U.S. patent application number 10/442019 was filed with the patent office on 2003-12-25 for probe assembly for mapping and ablating pulmonary vein tissue and method of using same.
This patent application is currently assigned to SCIMED Life Systems, Inc.. Invention is credited to Hartzog, Anna, Hegde, Anant V., McMillan, Alan, O'Brien, Dennis M., Swanson, David K..
Application Number | 20030236455 10/442019 |
Document ID | / |
Family ID | 29251409 |
Filed Date | 2003-12-25 |
United States Patent
Application |
20030236455 |
Kind Code |
A1 |
Swanson, David K. ; et
al. |
December 25, 2003 |
Probe assembly for mapping and ablating pulmonary vein tissue and
method of using same
Abstract
The present invention relates to a probe assembly for mapping
and ablating pulmonary vein tissue and method of using the same.
The probe assembly includes an expandable and collapsible basket
assembly having multiple splines. One or more of the splines carry
one or more electrodes adapted to sense electrical activity in the
pulmonary vein tissue. The basket assembly defines an interior, and
a microporous expandable and collapsible body is disposed in the
interior of the basket assembly and defines an interior adapted to
receive a medium containing ions. An internal electrode is disposed
within the interior of the body and is adapted to transmit
electrical energy to the medium containing ions. The body includes
at least one microporous region having a plurality of micropores
therein sized to passions contained in the medium without
substantial medium perfusion therethrough, enabling ionic transport
of electrical energy from the internal electrode, through
ion-containing medium to an exterior of the body to ablate
pulmonary vein tissue. In other aspects of the invention, the
microporous body may be replaced by a non-porous expandable and
collapsible body that receives a fluid medium for expanding the
nonporous body to exclude blood from the electrodes on the splines,
or the probe assembly may not include any expandable and
collapsible body in the basket assembly interior (one or more
electrodes on splines sense electrical activity in the pulmonary
vein tissue and ablate the pulmonary vein tissue).
Inventors: |
Swanson, David K.;
(Campbell, CA) ; Hegde, Anant V.; (Newark, CA)
; Hartzog, Anna; (Sunnyvale, CA) ; McMillan,
Alan; (Westchester, PA) ; O'Brien, Dennis M.;
(Santa Barbara, CA) |
Correspondence
Address: |
Bingham McCutchen, LLP
Three Embarcadero, Suite 1800
San Francisco
CA
94111-4067
US
|
Assignee: |
SCIMED Life Systems, Inc.
Maple Grove
MN
|
Family ID: |
29251409 |
Appl. No.: |
10/442019 |
Filed: |
May 19, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10442019 |
May 19, 2003 |
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09684559 |
Oct 5, 2000 |
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6640120 |
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Current U.S.
Class: |
600/374 ;
600/381; 606/41 |
Current CPC
Class: |
A61B 2018/00238
20130101; A61B 18/1492 20130101; A61B 2018/00214 20130101; A61B
2018/00375 20130101; A61B 2018/00839 20130101; A61B 2018/00267
20130101; A61B 2018/00065 20130101 |
Class at
Publication: |
600/374 ;
600/381; 606/41 |
International
Class: |
A61B 005/04; A61B
018/14 |
Claims
We claim:
1. A probe assembly for mapping and ablating pulmonary vein tissue,
comprising an expandable and collapsible basket assembly including
multiple splines, one or more of said splines carrying one or more
electrodes adapted to sense electrical activity in said pulmonary
vein tissue, said basket assembly defining an interior; and an
expandable and collapsible body disposed in the interior of said
basket assembly and defining an interior adapted to receive a fluid
medium for expanding said expandable and collapsible body.
2. The assembly of claim 1, wherein said expandable and collapsible
body is a microporous expandable and collapsible body defining an
interior adapted to receive a medium containing ions, an internal
electrode disposed within said interior of said body and adapted to
transmit electrical energy to said medium containing ions, said
body including at least one microporous region having a plurality
of micropores therein sized to pass ions contained in the medium
without substantial medium perfusion therethrough, to thereby
enable ionic transport of electrical energy from the internal
electrode, through the ion-containing medium to an exterior of the
body to ablate pulmonary vein tissue.
3. The assembly of claim 2, wherein the body is made of a
poly(vinylidene fluoride) and poly(vinylpyrrolidone)
combination.
4. The assembly of claim 2, wherein said body includes at least one
customized microporous region with a predetermined geometry to more
efficiently produce a desired lesion characteristics.
5. The assembly of claim 2, wherein said body is adapted to extend
between and beyond the circumferential region defined by said
basket assembly when said basket assembly and said body are in an
expanded state.
6. The assembly of claim 2, wherein said body when expanded is
sized to create a circumferential lesion in the pulmonary vein or
around the ostium.
7. The assembly of claim 2, wherein said body when expanded is
smaller in size than the vein orifice so as to allow blood flow
thereby, and said body is adapted to sectionally ablate the
pulmonary vein or vein ostium.
8. The assembly of claim 2, wherein said microporous body is
integrated with said basket assembly.
9. The assembly of claim 2, wherein said microporous body is
removable from said basket assembly.
10. The assembly 2, wherein said microporous body and basket
assembly are separately steerable.
11. The assembly of claim 2, wherein said one or more electrodes
are adapted to also ablate pulmonary vein tissue.
12. The assembly of claim 11, wherein said microporous body when
expanded is adapted to exclude blood from said electrodes.
13. The assembly of claim 2, wherein said microporous body is
adapted to be maintained in an expanded condition at a
substantially constant pressure by a continuous flow of said medium
therethrough, providing a cooling effect in said microporous body
and pulmonary vein tissue.
14. The assembly of claim 13, further including an inlet lumen
adapted to continuously deliver said medium to said microporous
body and an outlet lumen adapted to continuously withdraw said
medium from said microporous body.
15. The assembly of claim 1, wherein said body is a non-porous
expandable and collapsible body.
16. The assembly of claim 15, wherein said one or more electrodes
are adapted to also ablate pulmonary vein tissue.
17. The assembly of claim 16, wherein said microporous body when
expanded is adapted to exclude blood from said electrodes.
18. The assembly of claim 15, wherein said non-porous expandable
and collapsible body is adapted to be maintained in an expanded
condition at a substantially constant pressure by a continuous flow
of said medium therethrough, providing a cooling effect in said
microporous body and pulmonary vein tissue.
19. The assembly of claim 18, further including an inlet lumen
adapted to continuously deliver said medium to said microporous
body and an outlet lumen adapted to continuously withdraw said
medium from said microporous body.
20. The assembly of claim 1, wherein said expandable and
collapsible body includes an interior adapted to receive a
cryogenic medium to thereby enable cryogenic ablation of pulmonary
vein tissue via said cryogenic medium and said body.
21. The assembly of claim 1, wherein said probe assembly includes a
drug delivery mechanism adapted to deliver one or more drugs to
pulmonary vein tissue or adjacent tissue.
22. A probe assembly for mapping and ablating pulmonary vein
tissue, comprising an expandable and collapsible basket assembly
including multiple splines, one or more of said splines carrying
one or more electrodes, at least one of said one or more electrodes
adapted to sense electrical activity in said pulmonary vein tissue
and ablate said pulmonary vein tissue.
23. The probe assembly of claim 22, wherein each of said one or
more electrodes at least partially surround a temperature
sensor.
24. A probe assembly for mapping and ablating pulmonary vein
tissue, comprising an expandable and collapsible basket assembly
including multiple splines, one or more of said splines carrying
one or more electrodes, at least one of said one or more electrodes
adapted to sense electrical activity in said pulmonary vein tissue,
and said probe assembly further including an ablating element
adapted to ablate said pulmonary vein tissue.
25. The assembly of claim 24, wherein said ablating element is an
electrode adapted to ablate pulmonary vein tissue by the
transmission of RF energy through the pulmonary vein tissue.
26. The assembly of claim 24, wherein the probe assembly includes a
body having an interior adapted to receive a cryogenic medium to
thereby enable cryogenic ablation of pulmonary vein tissue via said
cryogenic medium and said body.
27. The assembly of claim 24, wherein said probe assembly includes
a laser adapted to deliver laser light to ablate pulmonary vein
tissue.
28. The assembly of claim 24, wherein said probe assembly includes
an ultrasound transmitter adapted to deliver ultrasonic energy to
ablate pulmonary vein tissue.
29. The assembly of claim 24, wherein said probe assembly includes
a drug delivery mechanism adapted to deliver one or more drugs to
pulmonary vein tissue or adjacent tissue.
