient force to move into
apposition with the vein wall, and the formed leads do not have
sufficient strength to prevent the reduction of the diameter of the
vein when energy is applied by the distal end of the leads.
3. The apparatus of claim 1, further comprising a secondary lead
having a distal secondary end, the secondary lead being coupled
with the inner member such that the distal secondary end of
secondary lead is extended out of the opening at the working end of
the catheter when the inner member is moved relative to the sheath,
wherein the distal ends of the leads are located between the distal
secondary end of the secondary lead and the inner member.
4. The apparatus of claim 3, wherein the leads are electrically
connected to a power source such that the polarity of each lead can
be switched.
5. The apparatus of claim 3, wherein the plurality of leads and the
secondary lead are electrically connected to a power source such
that the polarity of the plurality of leads can be changed
independently of the polarity of the secondary lead.
6. The apparatus of claim 3, wherein the plurality of leads and the
secondary lead are electrically connected to a power source,
wherein the polarity of the plurality of leads can be switched to
have either the same polarity or to have opposing polarities for
adjacent distal ends of the leads, and the polarity of the
secondary lead can be switched between having a polarity and being
neutral.
7. The apparatus of claim 1, wherein the balloon includes openings
exposed to the fluid in the anatomical structure, and the openings
allow fluid from the hollow anatomical structure to flow into and
expand the balloon.
8. An apparatus for ligating a hollow anatomical structure,
comprising: a catheter having a sheath and a working end, wherein a
tip and a port are located at the working end of the catheter, and
the port is in fluid communication with a lumen; a balloon located
at the working end of the catheter, wherein the port is located
between the balloon and the tip; a plurality of bowable arms, each
arm having a section, wherein the arms being capable of moving the
sections away from the catheter and toward the anatomical
structure; a plurality of electrodes, wherein at least one
electrode is located on the section of at least one arm, and
wherein the electrode is capable of delivering energy to the
anatomical structure.
9. The apparatus of claim 8, wherein the balloon includes openings
exposed to the fluid in the anatomical structure, and the openings
allow fluid in the anatomical structure to flow into and expand the
balloon.
10. The apparatus of claim 8, wherein the anatomical structure is a
vein, and the formed leads have sufficient force to move into
apposition with the vein wall, and the formed leads do not have
sufficient strength to prevent the reduction of the diameter of the
vein when energy is applied by the distal end of the leads.
11. The apparatus of claim 8, further comprising at least one
aperture formed in the working end of the catheter to allow the
delivery of fluid therethorugh.
12. The apparatus of claim 11, wherein the fluid has a high
impedance.
13. The apparatus of claim 11, wherein the fluid includes heparin
and water.
14. An apparatus for ligating a hollow anatomical structure,
comprising: a catheter having a sheath, a working end, and an
opening are located at the working end of the catheter; an inner
member disposed within the sheath such that the inner member and
the sheath are capable of being moved relative to one another; a
plurality of leads, each lead having a distal end, the plurality of
leads being coupled with the inner member such that the distal ends
of the plurality of leads become extended out of the opening at the
working end of the catheter when the inner member is moved relative
to the sheath, each lead being formed to move the distal end away
from a longitudinal axis defined by the sheath when the plurality
of leads are extended out the opening, the distal end of each lead
is capable of delivering energy to the anatomical structure; a
flexible, impermeable cover spanning the area between the leads
along the circumference of the catheter when the leads are extended
out the opening, such that the cover blocks fluid flow within the
hollow anatomical structure.
15. The apparatus of claim 14, further comprising at least one
aperature formed in the working end of the catheter to allow the
delivery of fluid therethorugh.
16. The apparatus of claim 15, wherein the fluid has a high
impedance.
17. The apparatus of claim 15, wherein the fluid includes heparin
and water.
18. The apparatus of claim 14, wherein the anatomical structure is
a vein, and the formed leads have sufficient force to move into
apposition with the vein wall, and the formed leads do not have
sufficient strength to prevent the reduction of the diameter of the
vein when energy is applied by the distal end of the leads.
19. A method of applying energy from a power source to a hollow
anatomical structure from within the structure, the method
comprising the steps of: introducing into the hollow anatomical
structure a catheter having a working end, and a plurality of leads
disposed at the working end, each lead having a distal end, each
lead being connected to the power source; blocking the hollow
anatomical structure by expanding the circumference of the catheter
adjacent the distal ends of the leads; expanding the leads
outwardly from the working end of the catheter, wherein the distal
ends of the leads move away from each other and into contact with
the anatomical structure; applying energy to the anatomical
structure from the distal end of the leads until the anatomical
structure collapses.
20. The method of claim 19, wherein the step of blocking the hollow
anatomical structure further includes the step of inflating a
balloon on the catheter.
21. The method of claim 19, further comprising the step of
delivering fluid to the hollow anatomical structure to displace
other fluids present around the working end of the catheter in the
hollow anatomical structure.
22. The method of claim 21, further comprising the step of
delivering a fluid having a high impedance value to the hollow
anatomical structure, the high impedance fluid displacing other
fluids present around the working end of the catheter in the hollow
anatomical structure.
23. The method of claim 21, further comprising the step of
delivering heparin and a fluid having a high impedance value to the
hollow anatomical structure, the heparin and the high impedance
fluid displacing other fluids present around the working end of the
catheter in the hollow anatomical structure.
24. The method of claim 21, further comprising the step of
delivering a heparin and saline to the hollow anatomical structure,
wherein the heparin and saline displaces other fluids present
around the working end of the catheter in the hollow anatomical
structure.
25. The apparatus of claim 19, wherein the hollow anatomical
structure is a vein, and the formed leads in the step of expanding
have sufficient force to move into apposition with the vein wall,
and the formed leads do not have sufficient strength to prevent the
reduction of the diameter of the vein when energy is applied by the
distal end of the leads.
Description
[0001] This is a continuation-in-part of co-pending application
Ser. No. 08/927,251 filed on Sep. 11, 1997.
BACKGROUND OF THE INVENTION
[0002] The invention relates generally to a method and apparatus
for applying energy to shrink a hollow anatomical structure such as
a vein, and more particularly, to a method and apparatus using an
electrode device having multiple leads for applying said
energy.
[0003] The human venous system of the lower limbs consists
essentially of the superficial venous system and the deep venous
system with perforating veins connecting the two systems. The
superficial system includes the long or great saphenous vein and
the short saphenous vein. The deep venous system includes the
anterior and posterior tibial veins which unite to form the
popliteal vein, which in turn becomes the femoral vein when joined
by the short saphenous vein.
[0004] The venous system contains numerous one-way valves for
directing blood flow back to the heart. Venous valves are usually
bicuspid valves, with each cusp forming a sack or reservoir for
blood which, under retrograde blood pressure, forces the free
surfaces of the cusps together to prevent retrograde flow of the
blood and allows only antegrade blood flow to the heart. When an
incompetent valve is in the flow path, the valve is unable to close
because the cusps do not form a proper seal and retrograde flow of
the blood cannot be stopped. When a venous valve fails, increased
strain and pressure occur within the lower venous sections and
overlying tissues, sometimes leading to additional valvular
failure. Two venous conditions which often result from valve
failure are varicose veins and more symptomatic chronic venous
insufficiency.
[0005] The varicose vein condition includes dilation and tortuosity
of the superficial veins of the lower limbs, resulting in unsightly
discoloration, pain, swelling, and possibly ulceration. Varicose
veins often involve incompetence of one or more venous valves,
which allow reflux of blood within the superficial system. This can
also worsen deep venous reflux and perforator reflux. Current
treatments of vein insufficiency include surgical procedures such
as vein stripping, ligation, and occasionally, vein-segment
transplant.
[0006] Ligation involves the cauterization or coagulation of
vascular lumina using electrical energy applied through an
electrode device. An electrode device is introduced into the vein
lumen and positioned so that it contacts the vein wall. Once
properly positioned, RF energy is applied to the electrode device
thereby causing the vein wall to shrink in cross-sectional
diameter. A reduction in cross-sectional diameter, as for example
from 5 mm (0.2 in) to 1 mm (0.04 in), significantly reduces the
flow of blood through the vein and results in an effective
ligation. Though not required for effective ligation, the vein wall
may completely collapse thereby resulting in a full-lumen
obstruction that blocks the flow of blood through the vein.
[0007] One apparatus for performing venous ligation includes a
tubular shaft having an electrode device attached at the distal
tip. Running through the shaft, from the distal end to the proximal
end, are electrical leads. At the proximal end of the shaft, the
leads terminate at an electrical connector, while at the distal end
of the shaft the leads are connected to the electrode device. The
electrical connector provides the interface between the leads and a
power source, typically an RF generator. The RF generator operates
under the guidance of a control device, usually a
microprocessor.
[0008] The ligation apparatus may be operated in either a monopolar
and bipolar configuration. In the monopolar configuration, the
electrode device consists of an electrode that is either positively
or negatively charged. A return path for the current passing
through the electrode is provided externally from the body, as for
example by placing the patient in physical contact with a large
low-impedance pad. The current flows from the ligation device to
the low impedance pad. In a bipolar configuration, the electrode
device consists of a pair of oppositely charged electrodes
separated by a dielectric material. Accordingly, in the bipolar
mode, the return path for current is provided by the electrode
device itself. The current flows from one electrode, through the
tissue, and returns by way of the oppositely charged electrode.
