U.S. patent application number 11/403038 was filed with the patent office on 2006-11-30 for methods and apparatus to achieve a closure of a layered tissue defect.
This patent application is currently assigned to Cierra, Inc.. Invention is credited to Jose Alejandro, Erik Engelson, Dominique Filloux, Dan Francis, Kenneth Horne, Lucia Kim, Uday N. Kumar, Doug Sutton, Miriam H. Taimisto, Andy Uchida.
Application Number | 20060271030 11/403038 |
Document ID | / |
Family ID | 37087676 |
Filed Date | 2006-11-30 |
United States Patent
Application |
20060271030 |
Kind Code |
A1 |
Francis; Dan ; et
al. |
November 30, 2006 |
Methods and apparatus to achieve a closure of a layered tissue
defect
Abstract
Methods for treating anatomic tissue defects such as a patent
foramen ovate generally involve positioning a distal end of a
catheter device at the site of the defect, exposing a housing and
energy transmission member from the distal end of the catheter,
engaging the housing with tissues at the site of the defect,
applying suction or other approximating tool to the tissue via the
housing to bring the tissue together, and applying energy to the
tissue with the energy transmission member or to deliver a clip or
fixation device to substantially close the defect. Apparatus
generally include a catheter body, a housing extending from a
distal end of the catheter body for engaging tissue at the site of
the defect, and further adapted to house a fusing or fixation
device such as an energy transmission member adjacent a distal end
of the housing, or a clip or fixation delivery element.
Inventors: |
Francis; Dan; (Mountain
View, CA) ; Alejandro; Jose; (Sunnyvale, CA) ;
Engelson; Erik; (Menlo Park, CA) ; Filloux;
Dominique; (Redwood City, CA) ; Horne; Kenneth;
(San Francisco, CA) ; Kim; Lucia; (San Jose,
CA) ; Kumar; Uday N.; (San Francisco, CA) ;
Sutton; Doug; (Pacifica, CA) ; Taimisto; Miriam
H.; (San Jose, CA) ; Uchida; Andy; (Mountain
View, CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
Cierra, Inc.
Redwood City
CA
|
Family ID: |
37087676 |
Appl. No.: |
11/403038 |
Filed: |
April 11, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60670535 |
Apr 11, 2005 |
|
|
|
Current U.S.
Class: |
606/27 ; 606/32;
606/41 |
Current CPC
Class: |
A61M 2025/1054 20130101;
A61B 17/0057 20130101; A61B 2018/1407 20130101; A61B 2017/00504
20130101; A61B 2017/00575 20130101; A61B 2017/22069 20130101; A61M
2025/105 20130101; A61M 2025/1052 20130101; A61B 18/1492 20130101;
A61B 2090/061 20160201; A61B 2018/00351 20130101; A61B 2017/00557
20130101; A61M 25/0069 20130101; A61M 25/10 20130101; A61B
2017/00561 20130101; A61B 2018/0063 20130101 |
Class at
Publication: |
606/027 ;
606/032; 606/041 |
International
Class: |
A61B 18/04 20060101
A61B018/04; A61B 18/18 20060101 A61B018/18 |
Claims
1. An apparatus for fusing a layered tissue structure, the
apparatus comprising: a catheter body having a proximal end and a
distal end; a housing on a distal portion of the catheter body, the
housing adapted to appose tissue and having an inside volume; an
energy transmission member positioned within the housing; and means
on the housing to facilitate the housing to expand and/or collapse
thereby changing the inside volume of the housing.
2. An apparatus as in claim 1, wherein the housing has a shape
adapted to effectively cover and appose a layered tissue
structure.
3. An apparatus as in claim 2, wherein the housing shape comprises
a nose protruding from the housing.
4. An apparatus as in claim 1, wherein the housing is
resilient.
5. An apparatus as in claim 1, wherein the housing comprises one or
more hinged joints.
6. An apparatus as in claim 1, wherein the housing is adapted to
maintain its shape sufficiently to maintain a flow of suction
within the housing.
7. An apparatus as in claim 1, wherein the means comprises a
structure over an exterior lip of the housing surrounding an
opening in the housing.
8. An apparatus as in claim 6, wherein the housing is collapsible
into a small diameter introducer sheath.
9. An apparatus as in claim 8, wherein the housing is collapsible
into a 16F sheath or smaller.
10. An apparatus as in claim 8, wherein the housing has an
electrode sized to treat a patent foramen ovale up to 30 mm in
diameter, and wherein the electrode is collapsible into a 16F
sheath or smaller.
11. An apparatus as in claim 1, wherein the means comprises a
reinforcement in a roof of the housing and the reinforcement
inhibits the housing from substantially collapsing and facilitates
the housing to maintain its shape sufficiently to maintain a flow
of suction within the housing, while the housing is apposed to the
tissue structure and a vacuum is applied to the inside volume.
12. An apparatus as in claim 11, wherein the reinforcement
comprises a thickened region, a hardened region, or a stiffening
element.
13. An apparatus as in claim 11, wherein the reinforcement
comprises a metal structure spanning at least a portion of the
roof.
14. An apparatus as in claim 1, wherein the means comprises a ring
circumscribing at least a portion of the housing.
15. An apparatus as in claim 14, wherein the ring circumscribes a
midpoint of the housing.
16. An apparatus as in claim 14, wherein the ring defines a lower
flange in the housing.
17. An apparatus as in claim 14, wherein the ring circumscribes the
lower portion of the inside volume.
18. An apparatus as in claim 1, wherein fluid flow is a means to
assist in expansion of the housing.
19. An apparatus as in claim 1, wherein an electrode is a means to
facilitate the housing to expand.
20. An apparatus as in claim 1, further comprising a collapsing
introducer adapted to collapse the housing prior to the housing
being slidably disposed into an introducer sheath.
21. An apparatus as in claim 20, wherein the collapsing introducer
is shorter than the catheter body.
22. An apparatus as in claim 20, wherein the collapsing introducer
is shorter than the introducer sheath.
23. An apparatus as in claim 20, wherein the collapsing introducer
has a length in the range from 0.5 inches to 10 inches.
24. An apparatus for fusing a layered tissue structure, the
apparatus comprising: a catheter body having a proximal end and a
distal end; a housing on a distal portion of the catheter body; an
energy transmission member positioned within the housing; and means
associated with the housing for apposing the layered tissue
structure to engage the housing against the layered tissue
structure.
25. An apparatus as in claim 24, wherein the means comprises a
clamp contained within the housing which is deployed in response to
the application of a vacuum to the housing.
26. An apparatus as in claim 25, wherein the clamp comprises
structure of the housing which collapses the housing walls to grasp
tissue when the vacuum is applied.
27. An apparatus as in claim 24, wherein the means comprises a
movable element in the housing adapted to capture the layered
tissue between the movable element and a portion of the
housing.
28. An apparatus as in claim 24, wherein the means comprises a
vacuum applied to the housing.
29. An apparatus as in claim 28, wherein the vacuum is applied
circumferentially to the housing.
30. An apparatus as in claim 24, wherein the means comprises a
movable element having a plurality of apertures adapted to capture
the layered tissue upon application of a vacuum.
31. An apparatus as in claim 30, further comprising a second
element disposed in the housing and having a plurality of
apertures, wherein the layered tissue is captured between the first
movable element and the second element.
32. An apparatus as in claim 24, wherein the means comprises a
clamp adapted to penetrate the tissue structure and engage a rear
side of the tissue structure while the housing engages a front side
of the tissue structure.
33. An apparatus as in claim 25, wherein the clamp comprises a
penetrating tube and a deployable anchor.
34. An apparatus as in claim 33, wherein the deployable anchor
comprises a coil.
35. An apparatus as in claim 25, wherein the clamp comprises at
least one magnetic element to provide a clamping force.
36. An apparatus as in claim 35, wherein the magnetic element
comprises a permanent magnet.
37. An apparatus as in claim 35, wherein the magnetic element
comprises an electromagnet.
38. An apparatus as in claim 24, wherein the opposing means
comprises at least one gripper on the housing which engages the
tissue when a vacuum is applied through the housing.
39. An apparatus as in claim 24, wherein the means comprises a
movable vacuum tube contained within the housing adapted to pull
layered tissue toward the housing and against an element disposed
on the housing having a plurality of apertures.
40. An apparatus as in claim 24, wherein the means comprises an
elongate member having a deployable anchor.
41. An apparatus as in claim 24, wherein the deployable anchor
comprises a pivotable puncture tube.
42. An apparatus as in claim 24, further comprising a collapsing
introducer adapted to collapse the housing prior to slidably
disposing the housing into an introducer sheath.
43. An apparatus as in claim 42, wherein the collapsing introducer
is shorter than the catheter body.
44. An apparatus as in claim 42, wherein the collapsing introducer
is shorter than the introducer sheath.
45. An apparatus as in claim 42, wherein the collapsing introducer
has a length in the range from 0.5 inches to 10 inches.
46. An apparatus for fusing a layered tissue structure, the
apparatus comprising: a catheter body having a proximal end and a
distal end; a housing on a distal portion of the catheter body; and
an energy transmission member positioned within the housing,
wherein the energy transmission is adapted to engage and appose
tissue.
47. An apparatus as in claim 46, wherein the member comprises
jaws.
48. An apparatus as in claim 47, wherein the jaws are bipolar
electrodes.
49. An apparatus as in claim 46, wherein the member comprises a
ring which can snare tissue.
50. An apparatus as in claim 49, wherein the ring is a return
electrode.
51. An apparatus as in claim 46, wherein the member comprises a
tissue-penetrating electrode.
52. An apparatus as in claim 51, wherein the tissue-penetrating
electrode includes a distal anchor to allow the electrode to be
pulled back to appose the layered tissue structure.
53. An apparatus as in claim 52, wherein the housing is a return
electrode.
54. An apparatus as in claim 46, further comprising a collapsing
introducer adapted to collapse the housing prior to slidably
disposing the housing into an introducer sheath.
55. An apparatus as in claim 54, wherein the collapsing introducer
is shorter than the catheter body.
56. An apparatus as in claim 54, wherein the collapsing introducer
is shorter than the introducer sheath.
57. An apparatus as in claim 54, wherein the collapsing introducer
has a length in the range from 0.5 inches to 10 inches.
58. A system for fusing layered tissue structures, the system
comprising: a catheter body having a proximal end and a distal end;
a housing on a distal portion of the catheter body; an introducer
sheath slidably disposed over at least a portion of the catheter
body and having a main body, a proximal end and a distal end; and
an energy transmission member positioned within the housing.
59. A system as in claim 58, wherein the energy transmission member
and the housing are collapsible and slidably movable relative to
the introducer sheath, from a collapsed position within the
introducer sheath to an expanded position beyond the distal end of
the introducer sheath.
60. A system as in claim 59, wherein the introducer sheath has a
softer durometer distal tip than the introducer sheath main body
and the softer durometer distal tip facilitates movement of the
housing and the energy transmission member from the expanded
position to the collapsed position within the introducer
sheath.
61. A system as in claim 60, wherein the softer durometer distal
tip is integral with the main body.
62. A system as in claim 60, wherein the softer durometer distal
tip is fixedly connected to the main body.
63. A system as in claim 58, wherein the introducer sheath
comprises a valve adapted to accommodate the housing and wherein
the valve minimizes blood loss from the introducer sheath.
64. A system as in claim 63, wherein the valve is a hemostasis
valve.
65. A system as in claim 64, wherein the hemostasis valve comprises
one or more valve membranes having a top surface and a bottom
surface, and wherein both the top surface and the bottom surfaces
are scored.
66. A system as in claim 65, wherein the scoring comprises two
orthogonal lines.
67. A system as in claim 65, wherein the valve membrane is a
disk.
68. A system as in claim 58, further comprising a collapsing
introducer adapted to collapse the housing prior to slidably
disposing the housing into the introducer sheath.
69. A system as in claim 68, wherein the collapsing introducer is
shorter than the catheter body.
70. A system as in claim 68, wherein the collapsing introducer is
shorter than the introducer sheath.
71. A system as in claim 68, wherein the collapsing introducer has
a length in the range from 0.5 inch to 10 inches.
72. A method for fusing apposed layered tissue structures, the
method comprising: positioning a closure device at a first
treatment site having a first layer of tissue and a second layer of
tissue; approximating the layers of tissue; and applying energy
from the closure device to the apposed layers of tissue thereby
fusing the apposed layers of tissue.
73. A method as in claim 72, further comprising
electrophysiological monitoring of the layered tissue and adjacent
tissue to minimize creation of aberrant conductive paths.
74. A method as in claim 72, further comprising minimizing energy
delivery.
75. A method as in claim 72, further comprising minimizing surface
area of an active electrode.
76. A method for closing a layered tissue structure, the method
comprising: implanting a first magnetic material on one side of the
structure; and implanting a second magnetic material on an opposed
side of the structure; wherein the magnetic materials create a
magnetic force which compresses the layered tissue structure.
77. A method as in claim 76, wherein the layered tissue structure
is a patent foramen ovale.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a non-provisional of U.S. patent
application Ser. No. 60/670,535 (Attorney Docket No.
022128-000700US), filed Apr. 11, 2005, the full disclosure of which
is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The invention generally relates to medical devices and
methods. More specifically, the invention relates to positioning
closure devices, including energy based devices and methods for
treatment of anatomic defects in human tissue, such as a patent
foramen ovale (PFO), atrial septal defect (ASD), ventricular septal
defect (VSD), patent ductus arteriosis (PDA), left atrial
appendages (LAA), blood vessel wall defects and other defects
having layered and apposed tissue structures.
[0003] The following is an example of how one particular type of
anatomical defect, a PFO, is formed. Fetal blood circulation is
very different from adult circulation. Because fetal blood is
oxygenated by the placenta, rather than the fetal lungs, blood is
generally shunted past the lungs to the peripheral tissues through
a number of vessels and foramens that remain patent (i.e., open)
during fetal life and typically close shortly after birth. For
example, fetal blood passes directly from the right atrium through
the foramen ovale into the left atrium, and a portion of blood
circulating through the pulmonary artery trunk passes through the
ductus arteriosus to the aorta. This fetal circulation is shown in
FIG. 1.