30. A method of mapping and ablating pulmonary vein tissue,
comprising: providing an integrated probe assembly in a target
region of a pulmonary vein, the integrated probe assembly
including: an expandable and collapsible basket assembly including
multiple splines, one or more of said splines carrying one or more
electrodes adapted to sense electrical activity in said pulmonary
vein tissue and transmit electrical energy to ablate the pulmonary
vein tissue; expanding said basket assembly of said probe assembly
so that one or more of said electrodes contact said pulmonary vein
tissue; mapping electrical activity in said pulmonary vein tissue
with said one or more electrodes; and without removing the basket
assembly and one or more electrodes, ablating one or more targeted
regions of pulmonary vein tissue determined by said mapping step by
transmitting electrical energy to the electrodes, ablating the
pulmonary vein tissue.
31. The method of claim 30, further comprising rotating the probe
assembly one or more times and ablating the pulmonary vein tissue
so that a contiguous lesion lesion is created in the pulmonary vein
tissue.
32. The method of claim 30, wherein the basket assembly includes an
interior, a microporous expandable and collapsible body located in
said interior, said microporous expandable and collapsible body
defining an interior adapted to receive a medium containing ions,
an internal electrode disposed within said interior of said body
and adapted to transmit electrical energy to said medium containing
ions, said body including at least one microporous region having a
plurality of micropores therein sized to pass ions contained in the
medium without substantial medium perfusion therethrough, to
thereby enable ionic transport of electrical energy from the
internal electrode, through the ion-containing medium to an
exterior of the body to ablate pulmonary vein tissue, the method
further including expanding the microporous porous expandable and
collapsible body and excluding blood from said electrodes, and
ablating one or more targeted regions of pulmonary vein tissue by
ionic transport of electrical energy from the internal electrode,
through the ionic-containing medium, and into the pulmonary vein
tissue.
33. The method of claim 30, wherein the basket assembly includes an
interior, a non-porous expandable and collapsible body located in
said interior, the method further including expanding the
non-porous expandable and collapsible body and excluding blood from
said electrodes.
34. A method of mapping and ablating pulmonary vein tissue,
comprising: providing a probe assembly in a target region of a
pulmonary vein, the probe assembly including: an expandable and
collapsible basket assembly including multiple splines, one or more
of said splines carrying one or more electrodes adapted to sense
electrical activity in said pulmonary vein tissue, said basket
assembly defining an interior; and a microporous expandable and
collapsible body defining an interior adapted to receive a medium
containing ions, an internal electrode disposed within said
interior of said body and adapted to transmit electrical energy to
said medium containing ions, said body including at least one
microporous region having a plurality of micropores therein sized
to pass ions contained in the medium without substantial medium
perfusion therethrough, to thereby enable ionic transport of
electrical energy from the internal electrode, through the
ion-containing medium to an exterior of the body to ablate
pulmonary vein tissue expanding said basket assembly of said probe
assembly so that one or more of said mapping electrodes contact
said pulmonary vein tissue; mapping electrical activity in said
pulmonary vein tissue with said one or more electrodes; and without
removing the basket assembly and one or more electrodes, ablating
one or more targeted regions of pulmonary vein tissue determined by
said mapping step by ionic transport of electrical energy from the
internal electrode, through the ionic-containing medium, and into
the pulmonary vein tissue.
35. The method of claim 34, wherein said body is adapted to extend
between and beyond the circumferential region defined by said
basket assembly when said basket assembly and said body are in an
expanded state, and the method further including ablating said
pulmonary vein tissue with a microporous portion of said body
extending between and beyond the circumferential region defined by
said basket assembly.
36. The method of claim 34, further including expanding said body
and ablating said tissue to create a circumferential lesion in the
pulmonary vein or around the ostium.
37. The method of claim 34, further including expanding said body
to a size smaller than the vein orifice so as to allow blood flow
thereby, and ablating one or more sectors of the pulmonary vein or
vein ostium.
38. The method of claim 34, wherein providing a probe assembly in a
target region of a pulmonary vein includes providing an integrated
microporous body and basket assembly simultaneously in a target
region of a pulmonary vein.
39. The method of claim 34, wherein providing a probe assembly in a
target region of a pulmonary vein includes providing a basket
assembly in a target region of a pulmonary vein, and separately
introducing the microporous body in the basket assembly.
40. The method of claim 34, further including separately steering
said microporous body and basket assembly to a target region of a
pulmonary vein.
41. The method of claim 34, further including ablating said
pulmonary vein tissue with said one or more electrodes.
42. The method of claim 34, further including expanding said
microporous body and excluding blood from said electrodes.
43. The method of claim 34, further including constantly
circulating said medium through said microporous body so as to
maintain said microporous body in an expanded condition at a
substantially constant pressure.
44. The method of claim 43, wherein said probe assembly includes an
inlet lumen for supplying the medium to the microporous body and an
outlet lumen to withdraw the medium from the microporous body.
45. The method of claim 44, further including applying a vacuum
pressure to said outlet lumen.
46. The method of claim 44, wherein said inlet lumen includes a
pressure control valve adapted to release pressure in said inlet
lumen when the pressure exceeds a predetermined pressure limit.
47. A method of mapping and ablating pulmonary vein tissue,
comprising: providing an integrated probe assembly in a target
region of a pulmonary vein, the integrated probe assembly
including: an expandable and collapsible basket assembly including
multiple splines, one or more of said splines carrying one or more
electrodes adapted to sense electrical activity in said pulmonary
vein tissue; expanding said basket assembly of said probe assembly
so that one or more of said electrodes contact said pulmonary vein
tissue; mapping electrical activity in said pulmonary vein tissue
with said one or more electrodes; and without removing the basket
assembly and one or more electrodes, ablating one or more targeted
regions of pulmonary vein tissue determined by said mapping step
with an ablating element.
48. The method of claim 47, wherein said ablating element is an
electrode and ablating one or more targeted regions of pulmonary
vein tissue includes ablating pulmonary vein tissue by the
transmission of RF energy through the pulmonary vein tissue.
49. The method of claim 47, wherein said ablating element is an
electrode body having an interior adapted to receive a cryogenic
medium and ablating one or more targeted regions of pulmonary vein
tissue includes cryogenically ablating pulmonary vein tissue via
said cryogenic medium and said body.
50. The method of claim 47, wherein said ablating element is a
laser and ablating one or more targeted regions of pulmonary vein
tissue includes delivering laser light to the pulmonary vein tissue
to ablate the pulmonary vein tissue.
51. The method of claim 47, wherein said ablating element is an
ultrasound transmitter and ablating one or more targeted regions
includes delivering ultrasonic energy to the pulmonary vein tissue
to ablate the pulmonary vein tissue.
52. The method of claim 47, further including the step delivering
one or more drugs to pulmonary vein tissue or adjacent tissue with
a drug delivery mechanism.
Description
FIELD OF THE INVENTION
[0001] The present invention relates, in general, to electrode
probe assemblies and methods for mapping and/or ablating body
tissue, and, in particular, to electrode probe assemblies and
methods for mapping and/or ablating pulmonary vein tissue.
BACKGROUND OF THE INVENTION
[0002] Aberrant conductive pathways can develop in heart tissue and
the surrounding tissue, disrupting the normal path of the heart's
electrical impulses. For example, anatomical obstacles, called
"conduction blocks," can cause the electrical impulse to degenerate
into several circular wavelets that circulate about the obstacles.
These wavelets disrupt the normal activation of the atria or
ventricles. The aberrant conductive pathways create abnormal,
irregular, and sometimes life-threatening heart rhythms called
arrhythmias. An arrhythmia can take place in the atria, for
example, as in atrial tachycardia ("AT") or atrial fibrillation
("AF"). The arrhythmia can also take place in the ventricle, for
example, as in ventricular tachycardia ("VT").
[0003] In treating arrhythmias, it is sometimes essential that the
location of the sources of the aberrant pathways (called focal
arrhythmia substrates) be located. Once located, the focal
arrhythmia substrate can be destroyed, or ablated, e.g., by
surgical cutting or the application of heat. In particular,
ablation can remove the aberrant conductive pathway, thereby
restoring normal myocardial contraction. An example of such an
ablation procedure is described in U.S. Pat. No. 5,471,982 issued
to Edwards et al.
[0004] Alternatively, arrhythmias may be treated by actively
interrupting all of the potential pathways for atrial reentry
circuits by creating complex lesion patterns on the myocardial
tissue. An example of such a procedure is described in U.S. Pat.
No. 5,575,810, issued to Swanson et al.
