U.S. patent number 5,462,521 [Application Number 08/171,213] was granted by the patent office on 1995-10-31 for fluid cooled and perfused tip for a catheter.
This patent grant is currently assigned to Angeion Corporation. Invention is credited to Greg G. Brucker, Jerome P. Saul, Steven D. Savage.
United States Patent |
5,462,521 |
Brucker , et al. |
October 31, 1995 |
**Please see images for:
( Certificate of Correction ) ** |
Fluid cooled and perfused tip for a catheter
Abstract
The invention relates to an ablation catheter which controls the
temperature and reduces the coagulation of biological fluids on a
tip of a catheter, prevents the impedance rise of tissue in contact
with the catheter tip, and maximizes the potential energy transfer
to the tissue, thereby allowing an increase in the lesion size
produced by the ablation. The ablation catheter includes a catheter
body. The ablation catheter also includes a tip for monitoring
electrical potentials, and applying electrical energy to a
biological tissue. A fluid source is positioned at one end of the
catheter for supplying a fluid flow through the catheter to the tip
means. Passages are positioned within the tip in a variety of
manners for directing the fluid flow through the tip means to the
exterior surface of the tip to control the temperature and form a
protective fluid layer around the tip. Monitoring structure is also
positioned within the tip structure for measurement of the
electrical potentials in a biological tissue. Ablation structure is
also positioned within the tip for application of ablative energy
to the biological tissue.
Inventors: |
Brucker; Greg G. (Minneapolis,
MN), Saul; Jerome P. (Newton, MA), Savage; Steven D.
(Brooklyn Center, MN) |
Assignee: |
Angeion Corporation (Plymouth,
MN)
|
Family
ID: |
22622944 |
Appl.
No.: |
08/171,213 |
Filed: |
December 21, 1993 |
Current U.S.
Class: |
604/20; 606/46;
606/31 |
Current CPC
Class: |
A61B
18/1492 (20130101); A61M 25/0069 (20130101); A61M
25/0068 (20130101); A61M 25/0082 (20130101); A61B
2018/00011 (20130101); A61B 2018/00357 (20130101); A61B
2018/00577 (20130101); A61B 2018/1467 (20130101); A61B
2018/00005 (20130101); A61B 2017/22038 (20130101); A61M
1/85 (20210501); A61B 18/1402 (20130101); A61B
2018/1253 (20130101); A61B 2018/00982 (20130101); A61B
2017/00084 (20130101); A61B 2218/002 (20130101); A61B
2018/00065 (20130101); A61F 2002/30968 (20130101); A61B
2018/00029 (20130101); A61B 2018/00791 (20130101); A61B
5/283 (20210101); A61M 2025/0073 (20130101) |
Current International
Class: |
A61B
18/14 (20060101); A61M 25/00 (20060101); A61B
18/00 (20060101); A61F 2/30 (20060101); A61B
5/0408 (20060101); A61B 5/042 (20060101); A61B
17/00 (20060101); A61M 1/00 (20060101); A61M
025/00 () |
Field of
Search: |
;607/120,122,102
;128/642 ;604/28,20,113 ;606/31,41,46 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Willkampf, F. H. et al., Radiofrequency Ablation with a Cooled
Porous Electrode Catheter, Abstract, JACC, vol. 11, No. 2, p. 17A
(1988). .
Huang et al., Increase in the Lesion Size and Decrease in the
Impedance Rise with a Saline Infusion Electrode Catheter for
Radiofrequency (1989) Catheter Ablation, Abstract, Circulation,
vol. 80, No. 4, pp. II-324. .
Ruffy, Rodolphe, Radiofrequency Delivery Through an Endocardial
Cooled Catheter Results in Increased Lesion Size, Abstract,
Circulation, vol. 88, No. 4, Part 2, (1993). .
Bergau, Dennis, Porous Metal Tipped Catheter Produces Larger
Radiofrequency Lesions Through Tip Cooling, Abstract, Circulation,
vol. 88, No. 4, Part 2 (1993). .
Article entitled "Pacific Sintered Metals". .
Dialog summary of abstracts and titles in the scientific and
medical device databases, pp. 1-9..
|
Primary Examiner: Rosenbaum; C. Fred
Assistant Examiner: Van Over; Perry E.