[0009] To protect against tissue damage; i.e., charring, due to
cauterization caused by overheating, a temperature sensing device
is attached to the electrode device. The temperature sensing device
may be a thermocouple that monitors the temperature of the venous
tissue. The thermocouple interfaces with the RF generator and the
controller through the shaft and provides electrical signals to the
controller which monitors the temperature and adjusts the energy
applied to the tissue, through the electrode device,
accordingly.
[0010] The overall effectiveness of a ligation apparatus is largely
dependent on the electrode device contained within the apparatus.
Monopolar and bipolar electrode devices that comprise solid devices
having a fixed shape and size limit the effectiveness of the
ligating apparatus for several reasons. Firstly, a fixed-size
electrode device typically contacts the vein wall at only one point
on the circumference or inner diameter of the vein wall. As a
result, the application of RF energy is highly concentrated within
the contacting venous tissue, while the flow of RF current through
the remainder of the venous tissue is disproportionately weak.
Accordingly, the regions of the vein wall near the point of contact
collapse at a faster rate then other regions of the vein wall,
resulting in non-uniform shrinkage of the vein lumen. Furthermore,
the overall strength of the occlusion may be inadequate and the
lumen may eventually reopen. To avoid an inadequate occlusion RF
energy must be applied for an extended period of time. Application
of RF energy as such increases the temperature of the blood and
usually results in a significant amount of heat-induced coagulum
forming on the electrode and in the vein which is not
desirable.
[0011] Secondly, the effectiveness of a ligating apparatus having a
fixed electrode device is limited to certain sized veins. An
attempt to ligate a vein having a diameter that is substantially
greater than the electrode device can result in not only
non-uniform shrinkage of the vein wall as just described, but also
insufficient shrinkage of the vein. The greater the diameter of the
vein relative to the diameter of the electrode device, the weaker
the energy applied to the vein wall at points distant from the
point of contact. Accordingly the vein wall is likely to not
completely collapse prior to the venous tissue becoming over
cauterized at the point of electrode contact. While coagulation as
such may initially occlude the vein, such occlusion may only be
temporary in that the coagulated blood may eventually dissolve and
the vein partially open. One solution for this inadequacy is an
apparatus having interchangeable electrode devices with various
diameters. Such a solution, however, is both economically
inefficient and tedious to use.
[0012] Hence those skilled in the art have recognized a need for an
expandable electrode device and a method capable of evenly
distributing RF energy along a circumferential band of a vein wall
where the vein wall is greater in diameter than the electrode
device, and thereby provide more predictable and effective
occlusion of veins while minimizing the formation of heat-induced
coagulum. The invention fulfills these needs and others.
SUMMARY OF THE INVENTION
[0013] Briefly, and in general terms, the present invention
provides an apparatus and method for applying energy along a
generally circumferential band of a vein wall. The application of
energy as such results in a more uniform and predictable shrinkage
of the vein wall.
[0014] In one aspect of the invention, an apparatus for delivering
energy to ligate an anatomical structure comprises a catheter
having a sheath, a working end, and an opening formed at the
working end of the catheter; an inner member disposed within the
sheath such that the inner member and the sheath are capable of
being moved relative to one another; a plurality of leads, each
lead having a distal end, the plurality of leads being coupled with
the inner member such that the distal ends of the plurality of
leads extend out of the opening at the working end of the catheter
when the position of the sheath changes in one direction relative
to the inner member, each lead being formed to move the distal end
away from a longitudinal axis defined by the sheath when the
plurality of leads are extended out the opening; wherein the distal
ends of the leads are configured to deliver energy to the
anatomical structure.
[0015] In another aspect of the invention, the apparatus includes a
secondary lead having a secondary distal end. The secondary lead is
coupled with the inner member such that the distal end of the
secondary lead is extended out of the opening at the working end of
the catheter when the position of the inner member changes in one
direction relative to the sheath.
[0016] In another aspect of the invention, the distal ends of the
leads are electrically connected to a power source such that the
polarity of each lead can be switched. Where there is a secondary
lead electrode, the plurality of leads can be connected to the
power source such that the polarity of the leads can be changed
independently of the polarity of the secondary lead.
[0017] In another aspect, the leads include primary leads which
generally surround the secondary lead at the working end of the
catheter. The distal ends of the primary leads are located between
the distal end of the secondary lead and the inner member.
[0018] In yet another aspect, the invention comprises a method of
applying energy to a hollow anatomical structure from within the
structure. The method includes the step of introducing a catheter
into the anatomical structure; the catheter having a working end
and a plurality of leads, each lead having a distal end, and each
lead being connected to a power source. The method also includes
the step of expanding the leads outwardly through the distal
orifice and expanding the leads until each electrode contacts the
anatomical structure. The method further includes the step of
applying energy to the anatomical structure from the distal end of
the leads, until the anatomical structure collapses.
[0019] In another aspect of the invention, the method also includes
the step of introducing a catheter into the anatomical structure
where the catheter has a secondary lead that has a distal portion
that is greater in length than the primary-lead distal portions and
is generally surrounded by the primary leads. The secondary lead
also has an electrode at the distal end. The method also includes
the steps of extending the primary and secondary leads through the
orifice until each primary-lead electrode contacts the anatomical
structure, and controlling the power source so that adjacent
primary leads are of opposite polarity while maintaining the
secondary lead so that it is electrically neutral. Upon collapse of
the anatomical structure around the primary leads, the polarity of
the primary leads is switched so that they are all of the same
polarity. Upon switching the polarity of the primary leads so that
they are of the same polarity, controlling the power source so that
the secondary lead is of opposite polarity relative to the primary
leads. The method, in a further aspect, comprises the step of
moving the catheter in the anatomical structure while continuing to
apply energy to the anatomical structure to lengthen the area of
ligation.
[0020] In another aspect of the invention, external compression is
used to initially force the wall of the vein to collapse toward the
catheter. The application of energy molds the vein to durably
assume the collapsed state initially achieved mechanically by the
external compression. A tourniquet can be used to externally
compress or flatten the anatomical structure and initially reduce
the diameter of the hollow anatomical structure. The pressure
applied by the tourniquet can exsanguinate blood from the venous
treatment site, and pre-shape the vein in preparation to be molded
to a ligated state. An ultrasound window formed in the tourniquet
can be used to facilitate ultrasound imaging of the anatomical
structure being treated through the window.
[0021] In yet another aspect of the invention, a balloon is
provided to occlude the vein before the application of energy, such
that the need for an external compression by a tourniquet is not
required to stop blood flow. This also allows the vein to be
occluded even for the deep veins where a compressive tourniquet may
not be able to compress the vein to occlusion.
[0022] In yet another aspect of the invention, a flexible covering,
relatively impermeable to fluid, spans the area between the leads
along the circumference of the catheter when the leads are extended
out, such that the webbed covering blocks blood flow within the
vein.
[0023] In yet another aspect of the invention, a flexible
balloon-like covering is located on the catheter, having openings
to the concave side and a convex side facing the working end of the
catheter. The covering fills with blood and expands. When the
covering balloons out to the diameter of the vein, blood flow is
stopped.
[0024] In yet another aspect of the invention, mechanically
blocking blood flow with the catheter is combined with infusion of
a high-impedance fluid. The fluid may also be an anticoagulant. The
fluid displaces any remaining blood from the venous treatment site
and prevents energy from being dissipated away from the vein which
is in apposition with the electrodes.