[0004] At birth, as a newborn begins breathing, blood pressure in
the left atrium rises above the pressure in the right atrium. In
most newborns, a flap of tissue closes the foramen ovale and heals
together. In approximately 20,000 babies born each year in the
U.S., the flap of tissue is missing, and the hole remains open as
an atrial septal defect (ASD). In a more significant percentage of
the population (estimates range from 5% to 20% of the entire
population), the flap is present but does not heal together. This
condition is known as a patent foramen ovale (PFO). Whenever the
pressure in the right atrium rises above that in the left atrium,
blood pressure can push this patent channel open, allowing blood to
flow from the right atrium to the left atrium. Blood shunting also
occurs in a patent ductus arteriosis (PDA), where a tubular
communication exists between the pulmonary artery and the aorta.
The PDA typically closes shortly after birth.
[0005] Patent foramen ovale has long been considered a relatively
benign condition, since it typically has little effect on the
body's circulation. More recently, however, it has been found that
a significant number of strokes may be caused at least in part by
PFOs. In some cases, a stroke may occur because a PFO allows blood
containing small thrombi to flow directly from the venous
circulation to the arterial circulation and into the brain, rather
than flowing to the lungs where the thrombi can become trapped and
gradually dissolved. In other cases, a thrombus might form in the
patent channel of the PFO itself and become dislodged when the
pressures cause blood to flow from the right atrium to the left
atrium. It has been estimated that patients with PFOs who have
already had cryptogenic strokes may have a risk of having another
stroke.
[0006] Further research is currently being conducted into the link
between PFO and stroke. At the present time, if someone with a PFO
has two or more strokes, the healthcare system in the United States
may reimburse a surgical or other interventional procedure to
definitively close the PFO. It is likely, however, that a more
prophylactic approach would be warranted to close PFOs to prevent
the prospective occurrence of a stroke. The cost and potential
side-effects and complications of such a procedure must be low,
however, since the event rate due to PFOs is relatively low. In
younger patients, for example, PFOs sometimes close by themselves
over time without any adverse health effects.
[0007] Another highly prevalent and debilitating condition, chronic
migraine headache, has also been linked with PFO. Although the
exact link has not yet been explained, PFO closure has been shown
to eliminate or significantly reduce migraine headaches in many
patients. Again, prophylactic PFO closure to treat chronic migraine
headaches might be warranted if a relatively non-invasive procedure
were available.
[0008] Currently available interventional therapies for defect
closure are generally fairly invasive and/or have potential
drawbacks. One strategy is simply to close a defect during open
heart surgery for another purpose, such as heart valve surgery.
This can typically be achieved via a simple procedure such as
placing a stitch or two across the defect with vascular suture.
Performing open heart surgery purely to close an asymptomatic PFO
or even a very small ASD, however, would be very hard to
justify.
[0009] A number of interventional devices for closing defects
percutaneously have also been proposed and developed. Most of these
devices are the same as or similar to ASD closure devices. They are
typically "clamshell" or "double umbrella" shaped devices which
deploy an area of biocompatible metal mesh or fabric (ePTFE or
Dacron, for example) on each side of the atrial septum, held
together with a central axial element, to cover the defect. This
umbrella then heals into the atrial septum, with the healing
response forming a uniform layer of tissue or "pannus" over the
device. Such devices have been developed, for example, by companies
such as Nitinol Medical Technologies, Inc. (Boston, Mass.) and AGA
Medical, Inc. (White Bear Lake, Minn.). U.S. Pat. No. 6,401,720
describes a method and apparatus for thoracoscopic intracardiac
procedures which may be used for treatment of PFO.
[0010] Although available devices may work well in some cases, they
also face a number of challenges. Relatively frequent causes of
complications include, for example, improper deployment, device
embolization into the circulation and device breakage. In some
instances, a deployed device does not heal into the septal wall
completely, leaving an exposed tissue which may itself be a nidus
for thrombus formation. Furthermore, currently available devices
are generally complex and expensive to manufacture, making their
use for prophylactic treatment of PFO and other defects
impractical. Additionally, currently available devices typically
close a PFO by placing material on either side of the tunnel of the
PFO, compressing and opening the tunnel acutely, until blood clots
on the devices and causes flow to stop.
[0011] Research into methods and compositions for tissue welding
has been underway for many years. Of particular interest are
technologies developed by McNally et. al., (as shown in U.S. Pat.
No. 6,391,049) and Fusion Medical (as shown in U.S. Pat. Nos.
5,156,613; 5,669,934; 5,824,015 and 5,931,165). These technologies
all disclose energy delivery to tissue solders and patches to join
tissue and form anastomoses between arteries, bowel, nerves, etc.
Also of interest are a number of patents by inventor Sinofsky,
relating to laser suturing of biological materials (e.g., U.S. Pat.
Nos. 5,725,522; 5,569,239; 5,540,677 and 5,071,417). None of these
disclosures, however, show methods or apparatus suitable for
positioning the tissues of an anatomic defect for welding or for
delivering the energy to an anatomic defect to be welded. These
disclosures do not teach methods that would be particularly useful
for welding layered tissue structures such as PFOs, nor do they
teach bringing together tissues of a defect such that a tissue
overlap is created that can then be welded together.
[0012] Causing thermal trauma to close a patent foramen ovale has
been described in two patent applications by Stambaugh et al. (PCT
Publication Nos. WO 99/18870 and WO 99/18871). The intent is to
eventually cause scar tissue formation which will close the PFO.
Blaeser et al. (U.S. Patent Publication US2003/0208232), describes
causing trauma, or abrading, and holding the abraded tissue in
apposition to allow the tissue to heal together. Using such devices
and methods, the PFO typically remains patent immediately after the
procedure, or abrasion, and only closes sometime later, or is
treated and then held together to heal over time. Frequently, scar
tissue may fail to form or may form incompletely, resulting in a
still patent PFO.
[0013] In addition to PFO, a number of other anatomic tissue
defects, such as other ASDs, ventricular septal defects (VSDs),
patent ductus arteriosis (PDA), aneurysms and other blood vessel
wall defects, atrial appendages and other naturally occurring
cavities within which blood clots can form, and the like cause a
number of different health problems (note that the term "defect"
may include a naturally occurring structure that results a
potential health risk such as the clot forming in the atrial
appendage). U.S. patent application Ser. No. 2004/0098031 (Van der
Burg), and U.S. Pat. Nos. 6,375,668 (Gifford) and 6,730,108 (Van
Tassel et al.), the full disclosures of which are incorporated
herein by reference, disclose a variety of techniques and devices
for treating anatomic defects. In addition, the inventors of the
present invention have described a number of improved devices,
methods and systems for treating a PFO, many of which may be
adapted for treating other anatomic tissue defects as well. For
example, related patent applications assigned to the assignee of
the present invention include U.S. patent application Ser. Nos.:
10/665974 (Attorney Docket No. 022128-000300US), filed on Sep. 16,
2003; 10/679245 (Attorney Docket No. 022128-000200US), filed Oct.
2, 2003; 10/952,492 (Attorney Docket No. 022128-000220US), filed
Sept. 27, 2004; 10/873,348 (Attorney Docket No. 022128-000210US),
filed on Jun. 21, 2004; 11/049,791 (Attorney Docket No.
022128-000211US), filed on Feb. 2, 2005; 10/787532 (Attorney Docket
No. 022128-000130US), filed Feb. 25, 2004; 10/764,148 (Attorney
Docket No. 022128-000510US), filed Jan. 23, 2004; 10/811,228
(Attorney Docket No. 022128-000400US), filed Mar. 26, 2004; and
U.S. Provisional Application No. 60/670/535 (Attorney Docket No.
022128-000700US), filed Apr. 11, 2005, the full disclosures of
which are incorporated herein by reference.
[0014] Despite improvements made thus far, it would be advantageous
to have even further improved methods, systems, and apparatus for
treating anatomic tissue defects such as PFOs and the other
anatomic structures mentioned above. Ideally, such methods and
apparatus would help position a closure device so that a complete
seal of a PFO or other anatomic tissue defect can be achieved
reliably and in a predictable fashion. Also, such devices and
methods would leave no foreign material (or very little material)
in a patient's heart. Furthermore, such methods and apparatus would
preferably be relatively simple to manufacture and use, thus
rendering prophylactic treatment of PFO and other tissue defects a
viable option. Ideally, such methods and apparatus could also be
used in a minimally invasive manner, with low profile for ease of
introduction into the body, while effectively closing the PFO
quickly, effectively and without causing damage to other portions
of the body. When success of the closure procedure can be well
predicted, physicians are more likely to recommend such a procedure
prophylacticly. At least some of these objectives will be met by
the present invention.
BRIEF SUMMARY OF THE INVENTION
[0015] The present invention provides apparatus, systems and
methods for treating anatomic defects in human tissues,
particularly defects involving tissue layers where it is desired to
weld or fuse the layers together, such as a patent foramen ovale
(PFO). The methods will also find use with closing a variety of
other defects which may or may not display layered tissue
structures, such as atrial septal defects, ventricular septal
defects, patent ductus arteriosis, left atrial appendages, blood
vessel wall defects, and the like. For the treatment of PFOs, the
apparatus will usually comprise endovascular/intravascular
catheters having an elongate catheter body with a proximal end and
a distal end. A housing may be positioned at or near a distal end
of the catheter body, where the housing has an opening for engaging
a tissue surface where the tissue defect may be present. Usually,
the housing will be connectable to a vacuum source to enhance
engagement of the housing against the tissue, and an energy
transmission member, such as an electrode, may be positioned at or
near the opening in the housing to apply energy to the tissue to
effect welding and closure. For purposes of this disclosure, the
terms sealing, closing, welding, fusing are used interchangeably to
describe bringing tissues of a defect together so as to result in a
substantial seal e.g. no physiologic leak of biological fluid or
operator infused fluid across the sealed area. Although a variety
of mechanisms may work to achieve this, the sealing or closing of
the defect can occur via the presence or absence of a variety of
biologic processes, some of which may be fusion or lamination of
the tissue cells, layers or collagen, expression/combination of
factors from the tissue that are expressed upon application of
energy, denaturation and re-naturation of tissue elements,
crosslinking, necrosis or partial necrosis or other cellular
phenomena present at the treatment site upon application of the
energies described herein, or combinations thereof.
[0016] Alternatively, instead of an electrode, the suction housing
may be adapted for passage of a closure device such as a clip or
fixation element that may be placed through the tissue of the
defect while it is stabilized by the suction housing. The following
description will often focus on PFO treatment, but at least many of
the inventive embodiments may be employed for treating other tissue
defects and in other contexts.
[0017] In a first aspect of the present invention, an apparatus for
fusing a layered tissue structure comprises a catheter body with a
proximal and distal end as well as a housing on a distal portion of
the catheter body. The housing is adapted to appose tissue and has
an inside volume. An energy transmission member is positioned
within the housing and means on the housing facilitate expansion
and/or contraction of the housing which results in a change in the
housing inside volume.
[0018] The housing shape is adapted to effectively cover and appose
a layered tissue structure. It is also is resilient and can be
shaped to include a protruding nose. In some embodiments, the
housing comprises hinged joints, and is adapted to maintain its
shape sufficiently to maintain a flow of suction within the
housing. The housing is collapsible into a small diameter
introducer sheath, preferably 16 French or smaller. Additionally,
the housing may include an electrode sized to treat a patent
foramen ovale up to 30 mm in diameter and the electrode also can be
collapsed in the same introducer sheath.
[0019] The means on the housing may be a structure over an exterior
lip of the housing surrounding an opening in the housing, or the
means may be a reinforcement in the roof of the housing which
inhibits the housing from substantially collapsing while also
facilitating the housing to maintain its shape sufficiently to
maintain a flow of suction within, while the housing is apposed to
the tissue structure and a vacuum is applied to the inside volume.
The reinforcement may be a thickened region, a hardened region or a
stiffening element. Alternatively, the reinforcement may comprise a
metal structure spanning at least a portion of the roof. In other
embodiments, the means comprises a ring that circumscribes a
portion of the housing including a midpoint of the housing. The
ring can also define a lower flange in the housing or the ring can
circumscribe the lower portion of the inside volume.
[0020] The housing is expandable and fluid flow is a means to
assist in the expansion. An electrode may also be a means to
facilitate expansion. Other embodiments include a collapsing
introducer which is able to collapse the housing prior to slidably
disposing the housing into an introducer sheath. Typically, the
collapsing introducer is shorter than the catheter body and the
introducer sheath. In some embodiments, the length of the
collapsing introducer ranges from about 0.5 to 10 inches long.
[0021] In another aspect of the present invention, an apparatus for
fusing a layered tissue structure comprises a catheter body having
a proximal end and a distal end, a housing on a distal portion of
the catheter body, an energy transmission member within the housing
and means associated with the housing for apposing the layered
tissue structure to engage the housing against the layered tissue
structure.
[0022] The means may comprise a clamp within the housing, deployed
in response to the application of a vacuum to the housing. The
clamp can include structure of the housing which collapses the
housing walls to grasp tissue when vacuum is applied. The means may
also comprise a movable element in the housing adapted to capture
the layered tissue between the movable element and a portion of the
housing. The means can also be a vacuum applied circumferentially
to the housing, or in other patterns.
[0023] The means can also comprise a movable element having a
plurality of apertures adapted to capture the layered tissue upon
application of a vacuum. The movable element may include a second
element disposed in the housing with a plurality of apertures, and
the layered tissue is captured between the first movable element
and the second element.
[0024] In the apparatus, the means may comprise a clamp adapted to
penetrate the tissue structure and engage a rear side of the
structure while the housing engages a front side of the tissue
structure. The clamp can also include a penetrating tube and a
deployable anchor which in some cases is a coil. The clamp could
also be a magnetic element such as a permanent magnet or
electromagnet, that provides a clamping force.
[0025] In other embodiments, the apposing means comprises at least
one gripper on the housing which can engage the tissue when a
vacuum is applied through the housing. The means may comprise a
movable vacuum tube contained within the housing adapted to pull
layered tissue toward the housing and against an element disposed
on the housing having a plurality of apertures. The means can also
be an elongate member having a deployable anchor which can be a
pivotable puncture tube.
[0026] Often, the apparatus includes a collapsing introducer which
is adapted to collapse the housing prior to sliding the housing
into an introducer sheath. Typically, this collapsing introducer is
shorter than the catheter body and the introducer sheath and can
range in length from 0.5 inches to 10 inches.