Attorney, Agent or Firm: Patterson & Keough
Claims
What is claimed is:
1. A catheter tip for cardiac signal measurement and monitoring,
comprising:
a) a tip structure positioned at an end of a catheter, the tip
structure having an exterior surface;
b) means formed within the tip structure for providing fluid
communication and commensurate flow of fluid originating inside the
tip structure to portions of the tip structure exterior surface
through a plurality of passages which direct the fluid flow from
inside the tip structure over the exterior surface of the tip
structure to provide a fluid protective layer surrounding the tip
structure to minimize contact of the tip structure with biological
materials; and
c) monitoring means within the tip structure for measurement of
electrical potentials in a biological tissue.
2. The catheter-tip of claim 1 wherein the tip structure comprises
a metallic material.
3. The catheter tip of claim 1 wherein the tip structure comprises
a ceramic material including metallic members.
4. The catheter tip of claim 1, further comprising a plurality of
directional channels disposed in the exterior surface of the tip
structure to direct fluid flow in an axial direction over the
exterior surface of the tip structure.
5. The catheter tip of claim 1, further comprising directional
channel means for directing fluid flow in a radial direction over
the exterior surface of the tip structure.
6. The catheter tip of claim 1 wherein the tip structure comprises
a microporous material.
7. The catheter tip of claim 1 wherein the fluid protective layer
is between about 0.001 millimeters (mm) and one mm in
thickness.
8. The catheter tip of claim 1 wherein the monitoring means
measures and adjusts the rate of fluid flow through the tip
structure relative to biological parameters.
9. The catheter tip of claim 1 further comprising temperature
sensing means within the tip structure for sensing the temperature
of the tip structure.
10. The catheter tip of claim 1 further comprising temperature
sensing means within the tip structure for sensing the temperature
of the biological tissue in contact with the tip structure.
11. The catheter tip of claim 1 further comprising temperature
sensing means within the tip structure for sensing the temperature
of the tip structure and adjusting the fluid flow rate to maintain
the temperature of the tip structure within a designated range of
temperatures.
12. The catheter tip of claim 1 further comprising temperature
sensing means within the tip structure for sensing the temperature
of the tissue and adjusting the fluid flow rate to maintain the
temperature of the tissue within a designated range of
temperatures.
13. The catheter tip of claim 1, wherein the fluid is selected from
the group consisting of biologically compatible liquids and
gases.
14. The catheter tip of claim 1 wherein the fluid is selected from
the group of fluids consisting of carbon dioxide, nitrogen, helium,
water, and saline.
15. The catheter tip of claim 1 wherein the monitoring means
includes an electrode.
16. The catheter tip of claim 1, wherein the means for providing
fluid communication and fluid flow is disposed within the
monitoring means.
17. The catheter tip of claim 1, wherein the fluid protective layer
is a continuous fluid protective layer.
18. The catheter tip of claim 1, wherein the fluid protective layer
covers all of the exterior surface of the tip structure.
19. A catheter tip for use in cardiac signal measurement,
comprising:
a) a tip structure on a distal end of a catheter, the tip structure
having an interior and comprising a porous material;
b) a plurality of randomly disposed interstitial spaces formed
within the porous material of the tip structure and in fluid
communication with a source of fluid in the interior of the tip
structure, the interstitial spaces directing a flow of fluid from
the source of fluid in the interior of the tip structure over the
exterior surface of the tip structure to provide a fluid protective
layer surrounding the tip structure to minimize the contact of the
tip with biological materials; and
c) a monitoring device within the tip structure for measurement of
electrical potentials in a biological tissue.
20. The catheter tip of claim 19 wherein the monitoring device
comprises metallic members.
21. The catheter tip of claim 19 further comprising a plurality of
directional channels disposed in the exterior surface of the tip
structure to direct fluid flow in an axial direction over the
exterior surface of the tip structure.
22. The catheter tip of claim 19, further comprising directional
channel means for directing fluid flow in a radial direction over
the exterior surface of the tip structure.
23. The catheter tip of claim 19 wherein the monitoring device
measures and adjusts the rate of fluid flow through the tip
structure relative to biological parameters.
24. The catheter tip of claim 19 further comprising temperature
sensing means within the tip structure for sensing the temperature
of the tip structure.
25. The catheter tip of claim 19 further comprising temperature
sensing means within the tip structure for sensing the temperature
of the biological tissue in contact with the tip structure.
26. The catheter tip of claim 19 further comprising temperature
sensing means within the tip structure for sensing the temperature
of the tip structure and adjusting the fluid flow rate to maintain
the temperature of the tip structure within a designated range of
temperatures.
27. The catheter tip of claim 19 further comprising temperature
sensing means within the tip structure for sensing the temperature
of the tissue and adjusting the fluid flow rate to maintain the
temperature of the tissue within a designated range of
temperatures.
28. The catheter tip of claim 19, wherein the fluid is selected
from the group consisting of biologically compatible liquids and
gases.