[0025] These and other aspects and advantages of the present
invention will become apparent from the following more detailed
description, when taken in conjunction with the accompanying
drawings which illustrate, by way of example, embodiments of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a diagram of an energy application system with a
partial cutaway view of a catheter showing both the working end and
the connecting end and incorporating a preferred embodiment of the
present invention;
[0027] FIG. 2 is a cross-sectional view of the working end of a
first embodiment of a catheter in accordance with the invention
depicting the electrodes in a fully extended position;
[0028] FIG. 2a is an end view of the working end of the first
embodiment of the catheter taken along line 2a-2a of FIG. 2;
[0029] FIG. 3 is a cross-sectional view of the working end of the
first embodiment depicting the electrodes in a fully retracted
position;
[0030] FIG. 4 is a cross-sectional view of the working end of a
second catheter in accordance with principles of the invention
depicting the electrodes in a fully extended position;
[0031] FIG. 4a is an end view of the second embodiment of the
invention taken along line 4a-4a of FIG. 4;
[0032] FIG. 5 is a cross-sectional view of the working end of the
second embodiment of the catheter of FIG. 4 depicting the
electrodes in a fully retracted position;
[0033] FIG. 6 is a cross-sectional view of an anatomical structure
containing the catheter of FIG. 2 with the electrodes in apposition
with the anatomical structure;
[0034] FIG. 6a is an end view of the anatomical structure
containing the catheter taken along line 6a-6a of FIG. 6;
[0035] FIGS. 7a through 7c are cross-sectional views of the
anatomical structure containing a catheter in accordance with the
first embodiment of the invention and depicting the anatomical
structure at various stages of ligation;
[0036] FIG. 8 is a cross-sectional view of an anatomical structure
containing a catheter in accordance with the second embodiment of
the invention as depicted in FIG. 4;
[0037] FIG. 8a is an end view of the anatomical structure
containing the catheter taken along line 8a-8a of FIG. 8; and
[0038] FIGS. 9a and 9b are cross-sectional views of the anatomical
structure containing the catheter in accordance with the second
embodiment of the invention and depicting the anatomical structure
at various stages of ligation;
[0039] FIG. 10 is a cross-sectional view of the working end of a
third embodiment of a catheter in accordance with the invention
depicting the electrodes in a fully extended position;
[0040] FIG. 10a is an end view of the working end of the third
embodiment of the catheter taken along line 10a-10a of FIG. 10;
[0041] FIG. 11 is a cross-sectional view of the working end of the
third embodiment depicting the electrodes in a fully retracted
position;
[0042] FIG. 12 is a cross-sectional view of an anatomical structure
containing the catheter of FIG. 10 with the electrodes in
apposition with the anatomical structure;
[0043] FIG. 13 is a cross-sectional view of the anatomical
structure containing the catheter of FIG. 10 where the anatomical
structure is being ligated by the application of energy from the
electrodes;
[0044] FIG. 14 is a cross-sectional view of an anatomical structure
containing the catheter of FIG. 10 with the electrodes in
apposition with the anatomical structure where external compression
is being applied to reduce the diameter of the hollow structure
before the application of energy from the electrodes to ligate the
structure;
[0045] FIG. 15 is a side view of another embodiment of an electrode
catheter having a balloon and a coaxial fluid channel;
[0046] FIG. 16 is a partial cross-sectional view of the balloon and
catheter of FIG. 15;
[0047] FIG. 17 is a cross-sectional view of an anatomical structure
containing another embodiment of the catheter having a balloon and
bowable arms with electrodes;
[0048] FIG. 18 is a side view of another embodiment of an electrode
catheter having a covering spanning the splayed leads of the
electrodes extended out the catheter; and
[0049] FIG. 19 is a side view of another embodiment of an electrode
catheter having a balloon and a coaxial fluid channel;
[0050] FIG. 20 is a side view of another embodiment of an electrode
catheter having a balloon and a coaxial fluid channel;
[0051] FIG. 21 is a partial cross-sectional side view of another
embodiment of an electrode catheter having an expandable section;
and
[0052] FIG. 22 is a partial cross-sectional side view of the
embodiment of an electrode catheter of FIG. 21 in an expanded
condition.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0053] Turning now to the drawings with more particularity wherein
like reference numerals indicate like or corresponding elements
among the figures, shown in FIG. 1 is a catheter 10 for applying
energy to an anatomical structure such as a vein. The catheter 10
includes an outer sheath 12 having a distal orifice 14 at its
working end 15. The connector end 17 of the outer sheath 12 is
attached to a handle 16 that includes an electrical connector 18
for interfacing with a power source 22, typically an RF generator,
and a microprocessor controller 23. The power source 22 and
microprocessor 23 are usually contained in one unit. The controller
23 controls the power source 22 in response to external commands
and data from a sensor, such as a thermocouple, located at an
intraluminal venous treatment site. In another embodiment, the user
can select a constant power output so that automated temperature
control is not present and the user can manually adjust the power
output in view of the temperature on a display readout. The
catheter 10 includes an expandable electrode device 24 (partially
shown) that moves in and out of the outer sheath 12 by way of the
distal orifice 14. The electrode device includes a plurality of
electrodes which can be expanded by moving the electrodes within
the shaft, or by moving the outer shaft relative to the electrodes.
Although FIG. 1 illustrates a plurality of electrodes surrounding a
single central electrode, different electrode configurations will
be described for the catheter.
[0054] Contained within the outer sheath 12 is an inner sheath 28
or inner member. A fluid port 21 communicates with the interior of
the outer sheath 12. The catheter 10 can be periodically flushed
out with saline through the port 21. The flushing fluid can travel
between the outer sheath and the inner sheath. The port also allows
for the delivery of drug therapies. Flushing out the catheter
prevents the buildup of biological fluid, such as blood, within the
catheter 10. The treatment area of the hollow anatomical structure
such as a vein can be flushed with a fluid such as saline, or a
dielectric fluid, in order to evacuate blood from the treatment
area of the vein so as to prevent the formation of coagulum or
thrombosis. The use of a dielectric fluid can minimize unintended
heating effects away from the treatment area. The dielectric fluid
prevents the current of RF energy from flowing away from the vein
wall.
[0055] In one embodiment, the catheter 10 includes a lumen which
begins at the. distal tip of the outer sheath 12 and runs
substantially along the axis of the outer sheath 12 before
terminating at the guide-wire port 20 of the handle 16. A guide
wire can be introduced through the lumen of the catheter 10 for use
in guiding the catheter to the desired treatment site. Where the
catheter is sized to treat smaller veins, the outer diameter of the
catheter may not allow for a fluid flush between the outer sheath
12 and the inner sheath 28. However, a fluid flush can be
introduced through the lumen for the guide wire in such an
embodiment.
[0056] Referring now to FIGS. 2, 2a, 3, 4, 4a and 5, the outer
sheath 12 includes a shell 44 and a tip portion 46. To provide an
atraumatic tip for the catheter 10 as it is manipulated through the
vein, the tip 46 is preferably tapered inward at its distal end or
is "nosecone" shaped. The tip 46, however, can have other shapes
that facilitate tracking of the catheter 10 over a guide wire and
through the bends in the venous vascular system. The
nosecone-shaped tip 46 can, for example, be fabricated from a
polymer having a soft durometer, such as 70 Shore A. The shell 44
comprises a biocompatible material having a low coefficient of
friction. In one configuration, the outer sheath 12 is sized to fit
within a venous lumen and for example may be between 5 and 9
French, which corresponds to a diameter of between 1.7 mm (0.07 in)
and 3.0 mm (1.2 in), or other sizes as appropriate.
[0057] The electrode device 24 contains a number of leads,
including insulated primary leads 30 and, in some embodiments, a
secondary lead 31. Preferably, the leads are connected to the power
source 22 (FIG. 1) such that the polarity of the leads may be
switched as desired. Alternately, a microprocessor controller can
be used to switch the polarity, as well as control other
characteristics of the power for the electrode device. Thus the
electrode device can operate in either a bipolar or a monopolar
configuration. When adjacent primary leads 30 have opposite
polarity the electrode device 24 operates as a bipolar electrode
device. When the primary leads 30 are commonly charged the
electrode device 24 can operate as a monopolar electrode device.
When the primary leads 30 are commonly charged, and a secondary
lead 31 has an opposite polarity, the electrode device 24 operates
as a bipolar electrode device. The embodiment of the invention
shown in FIGS. 2 and 3 depict an electrode device 24 having four
primary leads 30 and a secondary lead 31, while the embodiment of
the invention shown in FIGS. 4 and 5 depict an electrode device 24
having only four primary leads. The invention is not limited to
four primary leads 30; more or fewer leads may be used in either
embodiment. The number of leads can be dependent on the size or
diameter of the hollow anatomical structure to be treated. The
apposed electrodes should be kept within a certain distance of one
another. Larger vessels may require more primary leads to ensure
proper current density and proper heat distribution.
[0058] The insulation on each of the leads 30, 31 may be removed at
the distal end 32, 33 to expose the conductive wire. In the first
configuration as shown in FIGS. 2, 2a, and 3, the electrode 34 has
a hemispherical shape. In a second configuration, the electrode can
have either a generally spherical shape or a spoon shape. As shown
in FIGS. 4, 4a and 5, the electrodes have a spoon shape which can
be combined to form a sphere or other shape so as to minimize its
profile when the vein collapses. The electrodes 34 are either
integrally formed at the distal end 32, soldered, or otherwise
formed to the distal end of each primary lead 30. It is to be
understood that when the distal end 32 is referred to as acting as
an electrode, this is not limited to where the electrode 34 is
integrally formed at the distal end 32. For example, the distal end
can apply energy to the surrounding tissue where there is an
electrode integrally formed at the distal end, or where an
electrode is separately soldered to the distal end, or where there
is another energy delivery device located at the distal end. The
electrode 34 typically has a diameter greater than the diameter of
the primary lead 30. For example, the primary lead 30 may have a
diameter ranging from 0.18 mm (0.007 in.) to 0.28 mm (0.011 in.),
while the electrode 34 has a diameter of 0.36 mm (0.014 in.) to
0.51 mm (0.020 in.). The primary leads 30 and the electrodes 34 are
preferably made from a biologically-compatible material such as
stainless steel. The insulation surrounding the primary leads 30
generally has a thickness of between 0.03 mm (0.001 in.) and 0.06
mm (0.0025 in.), resulting in a combined lead-insulation diameter
of between 0.23 mm (0.009 in.) and 0.41 mm (0.016 in.). In an
alternate configuration, as shown in FIGS. 2 and 3, each primary
lead 30 is strip-shaped with a width from 0.76 mm (0.03 in.) to 1.0
mm (0.04 in) and a thickness of approximately 0.13 mm (0.005 in.),
while the secondary lead 31 is typically tubular-shaped. It should
be noted that these dimensions are provided for illustrative
purposes, and not by way of limitation. A hemispherical electrode
34 is shaped at the distal end, as for example, by sanding down a
sixteenth-inch (1.6 mm) diameter sphere which is soldered to the
distal end 32 of the primary lead 30. The electrodes can also be
constructed by stamping the desired shape or configuration from the
conductive lead. The electrode is integral with the lead, and the
remainder of the lead is insulated. The distal end 33 of the
secondary lead 31 preferably includes a generally
spherically-shaped electrode 35.