[0027] In yet another aspect of the present invention, an apparatus
for fusing a layered tissue structure comprises a catheter body
with a proximal and distal end, a housing on a distal portion of
the catheter body and an energy transmission member positioned
within the housing, and adapted to engage and appose tissue. The
member can be jaws which act as bipolar electrodes or the member
can be a ring which snares tissue. In some instances, the ring
serves as a return electrode. The member also can comprise a tissue
penetrating electrode which may include a distal anchor to allow
the electrode to be pulled back to appose the layered tissue
structure. In other embodiments, the housing serves as a return
electrode.
[0028] Often, the apparatus includes a collapsing introducer which
is adapted to collapse the housing prior to slidably disposing the
housing into an introducer sheath. Typically, the collapsing
introducer is shorter than the catheter body and the introducer
sheath, and typically has a length in the range from about 0.5
inches to about 10 inches.
[0029] In another aspect of the present invention, a system for
fusing layered tissue structures comprises a catheter body having a
proximal and distal end, a housing on a distal portion of the
catheter body, an introducer sheath having a main body as well as
proximal and distal ends, that is slidably disposed over a portion
of the catheter body and an energy transmission member positioned
within the housing. The energy transmission member and the housing
are collapsible and slidably movable relative to the introducer
sheath from a collapsed position within the introducer sheath to an
expanded position beyond the distal end of the introducer sheath.
Preferably, the introducer sheath has a softer durometer distal tip
than the main body of the introducer sheath and this tip
facilitates movement of the housing and the energy transmission
member from the expanded position to the collapsed position within
the introducer sheath. The softer durometer tip may be integral
with the main body or it may be fixedly connected to the main
body.
[0030] In the system, the introducer sheath may comprise a valve
adapted to accommodate the housing and this valve also minimizes
blood loss from the introducer sheath. Typically the valve is a
hemostasis valve which may include one or more valve membranes such
as disks which have a top surface and a bottom surface, both of
which are scored. They may be scored orthogonally or at other
angles.
[0031] The system often also includes a collapsing introducer which
is adapted to collapse the housing prior to slidably disposing the
housing into the introducer sheath. Often, the collapsing
introducer is shorter than the catheter body and the introducer
sheath, and typically is in the range of from about 0.5 inches to
about 10 inches long.
[0032] In still another aspect of the present invention, a method
for fusing apposed layered tissue structures comprises positioning
a closure device at a first treatment site having a first layer of
tissue as well as a second layer to tissue. The layers of tissue
are approximated and energy is applied from the closure device to
the tissue thereby fusing the layers of tissue. The method can also
include electrophysiological monitoring of the layered tissue as
well as adjacent tissue so that creation of aberrant conductive
pathways is minimized. This can be accomplished by minimizing
delivery of energy as well as minimizing the surface area of the
active electrode and/or distance of the treatment zone to the AV
node of a patient's heart.
[0033] In still another aspect of the present invention, a method
for closing layered tissue structures comprises implanting a first
magnetic material on one side of the structure and implanting a
second magnetic material on an opposed side of the structure. The
magnetic material create a magnetic force which compresses the
layered tissue structure. Often, the layered tissue structure is a
patent foramen ovale.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 illustrates the anatomy of fetal circulation,
including a PFO and PDA.
[0035] FIGS. 2A-2I show various anatomies of a PFO.
[0036] FIGS. 3A-3D show various orientations of PFOs.
[0037] FIGS. 4A-4D show how a treated PFO may not be fully
sealed.
[0038] FIGS. 5A-5F show various treated regions that successfully
seal the PFO.
[0039] FIG. 6 shows a balloon properly positioning a closure device
with respect to a layered tissue defect such as a PFO.
[0040] FIGS. 7A and 7B show tapered elongated members or a tapered
balloon on the distal end of a catheter used to position the
catheter.
[0041] FIG. 8 shows a dual layer balloon in a layered tissue
defect.
[0042] FIGS. 9-9A illustrate how expandable mechanical elements may
be used to properly position a closure device at a layered tissue
defect.
[0043] FIGS. 9B-9D show expandable mechanical elements on a
catheter shaft.
[0044] FIGS. 10A-10B show an alternative embodiment of expandable
mechanical positioning elements.
[0045] FIG. 11 shows how radiopaque markers on a flexible wire may
be used to position a catheter and estimate tissue defect size.
[0046] FIG. 12 shows an alternative embodiment of a treatment
device with flexible wires used for positioning and radiopaque
markers for sizing and indicating treatment region.
[0047] FIG. 12A shows a crossing catheter with a guidewire
lumen.
[0048] FIG. 13 is a cross-sectional view of a positioning device in
the tunnel of a layered tissue defect.
[0049] FIG. 14 illustrates how whiskers on a catheter position the
device and indicate the width of the tunnel entrance.
[0050] FIGS. 15A-15D shows a positioning device with retractable
whiskers.
[0051] FIGS. 16A-16E illustrates a positioning device utilizing a
looped wire design.
[0052] FIGS. 17A-17B show other features on the closure device
housing that facilitate with positioning.
[0053] FIGS. 18A-18B illustrate a compound bend in the closure
device that assists with device positioning.
[0054] FIGS. 19A-19B show various embodiments of a bipolar
positioning and sizing closure device.
[0055] FIG. 20 illustrates a closure treatment system.
[0056] FIG. 21 shows a closure treatment apparatus.
[0057] FIGS. 22A-22B illustrates an introducer sheath and
hemostasis valve used with a closure treatment apparatus.
[0058] FIG. 23 illustrates a collapsing introducer.
[0059] FIGS. 24A-24E show how the collapsing introducer of FIG. 23
is used.
[0060] FIGS. 25A-25B show various aspects of the treatment catheter
housing.
[0061] FIGS. 25C-25I show a bottom view of several housing and
electrode configurations.
[0062] FIGS. 26-36 show various ways a therapeutic element of a
treatment device can appose defect tissue.
[0063] FIG. 37 shows one embodiment of an apposition device.
[0064] FIGS. 38A-38D show an apposition device and how it apposes
tissue.
[0065] FIGS. 39A-39F show how an apposition device and a closure
treatment device work together to close a layered tissue defect
such as a PFO.
[0066] FIGS. 39G-39I show another apposition device and closure
treatment device working together to close a layered tissue defect
such as a PFO.
[0067] FIG. 40 shows an apposition device comprising magnets.
[0068] FIG. 41 illustrates how magnets on either side of a PFO are
used to bring the tissue layers together.
[0069] FIG. 42 shows magnets permanently implanted in order to
close a PFO.
[0070] FIG. 43 shows additional features on the housing to help
with tissue apposition.
[0071] FIGS. 44A and 44B show other features on the housing that
help with tissue apposition.
[0072] FIGS. 45A-45C show a preferred embodiment of the closure
device housing.
[0073] FIGS. 45D-45F show another embodiment of the closure device
housing.
[0074] FIGS. 46-49A show various embodiments of electrode
configurations.
[0075] FIGS. 50A-50B show a variable masking means.
[0076] FIG. 51 shows a means for actuating the variable masking of
FIGS. 50A-50B.
[0077] FIG. 51A shows a mesh electrode embodiment.
[0078] FIG. 52A-52B show a looped or petal electrode
configuration.
[0079] FIGS. 53-54 illustrate various electrode embodiments.
[0080] FIG. 55 shows a bipolar configuration.
[0081] FIG. 56 shows a monopolar configuration.
[0082] FIG. 57 shows a preferred embodiment of the electrode.
[0083] FIG. 57A illustrates a hinged electrode with flexible
connections to the housing.
[0084] FIG. 58A-58C show the electrode disposed in a housing and a
portion of the guidewire lumen exit aperture.
[0085] FIGS. 58D-58F illustrate various aspects of an
electrophysiological mapping system combined with the closure
treatment device.
[0086] FIG. 59 is a schematic representation of a closure treatment
system.
[0087] FIGS. 60-67 are graphs illustrating energy algorithms.
DETAILED DESCRIPTION OF THE INVENTION
[0088] Devices, systems, and methods of the present invention
generally provide for treatment of anatomic defects in human
tissue, such as a patent foramen ovale (PFO), atrial septal defect
(ASD), ventricular septal defect (VSD), left atrial appendage
(LAA), patent ductus arteriosis (PDA), vessel wall defects and/or
the like through application of energy. The present invention is
particularly useful for treating and fusing layered tissue
structures where one layer of tissue at least partly overlaps a
second layer of tissue as found in a PFO. Therefore, although the
following descriptions and the referenced drawing figures focus
primarily on treatment of PFO, any other suitable tissue defects,
such as but not limited to those just listed, may be treated in
various embodiments.
[0089] I. PFO Anatomy
[0090] As mentioned in the background section above, FIG. 1 is a
diagram of the fetal circulation. The foramen ovale is shown PFO,
with an arrow expanded view demonstrating that blood passes from
the right atrium RA to the left atrium LA in the fetus. After
birth, if the foramen ovale fails to close (thus becoming a PFO),
blood may travel from the right atrium RA to the left atrium LA or
vice versa, causing increased risk of stroke, migraine and possibly
other adverse health conditions, as discussed above.
[0091] FIGS. 2A-2I illustrate various PFO anatomies. For example,
FIG. 2A shows the secundum S overlapping with the primum P to form
a frown line F which is the entrance the PFO tunnel T and here,
which is narrow and slightly offset. The PFO tunnel T may also be
short and shallow as illustrated in FIG. 2B and cross-sectional
view in FIG. 2C, or the tunnel T may be wide and long as shown in
FIG. 2D. FIG. 2E and cross-sectional view FIG. 2F show a PFO tunnel
T that is long. Other PFO tunnel T anatomies include an offset
tunnel as in FIG. 2G, or an initially wide tunnel T which narrows
in FIG. 2H or an initially wide tunnel T that narrows and is offset
as illustrated in FIG. 21.
[0092] In addition to tunnel variations, the opening or frown F of
the PFO and height of the PFO limbus can also vary. FIG. 3A refers
to anatomic locations for FIGS. 3B-3D where superior points toward
the head, inferior points toward the feet, posterior is toward the
back of the body and anterior is toward the front. FIG. 3B shows
the overlap of the primum P with the secundum S forming a frown
line F which is the entrance to the PFO tunnel T. In FIG. 3B, the
PFO tunnel T has an anterior orientation, while in FIG. 3C the PFO
is inferior with an anterior tunnel T and FIG. 3D shows a superior
PFO with a posterior tunnel T.
[0093] II. Placement
[0094] Given the anatomical variations of a PFO, using a
traditional guidewire to guide a closure device to the defect for
treatment may not result in optimal placement all of the time. For
example, in FIG. 4A, a traditional guidewire GW placed through a
wide PFO tunnel T may direct the closure device to a treatment
region Tx that only includes a portion of the tunnel opening F,
leaving an untreated region UTx that results in a leak L, as shown
in FIG. 4B.
[0095] Similarly, as illustrated in FIGS. 4C and 4D, a single
strand guidewire GW placed through a deeper PFO tunnel T that is
somewhat offset, may align the device with the location of the
tunnel T, but not let the operator know that the device is not
placed in a position to affect the mouth or opening of the tunnel
F, and may therefore result in a treated region Tx that falls short
of sealing off the mouth of the tunnel, resulting in a leak path
L.
[0096] Proper positioning is achieved when the closure device is
placed optimally in relation to the defect to deliver the desired
closure device. Closure of the defect following accurate placement
of the device in a variety of PFO anatomies is illustrated in FIGS.
5A-5F. These figures show the overlap of the primum P with the
secundum S to form a frown line F which is the opening to the PFO
tunnel T. Various treatment regions Tx are shown which successfully
close the PFO tunnel T. Accurate placement allows the therapeutic
device to be more precise, and in addition, in the case of energy
delivery catheters to seal the PFO, deliver the energy just to the
opening on the defect so as to minimize the location and amount of
energy delivered to the heart tissue. As illustrated in FIGS.
5A-5F, various electrode configurations and treatment zones can be
employed accurately with use of the present invention.
[0097] III. Positioning
[0098] In any of these procedures, a key aspect to performing
closure of an anatomic defect is positioning the catheter or
treatment device at the optimal location over the defect to be
treated. Failure to place the device in the optimal location can
result in incomplete closure of the defect, and require either a
repeat application of the closure mechanism, or an additional
intervention (e.g. second procedure). For example if a traditional
single strand guidewire is placed through a PFO defect with a long
tunnel, or a wide tunnel, it is difficult to predict, where in that
tunnel the guidewire is going to reside and therefore even if a
closure catheter is tracked over the wire that is through the PFO,
it may not be directed to the center of the tunnel (in the case of
a wide PFO), or to the mouth of the tunnel (in the case of a longer
PFO tunnel). Various other misalignments can also occur depending
on the size, width, angle, and/or depth of the targeted defect.
[0099] Various steps may be undertaken prior to performing a
procedure to close a PFO, including sizing the defect, determining
the orientation of the defect, assessing the depth of the defect,
and determining any related or adjacent anatomic features such as a
septal aneurysm. PFOs can range in size from about 1 mm to 30 mm
although they are typically in the range from about 3 mm to 26 mm.
Sizing of the defect could be accomplished by placing gradations or
markers on a sizing device or a series of calibrated sizers could
be utilized. Any of these can be adapted to be radiopaque or
echogenic and therefore fluoroscopy, intravascular ultrasound, TEE,
ICE and other visualization techniques may be employed to visualize
and determine the foregoing so that the physician can better
determine how best to size and place the closure device to achieve
closure of the defect. For example, radiopaque markers mounted on a
balloon inflated in the PFO would permit the PFO tunnel diameter to
be observed and estimated under a fluoroscope. Other apparatus and
methods for characterizing the tissue defect are described
herein.
[0100] In addition, these visualization techniques may be employed
in combination with the intravascular devices of the present
invention to not only provide sizing information to the user, but
in some cases provide a mechanical guide or rail, over which to
accurately place a closure catheter. These features may be combined
into one device, or a series of devices to assess the geometry of
the PFO, place and position a closure device and ultimately deliver
the closure therapy (clip, energy, sutures, etc.)