29. The catheter tip of claim 28 wherein the fluid is selected from
the group of fluids consisting of carbon dioxide, nitrogen, helium,
water, and saline.
30. The catheter tip of claim 19 wherein the fluid protective layer
is between about 0.001 millimeters (mm) and one mm in
thickness.
31. The catheter tip of claim 19, wherein the plurality of randomly
disposed interstitial spaces are disposed within the monitoring
device.
32. The catheter tip of claim 19, wherein the fluid protective
layer is a continuous fluid protective layer.
33. The catheter tip of claim 19, wherein the fluid protective
layer covers all of the surface area of the tip structure.
34. An ablation catheter which reduces the coagulation of
biological materials on a tip of the catheter, reduces the
impedance rise of tissue in contact with the catheter tip, and
maximizes the energy transfer to the tissue, thereby allowing an
increase in lesion size, the ablation catheter comprising:
a) a proximal end, a distal end, and a central lumen;
tip means having an exterior surface, the tip means being
positioned at the distal end of the catheter for monitoring
electrical potentials and applying energy to a biological
tissue;
c) fluid source means positioned at the proximal end of the
catheter body for supplying a fluid flow through the catheter to
the tip means;
d) means formed within the tip means for directing the fluid flow
through a plurality of passages which direct the fluid flow from
the central lumen over the exterior surface of the tip to form a
protective fluid layer around the tip means to minimize contact of
the tip means with biological fluids, reduce the coagulation of
biological materials on the tip means and reduce tire resistance of
energy transfer to the tissue;
e) monitoring means within the tip means for measurement of
electrical potentials in a biological tissue; and
f) ablation means within the tip means for application of energy to
the biological tissue, the means for directing the fluid flow being
formed within the ablation means.
35. The catheter of claim 34 wherein the tip means comprises a
metallic material.
36. The catheter of claim 35 wherein the tip means comprises a
solid metal material having structure defining at least one passage
therethrough.
37. The catheter of claim 34 wherein the tip means comprises a
ceramic material having metallic pieces.
38. The catheter of claim 34 wherein the ablation means is selected
from the group of energy types consisting of RF, laser, microwave,
ultrasound, and direct current.
39. The catheter of claim 34 further comprising temperature sensing
means within the tip means for sensing the temperature of the tip
means.
40. The catheter of claim 34 further comprising temperature sensing
means within the tip means for sensing the temperature of the
biological tissue in contact with the tip means.
41. The catheter of claim 34 further comprising temperature sensing
means within the tip means for sensing the temperature of the tip
means and adjusting the fluid flow rate to maintain the temperature
of the tip means within a designated range of temperatures.
42. The catheter of claim 34 further comprising temperature sensing
means within the tip means for sensing the temperature of the
tissue and adjusting the fluid flow rate to maintain the
temperature of the tissue within a designated range of
temperatures.
43. The catheter of claim 34 further comprising temperature sensing
means within the tip means for sensing the temperature of the
tissue and adjusting the energy applied to the catheter to maintain
the temperature of the tissue within a designated range of
temperatures.
44. The catheter of claim 34 further comprising control means
within the catheter for regulating and controlling the distribution
of tissue temperature to affect lesion size.
45. The catheter of claim 44 wherein the control means includes
setting a voltage to a desired level to regulate and control the
lesion size.
46. The catheter of claim 34, wherein the fluid is selected from
the group consisting of biologically compatible liquids and
gases.
47. The catheter of claim 46 wherein the fluid is selected from the
group of fluids consisting of carbon dioxide, nitrogen, helium,
water, and saline.
48. The catheter of claim 34 wherein the monitoring means includes
an electrode.
49. The catheter of claim 34 further comprising a device positioned
within the central lumen of the catheter.
50. The catheter of claim 34 wherein the fluid protective layer is
between about 0.01 mm and one mm in thickness.
51. The ablation catheter of claim 34 further comprising
directional channel means for directing fluid flow in an axial
direction over the exterior surface of the tip means.
52. The ablation catheter of claim 34 further comprising
directional channel means for directing fluid flow in a radial
direction over the exterior surface of the tip means.
53. The ablation catheter of claim 34 wherein the tip means
comprises a solid metal material having structure defining a
plurality of passages therethrough.
54. The ablation catheter of claim 34, wherein the means for
directing fluid flow comprises a microporous structure.
55. The ablation catheter of claim 54, wherein the means for
directing fluid flow comprises apertures having a diameter less
than five hundred microns.
56. The ablation catheter of claim 34, wherein the fluid protective
layer is a continuous fluid protective layer.