[0005] Frequently, an arrhythmia aberration resides at the base, or
within one or more pulmonary veins, wherein the atrial tissue
extends. To treat such an aberration, physicians use multiple
catheters to gain access into interior regions of the pulmonary
vein tissue for mapping and ablating targeted tissue areas. A
physician must carefully and precisely control the ablation
procedure, especially during procedures that map and ablate tissue
within the pulmonary vein. During such a procedure, the physician
may introduce a mapping catheter to map the aberrant conductive
pathway within the pulmonary vein. The physician introduces the
mapping catheter through a main vein, typically the femoral vein,
and into the interior region of the pulmonary vein that is to be
treated.
[0006] Placement of the mapping catheter within the vasculature of
the patient is typically facilitated with the aid of an introducer
guide sheath or guide wire. The introducer guide sheath is
introduced into the left atrium of the heart using a conventional
retrograde approach, i.e., through the respective aortic and mitral
valves of the heart. Alternatively, the introducer guide sheath may
be introduced into the left atrium using a transeptal approach,
i.e., through the atrial septum. In either method, the catheter is
introduced through the introducer guide sheath until a probe
assembly at a distal portion of the catheter resides within the
left atrium. A detailed description of methods for introducing a
catheter into the left atrium via a transeptal approach is
disclosed in U.S. Pat. No. 5,575,810, issued to Swanson et al.,
which is fully and expressly incorporated herein by reference. Once
inside the left atrium, the physician may deliver the probe
assembly into a desired pulmonary vein by employing a steering
mechanism on the catheter handle. The physician situates the probe
assembly within a selected tissue region in the interior of the
pulmonary vein, adjacent to the opening into the left atrium, and
maps electrical activity in the pulmonary vein tissue using one or
more electrodes of the probe assembly.
[0007] After mapping, the physician introduces a second catheter to
ablate the aberrant pulmonary vein tissue. The physician further
manipulates a steering mechanism to place an ablation electrode
carried on the distal tip of the ablation catheter within the
selected tissue region in the interior of the pulmonary vein. The
ablation electrode is placed in direct contact with the tissue that
is to be ablated. The physician directs radio frequency energy from
the ablation electrode through tissue to an electrode to ablate the
tissue and form a lesion.
[0008] Problems with this approach include the possibility of
misdirecting or misplacing the ablation electrode and inadvertently
ablating non-aberrant, i.e., healthy, pulmonary vein tissue.
Further, this approach is time-consuming because the physician has
to introduce and remove two catheters. This leads to more patient
discomfort and room for physician error. Poorly controlled ablation
in the pulmonary vein can result in pulmonary vein stenosis. The
pulmonary vein stenosis can lead to pulmonary hypertension,
pulmonary edema, necrosis of lung tissue, and even complete
pulmonary failure of a lung or lung lobe. In severe and rare cases,
the only treatment may be a lung transplant.
SUMMARY OF THE INVENTION
[0009] The present invention includes the following three main
aspects that solve the problems with separate mapping catheters and
ablation catheters for mapping electrical activity in pulmonary
vein tissue and ablating the pulmonary vein tissue: 1) a probe
assembly with a microporous ablation body used with a basket
assembly for mapping and ablating pulmonary vein tissue; 2) a probe
assembly with a basket assembly for mapping and ablating pulmonary
vein tissue; and 3) a probe assembly with an expandable body used
with a basket assembly for mapping and ablating pulmonary vein
tissue. Each of these aspects is summarized in turn below.
[0010] 1. Probe Assembly with an Expandable Body used with a Basket
Assembly for Mapping and Ablating Pulmonary Vein Tissue:
[0011] A first aspect of the invention includes a probe assembly
for mapping and ablating pulmonary vein tissue. The probe assembly
includes an expandable and collapsible basket assembly including
multiple splines, one or more of the splines carrying one or more
electrodes adapted to sense electrical activity in the pulmonary
vein tissue, the basket assembly defining an interior, a
microporous expandable and collapsible body disposed in the
interior of the basket assembly and defining an interior adapted to
receive a medium containing ions, an internal electrode disposed
within the interior of the body and adapted to transmit electrical
energy to the medium containing ions, the body including at least
one microporous region having a plurality of micropores therein
sized to pass ions contained in the medium without substantial
medium perfusion therethrough, to thereby enable ionic transport of
electrical energy from the internal electrode, through the
ion-containing medium to an exterior of the body to ablate
pulmonary vein tissue. In an exemplary implementation of the first
aspect, the microporous expandable and collapsible body is adapted
to be maintained in an expanded condition at a substantially
constant pressure by a continuous flow of the medium through the
body, providing a cooling effect in the microporous body and the
pulmonary vein tissue.
[0012] 2. Probe Assembly with a Basket Assembly for Mapping and
Ablating Pulmonary Vein Tissue:
[0013] A second aspect of the invention involves a probe assembly
for mapping and ablating pulmonary vein tissue. The probe assembly
includes an expandable and collapsible basket assembly including
multiple splines, one or more of the splines carrying one or more
electrodes, and at least one of the one or more electrodes adapted
to sense electrical activity in the pulmonary vein tissue and
ablate the pulmonary vein tissue.
[0014] 3. Probe Assembly with an Expandable Body used with a Basket
Assembly for Mapping and Ablating Pulmonary Vein Tissue:
[0015] A third aspect of the invention includes a probe assembly
for mapping and ablating pulmonary vein tissue. The probe assembly
includes an expandable and collapsible basket assembly including
multiple splines, one or more of the splines carrying one or more
electrodes adapted to sense electrical activity in the pulmonary
vein tissue, the basket assembly defining an interior, and a
non-porous expandable and collapsible body disposed in the interior
of the basket assembly and defining an interior adapted to receive
a fluid medium for expanding the expandable and collapsible body to
exclude blood from the electrodes. In an exemplary implementation
of the third aspect, the non-porous expandable and collapsible body
is adapted to be maintained in an expanded condition at a
substantially constant pressure by a continuous flow of the medium
through the body, providing a cooling effect in the body and the
pulmonary vein tissue.
[0016] Other and further objects, features, aspects, and advantages
of the present inventions will become better understood with the
following detailed description of the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0017] The drawings illustrate both the design and utility of
preferred embodiments of the present invention, in which like
elements are referred to with common reference numerals.
[0018] FIG. 1 is a schematic illustration of a RF mapping and
ablation catheter system including a probe assembly constructed in
accordance with a first aspect of the invention.
[0019] FIG. 2 is an enlarged elevational view of the probe assembly
illustrated in FIG. 1, taken in the region of 2-2 of FIG. 1.
[0020] FIG. 3A is an enlarged side view of an alternative
embodiment of a probe assembly with a fewer number of splines than
that depicted in FIGS. 1 and 3.
[0021] FIG. 3B is an enlarged cross sectional view of one of the
splines of FIG. 3A taken along line 3B-3B.
[0022] FIG. 4 is an enlarged side elevational view of a portion of
the catheter, taken in the region of 4-4 of FIG. 2.
[0023] FIG. 5 is an enlarged cross sectional view of the probe
assembly, taken along line 5-5 of FIG. 2.
[0024] FIG. 6 is an enlarged side elevational view of a distal
portion of the catheter illustrated in FIG. 1, with a portion of
the catheter body removed to show the probe assembly in a collapsed
condition.
[0025] FIG. 7 is an enlarged side elevational view of an alternate
embodiment of the probe assembly.
[0026] FIG. 8 is an enlarged side elevational view of a further
embodiment of the probe assembly.
[0027] FIG. 9 is an enlarged side elevational view of a probe
assembly constructed in accordance with a second aspect of the
invention.
[0028] FIGS. 10A-10C are cross sectional views of the probe
assembly illustrated in FIG. 9, and depict alternative embodiments
of lesion creating techniques.
[0029] FIG. 11 is an enlarged side elevational view of the probe
assembly illustrated in FIG. 9 placed at the ostium of a pulmonary
vein.
[0030] FIG. 12 is an enlarged side elevational view of a probe
assembly constructed in accordance with a third aspect of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] The present invention involves a mapping and ablation probe
assembly for a catheter that solves the problems described above
associated with a separate mapping catheter for mapping electrical
activity in pulmonary vein tissue and ablation catheter for
ablating the pulmonary vein tissue. Three main aspects of the probe
assembly are described below. The first aspect is a probe assembly
with a microporous ablation body used with a basket assembly for
mapping and ablating pulmonary vein tissue. Along with a
description of this aspect of the probe assembly, an exemplary
catheter system that is applicable to all three main aspects will
also be described. The second aspect is a probe assembly with a
basket assembly for mapping and ablating pulmonary vein tissue. The
third aspect is a probe assembly with an expandable body used with
a basket assembly for mapping and ablating pulmonary vein tissue.
Each of these aspects will now be described in turn.