[0101] FIG. 6 illustrates a closure system 10 wherein a guiding
member 12 such as a catheter shaft or guidewire is inserted into
the PFO tunnel T created by the overlap of primum P and secundum S
layers of tissue. An inflatable member 14 such as a balloon mounted
on the guiding member 12 is then inflated thereby centering the
guiding member 12 and closure device 16 with the tissue defect. The
closure device may be advanced into apposition with the tissue
defect by pushing the closure system 10 forward towards the defect,
or a vacuum may be used to draw the tissue toward the closure
device. Other tissue apposition apparatus and methods are discussed
hereinafter. An example of a sizing/orientation apparatus is the
PTS.RTM. Sizing Balloon Catheter available from NuMed, Hopkington,
N.Y. The properly aligned closure device 16 can then successfully
treat and close the defect. The combined apparatus allows sizing
and or visual (radiographic, ultrasonic, etc.) feedback of PFO
anatomy, as well as guiding features (such as over the wire
placement of a closure catheter) so that closure catheters can be
correctly positioned in the vicinity of a PFO or other anatomic
defect to deliver a variety of closure devices including suture
delivery catheters, clip delivery catheters, patch delivery
catheters, energy welding catheters and the like. Examples closure
devices include, but are not limited to a suturing device as
described in U.S. Patent Publication 2005/0070923 (McIntosh); a
clip in U.S. Patent Publication 2005/0119675 (Adams); a transeptal
puncture in publication WO 05/046487 (Chanduszko); a coil electrode
in publication WO 05/074517 (Chanduszko); a clip in U.S. Patent
Publication 2005/0187568 (Klenk); a transeptal puncture and
electrode catheter in U.S. Patent Publication 2004/0243122 (Auth);
and a gathering clip in publication WO 05/027753 (Brenzel); the
full disclosures of which are incorporated herein by reference.
[0102] Another embodiment of a positioning device is shown in FIGS.
7A and 7B. In FIG. 7A, positioning device 20 comprises a guiding
member 22 such as a catheter or guidewire with a tapered set of
elongated members 24 near the distal tip 26 of the device. The
positioning device 20 may then be advanced into the PFO tunnel and
it is automatically centered as the tapered elongated members
engage the tunnel walls. In addition to positioning, the device
also facilitates sizing of the defect. A closure device may then be
introduced over the guiding member 22 so that it is properly
positioned and a closure treatment is then applied to the defect.
In another embodiment shown in FIG. 7B, a positioning device 30
comprises a catheter 34 having an expandable member 36 such as a
balloon disposed near the distal end of the device. The expandable
member is expanded in the PFO tunnel resulting in the centering of
the positioning of the device. Radiopaque markers 38 are disposed
on the balloon 36 allowing a physician to size the defect and
observe position. Once properly positioned, a closure device is
then delivered over the positioning device to the defect so that a
closing treatment may be applied. The tapered elongated members 24
from FIG. 7A may also be incorporated into this embodiment to
assist with positioning of the device. The catheter 34 may also
have a guidewire lumen to allow use of a guidewire 32.
[0103] With reference now to FIG. 8, a dual layer balloon is used
to position and size the tissue defect. A positioning device 40 has
an inner balloon 44 and an outer balloon 46 mounted on the distal
end of a catheter 42. The catheter 42 is advanced into the tunnel
of a PFO and the inner balloon 44 is then inflated until it engages
the walls of the of tunnel, thereby centering the device in the
tunnel. The outer balloon 46 may then be inflated with contrast
media and holes 48 in the outer balloon allow contrast media to
weep out 50. Hole geometry may be varied to provide appropriate
contrast flow rates. This may be observed under fluoroscopy and
therefore the tissue defect anatomy and dimensions can be estimated
including tunnel length, as well as allowing verification that the
device is properly positioned. A closure device is then introduced
over the positioning catheter to the defect and a closure treatment
is applied. Visualizing the contrast media also helps to verify
that the closure device is properly positioned with respect to the
defect prior to treatment.
[0104] Another embodiment of a mechanical expansion device used for
positioning is shown in FIGS. 9 and 9A-9D. In FIG. 9, a closure
system 60 is illustrated having a catheter 62 with mechanical
positioning elements 66 in the collapsed position, mounted on the
distal end of the catheter 62. The catheter 62 and positioning
elements 66 are advanced into the tunnel T of the PFO and then the
mechanical elements 66 are expanded until they engage the defect
walls and the device is positioned as illustrated in FIG. 9A. A
closure device 64 also disposed on the catheter 62 is therefore
also simultaneously positioned against the tissue defect and then a
treatment can be applied to close the PFO defect. FIG. 9A shows the
closure system when the mechanical elements 66 are expanded and
engaged with the PFO tunnel, T.
[0105] FIGS. 9B-9D illustrate how the mechanical expansion elements
66 function. In FIG. 9B the mechanical elements 66 are unexpanded
and remain in a low profile position against the catheter 62. When
the catheter 62 is actuated as shown by the arrows in FIG. 9C, the
mechanical expansion members 66 flex and bow outward to various
diameters depending on how far the catheter 62 is actuated. In FIG.
9C four expansion members are illustrated, although more or less
may be employed, as shown in FIG. 9D where two members are shown.
The expansion members may be fabricated from polymers or metals
having a spring temper or superelastic alloys such as nitinol.
[0106] Another mechanical expansion embodiment is shown in FIG. 10A
and 10B. In FIG. 10A, a positioning device 70 comprises a catheter
72 which is introduced into the tunnel T of the PFO defect.
Expansion members 74 are then expanded thereby properly positioning
the device within the tunnel. In this embodiment, the expansion
elements 74 are retractable into openings 76 in the catheter. The
expansion elements 74 are actuated directly to control their
expansion, and when unexpanded, have an even lower profile than the
embodiment of FIG. 9C.
[0107] With reference now to FIG. 11, a positioning device 80 may
include single or multiple flexible members 84 with both ends fixed
to an elongate member such as a catheter 82. A part of the catheter
shaft 85 may act as a core member between the flexible members 84
to further add rigidity to the positioning device 80 to assist with
its pushability toward and through a tissue defect. The positioning
device 80 may be deployed through a closure device, or through a
separate introducer catheter that is then removed, leaving the
positioning device in place. Radiopaque markers 86 or coatings may
be placed on various segments of the flexible members 84 to allow
the user to view the orientation and spacing of the flexible
members 84 and correlate them to the defect anatomy. For example,
markers may be useful on the widest point of the flexible members
to show the width of the PFO frown or opening, F, and may also
continue along the length of the flexible members to help delineate
the tunnel T (e.g. see the angle, show tunnel width, etc.). At
least a portion of the flexible members are preferably placed
between the tissue of the PFO with the main catheter 82 extending
into or through the defect tunnel. The flexible members 84 extend
laterally from the main body of the catheter to provide definition
of the outer edges of the PFO, transitioning to define the location
(angle) and size or width of the defect tunnel. The radiopaque
markers 86 in FIG. 11 are visible under fluoroscopy and permit
orientation of the defect and location of the frown or opening to
be discerned based on observation of the geometry of the flexible
members placed within the defect.
[0108] FIG. 12 shows how a treatment device may be used with a
positioning device. In FIG. 12, a closure treatment catheter 90 has
an elongate shaft 92 and a housing 100 on the distal end. A
treatment region 96 is disposed within the housing 100 and
radiopaque markers 98 outline the treatment area 96. A positioning
device 94 is advanced to a layered tissue defect such as a PFO
until the distal end 104 extends beyond the defect. Flexible
elongate members 106 delineate the tunnel of the PFO and radiopaque
markers 102 allow the physician to see the defect under
fluoroscopy. The closure treatment catheter 90 is then advanced
over the positioning device 94 until the radiopaque markers of
treatment region 98 are aligned with the radiopaque markers 102 of
the positioning device and it is clear that the treatment catheter
90 is positioned over the defect properly for treatment. The
positioning device 94 may then be removed and a closure treatment
can then be applied to the defect to close the layered tissue
defect. If the treatment device 90 is placed directly over the
positioning device 94, the positioning device 94 is preferably
constructed so that it can be removed with the treatment device 90
left in place. For example, in this embodiment, it is preferable
that the flexible elongate members 106 can be pulled back through a
lumen of the treatment device 90.
[0109] FIG. 12A shows a crossing catheter similar to the embodiment
described in FIG. 12 above. In FIG. 12A, the crossing catheter 1300
is also used with a positioning device. Here, the crossing catheter
1300 has an elongate shaft 1310 and a housing 1308 on the distal
end of the shaft. An inner lumen shown by dotted lines is axially
disposed within the crossing catheter elongate shaft 1310 and has
an exit port 1312 in the housing. The crossing catheter 1300 is
used with a positioning device 1314 that is advanced to the layered
tissue defect (such as a PFO) until the distal end 1304 extends
over the defect. The positioning device 1314 has flexible elongate
members 1306 that mark the boundaries of the tissue defect. In the
case of a PFO, the flexible elongate members 1306 indicate the
tunnel of the PFO and radiopaque markers 1302 permit a physician to
observe the defect under fluoroscopy. Once the positioning device
1314 has been delivered, the crossing catheter 1300 is then
advanced over the positioning device 1314 until the housing 1308 is
disposed over the tissue defect as indicated by the radiopaque
markers. A vacuum may then be applied to the crossing catheter,
either via the inner lumen or another lumen so that the housing
1308 is apposed with the tissue defect. Once apposition is
obtained, the positioning device 1314 may be removed and a
treatment device, or a guidewire over which a treatment device may
be delivered, may be advanced axially along the catheter elongate
shaft 1310 through the inner lumen or another lumen until the
distal end of the treatment device exits the inner lumen port 1312.
For example, the inner lumen port may be curved laterally such
that, in the case of placing a guidewire, the guidewire exits the
inner lumen at an angle sufficient to direct the guidewire
transeptally, or through the tissue of the layered defect (for
example from right atrium to left atrium either through the primum,
through the secundum or through both tissue structures as depicted
in FIG. 38B hereinbelow). Once the guidewire is placed transeptally
and centered optimally with respect to the defect, a closure
catheter may be passed over the guidewire such that it may be
deployed across the atrial septum at a point that is substantially
centered, or positioned to close the PFO. For purposes of this
disclosure, "centered" or "positioned" may be descriptors of how
the crossing catheter is optimally positioned to guide a transeptal
puncture device in order to position a separate treatment catheter
at the position on or over the tissue defect such that when a
closure device is deployed, it substantially closes the defect.
Once the layered tissue defect is repaired, the closure treatment
device and crossing catheter may then be removed from the treatment
site.
[0110] FIG. 13 shows a cross-sectional view of a portion 114 of a
positioning device 110 in a PFO tunnel. A portion of the
positioning device 110 extends past the tunnel exit 116, while the
proximal end of the device is outside of the tunnel, 112. FIG. 14
shows another embodiment of a positioning device. Positioning
device 120 represents a guidewire with whiskers 126 at the distal
end to seat the wire device through a PFO and also to assist in
sizing the width and locating the tunnel entrance or mouth F. The
whiskers 126 may be fabricated from a pre-formed resilient material
(e.g. nitinol, spring temper steel, Elgiloy.RTM., formed or coiled
stainless steel wire) such that when the guidewire is deployed from
a catheter, the whiskers 126 deploy outwardly to seat within the
comers of the PFO tunnel T. Once in place, the closure device can
be tracked over the guidewire 122. The closure device may include
radiopaque markers that can be aligned with guidewire markers (not
shown) to seat over the outer limits of the width of the PFO and to
include the tunnel entrance. Once in place the guidewire can be
removed through the guidewire lumen in the closure device. In the
case of the whisker wire, the whiskers would flex upwards to be in
line with the main wire and all be pulled out through the guidewire
lumen. Additionally, the whisker elements may be spring loaded to
ensure that they extend out to the farthest width of the defect
that they are measuring or positioning. It is also within the scope
of the invention that the guidewire device may be a separate
catheter and while it provides a visual docking target, the closure
catheter and the guidewire/positioning catheter are not physically
linked, but are placed separately from each other.
[0111] FIGS. 15A-15D shows one embodiment of the whiskers
positioning device discussed above with respect to FIG. 14. In FIG.
15A, a positioning device 130 has a sheath housing 136 with slits
138. A positioning catheter 132 lies in the sheath 136 and
positioning whiskers 134 also remain covered by the sheath 136.
Once the positioning device 130 is placed within a PFO, the
whiskers 134 may be released from the sheath 136, and the whiskers
then expand through the slits 138 in the sheath 136, as shown in
FIG. 15B. The whiskers 134 spring to a fully deployed position
thereby properly positioning the device 130 and allowing PFO
sizing, shown in FIG. 15C. Once the positioning device 130 is no
longer required, the whiskers 134 may be retracted into the sheath
136 which is illustrated in FIG. 15D.
[0112] In another embodiment shown in FIGS. 16A-16C, a looped wire
design is employed. In this embodiment, a looped guidewire type of
positioner is used to position the device. In FIG. 16A, a closure
device 140 has an elongated catheter shaft 142 and a distal housing
150. A treatment region 144 is disposed on the housing 150 along
with placement wire apertures 146 and a guidewire aperture 148. The
looped guidewire in FIG. 16B with high flexibility is retractable
into apertures 146 and can be extended into the defect in a looped
configuration to form a sizing and positioning device, as well as
serving as a rail over which closure device can be placed
accurately at a treatment site. In FIG. 16C, the looped wire 154 is
advanced until it engages the walls of the layered tissue defect. A
guidewire 148 may also be used to help deliver the closure device
140 to the tissue defect, and it exits out of aperture 148. FIG.
16D shows how the guidewire 152 and looped wire 154 fit into a PFO
tunnel T and position the closure device housing 150 over the
entrance of the defect, F. The looped wire 154 may be designed with
variable stiffness along its length to facilitate sizing and
positioning. For example, the looped wire 154, shown in a
straightened out configuration in FIG. 16E may have a stiff section
156 for accommodating the widest PFOs, a less stiff section 158
adjacent to the stiffest section 156 and a flexible section 159 in
the middle of the loop wire.