[0059] An alignment device 36 arranges the leads 30, 31 such that
they are mounted to the catheter at only their proximal ends and so
that separation is maintained between the leads within, and distal
to the alignment device. The leads can form cantilevers when
mounted on the alignment device. A preferred configuration of the
alignment device 36 includes a plurality of off-center,
axially-aligned lumina 38 which are substantially symmetrically
positioned relative to the axis of the alignment device 36. The
alignment device 36 is formed, for example, by extruding the
plurality of axially-aligned lumina 38 through a solid cylinder
composed of a dielectric material, such as polyamide. Each lead 30
passes through an individual off-center lumen 38 and exits out the
rear of the alignment device 36. The alignment device 36 may
further include a central lumen 48 that may be aligned with the
axis. In some embodiments the central lumen 48 is used for
accepting a guide wire or for the delivery or perfusion of medicant
and cooling solution to the treatment area during application of RF
energy. In other embodiments, the central lumen 48 may be used for
the secondary lead 31. The alignment device 36 may also further
include an auxiliary lumen 47 for additional leads, such as the
leads of a thermocouple used as a temperature sensor. The alignment
device 36 comprises a dielectric material to prevent or minimize
any coupling effect the leads 30, 31 may have with each other and,
if present, the guide wire. The length of the alignment device is,
for example, 12.5 mm (0.5 in.) to 19.0 mm (0.75 in.) in one
embodiment. However, these dimensions are provided for purposes of
illustration and not by way of limitation.
[0060] In the embodiment of the invention shown in FIGS. 2, 2a and
3, the inner sheath 28 is attached to the alignment device 36 and
extends beyond the rear 37 of the alignment device. Preferably, the
inner sheath 28 completely surrounds the exterior wall of the
alignment device 36 and is mounted to it by adhesive or press fit
or in other manner such that it remains in a fixed position
relative to the inner sheath. The inner sheath and alignment device
can act as an inner member relative to the outer sheath. The inner
sheath 28 comprises a biocompatible material with a low coefficient
of friction. The inner sheath 28 provides a pathway for the
interconnection between the leads 30, 31 and the electrical
connector 18 (FIG. 1). This interconnection may occur in any of
several ways. The leads 30, 31 themselves may be continuous and run
the entire length of the inner sheath 28. In the alternative (not
shown), the positively charged leads 30, 31 may couple with a
common positively charged conductor housed in the inner sheath 28.
Likewise, the negatively charged leads 30, 31 may couple with a
common negative conductor. Preferably, the leads 30, 31 are
connected to a conductor that allows for the polarity of the leads
to be switched. The conductor may comprise, for example, a 36 gauge
copper lead with a polyurethane coating. The coupling may occur at
any point within the inner sheath 28. To reduce the amount of wire
contained in the catheter, it is advantageous to couple the leads
30, 31 at the point where the leads exit the rear 37 of the
alignment device 36. To add further stability to the electrode
device 24, it is preferred that bonding material 40 surround the
leads 30, 31 at the front end of the alignment device 36. In this
embodiment, the leads 30, 31 exit through the distal orifice 14 as
the outer sheath 12 is retracted backwards over the alignment
device 36. The inwardly tapered tip 46 impedes the retracting
movement of the outer sheath 12 to prevent the exposure of the
alignment device 36.
[0061] FIG. 3 shows the leads 30 and 31 in the retracted position
where all leads are within the nosecone-shaped tip portion 46 and
the outer shell 44. The alignment device 36 has been moved relative
to the outer shell 44. The soft nosecone provides an atraumatic tip
for when the catheter is maneuvered through the tortuous venous
system. The electrode at the distal end of the secondary lead 31
can be sized to approximately the same size as the opening formed
in the nosecone 46. The nosecone forms a closed atraumatic tip
together with the electrode of the secondary lead when the
alignment device is retracted into the outer sheath of the
catheter. This can present an atraumatic tip even where the
nosecone is not constructed from a material having a soft
durometer.
[0062] Referring now to FIGS. 4 and 5, in another embodiment, the
alignment device 36 is attached to the outer sheath 12 and thereby
remains immobile in relation to it. The inner sheath 28 is movably
positioned at the rear of the alignment device 36 and again
provides a pathway for the interconnection between the primary
leads 30 and the electrical connector 18 (FIG. 1). In some
embodiments the inner sheath 28 contains a guide-wire tube 49 that
runs the entire length of the inner sheath. The guide-wire tube 49
is aligned to communicate with the central lumen 48 of the
alignment device 36 at one end and with the guide-wire port 20
(FIG. 1) at the other end. The primary leads 30 may be continuous
and run the entire length of the inner sheath 28 or they may be
coupled to common leads as previously described. The primary leads
30 are secured to the front end 27 of the inner sheath 28, as for
example with a potting material 50, so that the movement of the
inner sheath 28 results in a corresponding movement of the primary
leads 30 through the lumina 38 of the alignment device 36. In this
embodiment, the primary leads 30 are not secured to the alignment
device 36 and in essence are free-floating leads in the axial
direction. The primary leads 30 travel through the alignment device
36 and exit through the distal orifice 14 as the front end of the
inner sheath 28 is moved toward the rear 37 of the alignment device
36.
[0063] In the above embodiments, the primary leads 30 are formed,
e. g., arced or bent, to move away from each other and thereby
avoid contact. The "distal portion" of the primary leads 30 is the
portion of the lead which extends from the front end of the
alignment device 36 when the leads are fully extended through the
distal orifice 14. It is preferred that the distal portions 42 are
formed to move radially outward from each other relative to the
axis of the alignment device 36 and form a symmetrical arrangement.
This is shown in both the embodiments of FIG. 2a and FIG. 4a. The
degree of arc or bend in the primary leads 30 may be any that is
sufficient to radially expand the leads as they exit the outer
sheath 12 through the distal orifice 14. It is essential that the
degree of the arc or bend be sufficient to provide enough force so
that the primary leads 30 expand through blood and the electrodes
34 come in apposition with the vein wall. The electrodes are
preferably partially embedded in the vein wall to assure full
contact. The rounded portion of the electrode is embedded into the
vein wall to achieve full surface apposition so that the entire
uninsulated surface area of the electrode is in contact with venous
tissue for effective current distribution. The surface area of the
electrodes in contact with the venous tissue preferably is
sufficient to avoid a high current density which may lead to spot
heating of the venous tissue. The heating effect is preferably
distributed along a circumferential band of the vein. The apposed
electrodes should be spaced no more than 4 or 5 millimeters from
one another along the circumference of the vein. Thus, the
electrode arrangement is related to the size or diameter of the
vein being treated. Other properties of the primary leads 30, such
as lead shape and insulation thickness, affect the push force of
the lead and the degree of arc or bend must be adjusted to
compensate for these factors. For example, in one configuration of
the electrode device 24, a wire having a diameter of between 0.18
mm (0.007 in) and 0.28 mm (0.011 in) with a total insulation
thickness of between 0.05 mm (0.002 in) to 0.13 mm (0.005 in) is
arced or bent at an acute angle to provide sufficient apposition
with the anatomical structure. It is to be understood that these
dimensions are provided for illustrative purposes, and not by way
of limitation.
[0064] Other techniques for expanding the leads outwardly once they
have been extended from the working end of the catheter may be
possible. For example, the leads may be straight but are mounted in
the alignment device at an angle such that they are normally
directed outward.
[0065] For increased appositional force, it is preferred that the
primary leads 30 be strip-shaped, that is rectangular in cross
section, with dimensions, for example, of a width from 0.76 mm
(0.030 in.) to 1.0 mm (0.039 in) and a thickness of approximately
0.13 mm (0.005 in.). The rectangular cross section provides
increased resistance to bending in the width dimension but allows
bending more freely in the thickness dimension. This strip-shaped
configuration of the primary leads 30 is shown in FIGS. 2, 2a, and
3 and provides for increased stability in the lateral direction
while allowing the necessary bending in the radial direction. In
FIGS. 2, 2a, and 3, each primary lead comprises a rectangular cross
section mounted in relation to the catheter such that the thinner
dimension of the rectangular cross section is aligned with the
direction of expansion of the lead. The leads are less likely to
bend sideways when expanded outward, and a uniform spacing between
leads is more assured. Uniform spacing promotes uniform heating
around the venous tissue which is in apposition with the electrodes
at the distal ends of the leads.