[0032] 1. Probe Assembly with an Expandable Body used with a Basket
Assembly for Mapping and Ablating Pulmonary Vein Tissue:
[0033] With reference to FIGS. 1 and 2, a catheter 10 including a
probe assembly 14 for mapping and ablating pulmonary vein tissue
and constructed in accordance with a first aspect of the invention
will now be described. Although the probe assembly 14 and
alternative probe assembly embodiments described further below are
described in conjunction with mapping and ablating pulmonary vein
tissue, it will be readily apparent to those skilled in the art
that the probe assemblies may be used to map and ablate other body
tissues such as, but not by way of limitation, myocardial tissue.
Further, it should be noted, the probe assembly 14 and catheter 10
illustrated in drawings are not necessarily drawn to scale. The
probe assembly 14 will first be described, followed by a
description of the rest of the catheter system and a method of
using the probe assembly.
[0034] A. Probe Assembly:
[0035] With reference to FIG. 2, the probe assembly 14 may include
an expandable and collapsible basket 18 and a microporous body 22
located in an interior region 26 of the basket 18.
[0036] The geometry of the microporous body 22 may be altered
between a collapsed geometry (FIG. 6) and enlarged expanded
geometry (FIGS. 2, 5) by injecting and removing a pressurized and
conductive inflation medium 30 into and from an interior 36 of the
microporous body 22. The pressurized inflation medium 30 also
maintains the microporous body 22 in the expanded geometry. The
inflation medium 30 is composed of an electrically conductive
liquid that establishes an electrically conductive path from a ring
electrode 40 to the surface of the microporous body 22. Preferably,
the electrically conductive medium 30 possesses a low resistivity
to decrease ohmic losses and, thus, ohmic heating effects, within
the microporous body 22. The composition of the electrically
conductive medium 30 can vary. In the illustrated embodiment, the
electrically conductive medium 30 comprises a hypertonic saline
solution having a sodium chloride concentration at or about 100%
weight by volume. The medium may include a 70:30 mixture of 10%
saline and radio-opaque solution. An exemplary radio-opaque
solution that may be used is sold as Omnipaque.RTM. by Nycomed
Amersham Imaging of Princeton, N.J. A medium 30 with a radio-opaque
solution allows the body 22 to be visualized using fluoroscopy.
[0037] The ring electrode 40 is located within the interior region
36 of the microporous body 22. The ring electrode 40 transmits RF
energy that is delivered to pulmonary vein tissue via ionic
transport through the conductive inflation medium 30 and micropores
in the microporous body 22. In this regard, the ring electrode 40
is composed of a material having both a relatively high electrical
conductivity and a relatively high thermal conductivity, e.g.,
gold, platinum, or platinum/iridium.
[0038] It should be noted that the ring-like structure of the
electrode 40 provides a relatively large circumferential exterior
surface in communication with the inflation medium 30 in the
interior region 36 of the microporous body 22, providing an
efficient means of energizing the inflation medium 30. Although the
electrode 40 is described as a ring, the electrode 40 can take the
form of any suitable structure that can contact the inflation
medium 30. The length of the electrode 40 can be accordingly varied
to increase or decrease the amount of RF energy delivered to the
inflation medium 30. The location of the electrode 40 can also be
varied.
[0039] Although in the embodiment shown and described, the
operative ablative element is a RF electrode 40 and tissue is
ablated through the delivery of RF energy, in alternative
embodiments, the ablative element may be adapted to ablate body
tissue using an ultrasound transmitter, a laser, a cryogenic
mechanism, or other similar means. For example, the body 22 may be
adapted to receive a cryogenic medium to thereby enable cryogenic
ablation of pulmonary vein tissue via said cryogenic medium and
said body 22.
[0040] The microporous body 22 is preferably made of an
electrically nonconductive material including micropores in at
least a portion of the body 22. The micropores are preferably
0.0001 to about 0.1 microns in diameter. The microporous structure
of the microporous body 22 acts as the energy-emitting surface,
establishing ionic transport of RF energy from the RF electrode 40,
through the inflation medium 30, and into the tissue outside of the
microporous body 22, thereby creating a lesion.
[0041] The geometry of the energy-emitting surface of the
microporous body 22 can be customized to more efficiently produce
the desired lesion characteristics. In particular, the delivery of
RF energy from the electrode 40 to the microporous body 22 can be
concentrated in certain regions of the microporous body 22. For
example, the microporous body 22 may include a microporous region
32 that runs around a central circumferential portion of the
microporous body 22. Additionally or alternatively, the microporous
region 32 may run along another portion of the body 22 such as
adjacent to a proximal base of the body 22 or adjacent to a distal
tip of the body 22. One way to concentrate the delivery of RF
energy from one or more regions of the microporous body 22 is by
masking the micropores of the microporous body 22 in the regions
where RF energy delivery is not desired.
[0042] The electrical resistivity of the microporous body 22 has a
significant influence on the tissue lesion geometry and
controllability. Ablation with a low-resistivity microporous body
22 enables more RF power to be transmitted to the tissue and
results in deeper lesions. On the other hand, ablation with a
high-resistivity microporous body 22 generates more uniform
heating, therefore improving the controllability of the lesion.
Generally speaking, lower resistivity values for the microporous
body 22 (below about 500 ohm-cm) result in deeper lesion
geometries, while higher resistivity values for the microporous
body 22 (above about 500 ohm-cm) result in shallower lesion
geometries.
[0043] The electrical resistivity of the microporous body 22 can be
controlled by specifying the pore size of the material, the
porosity of the material (space on the body that does not contain
material), and the water absorption characteristics (hydrophilic
versus hydrophobic) of the material. In general, the greater the
pore size and porosity, the lower the resistivity of the
microporous body 22. In contrast, the lesser the pore size and
porosity, the greater the resistivity of the microporous body 22.
The size of the pores is selected such that little or no liquid
perfusion through the pores results, assuming a maximum liquid
pressure within the interior region of the microporous body 22.
Thus, the pores are sized to pass ions contained in the medium
without substantial medium perfusion therethrough to thereby enable
ionic transport of electrical energy from the ion-containing medium
30 to an exterior of the body 22 to ablate pulmonary vein
tissue.
[0044] In general, hydrophilic materials possess a greater capacity
to provide ionic transfer of radio frequency energy without
significant perfusion of liquid through the microporous body 22
than do hydrophobic materials. Additionally, hydrophilic materials
generally have lower coefficients of friction with body tissues
than have hydrophobic materials, facilitating routing of the
catheter through the vasculature of the patient. Exemplary
materials that can be used to make the microporous body 22 include,
but not by way of limitation, regenerated cellulose, nylon, nylon
6, nylon 6/6, polycarbonate, polyethersulfone, modified acrylic
polymers, cellulose acetate, poly(vinylidene fluoride),
poly(vinylpyrrolidone), and a poly(vinylidene fluoride) and
poly(vinylpyrrolidone) combination. A microporous body made of a
poly(vinylidene fluoride) and poly(vinylpyrrolidone) combination is
disclosed in Hegde, et al., U.S. Application No. ______ (Unknown)
entitled "POROUS MEMBRANES", filed on May 22, 2000, the
specification of which is fully and expressly incorporated herein
by reference. Also, further details concerning the manufacture of
the microporous body 22, including the specification of the
material, pore size, porosity, and water absorption characteristics
of the material, are disclosed in Swanson, et al., U.S. Pat. No.
5,797,903, the specification of which is fully and expressly
incorporated herein by reference.
[0045] The basket 18 includes multiple flexible splines 44. Each of
the splines 44 is preferably made of a resilient inert material
such as Nitinol metal or silicone rubber; however, other materials
may be used. Multiple electrodes 48 are located on each sphine 44.
Connected to each mapping electrode 48 are signal wires 52 made
from a highly conductive metal such as copper. The signal wires 52
preferably extend through each sphine 44 and into catheter body 80.
The splines 44 are connected to a base member 56 and an end member
60. The sphines 44 extend circumferentially between the base member
56 and the end member 60 when in the expanded geometry. Plastic
tubing may be used to cover the splines 44 and contain the signal
wires 52 running from the electrodes 48.
[0046] Although the electrodes 48 are described below as mapping
electrodes, in alternative embodiments, the electrodes 48 may be
multi-functional electrodes used for mapping, pacing, and/or
ablating body tissue. In a further embodiment, the splines 44 may
not include any electrodes. Any or all of the embodiments described
below may also include splines 44 having multi-functional
electrodes 48 or no electrodes.