[0113] Additional catheter features may also be employed in order
to aid in placement and sizing. For example, in FIG. 17A, a closure
device 170 has a retractable catheter shaft 175 with a housing 176
attached to the catheter shaft 175. The housing 176 has a treatment
region 174 on the housing and extensible positioning rails 178
serve as feelers to help stabilize the treatment device 170. The
housing 176 and positioning rails 178 are retractable into sheath
172. Alternatively, the housing shape may be modified to include an
extended nose 179 as seen in FIG. 17B. This shape helps position
the closure device 170 against the tissue defect. A moveable
guidewire lumen (not shown) may also be used to facilitate
placement and sizing. A compound bend can also help the closure
device to be properly positioned adjacent to a tissue defect as
shown in FIG. 18A. In FIG. 18A, several bends 194, 196 in the shaft
192 of a closure device 190 help to properly position the treatment
portion of the device 190 against the tissue defect. In FIG. 18A,
typical ranges for the first bend indicated by angle .alpha. is up
to 75.degree. while a second bend indicated by angles .beta. and
.gamma. are up to 60.degree. and 75.degree. respectively. FIG. 18B
shows a back view of the of the treatment device shaft where angles
.theta. and .DELTA. both typically can range up to positions that
encompass a range up to 80.degree..
[0114] In an alternative embodiment, a wire sizing, positioning and
treatment device may also include an electrode or multiple
electrodes for applying energy to the defect while it is in
position or near the position to close the defect. The electrode
may be formed or treated to be radiopaque to assist in sizing of
the defect. Wire forms the bipolar electrode configurations, and
sizes, orients and applies energy to close the defect. In FIG. 19A,
a wire sizing, positioning and treatment device 210 is placed in a
PFO. Wires 218 and 220 position the device 210 within the tunnel,
and also serve as electrodes. A radiopaque marker band 214 may be
employed to indicate device position and vacuum lumens 216 may also
be employed to allow the treatment device to approximate the defect
surfaces prior to, during or following the application of sealing
energy. In an alternative embodiment, FIG. 19B shows a design where
the electrodes 234, 236 are modified on positioning, sizing and
treatment device 230 with tips 238 that help the device to be
removed after application of energy without disturbing the weld
created.
[0115] IV. Cathter Device
[0116] Referring now to FIG. 20, in an exemplary catheter device
250 which may be modified according to the present invention for
treating an anatomic tissue defect includes an elongate catheter
shaft 260 having a proximal end 264 and a distal end 266, a sheath
256 (or "sleeve") optionally disposed over at least part of shaft
260, a handle 268 coupled with a proximal end of sheath 256, and a
housing 262 coupled with catheter shaft distal end 266. A distal
opening 272 for opposing tissue, an electrode 274 (or other
suitable energy transmission member in alternative embodiments for
transmitting radiofrequency (RF) energy to tissues, attachment
members 276 (or "struts") for coupling electrode 274 with housing
262 and for providing support to housing 262, and radiopaque
markers (not shown) for coupling attachment members 276 with
housing 262 and/or catheter body distal end 266 and for
facilitating visualization of device 250. A guidewire 280 is passed
through catheter 250 from the proximal end through the distal end.
In the embodiment shown, catheter body proximal end 264 includes an
electrical coupling arm 282, a guidewire port 284 in communication
with a guidewire lumen (not shown), a fluid infusion arm 286 in
fluid communication with the guidewire lumen, a suction arm 289
including a suction port 294, a fluid drip port 288, and a valve
switch 290 for turning suction on and off.
[0117] Fluid drip port 288 allows fluid to be passed into a suction
lumen to clear the lumen, while the suction is turned off. A flush
port with stopcock valve 298 is coupled with sheath 256. Flush port
and stopcock valve 298 allows fluid to be introduced between sheath
256 and catheter body 260, to flush that area. Additionally, sheath
256 has a hemostasis valve 296 for preventing backflow of blood or
other fluids. The distal tip of the sheath also has a soft tip 258
for facilitating entry and release of the catheter housing 262
during delivery. The catheter device 250 also includes a collapsing
introducer 300 partially disposed in handle 268.
[0118] The collapsing introducer facilitates expansion and
compression of the catheter housing 262 into the introducer sheath
256. By temporarily introducing the collapsing introducer sheath
300 into introducer sheath 256 the catheter housing 262 may be
inserted into introducer sheath 256 and then removed, thereby
allowing the introducer sheath 256 to accommodate a larger housing
262 without having to simultaneously accommodate the collapsing
introducer 300 as well. The collapsing introducer 300 also has a
side port for fluid flushing 302 and a valve (not shown) prevents
fluid backflow. Locking screw 292 disposed in the handle 268 may be
tightened to control the amount of catheter shaft 260 movement.
Finally, an energy supply 254 is connected to the catheter via the
electrical coupling arm 282 and a controller 252 such as a computer
is used to control energy delivery. In operation, it may also be
possible to de-couple the handle from the device if desired, or to
remove the handle altogether.
[0119] FIG. 21 illustrates the treatment catheter device 350 only.
The treatment catheter 350 has an elongate catheter shaft 366
having a distal end 354. A housing 352 on the distal 30 end of the
catheter shaft 354 delivers a treatment to a layered tissue defect
to close the defect. The catheter shaft 366 is axially aligned with
a handle 372 and exits at a proximal end of the device and is
sealed with a hemostasis valve 378 to prevent fluid backflow. An
energy connector 380 and flush port 379 are also disposed on the
proximal catheter end along with a vacuum port 376 with additional
port 377. A screw 374 tightens the catheter shaft 366 within the
handle 372 to minimize motion between the two. A collapsing
introducer tube 368 with soft tip 364 and flush port 370 is also
disposed partially in the handle 372 and is used to collapse the
housing 352 and introduce it into an introducer sheath 358. The
introducer sheath 358 also has a soft tip 356 which helps to
accommodate and collapse the housing 352 when it is being withdrawn
back into the introducer sheath 358 for removal from the body. A
radiopaque marker may also be placed near the soft tip 356 to
assist in visualization during a treatment procedure using
fluoroscopy. Both the collapsing introducer 368 and the introducer
sheath 358 have side ports 370, 362 for flushing. Valves in the
collapsing introducer (not shown) as well as a hemostasis valve in
the introducer sheath 360 prevent blood or other fluids from
backflowing.
[0120] FIG. 22A shows the introducer sheath preferably used in the
closure treatment system of FIG. 20. In FIG. 22A, introducer sheath
400 has an elongated shaft 404 which is used to introduce the
closure treatment device into the human body. The introducer sheath
400 in FIG. 22A is shown as an elongated sheath, however the sheath
may be angled or bent in different directions to assist with
placement of the closure treatment device. The introducer sheath
400 has a soft distal tip 402 and may include a radiopaque marker,
which helps to accommodate the larger size distal end of a
treatment catheter and collapse it into the sheath during removal
as well as facilitate visualization under fluoroscopy. A side port
408 with one or more flush ports 412 and a stopcock valve 410 is
also useful for flushing the introducer sheath and a hemostasis
valve 406 prevents blood or fluid backflow when the treatment
catheter is placed in the sheath. FIG. 22B illustrates one
embodiment of the hemostasis valve, where two silicone disks 416
are used to create the hemostasis valve membrane 414. In FIG. 22B
the silicone disk 416 is then scored partially through the top
surface and also partially through the bottom surface, but not all
the way through the disk. Two score lines are created 418, 419
transverse to one another. At the intersection of the score lines
417, the silicone disk is punctured all the way through. This
permits a catheter distal tip to penetrate the silicone disk and
when it is advanced further, the score lines separate enough to
accommodate the catheter while maintaining a seal. In preferred
embodiments, the silicone disk is approximately 0.352'' in diameter
and the slit widths can accommodate and seal over a 16 F shaft.
[0121] The collapsing introduce 420 is illustrated next in FIG. 23.
Collapsing introducer 420 has an elongate section 424 which can
accommodate a distal treatment catheter housing. By collapsing the
housing in the collapsing introducer, it can then be easily
introduced into the introducer sheath previously described. The
distal tip of the collapsing introducer is soft to help accommodate
the larger size treatment catheter housing. In a preferred
embodiment, the collapsing introducer has a length approximately 6
inches and its soft tip is fabricated with Pebax polymer having a
durometer of, for example, 35D while the elongate section 424
comprises, for example Pebax 72D durometer. Other relative
durometers may also be used in the scope of the present invention
to facilitated collapse of the catheter housing, while still
providing flexibility and torqueability of the catheter shaft.
While currently illustrated as round, the soft tip may also be
oval, crescent moon, or asymmetrically crescent shaped to
facilitate collapsing the housing. The proximal end of the
collapsing introducer has a hemostasis valve 428 designed to
accommodate the treatment catheter shaft as well as a flush port
426.
[0122] FIGS. 24A-24E illustrate how the collapsing introducer
works. In FIG. 24A, a treatment catheter 450 is inserted into the
collapsing introducer 452. In FIG. 24B, the collapsing introducer
452 is slidably moved towards the distal end of the treatment
catheter 450 until the housing 460 is collapsed and enclosed by the
collapsing introducer 452. The treatment catheter 450 with its
housing 460 collapsed in the collapsing introducer 452 is then
advanced and introduced into an introducer sheath 462 in FIG. 24C,
and the collapsing introducer 452 is pulled back, so that the
housing 460 is released from the collapsing introducer 452 but
still is constrained by the introducer sheath 462. In FIG. 24D the
treatment catheter 450 is advanced forward into the introducer
sheath 462 until the housing 460 exits the introducer sheath 462
and resumes its shape. The treatment catheter is advanced to a
layered tissue defect and a treatment is then applied. After the
treatment is competed, the catheter housing 460 is pulled back into
the introducer sheath 462 and the catheter 450 may be removed from
the patient's body.
[0123] In alternative embodiments as described in detail below,
additional features or fewer features may be included on catheter
device 250. For example, a number of modifications may be made to
catheter body distal end 266 in accordance with different aspects
of the invention. Some of these may include lubricious liners or
coatings on the device as well as heparin coatings for reducing
thrombus. Different configurations for fluid delivery and vacuum
are also possible. Additionally, a controller built into the power
generator can alleviate the need for a computer controller, except
for displaying treatment parameters. Therefore, the following
description of embodiments is intended to be primarily exemplary in
nature and should not be interpreted to limit the scope of the
invention as it is described in the claims.
[0124] V. Optimizing Tissue Apposition
[0125] A. Housing Design and Other Tools
[0126] One aspect of a successful tissue weld of a defect to be
treated, is the interface of the tissue at the therapeutic element
(electrode, heating element, or mechanical closing mechanism). This
interface may be impacted by the following variables, including any
leaks in the housing, leaks or shunts in the anatomy (e.g. through
the PFO), physical placement of the housing over the defect,
deformation of housing against tissue interface and resulting
housing volume, forces exerted by the housing, and the pressure
used to appose the treatment site with the housing. Various
embodiments are presented that may assist in tissue apposition
within or against the treatment element for closing a PFO or other
layered tissue defect. These designs may be used in conjunction
with any of the defect closure devices described in the co-pending
cases which have been previously incorporated by reference.
Particularly, closure catheter devices such as those detailed in
the co-pending applications Ser. Nos. 10/873,348; 10/952,492; and
11/049,791 may be enhanced by the following features.
[0127] Housing designs that maintain a sufficient chamber and
features to grip and appose the tissue of the defect, and maintain
the seal of the therapeutic element at the tissue interface may be
desirable. A representative embodiment of a catheter housing 475 is
shown in FIG. 25A. The housing 475, is attached to a catheter shaft
477 and is formed from 60A durometer silicone because of its high
tear strength and resistance to deformation at the temperatures
employed to weld tissue. Other durometers may also be employed and
in some cases a housing may be constructed of multiple durometer
polymers in one device, or a polymer and a reinforcing element such
as mesh or a filament. The housing 475 has a primary shape 476 and
a surface 479 adapted to appose the tissue defect. However, upon
application of vacuum through a lumen 480 in the catheter shaft
477, the housing may still flatten or collapse 478. Similarly,
skirt or flange of the housing can flatten as well. This can lead
to a shallower (shallower) housing volume within which tissue may
be apposed. As such, certain features may be designed into the
housing to define the optimum housing volume.
[0128] Some features that provide a more resilient housing, and in
turn allow greater tissue invagination upon vacuum activation,
include: reinforcing the roof of housing, taller housing, and
reinforcements in flange or skirt of housing. As depicted below,
areas of the housing may be selectively reinforced to aid in
sealing the treatment area within the device housing. In particular
the "roof" of the housing may be formed of a thicker material
(preferred material is silicone and it would be molded, the mold
cavity would be constructed to allow more material to flow into the
reinforced region). The reinforced roof allows the housing to
remain somewhat tented during vacuum apposition. For the roof
reinforcement, a stiffening element, such as spring steel or
nitinol may be used in thicknesses ranging from, for example
between 0.002''-0.005.'' Reinforcement in the roof region may also
be achieved by molding a thicker region using the material of the
housing, or adding material to the roof of the housing to make the
reinforced area in the range of 0.005'' to 0.025'' thick, for
example 0.01041 thick while still accommodating vacuum channels as
described in copending application Ser. No. 10/952,492, the full
disclosure of which has previously been incorporated by reference,
and allowing the housing to collapse. Some of these features are
incorporated into the embodiment of FIG. 25B. In FIG. 25B, the
housing 485 comprises a reinforced region 490 in the roof 488 of
the housing 485.
[0129] At the midpoint of the housing between the main housing and
the flange, stiffening elements 492 or extensions 496 may be
employed in a similar manner (e.g. additional molded material or
separate resilient extensions). For example, such extensions or
reinforcement may have a thickness of between 0.005'' to 0.050''
and between 1-3 mm in height.
[0130] In addition, a semi-rigid ring 494 may be incorporated into
the bottom of the flange to give hoop strength to the flange,
especially when vacuum is applied via a lumen 487 in the catheter
shaft 486 connected with the housing 485. In certain embodiments, a
1 mm.times.1 mm square in cross-section of material was molded at
the bottom of the flange. In another embodiment, a nitinol ring was
used, allowing the thickness of the region to be about 0.010'' or
slightly smaller and not square in cross-section which allows for
better collapsibility. In certain other embodiments, a polymer
O-ring may be employed. Such additional housing material and
reinforcement elements may be used alone or in combination with
each other for the desired rigidity, while still allowing the
housing to be collapsed within a guide catheter for deployment to
and retrieval from the treatment site. The housing element 485 may
be adapted to appose the tissue and keep it in place while a fusing
or fixation element is brought into contact to secure the tissue.