[0066] The length of the distal portion of the leads 30 also
affects the configuration of the electrode device 24. The maximum
distance between two mutually opposed electrodes 34; i.e., the
effective diameter of the electrode device 24, is affected by the
bend degree and length of the distal portion 42. The longer the
length of the distal portion 42 the greater the diameter of the
electrode device 24. Accordingly, by changing the distal portion 42
length and arc or bend degree, the catheter 10 can be configured
for use in differently sized anatomical structures.
[0067] Different numbers of leads 30, 31 can be employed with the
catheter. The number of leads 30, 31 is limited by the diameter of
the alignment device 36 and the number of lumina 36, 38, 47 that
can be extruded through the alignment device. In a bipolar
configuration, an even number of primary leads 30 are preferably
available to form a number of oppositely charged electrode pairs.
The electrodes in apposition with the anatomical structure should
be maintained within a certain distance of each other. In a
monopolar configuration, any number of commonly charged leads 30
can be present. In the monopolar mode, distribution of RF energy
through the anatomical tissue is obtained by creating a return path
for current through the tissue by providing a return device at a
point external from the tissue, such as a large metal pad.
[0068] Now referring again to FIG. 1, an actuator 25 controls the
extension of the electrode device 24 through the distal orifice 14.
The actuator 25 may take the form of a switch, lever, threaded
control knob, or other suitable mechanism, and is preferably one
that can provide fine control over the movement of the outer sheath
12 or the inner sheath 28, as the case may be. In one embodiment of
the invention, the actuator 25 (FIG. 1) interfaces with the outer
sheath 12 (FIGS. 2, 2a and 3) to move it back and forth relative to
the inner sheath 28. In another embodiment the actuator 25 (FIG. 1)
interfaces with the inner sheath 28 (FIGS. 4, 4a and 5) to move it
back and forth relative to the outer sheath 12. The relative
position between the outer sheath and inner sheath is thus
controlled, but other control approaches may be used.
[0069] Referring again to FIGS. 2, 2a , 3, 4, 4a and 5, the
catheter 10 includes a temperature sensor 26, such as a
thermocouple. The temperature sensor 26 is mounted in place on an
electrode 34 so that the sensor 26 is nearly or is substantially
flush with the exposed surface of the electrode 34. The sensor 26
is shown in the drawings as protruding from the electrodes for
clarity of illustration only. The sensor 26 senses the temperature
of the portion of the anatomical tissue that is in apposition with
the exposed electrode surface. Monitoring the temperature of the
anatomical tissue provides a good indication of when shrinkage of
the tissue is ready to begin. A temperature sensor 26 placed on the
electrode facing the anatomical tissue provides an indication of
when shrinkage occurs (70.degree. C. or higher) and when
significant amounts of heat-induced coagulum may begin to form on
the electrodes. Therefore maintaining the temperature above 70
degrees Centigrade produces a therapeutic shrinkage of the
anatomical structure. Application of the RF energy from the
electrodes 34 is halted or reduced when the monitored temperature
reaches or exceeds the specific temperature that was selected by
the operator, typically the temperature at which anatomical tissue
begins to cauterize. The temperature sensor 26 interfaces with the
controller 23 (FIG. 1) through a pair of sensor leads 45 which
preferably run through the auxiliary lumen 47 and then through the
inner sheath 28. The signals from the temperature sensor 26 are
provided to the controller 23 which controls the magnitude of RF
energy supplied to the electrodes 34 in accordance with the
selected temperature criteria and the monitored temperature. Other
techniques such as impedance monitoring, and ultrasonic pulse
echoing can be utilized in an automated system which shuts down or
regulates the application of RF energy from the electrodes to the
venous section when sufficient shrinkage of the vein is detected
and to avoid overheating the vein. Impedance can be used to detect
the onset of coagulum formation.
[0070] Referring now to FIGS. 6, 6a and 7a through 7c, in the
operation of one embodiment of the catheter 10, the catheter is
inserted into a hollow anatomical structure, such as a vein 52. The
catheter is similar to the embodiment discussed in connection with
FIGS. 2 and 3. The catheter 10 further includes an external sheath
60 through which a fluid can be delivered to the treatment site. In
this embodiment, the fluid port (not shown) communicates with the
interior of the external sheath 60, and fluid is delivered from
between the external sheath 60 and the outer sheath 12. The
external sheath 60 surrounds the outer sheath 12 to form a coaxial
channel through which fluid may be flushed.
[0071] Fluoroscopy, ultrasound, an angioscope imaging technique, or
other technique may be used to direct the specific placement of the
catheter and confirm the position in the vein. The actuator (not
shown) is then operated to shift the outer sheath relative to the
inner sheath by either retracting the outer sheath 12 backward or
advancing the inner sheath 28 forward to expose the leads 30, 31
through the distal orifice 14. As the leads 30, 31 exit the distal
orifice 14, the primary leads 30 expand radially outward relative
to the axis of the alignment device 36, while the secondary lead 31
remains substantially linear. The primary leads 30 continue to move
outward until apposition with the vein wall 54 occurs and the
outward movement of the primary leads 30 is impeded. The primary
leads 30 contact the vein along a generally circumferential band of
the vein wall 54. This outward movement of the primary leads 30
occurs in a substantially symmetrical fashion. As a result, the
primary-lead electrodes 34 are substantially evenly spaced along
the circumferential band of the vein wall 54. The central-lead
electrode 35 is suspended within the vein 52 without contacting the
vein wall 54.
[0072] When the electrodes 34 are positioned at the treatment site
of the vein, the power supply 22 is activated to provide suitable
RF energy. One suitable frequency is 510 kHz. One criterion used in
selecting the frequency of the energy to be applied is the control
desired over the spread, including the depth, of the thermal effect
in the venous tissue. Another criterion is compatibility with
filter circuits for eliminating RF noise from thermocouple
signals.
[0073] In bipolar operation, the primary leads 30 are initially
charged such that adjacent leads are oppositely charged while the
secondary lead is electrically neutral. These multiple pairs of
oppositely charged leads 30 form active electrode pairs to produce
an RF field between them. Thus, discrete RF fields are set up along
the circumferential band of the vein wall 54. These discrete fields
form a symmetrical RF field pattern along the entire
circumferential band of the vein wall 54, as adjacent electrodes 34
of opposite polarity produce RF fields between each other. A
uniform temperature distribution can be achieved along the vein
wall being treated.
[0074] The RF energy is converted within the adjacent venous tissue
into heat, and this thermal effect causes the venous tissue to
shrink, reducing the diameter of the vein. A uniform temperature
distribution along the vein wall being treated avoids the formation
of hot spots in the treatment area while promoting controlled
uniform reduction in vein diameter. The thermal effect produces
structural transfiguration of the collagen fibrils in the vein. The
collagen fibrils shorten and thicken in cross-section in response
to the heat from the thermal effect. As shown in FIG. 7a, the
energy causes the vein wall 54 to collapse around the primary-lead
electrodes 34. The wall 54 continues to collapse until further
collapse is impeded by the electrodes 34. The electrodes are
pressed farther and farther together by the shrinking vein wall 54
until they touch and at that point, further collapse or ligation of
the wall 54 is impeded. Upon collapse of the vein wall 54 around
the primary-lead electrodes 34, the polarity of the primary-lead
electrodes is switched so that all primary-lead electrodes are
commonly charged. The switching of polarity for the leads need not
be instantaneous. The application of RF energy can be ceased, the
polarity switched, and then RF energy is applied again at the
switched polarity. The secondary-lead electrode 35 is then charged
so that its polarity is opposite that of the primary-lead
electrodes 34. The RF field is set up between the primary-lead
electrodes 34 and the secondary-lead electrode 35.
[0075] The catheter 10 is then pulled back while energy is applied
to the electrode device. As shown in FIG. 7b, while the catheter 10
is being pulled back, the primary-lead electrodes 34 remain in
apposition with the vein wall 54 while the secondary-lead electrode
35 comes in contact with the portion of the vein wall previously
collapsed by the primary-lead electrodes 34. Accordingly, RF energy
passes through the vein wall 54 between the primary-lead electrodes
34 and the secondary-lead electrode 35 and the vein wall continues
to collapse around the secondary-lead electrode 35 as the catheter
10 is being retracted. As shown in FIG. 7c, ligation in accordance
with this method results in an occlusion along a length of the vein
52. A lengthy occlusion, as opposed to an acute occlusion, is
stronger and less susceptible to recanalization.
[0076] A similar result is achieved when the catheter 10 having
both primary and secondary leads is operated in a monopolar manner.
In a monopolar operation, the secondary-lead electrode 35 remains
neutral, while the primary leads 30 are commonly charged and act in
conjunction with an independent electrical device, such as a large
low-impedance return pad (not shown) placed in external contact
with the body, to form a series of discrete RF fields. These RF
fields are substantially evenly spaced around the circumference of
the vein and travel along the axial length of the vein wall causing
the vein wall to collapse around the primary-lead electrodes. Upon
collapse of the vein wall, the secondary-lead electrode is charged
to have the same polarity as that of the primary-lead electrodes.