[0047] The basket 18 is shown with specific number of splines 44
and electrodes 48 for each spline 44, i.e., 8; however, it will be
readily apparent to those skilled in the art that the number of
splines 44 and/or the number of electrodes 48 per spline 44 may
vary. For example, FIG. 3A depicts a basket structure with six
splines 44 (two splines 44 are hidden from view), with some of the
splines 44 having nine electrodes 48 and other splines 44 having
ten electrodes 48. Further, the shape of the splines 44 and
electrodes 48 may vary.
[0048] Because the electrodes 48 in this embodiment are mounted on
flexible splines 44, when the basket 18 is expanded in the
vasculature of a patient, the splines 44 conform to a large range
of different vein sizes and shapes. The flexibility and resiliency
of the splines 44 also allows for the basket structure to push
outward on the tissue. This increases the friction between the
electrodes 48 and the vein and thereby anchors the probe assembly
14 in position, yielding a more precise ablation location.
[0049] The splines 44 may carry one or more temperature sensors 50
that may take the form of thermistors, thermocouples, or the
equivalent, and are in thermal conductive contact with the exterior
of the probe assembly 14 to sense conditions in tissue outside the
probe assembly 14 during ablation. The temperature sensors 50 may
be located on the splines 44 such that when the splines 44 are
expanded, the temperature sensors 50 are located at or near the
largest diameter of the probe assembly 14. Although the basket 18
in FIG. 2 is shown with two temperature sensors 50 for each spline
44, it will be readily apparent to those skilled in the art that
the number of temperature sensors 50 per spline 44 may vary.
[0050] With reference to FIGS. 3A and 3B, in an alternative
embodiment, the electrodes 48 may comprise rings that surround the
temperature sensors 50, splines 44, and signal wires 52.
[0051] With reference to FIG. 5, the microporous body 22 may
include a construction that, when inflated, has a larger volume
than the volume V defined by the expanded basket 18, causing the
body 22 to extend or bulge between and beyond the circumferential
region or volume V defined by the basket assembly 18 when the
basket assembly 18 and the body 22 are in an expanded state. This
may help put the microporous body 22 in more direct contact with
the targeted pulmonary vein tissue, improving ablation treatment of
the tissue. This may also cause the delivery of RF energy from the
microporous body 22 to be concentrated in the bulging regions of
the microporous body 22, which may be desirable depending on the
targeted tissue that needs ablating. Additionally, the microporous
body 22 restricts blood flow to the ablation area, which reduces
the possibility of coagulated blood embolus. Finally, restricting
blood flow renders the relationship between ablation parameters
(power, time, and temperature) and lesion characteristics more
predictable, since the important lesion parameters of energy loss
attributable to the convective losses and to energy delivery are
more predictable.
[0052] B. Catheter System:
[0053] With reference generally to FIGS. 1-4 and 6, the remaining
components of the catheter system will now be described.
[0054] The catheter 10 can be functionally divided into four
regions: the operative distal probe assembly region 64, a
deflectable catheter region 68, a main catheter region 72, and a
proximal catheter handle region 76. A handle assembly 77 including
a handle 78 is attached to the proximal catheter handle region 76
of the catheter 10. With reference to FIG. 6, the catheter 10 also
includes a catheter body 80 that may include first and second
tubular elements 84 and 86, which form, in conjunction, the
structure of the distal probe assembly region 64; a third tubular
element 90, which forms the structure of the deflectable catheter
region 68; and a fourth tubular element 94, which forms the
structure of the main catheter region 72. It should be noted,
however, that the catheter body 80 may include any number of
tubular elements required to provide the desired functionality to
the catheter. The addition of metal in the form of a braided mesh
layer sandwiched in between layers of the plastic tubing may be
used, greatly increasing the rotational stiffness of the catheter.
This may be beneficial to practice one or more lesion creation
techniques described in more detail below.
[0055] With reference to FIG. 2, the operative distal probe
assembly region 64 includes the probe assembly 14. The catheter 10
may also include a sheath 98 that, when moved distally over the
basket 18, collapses the basket 18 (FIG. 6). In a preferred
embodiment, the microporous body 22 is collapsed (by the removal of
the inflation medium 30 therefrom) before the basket 18 is
collapsed; however, in an alternative embodiment, collapsing the
basket 18 may cause fluid to be removed from the microporous body
22 and, thus, the microporous body 22 to collapse. Conversely,
retracting the sheath 98 or moving the sheath 98 proximally away
from the probe assembly 14 may deploy the basket 18. This removes
the compression force causing the basket 18 to open to a prescribed
three-dimensional shape. Moving the sheath 98 distally in the
direction indicated by arrow 106 causes the sheath 98 to apply a
compressive force, thus, collapsing the basket 18. Moving the
sheath 98 proximally in the direction indicated by the arrow 110
removes the compressive force of the sheath 98, thus, allowing the
basket 18 to expand.
[0056] With reference to FIGS. 1, 2 and 6, the deflectable catheter
region 68 is the steerable portion of the catheter 10, which allows
the probe assembly 14 to be accurately placed adjacent the targeted
tissue region. A steering wire (not shown) may be slidably disposed
within the catheter body 80 and may include a distal end attached
between the second tubular element 86 and the third tubular element
90 and a proximal end suitably mounted within the handle 78. The
handle assembly 77 may include a steering member such as a rotating
steering knob 114 that is rotatably mounted to the handle 78.
Rotational movement of the steering knob 114 counter clockwise
relative to the handle 78, in the direction indicated by the arrow
118, may cause a steering wire to move proximally relative to the
catheter body 80 which, in turn, tensions the steering wire, thus
pulling and bending the catheter deflectable region 68 into an arc
(shown by broken lines in FIG. 1). On the contrary, rotational
movement of the steering knob 114 clockwise relative to the handle
78, in the direction indicated by the arrow 122, may cause the
steering wire to move distally relative to the catheter body 80
which, in turn, relaxes the steering wire, thus allowing the
resiliency of the third tubular element 90 to place the catheter
deflectable region 68 of the catheter back into a rectilinear
configuration. To assist in the deflection of the catheter, the
deflectable catheter region 68 is preferably made of a lower
durometer plastic than the main catheter region 72.
[0057] The catheter 10 may be coupled to a RF generator 126 such as
that described in Jackson et al., U.S. Pat. No. 5,383,874, the
specification of which is fully and expressly incorporated herein
by reference. The RF generator 126 provides the catheter 10 with a
source of RF ablation energy. The RF generator 126 includes a RF
source 130 for generating the RF energy and a controller 134 that
controls the amplitude of, and time during, which the RF source 130
outputs RF energy. The RF generator 126 is electrically coupled to
the catheter 10 via a cable 138. One or more signal wires 140 are
routed through an ablation wire tubular member 142 (FIG. 2, 4) in
the catheter body 80 and couple the ring electrode 40 to the cable
138. Operation of the RF generator 126 provides RF energy to the
ring electrode 40, which in turn is ionically transferred through
the inflation medium 30, and out through the pores of the
microporous body 22, into the targeted tissue region. Thus, when
operated, the RF generator 126 allows the physician to ablate body
tissue such as pulmonary vein tissue in a controlled manner,
resulting in a tissue lesion with the desired characteristics.
[0058] A mapping signal processor 146 may also be coupled to the
catheter 10, allowing a physician to map the electrical activity in
the target tissue site before, during and/or subsequent to the
ablation process. The mapping processor 146 may be part of the
controller 134. The mapping processor 146 is in electrical
communication with the mapping electrodes 48 via a mapping cable
150 and the signal wires 52. The signal wires 52 are preferably
routed through a mapping wire tubular member 156 (FIG. 2, 4) in the
catheter body 80.
[0059] An inflation medium reservoir and pump 160 may be coupled to
the catheter 10 for supplying the microporous body 22 with the
inflation medium 30. The reservoir and pump 160 may supply ionic
fluid at room temperature or may include a chiller for supplying
cool ionic fluid. A constant flow of ionic cooling fluid such as a
10% saline solution may be circulated through the microporous body
22 to cool the microporous body 22 and supply the ionic fluid
necessary to allow ionic transfer through the body for ablation. An
inlet lumen 354 and an outlet lumen 356 are adapted to communicate
at proximal ends, inlet port 355 and outlet port 357, with the
reservoir and pump 160 and at distal ends with the mouth or
interior of the microporous body 22. Preferably, the fluid lumens
354, 356 have the same length and internal diameters, resulting in
a microporous body pressure that is approximately half of that at
the inlet port 355. The pressures at the inlet port 355 and outlet
port 357 may be measured with respective inlet and outlet pressure
sensors, 358, 360. Thus, the microporous body pressure may be
estimated/controlled using the pressure measured at the inlet
sensor 358.
[0060] The fluid is preferably circulated at a rate and pressure
that maintains the fluid pressure in the microporous body 22 at a
predetermined pressure. Alternatively, the microporous body
pressure may be controlled by injecting the fluid into the inlet
port 355 at a known, controlled rate.