For example, the housing element 485 may be activated (suction
applied) and then a catheter device containing a clip or fixation
element may be advanced to the treatment site, and applied to the
apposed tissue. Examples of fixation elements may be clips such as
those described in pending applications Ser. Nos. 10/787532
(Attorney Docket No. 022128-000130US), filed Feb. 25, 2004; and
10/811,228 (Attorney Docket No. 022128-000400US), and further U.S.
application Ser. No. 10/948,445 (Publication 2005/0070923) to
McIntosh, U.S. application Ser. No. 10/856,493 (U.S. Publication
2004/0249398) to Ginn, and PCT publication WO/04/069055 to Frazier,
the full disclosures of which are incorporated herein by
reference.
[0131] Other housing configurations adapted to appose a layered
tissue defect such as a PFO are illustrated in FIGS. 25C through
25I, which shows a bottom view of the housing that apposes the
tissue defect. For example, in FIG. 25C, a housing 1320 has a
boomerang shaped side 1322 with a nose extending from the
triangular apex region that may provide better apposition with
certain tissue defects. FIG. 25D shows a triangular shaped side
1342 of the housing 1340 with apices radiused while FIG. 25E
illustrates a kidney bean shaped side 1362 of the housing 1360.
FIG. 25F shows a circular housing side 1382 while FIG. 25G depicts
a housing 1400 with a generally triangular shaped side 1402 but
with the base and apex modified to include nose-like protrusions.
FIGS. 25H and 25I also show variations on the triangular shaped
side of the housing for tissue apposition. In the case where an
electrode is used to close the layered tissue defect, the electrode
shape may match the housing or it may be modified to best match the
tissue defect. FIGS. 25C through 25I show various electrode
embodiments that may be used.
[0132] A cone shaped or domed housing can provide greater tissue
apposition, (optionally in combination with a "stepped" electrode
as set forth in application Ser. No. 10/952,492, the full
disclosure of which has previously been incorporated herein by
reference). An example of the stepped electrode 504 may be seen in
housing 500 of FIG. 26. The electrode may alternatively be planar
and optionally may be angled in the housing to accommodate tissue
thickness variations. This is illustrated as electrode 530 in
housing 525 of FIG. 27.
[0133] A hinged housing may also provide better tissue apposition
and defect closure by allowing the housing to better adapt to
anatomical variations in the tissue defect. In one embodiment shown
in FIG. 26A, a treatment device 1450 comprises an elongated
catheter shaft 1454 with a housing 1452 adjacent to its distal end.
The housing has a hinge mechanism 1456 that allows the housing to
articulate. When the housing articulates, its shape adjusts to
better conform with the anatomy of the tissue defect. In FIG. 26A,
an apposition surface 1462 is operatively coupled with the housing
so that it too can better conform to the tissue defect anatomy. The
apposition surface 1462 may only comprise a surface for apposition
or may additionally comprise a treatment region that can be used to
close the layered tissue defect. Furthermore, optional separate
vacuum ports 1458 and 1460 may be located in the housing to assist
the housing appose the tissue defect. In FIG. 26A, vacuum ports
1458 and 1460 are positioned within the housing so that they may
help draw in the primum and secundum tissue layers for better
apposition in a PFO defect.
[0134] In another embodiment shown in FIG. 26B, multiple hinges
1484 are utilized in the housing 1486 of a treatment device 1480.
An elongate shaft 1482 is connected to the housing 1486 and may be
used to articulate the housing into different configurations with
control rods or wires. The hinges may also be adapted to permit
flexing of the housing when it is pressed against a surface. An
apposition surface 1488 which generally takes the same form as
apposition surface 1462 in FIG. 26A is also operatively connected
to the housing 1486 so that its shape may be adjusted for better
apposition with the tissue defect. FIG. 26C illustrates how the
hinged housing 1506 of a treatment device 1500 provides an
alternative apposition surface 1508. Furthermore, vacuum ports
1524, 1526 may be used in the housing 1522 of a closure device
1520, as illustrated in FIG. 26D. Here, vacuum ports 1524 around
the circumference of the housing 1522 are combined with a centrally
placed vacuum port 1526 for enhanced apposition of the housing 1522
against the tissue defect.
[0135] In alternative embodiments, a screen or slotted member may
receive target tissue and oppose or "grip" the tissue during
treatment. The screen may also be an electrode (monopolar/bipolar).
FIG. 28A illustrates the primum P and secundum S tissue layers of a
PFO being received into a screen upon application of vacuum through
a lumen 556 in a catheter shaft 554 connected with the housing 552.
In this embodiment, the screen is also an electrode with an
electrical connector 560 running through a lumen 556 in the
catheter shaft 554. A cross-sectional view of the tissue 568 being
received into a screen 564 having a receiving aperture 566 is shown
in FIG. 28B. FIG. 29A illustrates another way in which tissue P, S
can be captured by the screen 584 and FIG. 29B shows a
cross-sectional view of the tissue P, S being received by an
aperture 588 in the screen 590. The screen 590 may also serve as an
electrode to weld the tissue layers together or a secondary
electrode may be deployed later during the procedure for
welding.
[0136] A recess in housing (or around skirt) 604 may assist in
opposing or gripping tissue once the tissue is brought into the
housing 600 using a vacuum. The screen 606 may be fixed to position
tissue, or may be moveable as shown by the arrows in FIG. 30.
Movement is controlled by an elongate member 610 through a lumen
612 in the catheter shaft 608 to further clamp tissue P, S against
the recess 604, and the screen 606 may be an electrode. This
embodiment is illustrated in FIG. 30.
[0137] In another embodiment shown in FIG. 31, a first screen 633,
usually with large interstices, may be employed together with a
second screen 632. The second screen 632 is moveable between a
first position and a second position as shown by arrows, or range
of positions, relative to the first screen 633 and can be employed
to trap the tissue P, S prior to treatment. Ideally, such screens
632, 633 could also be the electrode(s) for applying energy to join
the tissue flaps of the heart defect together. They may be
monopolar (one screen is energized while the other is totally
insulated), or bipolar (wherein both screens are energized to
create a bipolar energy field to assist in tissue fusing.
[0138] As shown in FIG. 32, the housing 652 may be actuated to
further grip tissue with the recess feature 664 previously
described above. Gripping action of the housing pivots the housing
from one position 662 to a second position 664 and can be employed
by actuatable struts (not shown) within housing material that
extend from a pivot point at the apex of the housing, or by
advancing a sheath (not shown) over the housing 652 to further
collapse the structure on the tissue P, S.
[0139] FIG. 32A illustrates an alternative approach to apposing
tissue. In FIG. 32A, a moveable vacuum tube 671 is advanced in
order to appose tissue P, S. Once vacuum is applied and the tissue
is engaged, the vacuum tube 671 may be pulled back into the housing
666 so that tissue is engaged against a screen 667 which can also
serve as an electrode. FIG. 32B shows that the vacuum tube 668 may
have an optional vacuum screen 670 at its distal end to facilitate
tissue engagement.
[0140] In a further embodiment depicted in FIG. 33, a bipolar
clamping device (electrode structure) 680 may be integrated into
the housing 676, or advanced as a separate element to grasp and
weld the tissues P, S of the heart defect together. In one
embodiment, the bipolar clamping element 680 may be deployed
distally of the catheter housing to grasp the defect to be treated
and draw it back into the housing for treatment. In this
embodiment, such clamping graspers 680 may be employed separately
or in conjunction with suction applied through a lumen 682
connected with the housing 676. The graspers 680 are controlled by
an elongate member 684 through a lumen 682 in the catheter shaft
678. The suction operates to maintain a seal in the treatment area,
and the clamp 680 can operate to not only clamp the tissue, but
also to keep the treatment catheter 675 positioned at the site of
the defect.
[0141] FIG. 34A shows another embodiment where a ring electrode 712
may be employed in the housing 702 or around the flange of the
housing (724 in FIG. 34B) to seal tissue. In the case of the ring
electrode 712 in the housing 702, it can either be fixed to the
walls of the housing, or separate and deployable about the acquired
tissue. FIG. 34A shows the ring electrode 712 separate from the
housing 708. In some cases it may be desired to cinch the electrode
from a larger diameter 710 to a smaller diameter 712 around the
tissue P, S, such as a snare type device. In the case of the ring
electrode 724 around the flange of the housing 722 depicted in FIG.
34B, the electrode structure can provide additional rigidity to the
flange region, thereby assisting with tissue apposition while also
being activated to delivery energy and seal.
[0142] Further, the ring electrode in either configuration
(cinched/snare ring or ring on outer housing) may be the return
electrode in a bipolar system as shown in FIG. 35. In FIG. 35, a
second active electrode 748 may be inserted into the tissue to be
treated P, S while a ring electrode 744 is disposed within the
housing 742 and serves as the return electrode. FIG. 36 shows an
alternative embodiment where a second active electrode 768 is
inserted into the treatment region P, S and a cinch or snare
electrode 770 is the return electrode.
[0143] With reference now to FIG. 37, an additional embodiment
shows an apposition device 780 of the present invention which may
include a mechanical device 784 deployed from the housing 782,
through the tissue or defect to be treated (see FIG. 38B), and
capable of pulling the tissue back into apposition with the housing
782. Such a mechanical assistance device 784 can be used alone or
in conjunction with vacuum apposition. The apposition device 784
would be very low profile in its "stowed" condition for placement
through tissue of the defect or through the defect opening, and
then deployed to an expanded condition as indicated by phantom
lines, whereupon it may be drawn back toward the catheter housing
782 to tension the tissue between the catheter housing 782 (and
electrode) and the expanded portion of the apposition device. One
embodiment of this device shown in FIG. 38A includes a molly bolt
type (or mallecott) apposition device 810 deployed through a needle
804 placed through defect or through defect tissues. The device is
shown placed through tissue in FIG. 38B. Once placed through
tissue, it is then expanded 808 to provide a backstop and hold
tissue, and is illustrated in FIG. 38B. In yet another embodiment
the apposition device may be a wire that expanded to a looped or
"petal" type configuration 812 as shown in FIG. 38C and a side view
in FIG. 38D. In any of these embodiments, the apposition device may
be deployed through the guidewire lumen of the treatment device, or
through a separate, dedicated lumen. These devices may be
positioned with respect to the defect to be treated by using the
positioning devices of the present invention described
previously.
[0144] In a further embodiment, an apposition device may be
deployed separately from the treatment device into the left atrium,
remote from the treatment site, to "bookend" the defect against
treatment catheter and thereby create enhanced tissue apposition.
Such a separately deployed apposition device would preferably be
low profile to allow the remote puncture site to heal naturally,
without requiring a therapeutic intervention to close the puncture.
FIGS. 39A-39E illustrate this with respect to a PFO closure, but
several other defects in the heart could be apposed and closed in a
similar manner. In FIG. 39A a needle cannula 826 is inserted from
the right atrium to the left, remote from the defect opening. A
tissue apposition device 828 is then deployed into the left atrium
toward the site of the defect or tissues to be apposed, as shown in
FIG. 39B. A treatment catheter 832 and the left atrial apposition
member 834 are then brought into alignment at the site of the
defect to be closed, which is illustrated in FIG. 39C. Force is
applied to assist in apposing the tissue closely within the housing
830 of the treatment device 832, shown in FIG. 39E. Once the defect
is closed, the treatment device 832 is removed and the apposition
device 836 is retracted into the needle cannula 826, after which
time the needle cannula 826 is removed and nothing is left on the
left atrial side of the heart. The needle cannula entry site may be
left to close naturally and the layered tissue defect is also
closed as seen in FIG. 39E. Another embodiment is shown in FIG. 39F
where a needle like structure 843 is used to penetrate the tissue
defect. An apposition member 842 is then released from the needle
structure 843 to provide a backstop. A pivot on the device 841 can
then be actuated, bringing the treatment housing 840 and backstop
842 together. The closure treatment may then be applied. After the
closure treatment is completed, the backstop 842 may be retracted
into the needle structure 843, and both are withdrawn into a sheath
844, and the entire device is removed from the patient or moved to
another treatment location.
[0145] FIGS. 39G-39I illustrates another embodiment for enhanced
apposition including a elongated guidewire 1530 with a flexible
T-shaped distal end 1532. In FIG. 39G, the elongated guidewire 1530
is placed through the PFO tunnel until the T-shaped end exits the
tunnel on the left side of the heart. The flexible whiskers 1532
which form the T-shaped end are then free to expand outwardly and
then can serve as an anchor point for the guidewire 1530. In FIG.
39H, the elongated guidewire 1530 is retracted which results in the
whiskers 1532 forcing the primum P against the secundum S, thereby
reducing the gap therebetween and permitting better fusing of the
two layers. A closure treatment device 1534 is then delivered to
the treatment site, here, delivery of the closure treatment device
1534 is advanced axially over the guidewire 1530. The closure
treatment device 1534 then applies a treatment to the tissue
defect, partially closing the defect, except for the region where
the guidewire 1530 rests. In FIG. 39I, after a partial closure of
the defect is obtained, the guidewire 1530 is removed from the
tunnel and the closure device 1534 may complete the treatment by
sealing the PFO and fusing the primum P and secundum S together
1538.
[0146] Using a similar technique, another approach to applying the
required tissue compression prior to defect closure utilizes
magnetic attraction as shown in FIGS. 40-42. By placing magnets or
electromagnets on either side of the layers of tissue that require
apposition, a compressive force can be applied without requiring a
physical link between the sides of the tissue. Any combination of
ferromagnetic material, magnet material, and/or electromagnetic
material can be used to create the desired force. While not
required, the use of rare earth permanent magnets such as Samarium
Cobalt (SmCo) or Iron-Neodymium (NdFeB) provide substantial levels
of magnetic flux for a given volume of material and are implantable
grade materials. Coupling such a magnet with a ferromagnetic
counterpart can simplify the use of magnetic attraction to create
force because orientation of the ferromagnetic portion of the
coupling does not require a specific orientation relative to the
permanent magnet in order to create an attractive force. Further,
use of an electromagnet can be beneficial since it can be
selectively activated (turned on and off).