The electrode device is retracted and the vein wall collapses as
described in the bipolar operation.
[0077] In either bipolar or monopolar operation the application of
RF energy is substantially symmetrically distributed through the
vein wall, regardless of the diameter of the vein 52. This
symmetrical distribution of RF energy increases the predictability
and uniformity of the shrinkage and the strength of the occlusion.
Furthermore, the uniform distribution of energy allows for the
application of RF energy for a short duration and thereby reduces
or avoids the formation of heat-induced coagulum on the electrodes
34. The leads, including the non-convex outer portion of the
electrode, are insulated to further prevent heating of the
surrounding blood.
[0078] Fluid can be delivered before and during RF heating of the
vein being treated through a coaxial channel formed between the
external sheath 60 and the outer sheath 12. It is to be understood
that another lumen can be formed in the catheter to deliver fluid
to the treatment site. The delivered fluid displaces or
exsanguinates blood from the vein so as to avoid heating and
coagulation of blood. Fluid can continue to be delivered during RF
treatment to prevent blood from circulating back to the treatment
site. The delivery of a dielectric fluid increases the surrounding
impedance so that RF energy is directed into the tissue of the vein
wall.
[0079] Referring now to FIGS. 8, 8a, 9a and 9b, in the operation of
an alternate embodiment of the catheter 10 that may be used with a
guide wire 53. As in the previous embodiment, the catheter 10 is
inserted into a hollow anatomical structure, such as a vein 52. The
guide wire 53 is advanced past the point where energy application
is desired. The catheter 10 is then inserted over the guide wire 53
by way of the central lumen 48 and the guide wire tube 49 (FIG. 4)
and is advanced over the guide wire through the vein to the desired
point. The guide wire 53 is typically pulled back or removed before
RF energy is applied to the electrode device 24.
[0080] The actuator 25 (FIG. 1) is then manipulated to either
retract the outer sheath 12 backward, or advance the inner sheath
28 forward to expose the leads 30 through the distal orifice 14.
The leads 30 exit the distal orifice 14 and expand radially outward
relative to the axis of the alignment device 36. The leads 30
continue to move outward until apposition with the vein wall 54
occurs. The leads 30 contact the vein along a generally
circumferential band of the vein wall 54. This outward movement of
the leads occurs in a substantially symmetrical fashion. As a
result, the electrodes 34 are substantially evenly spaced along the
circumferential band of the vein wall 54. Alternately, the
electrodes can be spaced apart in a staggered fashion such that the
electrodes do not lie along the same plane. For example, adjacent
electrodes can extend different lengths from the catheter so that a
smaller cross-sectional profile is achieved when the electrodes are
collapsed toward one another.
[0081] When the electrodes 34 are positioned at the treatment site
of the vein, the power supply 22 is activated to provide suitable
RF energy to the electrodes 34 so that the catheter 10 operates in
either a bipolar or monopolar manner as previously described. As
shown in FIGS. 9a and 9b, the energy causes the vein wall 54 to
collapse around the electrodes 34 causing the leads to
substantially straighten and the electrodes to cluster around each
other. The wall 54 continues to collapse until further collapse is
impeded by the electrodes 34 (FIG. 9b). At this point the
application of energy may cease. The electrodes can be configured
to form a shape with a reduced profile when collapsed together. The
electrodes can also be configured and insulated to continue
applying RF energy after forming a reduced profile shape by the
collapse of the vein wall. The catheter 10 can be pulled back to
ligate the adjacent venous segment. If a temperature sensor 26 is
included, the application of energy may cease prior to complete
collapse if the temperature of the venous tissue rises above an
acceptable level as defined by the controller 23.
[0082] Where the catheter includes a fluid delivery lumen (not
shown), fluid can be delivered before and during RF heating of the
vein being treated. The fluid can displace blood from the treatment
area in the vein to avoid the coagulation of blood. The fluid can
be a dielectric medium. The fluid can include an anticoagulant such
as heparin which can chemically discourage the coagulation of blood
at the treatment site.
[0083] After completing the procedure for a selected venous
section, the actuator mechanism causes the. primary leads to return
to the interior of the outer sheath 12. Either the outer sheath or
the inner sheath is moved to change the position of the two
elements relative to one another. Once the leads 30 are within the
outer sheath 12, the catheter 10 may be moved to another venous
section where the ligation process is repeated. Upon treatment of
all venous sites, the catheter 10 is removed from the vasculature.
The access point of the vein is then sutured closed, or local
pressure is applied until bleeding is controlled.
[0084] Another embodiment of the catheter is illustrated in FIG.
10. The inner member or sheath 28 is contained within the outer
sheath 12. The inner sheath is preferably constructed from a
flexible polymer such as polyimide, polyethylene, or nylon, and can
travel the entire length of the catheter. The majority of the
catheter should be flexible so as to navigate the tortuous paths of
the venous system. A hypotube having a flared distal end 33 and a
circular cross-sectional shape is attached over the distal end of
the inner sheath 28. The hypotube is preferably no more than about
two to three centimeters in length. The hypotube acts as part of
the conductive secondary lead 31. An uninsulated conductive
electrode sphere 35 is slipped over the hypotube. The flared distal
end of the hypotube prevents the electrode sphere from moving
beyond the distal end of the hypotube. The sphere is permanently
affixed to the hypotube, such as by soldering the sphere both front
and back on the hypotube. The majority or the entire surface of the
spherical electrode 35 remains uninsulated. The remainder of the
hypotube is preferably insulated so that the sphere-shaped distal
end can act as the electrode. For example, the hypotube can be
covered with an insulating material such as a coating of parylene.
The interior lumen of the hypotube is lined by the inner sheath 28
which is attached to the flaired distal end of the hypotube by
adhesive such as epoxy.
[0085] Surrounding the secondary lead 31 and sphere-shaped
electrode 35 are a plurality of primary leads 30 which preferably
have a flat rectangular strip shape and can act as arms. As
illustrated in FIG. 11, the plurality of primary leads are
preferably connected to common conductive rings 62. This
configuration maintains the position of the plurality of primary
leads, while reducing the number of internal electrical
connections. The rings 62 are attached to the inner sheath 28. The
position of the rings and the primary leads relative to the outer
sheath follows that of the inner sheath. As earlier described, the
hypotube of the secondary lead 31 is also attached to the inner
sheath 28. Two separate conductive rings can be used so that the
polarity of different primary leads can be controlled separately.
For example, adjacent primary leads can be connected to one of the
two separate conductive rings so that the adjacent leads can be
switched to have either opposite polarities or the same polarity.
The rings are preferable spaced closely together, but remain
electrically isolated from one another along the inner sheath. Both
the rings and the hypotube are coupled with the inner sheath, and
the primary leads 30 that are connected to the rings move together
with and secondary lead while remaining electrically isolated from
one another. Epoxy or another suitable adhesive can be used to
attach the rings to the inner sheath. The primary leads from the
respective rings each alternate with each other along the
circumference of the inner sheath. The insulation along the
underside of the leads prevents an electrical short between the
rings.
[0086] The ring and primary leads are attached together to act as
cantilevers where the ring forms the base and the rectangular
primary leads operate as the cantilever arms. The leads 30 are
connected to the ring and are formed to have an arc or bend such
that the leads act as arms which tend to spring outwardly away from
the catheter and toward the surrounding venous tissue. Insulation
along the underside of the leads and the rings prevents unintended
electrical coupling between the leads and the opposing rings.
Alternately, the leads are formed straight and connected to the
ring at an angle, such that the leads tend to expand or spring
radially outward from the ring. The angle at which the leads are
attached to the ring should be sufficient to force the primary
distal ends and electrodes 34 through blood and into apposition
with the vein wall. Other properties of the primary leads 30, such
as lead shape and insulation thickness, affect the push force of
the lead and the degree of arc or bend must be adjusted to
compensate for these factors. The rectangular cross section of the
leads 30 can provide increased stability in the lateral direction
while allowing the necessary bending in the radial direction. The
leads 30 are less likely to bend sideways when expanded outward,
and a uniform spacing between leads is more assured. Uniform
spacing between the leads 30 and the distal ends promotes uniform
heating around the vein by the electrodes 34.
[0087] The distal ends of the primary leads 30 are uninsulated to
act as electrodes 34 having a spoon or hemispherical shape. The
leads can be stamped to produce an integral shaped electrode at the
distal end of the lead. The uninsulated outer portion of the distal
end electrode 34 which is to come into apposition with the wall of
the anatomical structure is preferably rounded and convex. The
flattened or non-convex inner portion of the distal end is
insulated to minimize any unintended thermal effect, such as on the
surrounding blood in a vein. The distal end electrodes 34 are
configured such that when the distal ends are forced toward the
inner sheath 12, as shown in FIG. 10a, the distal ends combine to
form a substantially spherical shape with a profile smaller than
the profile for the spherical electrode 35 at the secondary distal
end.