[0061] The pump 160 may impart the pressure necessary to circulate
the fluid through the microporous body 22 and the fluid may
passively flow out of the outlet port 357. Alternatively, the pump
160 may apply a vacuum pressure to the outlet port 357 to increase
the allowable flow rate through the microporous body 22.
[0062] An inlet control valve 362, e.g., pop-off valve, and/or
outlet control valve 364 at the inlet 355 and/or outlet 357 may be
used to prevent the microporous body 22 from being inflated above
the body's burst pressure or a lower predefined pressure to prevent
over-inflation or bursting, ensuring patient safety. A control
valve set to a low pressure value may also be used to ensure that
the body 22 remains inflated even when flow to the body 22 is
stopped, if the pressure value exceeds that required to maintain
body inflation.
[0063] A continuous flow of ionic fluid maintains the microporous
body 22 and ablation site at a cooler temperature, allowing for
more power delivery to the target tissue to make deeper lesions.
The continuous flow also enables the use of a smaller RF electrode
within the microporous body 22 because heat generated near the
electrode can be convected away from that electrode. Finally, the
continuous flow reduces the possibility that non-targeted adjacent
tissue will be damaged, thereby increasing patient safety.
[0064] An auxiliary member 172 may be coupled to the catheter 10
via an external connector 176 and further coupled to the probe
assembly 14 via an internal connector or carrier 180 (FIG. 4) in
the catheter body 80. The one or more temperature sensors 50 on one
or more of the splines 44 of the basket 18 may be connected to one
or more temperature sensor wires guided through the internal
connector or carrier 180 of the catheter body 80. The auxiliary
member 172 may be a controller that is coupled to the one or more
temperature sensor wires via the external connector 176. If the
auxiliary member 172 is a controller, it is preferably the same as
the controller 134 of the RF generator 126.
[0065] Temperatures sensed by the temperature sensors 50 are
processed by the controller 172. Based upon temperature input, the
controller 172 adjusts the time and power level of radio frequency
energy transmissions by the RF generator 126, and consequently the
ring electrode 40, to achieve the desired lesion patterns and other
ablation objectives and to avoid undesired tissue necrosis caused
by overheating.
[0066] Temperature sensing and controlling using the one or more
temperature sensors 50 of the splines 44 will now be described in
more detail. The controller 172 may include an input 182 for
receiving from the physician a desired therapeutic result in terms
of (i) the extent to which the desired lesion should extend beneath
the tissue-electrode interface to a boundary depth between viable
and nonviable tissue and/or (ii) a maximum tissue temperature
developed within the lesion between the tissue-electrode interface
and the boundary depth. The controller 172 may also include a
processing element 184 that retains a function that correlates an
observed relationship among lesion boundary depth, ablation power
level, ablation time, actual sub-surface tissue temperature, and
electrode temperature. The processing element 184 compares the
desired therapeutic result to the function and selects an operating
condition based upon the comparison to achieve the desired
therapeutic result without exceeding a prescribed actual or
predicted sub-surface tissue temperature.
[0067] The operating condition selected by the processing element
184 can control various aspects of the ablation procedure such as
controlling the ablation power level, limiting the ablation time to
a selected targeted ablation time, limiting the ablation power
level subject to a prescribed maximum ablation power level, and/or
the orientation of the microporous region 32 of the body 22,
including prescribing a desired percentage contact between the
region 32 and tissue.
[0068] If the ablating electrode(s) is the microporous body 22 or
conventional metal electrode(s) where an expandable body is used to
restrict blood flow around the electrode(s), the processing element
184 may rely upon the temperature sensors 50 to sense actual
maximum tissue temperature because the body 22 restricts blood flow
to the ablation site, minimizing convective cooling of the
tissue-electrode interface by the surrounding blood flow. As a
result, the region of maximum temperature is located at or close to
the interface between the tissue and the microporous body 22. The
temperature conditions sensed by the temperature sensors 50 closely
reflect actual maximum tissue temperature.
[0069] If the ablating electrode(s) is a conventional metal
electrode(s) and blood is free to flow over the electrode(s), the
processing element 302 may predict maximum tissue temperature based
upon the temperature sensed by the temperature sensors 50 at the
tissue-electrode interface. When using a conventional metal
electrode(s) to ablate tissue, the tissue-electrode interface is
convectively cooled by surrounding blood flow. Due to these
convective cooling effects, the region of maximum tissue
temperature is located deeper in the tissue. As a result, the
temperature conditions sensed by the temperature sensors 50
associated with metal electrode elements do not directly reflect
actual maximum tissue temperature. In this situation, maximum
tissue temperature conditions must be inferred or predicted by the
processor 184 from actual sensed temperatures.
[0070] In a preferred embodiment, the one or more temperature
sensors 50 are used to sense instantaneous localized temperatures
(Ti) of the thermal mass corresponding to the region 32. The
temperature Ti at any given time is a function of the power
supplied to the electrode 40 by the generator 126.
[0071] The characteristic of a lesion can be expressed in terms of
the depth below the tissue surface of the 50 degree C. isothermal
region, which will be called D.sub.50C. The depth D.sub.50C is a
function of the physical characteristics of the microporous region
32 (that is, its electrical and thermal conductivities,
resistivities, and size); the percentage of contact between the
tissue and the microporous region 32; the localized temperature Ti
of the thermal mass of the region 32; the magnitude of RF power (P)
transmitted by the interior electrode 40, and the time (t) the
tissue is exposed to the RF power.
[0072] For a desired lesion depth D.sub.50C, additional
considerations of safety constrain the selection of an optimal
operating condition among the operating conditions listed above.
The principal safety constraints are the maximum tissue temperature
TMAX and maximum power level PMAX.
[0073] The maximum temperature condition TMAX lies within a range
of temperatures that are high enough to provide deep and wide
lesions (typically between about 50 degree C. and 60 degree C.),
but are safely below about 65 degree C., the temperature at which
pulmonary stenosis is known to occur. It is recognized that TMAX
will occur somewhere between the electrode-tissue interface and
D.sub.50C. As discussed above, if the ablating electrode is the
microporous body 22 or a conventional electrode(s) and an
expandable body is used to restrict blood flow at the ablation
site, TMAX will be closer to the interface because of the lack of
convective cooling by the blood flow. If the ablating electrode is
a conventional metal electrode(s) and nothing restricts blood flow
to the ablation site, TMAX will be deeper in the tissue because of
the convective cooling of the electrode(s) by the blood flow.
[0074] The maximum power level PMAX takes into account the physical
characteristics of the interior electrode 40 and the power
generation capacity of the RF generator 126. The D.sub.50C function
for a given porous region 32 can be expressed in terms of a matrix
listing all or some of the foregoing values and their relationship
derived from empirical data and/or computer modeling. The
processing element 184 includes in memory this matrix of operating
conditions defining the D.sub.50C temperature boundary function for
multiple arrays of operating conditions.
[0075] The physician also uses the input 182 to identify the
characteristics of the structure 22, using a prescribed
identification code; set a desired maximum RF power level PMAX; a
desired time t; and a desired maximum tissue temperature TMAX.
[0076] Based upon these inputs, the processing element 184 compares
the desired therapeutic result to the function defined in the
matrix, and selects an operating condition to achieve the desired
therapeutic result without exceeding the prescribed TMAX by
controlling the function variables.
[0077] Using the microporous body 22, typical ablation conditions
are to control to sensed temperatures of 65 degree C. and apply RF
power for one minute.
[0078] With reference back to FIG. 4, the internal carrier 180 (or
an internal carrier similar to the internal carrier 18) may be used
as a transport lumen for drug delivery via the body 22 (if the
pores were large enough and/or the drug molecules small enough) or
other means. The internal carrier 180 may terminate in the handle
assembly 77, where a physician may inject the medicine into the
internal carrier 180 or the medicine may be supplied by the
auxiliary member 172. The medicine may travel through the internal
carrier 180 to the body 22. Additional or fewer auxiliary
components may be used depending on the application.
[0079] C. Method of Use
[0080] With reference to FIGS. 1-6, a method of using the catheter
10 and probe assembly 14 will now be described. Before the catheter
10 can be introduced into a patient's body, the probe assembly 14
must be in a collapsed condition (FIG. 6). If the catheter 10 is
not already in this condition, the probe assembly 14 can be
collapsed by moving the sheath 98 forward, towards the distal end
of the catheter 10 (in the direction indicated by the arrow
106).