[0147] The magnet and/or ferromagnetic components used for such an
application can be in singular elements, or an array of smaller
elements that may be more easily delivered to a remote location
through a patients vasculature. For example, magnetic components
856 may be coated or formed for implant in a human body, loaded
into a catheter 852 as shown in FIG. 40. The assembly 850 may be
delivered to relevant locations while contained, and then released
at the desired location with respect to the defect to be treated,
and deployed.
[0148] Alternatively, as shown in FIG. 41, magnetic elements 862,
864 are placed on either side of a PFO (one in the right atrium and
one in the left atrium). An energy treatment catheter 866 is placed
between the magnets 862, 864 in the right atrium to deliver the
tissue welding treatment once the tissue or brought together by the
magnetic force. Optionally, the magnet on the right atrium 862
could be incorporated into the energy treatment catheter. In this
embodiment, the magnetic device deployed in the left atrium 864,
could be placed with a similar needle catheter delivered remote
from the defect to be treated, and once magnetic apposition was
achieved and the defect closed, the left side magnetic 864
component would be removed.
[0149] It is also within the scope of the present invention, as
shown in FIG. 42, to permanently implant a magnetic coupler 875 to
close the anatomic defect. The magnetic coupler would have a first
magnetic element 876 placed on the left side of the defect, and a
second magnetic element 878 placed on the right side of the defect.
One or more inflatable balloons may be used as deployment tools,
for example to separate each magnetic element until proper
positioning is obtained. Once each element is properly placed, the
balloon can be deflated and removed, leaving the magnetic coupling
elements in place, and able to attract each other to seal the
defect.
[0150] B. Isolating Treatment Site
[0151] The ability to appose tissue and create a treatment area
conducive to welding tissue may be enhanced by the application of
negative pressure, i.e. vacuum, at the treatment site. In addition,
it may be desirable to infuse fluid into the treatment site for a
variety of reasons.
[0152] Sealing
[0153] Certain features of the housing may be constructed to assist
in creating a robust seal at the tissue interface, and maintaining
that seal for the duration of the treatment. To balance the housing
features that allow for greater tissue apposition (e.g. a more
resilient housing), the following features may be incorporated into
the housing flange.
[0154] Additional "grippers" or protrusions 894 in the rim of
housing 892 increase tissue apposition to the device 890. An
additional vacuum lumen 896 in the housing rim 892 may also be
useful to distribute the vacuum force toward the outer edge of the
housing at the housing/tissue interface. This is illustrated in
FIG. 43.
[0155] Alternatively, as illustrated in FIG. 44A, the location of
the grippers 908 and the additional vacuum port 906 may be
reversed. Furthermore, a gusset 904 may be added to the housing 902
to increase the sealing force of the flange, but still keep the
housing flexible. Gussets 924 may be placed circumferentially
around the outer housing flange 922 at various locations, and this
is seen in FIG. 44B.
[0156] FIGS. 45A-45C show a preferred embodiment of the housing
940. FIG. 45A illustrates a top view of the housing which
preferably has a flange or skirt 942 having a diameter of 0.921
inches and the housing itself has a diameter 944 of 0.730 inches.
An elongate member 950 represents the transition from the housing
940 to a catheter shaft. The housing has a slightly tapered profile
when observed from the side in FIG. 45B. The distal tip of the
housing 946 is the lowest point of the taper, and preferably has a
height of 0.140 inches while the proximal end of the housing 948 is
higher and is preferably 0.297 inches high. A front view of the
housing is seen in FIG. 45C and this view shows the flange or skirt
942 connected to the housing 944.
[0157] Another embodiment of the housing is illustrated in FIGS.
45D-45F. In FIG. 45D, a top view of the housing 1550 is shown. The
housing 1550 here has a nose-like front projection 1552 and a
rectangular-shaped 1554 rear projection. The housing is typically
attached to an elongate catheter shaft 1556. Both projections 1552
and 1554 form a skirt around the housing 1550, attached along the
housing rim 1558, and that helps the housing to match the tissue
defect anatomy and appose the defect. FIG. 45E is a side-view of
housing 1550 showing the skirt 1564 and a domed housing top 1562. A
front view of the housing 1550 is shown in FIG. 45F which
illustrates the skirt 1552 attached with the housing rim 1558.
[0158] Infusate
[0159] Successful welds of heart defects may be achieved in the
presence of infusate or drip fluids into the treatment region, as
described in application Ser. No. 10/952,492, the full disclosure
of which has previously been incorporated herein by reference, to
mediate the moisture content of the treatment area and maintain
patency of the catheter lumens. Infusate is used primarily to
prevent blood from stagnating within a treatment device distal
housing and thereby clotting. By providing constant infusate flow,
stagnation is avoided. Heparin can also be added to the infusate to
further minimize clotting. Alternatively, welds of heart defects
have also been achieved with relatively "dry" tissue (low or little
infusate).
[0160] For example, in the event that the use of an infusate is
desired, the following variables may affect the efficacy of the
tissue weld, namely, type of infusate (saline, D5W (Dextrose 5% and
water) or G5W (Glucose 5% and water), rate of infusion, flow
distribution at tissue interface (pattern, consistency),
temperature of infusate and the like. In an exemplary range,
infusion may be used in the following range 0-30 ml/min, and more
particularly in the range of 1-10 ml/min. The infusate is then
aspirated from the treatment site via the vacuum lumen. The vacuum
suction creates a continuous draw of flush through the infusion
lumen, passing through the distal housing, and back out the vacuum
lumen, for example a passive or "closed loop" infusion. The
infusate is then collected in a vacuum canister. Operation and
further detail on the infusion of fluid can be found in related
application Ser. No. 10/952,492 (Attorney Docket No.
022128-000220US), incorporated herein by reference. Adequate vacuum
seal can be determined by observation of the distal housing under
fluoroscopy (lack of movement, "flattening" as determined by
imaging of fluoroscopic markers or echogenicity of housing), and
observation of the color of the fluid suctioned to the vacuum
canister (e.g. by a change from blood to clear fluid as the
dominant fluid suctioned to the vacuum canister (fluid changed from
red to clear). Although a complete seal is desirable, an example of
a substantial seal that may still include an "acceptable leak rate"
is in the range of 0-150 ml/min, for example, in the range of 1-30
ml/min. This leak may be attributable to physiologic phenomena, as
well as mechanical issues with the housing seal against the
tissue.
[0161] C. Energy Application for Defect Closure: Electrode Design
and Energy Algorithm
[0162] Various parameters can be controlled to achieve the most
advantageous result in closing a PFO or other defect in the heart
with energy. As discussed above, greater tissue apposition can
function to increase the likelihood of consistently welding the PFO
tissues (primum and secundum), in a clinically acceptable procedure
time. In addition to greater tissue apposition, various parameters
related to the power algorithm can be controlled and optimized.
Certain parameters include developing a feedback loop to ensure
enough power is delivered to achieve the desired closure (plane of
welding), that the power delivery does not lead to unwanted "pops,"
that the power delivery does not lead to impedance spikes of the
kind that prohibit additional power delivery to tissue within the
specified procedure time, and the like. Others include design of
the electrode, including the size, thickness and other physical
features that effect energy delivery. The treatment device and the
power system of the present invention are depicted in FIG. 20 where
the power supply 254 hooks into port 282 with a standard medical
electrical connector.
[0163] Electrode Design
[0164] The configuration of the electrode may play a role in
optimum energy delivery. Certain features of an electrode or
heating element that may affect closure (welding) include, element
density, geometry, size, current density, surface features (gold
plating for radiopacity, coatings, electropolishing of conductive
surfaces), location of the power connection, and points of
insulation on the element.
[0165] For example, a larger electrode, although able to treat a
greater area of tissue, requires more power and therefore is less
efficient, and may lead to additional conduction in the tissue to
areas of the heart that the procedure is not intended to effect. An
electrode design that is matched (size, capacity) to provide
"localized energy density" to the intended treatment region can
function to limit the power required to achieve the intended
result, and therefore a more efficient, safer lesion is
created.
[0166] For example, in FIG. 46, a banded electrode 964 may be
adapted to concentrate the power delivery at the point over which
the defect comes together. This band can either be created by
cutting an electrode pattern that is in the desired shape or
masking a larger electrode such that only the desired band of
active electrode is exposed. In FIG. 46, banded electrode 964 is
cut into a rectangular shaped piece with a guidewire exit port 966
running through the electrode 964. Various other portions around
the electrode and housing are insulated 962 so that energy is only
delivered over the banded electrode 964. Additionally, openings
within the electrode 972 allow vacuum to be applied for tissue
apposition and struts 970 connect the electrode 964 to the housing
968 and help provide support. FIG. 48 shows an alternative
embodiment of the banded electrode 1028 wherein the active
electrode band pattern has been cut into the desired shape, here an
undulating wave-like pattern. Additional features such as an exit
port for a guidewire 1032, vacuum ports 1030, a thermocouple 1026,
insulated struts 1024 for support and a housing flange 1022 have
previously been discussed.
[0167] FIGS. 47 and 49 on the other hand employ the masking
embodiment. In FIG. 47, portions of the electrode are masked 996 so
that energy is only delivered via an active region 999. Other
features such as vacuum ports 994, support struts 998 are also
utilized. FIG. 49 shows a variation of masking, where portion of
the undulating wave-like pattern previously discussed above are
masked to control energy delivery. In FIG. 49, masking 1044
controls where the active electrode region is. Typical electrode
measurements are in the range of 30 mm wide by 20 mm tall, for
example 15 mm wide by 9 mm tall. The total area of the electrode
may vary depending on the chosen geometry. Electrodes may be
configured in a variety of shapes, including elliptical, circular,
rectangular, triangular, or have geometries that are a combination
of those approximate shapes in order to best fit the geometry of
the tissue to be treated. An alternative electrode embodiment is
illustrated in FIG. 49A. In FIG. 49A, a housing 1570 is disposed on
distal end of an elongate catheter shaft 1576. The housing 1570 has
a nose-like protrusion 1572 and a rectangular shaped rear
protrusion 1574. The nose-like protrusion 1573 may also be moved
closer to the electrode 1586, as shown by dotted line 1573, in
order to better appose the tissue. A partially oval shaped
electrode 1586 is disposed in the housing 1570 and a guidewire
lumen 1578 port 1580 exits through the electrode 1586. The
electrode 1586 is adapted to more accurately match PFO anatomy. In
the case of a PFO, the electrode is adapted to treat PFOs ranging
in size from 1 mm to 30 mm and more typically in the range from 3
mm to 26 mm.
[0168] Masking may be applied by spraying or dip coating and
typically employs a silicone layer, although other methods and
materials are well known in the art. Alternatively, it may be
desirable to design the masking element on the distal catheter
housing such that it can be variable wherein the mask opening only
exposes the desired amount of septal tissue to the chosen form of
energy. The opening may be round, oval or other shapes, such as a
crescent, to mimic the defect to be treated. Illustrative
embodiments of this are shown in FIGS. 50A and 50B. For example,
FIG. 50A shows a variable mask wherein the inner diameter 1056 can
be controlled, while in FIG. 50B an elliptically shaped aperture
1074 is controllable.
[0169] In operation and illustrated in FIG. 51, a treatment
catheter 1090 may be formed by using coaxial shafts 1092, 1094 that
allow relative axial rotation to twist an elastomeric tube 1096 or
otherwise create a valved effect (similar to an iris valve). Final
mask shape is then achieved by rotating one shaft relative to the
other until the desired mask shape is reached. The two shafts can
then be locked together to prevent the shape of the mask from
changing during treatment.
[0170] In a further embodiment, a mesh electrode 1097 is shown in
FIG. 51A, and may be employed, having an insulation coating 1098 or
sleeve. In use, tissue would be drawn into the cavity created by
the electrode and energy delivered. Alternatively, the insulating
sleeve may be withdrawn, exposing the desired amount of active
electrode.
[0171] FIG. 52A illustrates a further embodiment of an electrode
having lobes or "petals" 1104 which may be employed to the desired
size, either by using separate loops, or feeding out a length of
preformed nitinol wire to achieve the desired configuration.
Because an electrode such as this can be deployed once a seal by
the catheter housing 1102 has been obtained, it is possible for the
user to apply a certain amount of directional force with the
electrode against the tissue, which may be useful in creating
optimal tissue apposition with the target, on its own, or in
conjunction with other apposition devices and techniques disclosed
herein. A bottom view of the housing 1102 emphasizing the petals
1104 is seen in FIG. 52B.
[0172] In a further example and with reference to FIG. 53, the
active electrode may be an alternating current bipolar electrode
(requiring less energy, and in a more localized manner), and
configured as either an electrode commensurate with the size of the
housing, or less than the size of the housing, by masking,
otherwise insulating, or cutting the electrode to a smaller size.
Interdigitating active 1122 and return 1124 electrodes can be laid
out on a planar electrode substrate. Alternating active 1142 and
return 1144 electrodes across a planar electrode substrate may also
be employed as seen in FIG. 54.
[0173] The use of RF energy to generate a weld of a defect in
conjunction with the use of a magnetic coupler to create opposing
force could allow the RF system to be either monopolar or bipolar
depending on the configuration. For example as depicted in FIG. 55,
each half of the magnetic couple 1162, 1164 could be one pole of a
bipolar RF circuit. In addition, only one of the portions of the
magnetic couple 1184 is used as part of a monopolar RF circuit and
this is illustrated in FIG. 56. Further combinations that include
either one or more of the components of the magnetic couple in
either a monopolar or bipolar RF circuit are also possible. It is
within the scope of the present invention to also size, mask or
otherwise modify the electrode configurations described in
co-pending application Ser. No. 10/952,492, previously incorporated
herein by reference.