[0088] The outer sheath 12 can slide over and surround the primary
and secondary leads 30, 31. The outer sheath 12 includes an orifice
which is dimensioned to have approximately the same size as the
spherical electrode 35 at the secondary distal end which functions
as an electrode. A close or snug fit between the electrode 35 at
the secondary distal end and the orifice of the outer sheath 12 is
achieved. This configuration provides an atraumatic tip for the
catheter. The electrode 35 secondary distal end is preferably
slightly larger than the orifice. The inner diameter of the outer
sheath 12 is approximately the same as the reduced profile of the
combined primary distal end electrodes 34. The diameter of the
reduced profile of the combined primary distal end electrodes 34 is
preferably less than the inner diameter of the outer sheath.
[0089] A fluid port (not shown) can communicate with the interior
of the outer sheath 12 so that fluid can be flushed between the
outer sheath 12 and the inner sheath 28. Alternately, a fluid port
can communicate with a central lumen 48 in the hypotube which can
also accept a guide wire. As previously stated, the catheter 10 can
be periodically flushed with saline which can prevent the buildup
of biological fluid, such as blood, within the catheter 10. A guide
wire can be introduced through the lumen 48 for use in guiding the
catheter to the desired treatment site. As previously described, a
fluid can be flushed or delivered though the lumen as well. If a
central lumen is not desired, the lumen of the hypotube can be
filled with solder.
[0090] Preferably, the primary leads 30 and the connecting rings
are connected to a power source 22 such that the polarity of the
leads may be switched as desired. This allows for the electrode
device 24 to operate in either a bipolar or a monopolar
configuration. When adjacent primary leads 30 have opposite
polarity, a bipolar electrode operation is available. When the
primary leads 30 are commonly charged a monopolar electrode
operation is available in combination with a large return electrode
pad placed in contact with the patient. When the primary leads 30
are commonly charged, and a secondary lead 31 has an opposite
polarity, a bipolar electrode operation is available. More or fewer
leads may be used. The number of leads can be dependent on the size
or diameter of the hollow anatomical structure to be treated.
[0091] Although not shown, it is to be understood that the catheter
10 can include a temperature sensor, such as a thermocouple,
mounted in place on the distal end or electrode 34 so that the
sensor is substantially flush with the exposed surface of the
electrode 34. The sensor senses the temperature of the portion of
the anatomical tissue that is in apposition with the exposed
electrode surface. Application of the RF energy from the electrodes
34 is halted or reduced when the monitored temperature reaches or
exceeds the specific temperature that was selected by the operator,
such as the temperature at which anatomical tissue begins to
cauterize. Other techniques such as impedance monitoring, and
ultrasonic pulse echoing can be utilized in an automated system
which shuts down or regulates the application of RF energy from the
electrodes to the venous section when sufficient shrinkage of the
vein is detected and to avoid overheating the vein.
[0092] Referring now to FIGS. 12 through 14, in the operation of
one embodiment of the catheter 10, the catheter is inserted into a
hollow anatomical structure, such as a vein. Fluoroscopy,
ultrasound, an angioscope imaging technique, or another technique
may be used to direct and confirm the specific placement of the
catheter in the vein. The actuator is then operated to retract the
outer sheath 12 to expose the leads 30, 31. As the outer sheath no
longer restrains the leads, the primary leads 30 move outward
relative to the axis defined by the outer sheath, while the
secondary lead 31 remains substantially linear along the axis
defined by the outer sheath. The primary leads 30 continue to move
outward until the distal end electrode 34 of the primary leads are
placed in apposition with the vein wall 54 occurs and the outward
movement of the primary leads 30 is impeded. The primary leads 30
contact the vein along a generally circumferential area of the vein
wall 54. This outward movement of the primary leads 30 occurs in a
substantially symmetrical fashion so that the primary distal end
electrodes 34 are substantially evenly spaced. The central-lead
electrode 35 is suspended within the vein without contacting the
vein wall 54.
[0093] When the electrodes 34 are positioned at the treatment site
of the vein, the power supply 22 is activated to provide suitable
RF energy. In a bipolar operation, the primary leads 30 are
initially charged such that adjacent leads are oppositely charged
while the secondary lead is electrically neutral. These multiple
pairs of oppositely charged leads 30 form active electrode pairs to
produce an RF field between them, and form a symmetrical RF field
pattern along a circumferential band of the vein wall to achieve a
uniform temperature distribution along the vein wall being
treated.
[0094] The RF energy produces a thermal effect which causes the
venous tissue to shrink, reducing the diameter of the vein. As
shown in FIG. 13, the energy causes the vein wall 54 to collapse
until further collapse is impeded by the electrodes 34. The
electrodes are pressed closer together by the shrinking vein wall.
The electrodes 34 are pressed together to assume a reduced profile
shape which is sufficiently small so that the vein is effectively
ligated. Upon collapse of the vein wall 54 around the primary-lead
electrodes 34, the polarity of the primary-lead electrodes is
switched so that all of the primary-lead electrodes are commonly
charged. The secondary-lead electrode 35 is then charged so that
its polarity is opposite that of the primary-lead electrodes 34.
Where the primary electrodes 34 and the secondary electrode 35 are
spaced sufficiently close together, when the vein wall collapses
around the primary lead electrodes, the electrode at the distal end
of the secondary lead can also come into contact with the a portion
of the vein wall so that an RF field is created between the primary
electrodes 34 and the secondary electrode 35.
[0095] The catheter 10 is pulled back to ensure apposition between
the electrodes at the distal ends of the leads and the vein wall.
When the catheter 10 is being pulled back, the primary-lead
electrodes 34 remain in apposition with the vein wall 54 while the
secondary-lead electrode 35 comes in contact with the portion of
the vein wall previously collapsed by the primary-lead electrodes
34. RF energy passes through the venous tissue between the
primary-lead electrodes 34 and the secondary-lead electrode 35.
Ligation as the catheter is being retracted produces a lengthy
occlusion which is stronger and less susceptible to recanalization
than an acute point occlusion.
[0096] In a monopolar operation, the secondary-lead electrode 35
remains neutral, while the primary leads 30 are commonly charged
and act in conjunction with an independent electrical device, such
as a large low-impedance return pad (not shown) placed in external
contact with the body, to form RF fields substantially evenly
spaced around the circumference of the vein. The thermal effect
produced by those RF fields along the axial length of the vein wall
causes the vein wall to collapse around the primary-lead
electrodes. Upon collapse of the vein wall, the secondary-lead
electrode is charged to have the same polarity as that of the
primary-lead electrodes. The electrode device is retracted as
described in the bipolar operation.
[0097] In either bipolar or monopolar operation the application of
RF energy is substantially symmetrically distributed through the
vein wall. As previously described, the electrodes should be spaced
no more than 4 or 5 millimeters apart along the circumference of
the vein, which defines the target vein diameter for a designed
electrode catheter. Where the electrodes are substantially evenly
spaced in a substantially symmetrical arrangement, and the spacing
between the electrodes is maintained, a symmetrical distribution of
RF energy increases the predictability and uniformity of the
shrinkage and the strength of the occlusion.
[0098] As shown in FIG. 14, after the electrodes 34 come into
apposition with the vein wall (FIG. 12), and before the energy is
applied to ligate the vein (FIG. 13), an external tourniquet, such
as an elastic compressive wrap or an inflatable bladder with a
window transparent to ultrasound, is used to compress the anatomy,
such as a leg, surrounding the structure to reduce the diameter of
the vein. Although the compressive force being applied by the
tourniquet may effectively ligate the vein, or otherwise occlude
the vein by flattening the vein, for certain veins, this
compressive force will not fully occlude the vein. A fixed diameter
electrode catheter in this instance would not be effective. The
electrodes 34 which are expanded outward by the formed leads 30 can
accommodate this situation.
[0099] The reduction in vein diameter assists in pre-shaping the
vein to prepare the vein to be molded to a ligated state. The use
of an external tourniquet also exsanguinates the vein and blood is
forced away from the treatment site. Coagulation of blood during
treatment can be avoided by this procedure. Energy is applied from
the electrodes to the exsanguinated vein, and the vein is molded to
a sufficiently reduced diameter to achieve ligation. The external
tourniquet can remain in place to facilitate healing.
[0100] The catheter can be pulled back during the application of RF
energy to ligate an extensive section of a vein. In doing so,
instead of a single point where the diameter of the vein has been
reduced, an extensive section of the vein has been painted by the
RF energy from the catheter. Retracting the catheter in this manner
produces a lengthy ***occlusion which is less susceptible to
recanalization. The combined use of the primary and secondary
electrodes can effectively produce a reduced diameter along an
extensive length of the vein. The catheter can be moved while the
tourniquet is compressing the vein, of after the tourniquet is
removed.
[0101] Where the catheter includes a fluid delivery lumen, fluid
can be delivered to the vein before RF energy is applied to the
vein. The delivered fluid displaces blood from the treatment site
to ensure that blood is not present at the treatment site, even
after the tourniquet compresses the vein.