[0081] Placement of the catheter 10 within the vasculature of the
patient is typically facilitated with the aid of an introducer
guide sheath or guide wire, which was previously inserted into the
patient's vasculature, e.g., femoral vein. The introducer guide
sheath is introduced into the left atrium of the heart using a
conventional retrograde approach, i.e., through the respective
aortic and mitral valves of the heart. One or more well-known
visualization devices and techniques, e.g., ultrasound,
fluoroscopy, etc., may be used to assist in navigating and
directing the catheter 10 to and from the targeted region.
Alternatively, the introducer guide sheath may be introduced into
the left atrium using a conventional transeptal approach, i.e.,
through the vena cava and atrial septum of the heart. A detailed
description of methods for introducing a catheter into the left
atrium via a transeptal approach is disclosed in U.S. Pat. No.
5,575,810, issued to Swanson et al., which is fully and expressly
incorporated herein by reference.
[0082] In either method (conventional retrograde approach or
transeptal approach), the catheter 10 is introduced through the
introducer guide sheath until the probe assembly 14 resides within
the left atrium. Once inside the left atrium, the physician may
deliver the probe assembly 14 into a desired pulmonary vein through
rotational movement of the steering knob 114 on the catheter handle
78.
[0083] The physician situates the probe assembly 14 within a
selected tissue region in the interior of the pulmonary vein,
adjacent to the opening into the left atrium. The basket 18 is
deployed by moving the sheath 98 proximally in the direction
indicated by the arrow 110, causing the sheath 98 to slide away
from the basket 18 and removing the compression force thereon. The
basket 18 then expands, allowing one or more of the mapping
electrodes 48 to contact the pulmonary vein tissue.
[0084] The mapping electrodes 48 are used to sense electrical
activity in the pulmonary vein tissue, and may be used to pace
pulmonary vein tissue as well.
[0085] Mapping data received and interpreted by the mapping signal
processor 146 is displayed for use by the physician to locate
aberrant pulmonary vein tissue. The probe assembly 14 may be moved
one or more times which may require collapsing and deploying the
probe assembly 14 one or more times, in an effort to locate
aberrant pulmonary vein tissue.
[0086] When the physician has determined that the aberrant
pulmonary vein tissue has been located (basket 18 is deployed), the
physician may then expand the microporous body 22 by filling the
microporous body 22 with the inflation medium 30 to contact the
targeted pulmonary vein tissue. The pump 160 may be activated to
introduce the ionic fluid through the inlet lumen 354 and into the
microporous body 22 at a constant pressure, inflating the body 22.
The ionic fluid circulated may be cool or at room temperature. The
ionic fluid exits the microporous body 22 and flows through the
outlet lumen 356 to the outlet 357. The fluid may passively drip or
flow out of the outlet lumen 356, or may be drawn out of the outlet
lumen 356 with vacuum pressure from the pump 160. Inflating or
maintaining the microporous body 22 at less than full pressure is
desirable because a non-turgid microporous body 22 better conforms
to the tissue surface.
[0087] Once the physician has determined that the microporous body
22 is effectively inflated and in contact with the pulmonary vein
tissue, the physician may begin ablating the targeted tissue. RF
energy is preferably supplied to the ring electrode 40, which is
located within the microporous body 22 and surrounded by inflation
medium 30. Through ionic transport, the electrical energy from the
electrode 40 is transported through the inflation medium 30 and
through the pores of the microporous body 22, to the exterior of
the microporous body 22, into and through at least a portion of the
pulmonary vein tissue so as to ablate the targeted pulmonary vein
tissue, and to a return electrode.
[0088] If the electrodes 48 are also (or alternatively) used to
ablate the pulmonary vein tissue and saline or a fluid having
similar heat transfer characteristics is used to deploy the body
22, thermal transfer within the body may enable contiguous lesion
formation between the electrodes 48 to be created more
consistently.
[0089] Throughout this process the physician may monitor the
temperatures of the tissue region using the temperature sensors 50
to more accurately ablate the target tissue.
[0090] Once ablation is completed, or in between ablation
treatments, electrical activity in the pulmonary vein tissue may be
mapped using the mapping electrodes 48 to confirm effective
ablation treatment.
[0091] To collapse the probe assembly 14, the inflation medium 30
in microporous body 106 is removed, but no longer supplied, causing
the microporous body 106 to deflate. The basket 18 is also
collapsed by moving the sheath 98 forward, towards the distal end
of the catheter 10 (in the direction indicated by the arrow 106).
The catheter 10 is then removed from the patient's body or moved to
a different location for additional diagnosis and/or treatment.
[0092] Thus, the probe assembly 14 and method described above are
advantageous because they allow the physician to map and ablate the
targeted pulmonary vein region with a single probe assembly
positioning. Prior to the present invention, the physician would
introduce the mapping electrode and map the aberrant region of the
pulmonary vein, then remove that mapping electrode, and follow with
the ablation electrode to ablate the aberrant region. Problems with
the prior approach include the possibility of misdirecting or
misplacing the ablating electrode and inadvertently ablating
non-aberrant, i.e., healthy, pulmonary vein tissue, and the
excessive time-consumption because the physician had to introduce
and remove two catheters. This leads to more patient discomfort and
room for physician error. Further, the apparatuses and methods of
the present invention incorporate all the advantages of an
expandable and collapsible microporous body with those of a mapping
basket assembly.
[0093] With reference to FIG. 7, in an alternative embodiment, a
probe assembly 201 is comprised of elements from separate
catheters, namely, a microporous body 22 from an ablation catheter
202 and a basket 18 from a main catheter 203. The basket 18 may
include electrodes 48 that are adapted to map, pace, and/or ablate
pulmonary vein tissue.
[0094] The ablation catheter 202 is slidably removable with respect
to the main catheter 203 for positioning the microporous body 22
within or removing it from the basket 18. The catheter body 203 may
include an additional lumen 200 through which the ablation catheter
202 may be slidably disposed.
[0095] Both the distal portions of the ablation catheter 202 and
the main catheter 203 are preferably steerably controllable in a
manner similar to that described above with respect to the catheter
10.
[0096] The microporous body 22 may range in size in the expanded
state from the size of one of the electrodes 48 to just larger than
the diameter of the basket 18. The active band 32 of the body 22 is
preferably relatively large to better ensure lesion creation. In
one embodiment, the body 22, when expanded, is large enough to
create a circumferential lesion in the vein or around the
ostium.
[0097] However, placement of lesion around the entire circumference
is often not required to electrically isolate the pulmonary veins
in atrial fibrillation patients. Therefore, in another exemplary
embodiment, the expanded microporous body 22 is smaller than the
pulmonary vein diameter or vein orifice to create one or more
ablation sectors of the pulmonary vein, decreasing the probability
of creating clinically significant pulmonary stenosis compared to a
complete circumferential lesion. Additionally, a smaller
microporous body 22 enables blood flow in pulmonary veins to
continue during ablation.
[0098] A method of using the probe assembly 201 is similar to that
described above with respect to the probe assembly 14, except the
main catheter 203 and ablation catheter 202 may be introduced
separately to the targeted site. The ablation catheter 202 may be
introduced into the lumen 200 of the main catheter 203 via the
handle 78 and snaked through the lumen 200 until the collapsed
microporous body 22 is located within the basket 18. The physician
may then inflate the microporous body 22 and steer the body 22 so
that it contacts the targeted pulmonary vein tissue. As discussed
above, inflation of the microporous body 22 at a pressure
corresponding to a less than fully expanded state may be desirable
because a non-turgid body 22 better conforms to the tissue surface
than a turgid body 22. The microporous body 22 may be maintained in
an expanded state by continuously circulating a fluid medium
through the body 22 as described above or by inflating the body 22
with the medium and preventing the medium from exiting the
catheter.
[0099] For sectional ablation (i.e., non-circumferential ablation),
a relative small, expanded microporous body 22 such as that
illustrated in FIG. 7 may be used to ablate one or more targeted
areas. Additionally or alternatively, the electrodes 48 may be used
to ablate one or more targeted areas. If the electrodes 48 are used
to ablate tissue, the body 22 may be used to restrict blood flow
from the ablation area.
[0100] For circumferential ablation, a larger, expanded microporous
body 22 such as that illustrated in FIGS. 2 and 5 may be used. A
larger, expanded microporous body 22 restricts blood flow to the
ablation site, increasing the efficiency of the ablation since RF
currents flow substantially into the tissue only, and not into the
blood. Restricting blood flow also reduces the possibility of
coagulated blood embolus and renders the relationship between
ablation parameters (power, time and temperature) and lesion
characteristics more predictable since fewer uncontrolled variables
exists (mostly attributable to convective losses and to energy
delivery to tissue). Further, if the electrodes 48 are also used to
ablate the pulmonary vein tissue and saline or a fluid having
similar heat transfer characteristics is used to deploy the body
22, thermal transfer within the body 22 may enable contiguous
lesion formation between the electrodes 48 to be created more
consistently. Also, the microporous body 22 may create a lossy
electrical connection between the electrodes 48 that may enable
contiguous lesion formation between the electrodes 48 to be created
more consistently.