[0174] A preferred electrode embodiment is shown in FIG. 57. An
electrode 1200 is illustrated prior to attachment with a catheter
housing. Here, struts 1204, 1206, 1208 extending from the electrode
are designed for attachment to the housing in order to connect the
structures with one another. Struts 1204, 1206 and 1208 also serve
to provide support for the housing. Barbs 1202 may be employed on
the struts 1204 and 1208 to help attach them to the housing. A
monopolar electrode is formed from a series of parallel bars 1222
separated by a slit 1224. A set of bars 1222 is separated from an
adjacent set of bars by another gap 1218. An outer perimeter is
formed by a ring 1216 and apertures 1226 allow vacuum to be applied
as well as administration of an irrigation fluid. Tabs 1210, 1211
and 1212 allow a piece of tubing to be attached to the electrode to
facilitate guidewire entry and exit from the housing. In a
preferred embodiment, not intended to be limiting, the electrode
has a thickness of approximately 0.0029 inches and struts 1204,
1206 and 1208 are typically about 0.020 inches wide by 0.004 inches
thick. Ring 1216 width is about 0.012 inches, while the bar 1222
width is approximately 0.040 inches and slits 1224 are about 0.012
inches with gaps 1218 being about 0.030 inches wide. The slits in
this embodiment allow suction to be applied through the electrode,
help to minimize tissue from adhering to the electrode surface and
create an edge from which RF energy is delivered to tissue.
[0175] A floating electrode embodiment is illustrated in FIG. 57A.
In this figure, an electrode 1600, unattached with a catheter
housing is shown. Struts 1604, 1606 and 1608 are connected with the
housing and help to provide support to the housing during tissue
apposition and/or vacuum application. Barbs 1602 on the struts 1604
and 1608 also help to connect the struts 1604 and 1608 to the
catheter housing. A parallel series of bars 1622 is separated by a
slit 1624 therebetween, forming a monopolar electrode. Each set of
parallel bars 1622 is separated from an adjacent set off bars by
another gap 1618 and an outer perimeter is formed by a ring 1616.
The electrode bars 1622 connect with the perimeter 1616 via a
flexible elastomeric coupling 1628 such as silicone. The flexible
couplings 1628 allow the electrode to float and therefore the
electrode can adapt to various tissue defect anatomies more
effectively by compensating for changes in tissue thickness or
height. Additionally, the electrode bars 1622 are hinged 1630,
allowing further adjustability of the electrode surface to
accommodate are more diverse range of tissue anatomies. Other
aspects of this electrode embodiment include apertures 1626 within
the electrode which allow vacuum to applied as well as
administration of irrigation fluid. Tabs 1610 and 1612 allow tubing
to be attached to the electrode to facilitate guidewire entry and
exit from the housing. Electrode dimensions generally take the same
form as the electrode described in FIG. 57 above.
[0176] FIG. 58A shows the electrode of FIG. 57 mounted in a
catheter housing 1260. The housing 1260 has a flange 1256. Struts
are embedded in the housing and therefore, only the electrode 1254
is exposed. An aperture for a guidewire is more clearly visible in
FIG. 58A and is represented by 1258. FIG. 58C illustrates a piece
of tubing 1262 used to transition from the guidewire aperture 1258
into the guidewire lumen of the catheter shaft 1252 in FIG. 58A.
The tubing is a length polymer tube with two apertures adapted to
be placed over tabs 1210 and 1212 in FIG. 57 to secure the tubing
to the electrode. Tab 1212 may also be bent at an angle to further
facilitate guidewire entry and exit from the guidewire aperture
1258. FIG. 58B highlights the two apertures on the tubing. In a
preferred embodiment, not intended to be limited, this tubing is
approximately 0.044 inch outer diameter.times.0.039 inch inner
diameter polyimide with a length about 39 inches. The long aperture
1264 is approximately 0.687 inches from the distal tip of the
tubing and has a width of about 0.033 inches by 0.134 inches long
and a radius approximately 0.017 inches. The smaller aperture 1266
is approximately 0.038 inches by 0.028 inches.
[0177] In addition to applying energy for closure of a layered
tissue defect, the electrodes of such a device can be designed to
allow electrophysiology monitoring of the heart. Such mapping would
permit a physician to determine if the treatment device is too
close to sensitive areas of the heart, such as the AV node.
Additionally, monitoring could be used to ensure that during
treatment, aberrant conductive pathways were not being created.
Mapping also allows power delivery to be controlled so that minimal
required power is delivered and also permits the active surface of
the electrode to be controlled and minimized so that treatment
energy is not applied to an area greater than necessary.
[0178] As shown in FIG. 58D, two small circular electrode pairs
1654 may be placed on and insulated from the electrode 1656 or
housing 1652 and can serve as bipolar mapping electrodes. The
electrodes may take a number of configurations such as two pairs
side by side in FIG. 58D or in a linear arrangement 1684 as shown
in FIG. 58E. These electrodes 1694 may be 0.5 mm to 2 mm in
diameter as shown in FIG. 58F, and can be fabricated from stainless
steel although platinum or platinum-iridium are preferable as well
as nitinol. Cardiac electrophysiology mapping is well known in the
art and is well documented in the medical and scientific
literature. Exemplary products are manufactured by Boston
Scientific.
[0179] Algorithm
[0180] In the treatment of a PFO in a human heart, the following
welding algorithms may be successfully employed to achieve closure
or sealing of the PFO tissues using a range of parameters that
utilize feedback to vary the time and power applied to achieve a
tissue weld. The following are merely examples and not intended to
limit the scope of the present invention. In a preferred
embodiment, the algorithm would start at a low power (e.g. 1-10
Watts to 20-50 Watts) and gradually increase over time. This allows
the controller to evaluate how the defect is responding to the
application of energy. The objective of the algorithm is to deliver
the maximum amount of power during a desired duration, while not
over-treating the tissue. A software controller system may be
employed to ramp the power over the designated time and to respond
to the impedance readings or other user or manufacturer designated
feedback or settings.
[0181] A schematic depiction of the power supply is depicted in
FIG. 59. The power supply is connected to the treatment device and
a return electrode is connected to the generator. A variety of
feedback inputs may also be connected to the power supply or CPU,
including thermocouples, electrodes for sensing impedance and the
like. A software controller system utilizing a CPU can be employed
to adjust the power over the designated time and to respond to the
impedance readings (e.g. shut off/restart/restart at lower or
higher power as directed by the input algorithm). This system may
be further linked to a computer (laptop) or other user interface
for purposes of graphical interface and data collection.
[0182] In one example of a tissue welding algorithm for PFO
treatment, energy may be applied with an initial power setting of
20 Watts, and the power increased every 30 seconds by 5 Watts until
40 Watts is reached ("power ramp"). Following this initial ramp,
energy may be applied until either 1) a total run time of 10
minutes is reached, or 2) an impedance spike occurs. If the total
run time reaches 10 minutes the application of power is considered
complete for purposes of this example. If an impedance spike is
reached, an additional power ramp is reapplied until a total of
five spikes have occurred or until a subsequent spike occurs after
a cumulative run time of 7 minutes. The power ramp of this or other
embodiments may also be incremental, e.g. ramp increased over 30
seconds, up to 5 Watts, until 40 Watts is achieved. Alternatively,
the power ramp may begin at 20 Watts, increased to 25 Watts and
maintained at 25 Watts until the application is complete (7-10
minutes), as shown in FIG. 60. The application of a similar
algorithm in a different tissue sample, may produce results such as
those below; the variations may be due to tissue or other
anatomical variations, as shown in FIG. 61.
[0183] In another example of ramping, the system operates to apply
15 Watts, ramped by 5 Watts every 30 seconds after initial 45
seconds, for 10 minutes or first impedance spike after 7 minutes.
The overall number of impedance spikes is limited to 5. The system
in this example includes passive fluid infusion. A solution of D5W,
or other fluids such as normal saline may be employed for the
infusion. An example of this treatment using a banded electrode
(see description of banded electrode above), is shown in FIG.
62.
[0184] In addition, it may be advantageous to alter the starting
power, and time between ramps, for example allowing additional time
between step ups in power, for example 60 seconds. In the example
below, the initial power is 20 Watts, with a step up in power of 5
Watts every 60 seconds, to a maximum power of 40 Watts for a
duration of 10 minutes. If an impedance spike is encountered, then
applied power is reduced to 25 Watts for the remaining time up to
10 minutes, as shown in FIG. 63. Following the initial spike, if
the impedance reading does not exceed the minimum impedance by 2
Ohms, the power can be ramped up to 35 Watts for the remainder of
the procedure time, as shown in FIG. 64.
[0185] Alternatively, an algorithm where energy delivery is
initiated at a higher power (for example 50 Watts) and ramped down
in response to impedance spikes or "pops" may be employed as shown
in FIG. 65. For example, power may be applied starting at 50 Watts,
and a clinically acceptable procedure time followed (e.g. 5-15
minutes).
[0186] The power may then be reduced by 7 Watts each time the
impedance spikes after fewer than 2 minutes of power application
(an impedance "spike" in this example, is characterized by a rise
in tissue impedance to about 100 .OMEGA.). For example, if the
power is set to 50 Watts and runs for 1 minute 30 seconds before
spiking, energy application is stopped, power is reduced to 43
Watts and energy application is resumed. If the system then runs at
43 Watts for 3 minutes before spiking, the energy application is
stopped only briefly before being reapplied at 43 Watts again. If
there are spikes during the application of power, this process is
repeated until a maximum cumulative run time of between 6 and 12
minutes is reached. If there is a spike after a cumulative run time
of 6 minutes, the application of power is considered complete. If
there is no spike, the energy application is continued at a power
setting of 50 Watts for a maximum of 12 minutes.
[0187] An example of application of pulsed power is depicted in
FIG. 66A using a banded electrode. Forty (40) Watts of power was
applied in 15 second pulses, and temperature and impedance were
monitored and charted. In FIG. 66A each power application consisted
of approximately 5 seconds of warm-up where the impedance dropped,
after which the impedance resumed where it left off from a previous
power application. FIG. 66B depicts the same power application as
FIG. 66A however the chart reflects the data with the 5 seconds of
warm-up in each application of energy (included in the graph of
FIG. 66A) removed.
[0188] In a preferred embodiment of the algorithm, power is
delivered in multiple power runs or frames. In the first frame, RF
power is set to 20 Watts and power is increased by 5 Watts every 60
seconds until a maximum of 40 Watts is obtained. If during this
frame, impedance inflects and then returns to at least its initial
value or appears to be reaching a spike then power is turned off.
If power has been delivered for more than 7 minutes, application of
power is terminated and a cool down step is initiated. If power has
been delivered for less than 7 minutes, then additional power is
applied after a 30 to 120 second pause.
[0189] In the second power run or frame, if RF energy was delivered
for 180 seconds or less during the first run, the second frame may
be started at 15 Watts. If the impedance has not exceeded its
minimum from the second frame by 2.OMEGA. after 90 seconds, power
is increased to 25 Watts. If after another 90 seconds, the
impedance has not exceeded its minimum from the second frame, power
is again increased to 35 Watts. If the impedance inflects and then
returns to at least its initial value (of the current frame) or if
impedance appears to be reaching a spike, power is turned off.
Similar to the first frame, if power was on for more than a total
of 7 minutes, power is turned off and the cool down step is
initiated. If power has been run for a total of fewer than 7
minutes, then additional power should be applied in the third power
run after waiting 30 to 120 seconds.
[0190] If more than 180 seconds of RF was delivered during the
first frame then RF power is applied at 25 Watts. If the impedance
has not exceeded its minimum from the second frame by 2.OMEGA.
after 90 seconds, power is increased to 35 Watts. If the impedance
inflects and then returns to at least its initial value (of the
current frame) or appears to be reaching a spike, power is turned
off. If power has been delivered for more than a total of 7
minutes, the power is turned off and the cool down step is
initiated. Otherwise, if power has been delivered for fewer than 7
minutes, then additional power should be applied in a third power
run, after waiting 30 to 120 seconds.
[0191] In the third power frame, RF power is applied at the last
setting used in the second frame, e.g. either 15, 25 or 35 Watts.
If impedance inflects and then returns to at least its initial
value (of the current frame) or appears to be reaching a spike,
power delivery is terminated and the cool down step is
initiated.
[0192] In all power frames, when total power delivery time reaches
10 minutes, power is turned off and cool down is initiated. During
cool down, RF power delivery is stopped and tissue temperature is
monitored. Tissue is allowed to cool down for at least 30 seconds
or until tissue temperature is 40.degree. C. or lower before moving
the treatment device.
[0193] In FIG. 67, the preferred algorithm is utilized. Here, the
first application of power was less than 3 minutes therefore the
second application was initiated at 15 Watts, instead of 25 Watts.
There are still power spikes if the impedance is stagnant, as shown
in FIG. 67, where power is increased to 25 Watts because the
impedance did not exceed its minimum by 2 Ohms after 90 seconds. If
the impedance continued to remain stagnant, then after another 180
seconds, there is potential for another increase in power up to 35
Watts.
[0194] In all cases, power is applied at least once, but may be
applied additional times, in this example at most, three times,
although power may be delivered to help "burn off" and remove the
electrode from the tissue. Power may range from 100 Watts down to
10 Watts, for example from 50 Watts down to 25 Watts. The total
energy delivered to achieve a weld employing any of the algorithm
examples above, or any variations thereof may be in the range of
1,000 joules to 50,000 joules, in the case of a PFO weld, a
possible range of 6,000-15,000 joules.
[0195] Algorithm--Other Approaches, Adjustments
[0196] It is within the scope of the present invention to modify
the parameters of the algorithm to achieve the desired tissue weld,
to account for a number of variables, such as those described
earlier in this disclosure. For example, treating a PFO with a thin
primum may require longer application of power, higher power, or a
higher ramp of power, given the potential for energy dissipation
through the thinner tissue. Treating a different defect such as a
ASD or LAA may require bringing tissues together that result in a
thicker sample to weld, and therefore the treatment may utilize
less total energy or lower applied powers, for example 5-35 Watts,
or may include additional applications of power at multiple regions
along the defect to be sealed.
[0197] In addition, an algorithm utilizing a bipolar treatment
device such as those described earlier, may use a ramping algorithm
such as that set forth above, but may utilize less power somewhere
in the range of 1-25 Watts, for example 5-10 Watts and more
particularly 2-3 Watts in some cases. Treatment times for bipolar
application can range from 1-20 minutes.
[0198] Although the foregoing description is complete and accurate,
it has described only exemplary embodiments of the invention.
Various changes, additions, deletions and the like may be made to
one or more embodiments of the invention without departing from the
scope of the invention. Additionally, different elements of the
invention could be combined to achieve any of the effects described
above. Thus, the description above is provided for exemplary
purposes only and should not be interpreted to limit the scope of
the invention as set forth in the following claims.
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