57. The ablation catheter of claim 34, wherein the fluid protective
layer covers all of the exterior surface of the tip structure.
58. A method of reducing coagulation of biological materials on a
catheter tip, minimizing the resistance to energy transfer to
tissue, and maximizing the energy transfer to the tissue in
communication with the catheter tip, thereby allowing for an
increase of lesion size, comprising the steps of:
a) positioning a catheter having a tip within the body, the tip
having a plurality of randomly disposed passages therethrough;
b) directing a fluid flow through the catheter;
c) passing the fluid flow through the randomly disposed passages in
the catheter tip in an approximately radial direction to produce a
fluid flow originating within the catheter over the exterior
surface of the tip; and
d) forming a fluid layer around the catheter tip to maintain
biological materials at a distance from the catheter tip and
minimize contact of the catheter tip with the biological materials,
so as to reduce the coagulation of biological materials on the
catheter tip and minimize the resistance to energy transfer to
tissue in communication with the catheter tip.
59. The method of claim 58, wherein the forming step includes
forming a continuous fluid layer around the catheter tip.
60. The method of claim 58, wherein the forming step includes
forming a fluid layer around the catheter tip, the fluid layer
covering all of the surface area of the tip.
61. An ablation catheter which reduces the coagulation of
biological materials on a tip of the catheter, reduces the
impedance rise of tissue in contact with the catheter tip, and
maximizes the energy transfer to the tissue, thereby allowing an
increase in lesion size, comprising:
a) a catheter including a proximal end, a distal end, and a central
lumen;
b) tip means having an exterior surface, the tip means being
positioned at the distal end of the catheter for monitoring
electrical potentials, and applying energy to a biological
tissue;
c) fluid source means positioned at the proximal end of the
catheter body for supplying a fluid flow through the catheter to
the tip means;
d) directional channel means formed within the tip means for
directing the fluid flow through a plurality of passages which
direct the fluid flow from the central lumen over the exterior
surface of the tip means to form a protective fluid layer around
the tip means to minimize contact of the tip with biological
fluids, reduce the coagulation of biological materials on the tip
means and reduce the resistance to energy transfer to the tissue,
wherein the directional channel means is a microporous
structure;
e) monitoring means within the tip means for measurement of
electrical potentials in a biological tissue; and
f) ablation means within the tip means for application of energy to
the biological tissue.
Description
FIELD OF THE INVENTION
The invention relates to catheters. More specifically, the
invention relates to a fluid perfused tip used on the distal end of
an ablation catheter.
BACKGROUND OF THE INVENTION
The pumping action of the heart is controlled in an orderly manner
by electrical stimulation of myocardial tissue. Stimulation of this
tissue in the various regions of the heart is controlled by a
series of conduction pathways contained within the myocardial
tissue. The impulse to stimulate is started at the sino-atrial (SA)
node and is transmitted through the atria. The signals arrive at
the atrio-ventricular (AV) node which is at the junction of the
atria and ventricles. The signal passes through the AV node into
the bundle of HIS, through the Purkinje fiber system and finally
activates the ventricular muscle. At the completion of ventricular
stimulation, heart tissue rests to allow the cells to recover for
the next stimulation. The stimulation is at the cellular level, and
is a changing of the polarity of the cells from positive to
negative.
Cardiac arrhythmias arise when the pattern of the heartbeat is
changed by abnormal impulse initiation or conduction in the
myocardial tissue. The term tachycardia is used to describe an
excessively rapid heartbeat resulting from repetitive stimulation
of the heart muscle. Such disturbances often arise from additional
conduction pathways which are present within the heart either from
a congenital developmental abnormality or an acquired abnormality
which changes the structure of the cardiac tissue, such as a
myocardial infarction.
One of the ways to treat such disturbances is to identify the
conductive pathways and to sever part of this pathway by destroying
these cells which make up a portion of the pathway. Traditionally,
this has been done by either cutting the pathway surgically,
freezing the tissue, thus destroying the cellular membranes, or by
heating the cells, thus denaturing the cellular proteins. The
resulting destruction of the cells eliminates their electrical
conductivity, thus destroying, or ablating, a certain portion of
the pathway. By eliminating a portion of the pathway, the pathway
may no longer maintain the ability to conduct, and the tachycardia
ceases.