[0101] With reference to FIG. 8, in a further embodiment, a probe
assembly 310 includes a basket 18 located at a distal end of a
catheter 312 and a microporous body 22 integrated with the basket
18. The microporous body 22 may be located at the distal end of a
steerable member 314 that is steerable in a manner similar to that
described above with respect to catheter 10. The probe assembly 310
is similar to the probe assembly 201 described above with respect
to FIG. 7, except the microporous body 22 and steerable member 314
are not removable from the catheter 202. The catheter 312 is also
steerable in a manner similar to that described with respect to
catheter 10. The microporous body 22, when expanded, can range in
size from the size of a single spline electrode 48 to a large body
that will be large enough to fill the entire inner cavity of the
basket 18.
[0102] The method of using the probe assembly 310 is similar to
that described above with respect to probe assembly 201, except a
separate ablation catheter is not snaked through a main catheter or
removed therefrom because the microporous body 22 and steerable
member 314 are integrated with the basket 18.
[0103] 2. Probe Assembly with a Basket Assembly for Mapping and
Ablating Pulmonary Vein Tissue:
[0104] With reference to FIGS. 9 and 10A-10D, a second aspect of a
probe assembly 300 of a mapping and ablation catheter 302 will now
be described. Unlike the prior embodiments, the probe assembly 300
does not include a microporous body. Instead, the probe assembly
300 includes a basket 18 with a plurality of multi-functional
electrodes 48 adapted to map and ablate body tissue. The catheter
302 is preferably steerable in a manner similar to that described
above with respect to catheter 10.
[0105] The number of electrodes 48 that each spline 44 carries, the
spacing between the electrodes 48, and the length of the electrodes
48 may vary according to the particular objectives of the ablating
procedure: These structural features influence the characteristics
of the lesion patterns formed.
[0106] Segmented electrodes 48 may be well suited for creating
continuous, elongated lesion patterns provided that the electrodes
48 are adjacently spaced close enough together to create additive
heating effects when ablating energy is transmitted simultaneously
to the adjacent electrodes 48. The additive heating effects between
close, adjacent electrodes 48 intensify the desired therapeutic
heating of tissue contacted by the electrodes 48. The additive
effects heat the tissue at and between the adjacent electrode 48 to
higher temperatures than the electrode 48 would otherwise heat the
tissue, if conditioned to individually emit energy to the tissue.
The additive heating effects occur when the electrodes 48 are
operated simultaneously in a bipolar mode between electrodes.
Furthermore, the additive heating effects also arise when the
electrodes are operated simultaneously in a unipolar mode,
transmitting energy to an indifferent electrode.
[0107] Conversely, when the electrodes 48 are spaced sufficiently
far apart from each other, the electrodes 48 create elongated
lesion segments.
[0108] The length of each electrode 48 may also be varied. If the
electrode 48 is too long, the ability of the splines 44 to conform
to the anatomy of the pulmonary vein may be compromised. Also, long
electrodes may be subject to "hot spots" during ablation caused by
differences in current density along the electrode. Another
approach is to use multiple short electrodes 48 on each spline 44
to cover a large effective ablating length and avoid hot spots. An
electrode approximately 3 mm in length or less makes an adequate
lesion without hot spots, although other lengths may also work.
[0109] Ablating energy can be selectively applied individually to
just one or a selected group of electrodes, when desired, to
further vary the size and characteristics of the lesion
pattern.
[0110] A basket 18 including eight splines 44 should be adequate
for ablating in pulmonary veins of 10 to 15 mm in diameter;
however, the basket 18 may have a greater or lesser number of
splines 44, depending on the size of the target anatomy. A small
vein may require fewer splines 44 than a larger vein to form a
continuous circular lesion around the circumference of the
vein.
[0111] The method of using the probe assembly 300 is similar to
that described above for the probe assembly 14, except once the
basket 18 is at the appropriate location, the physician may begin
ablation using the same electrodes 48 that were used to map
electrical activity in the pulmonary vein tissue. Should the
physician decide that only one section or certain sections of the
vein 304 needs ablation, the physician may activate RF energy to
select electrodes 44 corresponding to the section or sections of
the vein 304.
[0112] With reference additionally to FIG. 10A, if the physician
decides that the entire circumference of the pulmonary vein 304
needs treatment and the vein 304 is relatively small relative to
the number of splines 44 of the probe assembly 300, the physician
may simply activate RF energy once to all the electrodes 48 or to
certain circumferential electrodes 44.
[0113] With reference to FIG. 10B, in an alternate lesion-making
technique, where a single ablation step such as that described
above with respect to FIG. 10A proves insufficient to form an
unbroken tesion line in larger veins 304, the catheter 302 may be
rotated slightly, and a second ablation may be performed. One or
more successive rotations and ablations with the probe assembly 300
may be necessary in order to make a contiguous lesion 305.
[0114] With reference to FIG. 10C, in a further lesion-making
technique, the catheter 302 may be rotated while simultaneously
ablating the pulmonary vein 304. The handle 76 (FIG. 1) of the
catheter 302 may be rotated slowly until the lesion 305 made by one
spline 44 begins to overlap the lesion 305 started by an adjacent
spline 44.
[0115] After a first round of ablation, the physician may then take
further electrode 44 readings, retract the basket 18, and
reposition the catheter 302 for further ablation procedures or, if
done, remove the catheter 302 from the patient's vasculature.
[0116] With reference to FIG. 11, an advantage to this aspect of
the invention is that the probe assembly 300 does not include a
structure likely to block significant blood flow 306 or otherwise
occlude the vein 304. Sufficient blockage can cause hemodynamic
compromise in some patients. In addition, blood flow 306 has a
beneficial cooling effect that allows the probe assembly 300 to
create deeper lesions at lower temperatures and inhibit damaging
non-target adjacent tissue. Finally, this embodiment contains
separate electrodes 48 that can create lesions at selected sections
of the vein 304 or around the entire circumference by one of the
lesion-creating techniques described above.
[0117] 3. Probe Assembly with an Expandable Body used with a Basket
Assembly for Mapping and Ablating Pulmonary Vein Tissue:
[0118] With reference to FIG. 12, a probe assembly 400 constructed
in accordance with a further aspect of the invention will now be
described. The probe assembly 400 is located at a distal end of a
catheter 402 that is preferably steerably controlled in a manner
similar to that described above with respect to catheter 10.
[0119] The probe assembly 400 is similar to probe assembly 300
described above with respect to FIG. 9, i.e., includes
multi-functional electrodes 48 that may map, pace and/or ablate,
except the probe assembly 400 further includes a non-porous,
non-electrically conducting expandable balloon 404. The nonporous,
non-electrically conducting balloon 404 includes the following two
primary functions: (1) to assist in maintaining the position of the
basket structure 18 by placing some force against the vein walls,
and (2) to restrict blood flow to the ablation area.
[0120] A method of using the probe assembly 400 will now be
described. A physician may guide the catheter 402 to the
appropriate location and deploy the basket 18. Electrical activity
in the pulmonary vein may be mapped using the multi-function
electrodes 48 on the splines 44. The physician may interpret the
resulting electrical activity data, and determine the proper
position of the probe assembly 400 for ablation.
[0121] Once satisfied that the position is accurate, the physician
may inflate the non-electrically conducting body 404 with a fluid
such as saline or CO.sub.2 and perform ablation of the targeted
tissue with the electrodes 48. As described above with respect to
body 22, the fluid may be constantly circulated though the body
404.
[0122] The expanded body 404 restricts blood flow to the ablation
site, increasing the efficiency of the ablation since RF currents
flow substantially into the tissue only, and not into the blood.
Restricting blood flow also reduces the possibility of coagulated
blood embolus and renders the relationship between ablation
parameters (power, time and temperature) and lesion characteristics
more predictable since fewer uncontrolled variables exist (mostly
attributable to convective losses and to energy delivery to
tissue). If saline or a fluid having similar heat transfer
characteristics is used to deploy the body 404, thermal transfer
within the body 404 may enable contiguous lesion formation between
the electrodes 48 to be created more consistently.
[0123] While preferred methods and embodiments have been shown and
described, it will be apparent to one of ordinary skill in the art
that numerous alterations may be made without departing from the
spirit or scope of the invention. Therefore, the invention is not
to be limited except in accordance with the following claims.
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