[0102] Where the tourniquet is an inflatable bladder with a window
transparent to ultrasound, an ultrasound transducer is used to
monitor the flattening or reduction of the vein diameter from the
compressive force being applied by the inflating bladder. The
window can be formed from polyurethane, or a stand-off of gel
contained between a polyurethane pouch. A gel can be applied to the
window to facilitate ultrasound imaging of the vein by the
transducer. Ultrasound visualization through the window allows the
operator to locate the desired venous treatment area, and to
determine when the vein has been effectively ligated or occluded.
Ultrasound visualization assists in monitoring any pre-shaping of
the vein in preparation of being molded into a ligated state by the
thermal effect produced by the RF energy from the electrodes.
[0103] After completing the procedure for a selected venous
section, the actuator causes the leads 30 to return to the interior
of the outer sheath 12. Once the leads 30 are within the outer
sheath 12, the catheter 10 may be moved to another venous section
where the ligation process is repeated.
[0104] In another embodiment, as illustrated in FIG. 15, a balloon
64 is located on the catheter, and can be inflated through ports 66
to occlude the vein. The inflated balloon obstructs blood flow and
facilitates the infusion of a high-impedance fluid to the vein in
order to reduce the occurrence of coagulation by directing the
energy into the vein wall. The inflation of the balloon to occlude
the vein before the application of energy can obviate the use of
the tourniquet to occlude the vein. Furthermore, this also allows
the vein to be occluded even for the deep veins where a compressive
tourniquet may not be able to compress the vein to occlusion. It is
to be understood that other mechanisms can be used to expand the
diameter of the catheter to create an impermeable barrier that
occludes the vein.
[0105] Fluid 61 can be delivered after inflation of the balloon 64
and before the RF heating of the vein being treated through a
coaxial channel 62 formed between the external sheath 60 and the
outer sheath 12. It is to be understood that another lumen can be
formed in the catheter to deliver fluid to the treatment site. For
example, the lumen through which the guide wire is passed may be
used for the delivery of fluid. The delivered fluid displaces or
exsanguinates the remaining blood from the treatment area of the
vein so as to avoid heating and coagulation of blood. Fluid can
continue to be delivered during RF treatment to prevent blood from
circulating back to the treatment site. The delivery of a
high-dielectric fluid increases the surrounding impedance so that
RF energy is directed into the tissue of the vein wall. Less energy
is used because the energy is directed to the target; i.e., the
vein wall, rather than being dissipated in the blood. Therefore,
the vein wall can reach the desired temperature more rapidly than
in the case where energy is permitted to reach the blood, which has
a cooling effect. Additionally, blood clotting is avoided with this
approach, because the blood has been replaced with another fluid
such as deionized water mixed with heparin to displace blood and
prevent the formation of blood clots.
[0106] A partial cross-sectional view of this embodiment is shown
in FIG. 16, where an inflation sheath 70 surrounds the external
sheath 60 to provide a coaxial inflation lumen 72 for the balloon
64. The inflation lumen 72 is in fluid communication with the ports
66. Saline or any other suitable fluid can be used to inflate the
balloon.
[0107] As shown in the FIG. 17, in one embodiment, the balloon 64
can be used in combination with bowable members or arms 76 having
electrodes, where perfusion holes 78 are formed in the catheter
between the balloon 64 and the bowable arms 76. The balloon 64 in
this embodiment is inflated through a balloon inflation lumen 72.
The use of bowable arms for treating veins is discussed in U.S.
patent application Ser. No. 08/610,911, which is hereby
incorporated by reference. The arms can be constructed so as to
spring radially outward from the catheter, yet offer little
resistance in moving back toward the catheter as-the vein diameter
is diminished to occlusion. An anti-coagulant or saline or a
high-impedance fluid can be introduced or flushed through the
perfusion holes 78 in the catheter. As discussed earlier, the
high-impedance fluid forces blood away from the venous treatment
area and prevents the energy from being dissipated in a more
conductive medium such as blood.
[0108] As shown in FIG. 18, in another embodiment, a flexible
covering 80 is wrapped around or inside the leads 30 of the
electrodes 34 to prevent blood flow in the vein. The covering 80
spans the area between the splayed leads along the circumference of
the catheter when the leads are extended out the opening, such that
the webbed covering blocks blood flow within the vein. The covering
may be thought of as webbing or an umbrella to keep blood on one
side away from the electrodes. When the electrodes come into
apposition with the vein wall, then the gap, if any, between the
electrodes 34 and the covering 80 should be eliminated or toherwise
minimized. The covering 80 should be impermeable to fluid. Suitable
materials include PET and nylon. Elastomeric materials are also
suitable as the leads will need to move close together as they are
retracted, and interference with the movement of the leads as the
vein diameter is reduced by the application of energy is preferably
minimized. Although this embodiment is illustrated with only
primary leads, it is to be understood that this embodiment is not
so limited and that a secondary lead may be included with the
catheter as well without affecting the use of the covering. As with
the balloon disclosed earlier, the covering occludes the vein
before the application of energy, such that the need for an
external compressive tourniquet is not required to stop blood flow.
Furthermore, this also allows the vein to be occluded even for the
deep veins where a compressive tourniquet may not be able to
compress the vein to occlusion. A high-impedance fluid such as
deionized water, or an anti-coagulant such as heparin or saline, or
both, or heparin with deionized water may be infused or flushed
thorugh the perfusion holes 78 before the application of energy as
well. The electrodes extend through the shaft lumen which also acts
as a conduit for the fluid being flushed through the perfusion
holes 78. A sclerosing fluid may also be delivered to the venous
treatment site to enhance the ligation effect from the application
of RF energy. The sclerosing fluid may be added in addition to, or
in substitution of, the previously discussed fluids.
[0109] In the embodiment shown in FIG. 19, a covering 80 having a
parachute shape can be orientated so that blood becomes trapped by
the concave portion of the covering and the volume of the blood
maintains the deployment of the covering. In this example, the
covering is a balloon having openings 84 which allow blood to
gather in the balloon, and expand the balloon. The covering 80 can
be permanently attached to the catheter shaft. The catheter can
still be moved along the vein, even with the balloon in an inflated
state.
[0110] In the embodiment shown in FIG. 20, the covering 80 is
coupled to an outer cannula 82 surrounding the catheter shaft and
connected to an actuation mechanism or lever. The outer cannula 82
can be slid along the longitudinal axis of the catheter to allow
one end of the parachute covering 80 to be moved axially along the
catheter shaft. During insertion of the catheter, the movable end
of the covering is pulled away from the connecting end of the
catheter to collapse the covering against the catheter. After the
catheter is delivered to the venous treatment site, the cannula is
slid toward the working end to deploy the covering which then fills
with blood entering thorugh the openings 84, thereby occluding the
vein. The covering expands as it fills with blood, and when the
covering comes into contact with the vein wall, the vein is
occluded. Fluid, as before, can be infused either through perfusion
holes 78 or a coaxial channel.
[0111] In the embodiment shown in the cross-sectional view of FIG.
21, the catheter 10 includes an expandable section having a
skeleton 90 disposed along a portion of the working end of the
catheter. The skeleton 90 is more flexible than the surrounding
shaft of the catheter, and can be constructed from a metal or
polymer braid. A flexible membrane 92 covers the skeleton 90, with
the ends of the membrane attached to the shaft of the catheter
adjacent the skeleton. The membrane is preferably constructed from
an elastomeric material. As shown in FIG. 22, when the tip of the
connecting end is moved toward the working end of the catheter, or
vice versa, the skeleton 90 is deformed and forces the membrane 92
out into contact with the vein wall. This embodiment does not
require a separate lumen to provide an inflation fluid to a
balloon. The skeleton 90 is preferably resilient so that it returns
to its original shape once the working end and connecting end are
no longer being forced toward one another. Mechanisms for moving
the connecting end toward the working end of the catheter for
expanding the diameter of a catheter are also discussed in U.S.
patent application Ser. No. 08/610,911, which has been incorporated
by reference. Although the exapandable section may be controlled
separately from the extension of the elecrodes, the expandable
section can be controlled by the same mechanism which extends the
electrodes away from the catheter.
[0112] The description of the component parts discussed above are
for a catheter to be used in a vein ranging in size from 2 mm (0.08
in) to 13 mm (0.51 in) in diameter. It is to be understood that
these dimensions do not limit the scope of the invention and are
merely exemplary in nature. The dimensions of the component parts
may be changed to configure a catheter 10 that may used in
various-sized veins or other anatomical structures.
[0113] Although described above as positively charged, negatively
charged, or as a positive conductor or negative conductor, these
terms are used for purposes of illustration only. These terms are
generally meant to refer to different electrode potentials and are
not meant to indicate that any particular voltage is positive or
negative. Furthermore, other types of energy such as light energy
from fiber optics can be used to create a thermal effect in the
hollow anatomical structure undergoing treatment.
[0114] While several particular forms of the invention have been
illustrated and described, it will be apparent that various
modifications can be made without departing from the spirit and
scope of the invention. Accordingly, it is not intended that the
invention be limited, except as by the appended claims.
* * * * *