One of the most common ways to destroy tissue by heating has been
the use of electromagnetic energy. Typically, sources such as
radiofrequency (RF), microwave, ultrasound, and laser energy have
been used. With radiofrequency energy, a catheter with a conductive
inner core and a metallic tip are placed in contact with the
myocardium and a circuit is completed with a patch placed on the
patient's body behind the heart. The catheter is coupled to a
radiofrequency generator such that application of electrical energy
creates localized heating in the tissue adjacent to the distal
(emitting) electrode. Because of the nature of radiofrequency
energy, both the metallic tip and the tissue are heated
simultaneously. The peak tissue temperatures during catheter
delivered application of RF energy to myocardium occur close to the
endocardial surface, such that the lesion size produced is
approximately limited by the thermodynamics of radial heat spread
from the tip. The amount of heating which occurs is dependent on
the area of contact between the electrode and the tissue and the
impedance between the electrode and the tissue. The higher the
impedance, the lower the amount of energy transferred into the
tissue.
One of the major problems with radiofrequency energy is the
coagulation of blood onto the tip of the catheter, creating a
higher impedance or resistance to passage of electrical energy into
the tissue. As the impedance increases, more energy is passed
through the portion of the tip without coagulation, creating even
higher local temperatures and further increasing coagulum formation
and the impedance. Finally enough blood is coagulated onto the tip
such that no energy passes into the tissue. The catheter must now
be removed from the vascular system, the tip area cleaned and the
catheter repositioned within the heart at the desired location. Not
only can this process be time consuming, but it may be difficult to
return to the previous location because of the reduced electrical
activity in the regions which have been previously ablated. Use of
temperature sensors in the tip to modulate the power input to keep
the electrode below the coagulation temperature of blood have been
used. These systems inherently limit the amount of power which can
be applied. Others have used closed loop cooling systems to
introduce water into the tip, but these systems are larger than
necessary because the coolant must be removed from the
catheter.
Increase of impedance was noted in radiofrequency (RF) ablation at
power levels above 7 watts (W) due to the formation of a thin
insulating layer of blood degradation products on the electrode
surface. Wittkampf, F. H. et al., Radiofrequency Ablation with a
Cooled Porous Electrode Catheter, Abstract, JACC, Vol. 11, No. 2,
Page 17A (1988). Wittkampf utilized an open lumen system at the
distal electrode which had several holes perpendicular to the
central lumen which could be cooled by saline. Use of the saline
kept the temperature of the electrode at a temperature low enough
so that the blood products would not coagulate onto the tip of the
electrode.
Impedance rise associated with coagulum formation during RF
catheter ablation was also noticed by Huang et al., Increase in the
Lesion Size and Decrease in the Impedance Rise With a Saline
Infusion Electrode Catheter for Radiofrequency Catheter Ablation,
Abstract, Circulation, Vol. 80, No. 4, page II-324 (1989). A
quadropolar saline infusion intraluminal electrode catheter was
used to deliver RF energy at different levels.
SUMMARY OF THE INVENTION
The invention relates to a catheter tip for cardiac signal
measurement and monitoring, including a tip structure which is
positioned at the end of the catheter. Path means are formed within
the tip structure for directing a fluid from the interior of the
tip structure to portions of the tip structure exterior surface,
thereby providing a fluid protective layer surrounding the tip
structure. Monitoring means are also included within the catheter
tip structure for measurement of electrical potentials in a
biological tissue.
The invention also relates to a catheter tip for use in cardiac
signal measurement which includes a tip structure comprising a
ceramic insulating material. Path means are formed within the tip
structure for directing the flow of the fluid through the tip
structure to provide a fluid protective layer surrounding the tip
structure. Monitoring means are also included within the tip
structure for measurement of electrical potentials in biological
tissue.
The invention also relates to an ablation catheter which reduces
the coagulation of biological fluids on a tip of a catheter,
regulates the impedance rise of tissue in contact with the catheter
tip, and maximizes the potential energy transfer to the tissue,
producing a larger size lesion. The ablation catheter includes a
catheter body. The ablation catheter also includes a tip for
monitoring electrical potentials, and applying electrical energy to
a biological tissue. A fluid source is positioned at one end of the
catheter for supplying a fluid flow through the catheter to the tip
means. Passages are formed within the tip for directing the fluid
flow through the tip means to the exterior surface of the tip means
to form a protective fluid layer around the tip. Monitoring means
are also positioned within the tip structure for measurement of the
electrical potentials in a biological tissue. Ablation means are
also positioned within the tip means for application of ablative
energy to the biological tissue.
The invention also relates to a method of reducing coagulation of
biological fluids on a catheter tip, minimizing the resistance to
energy transfer to tissue, and maximizing the potential energy
transfer to the tissue in communication with the catheter tip,
thereby producing an increased lesion size in the tissue. A
catheter with a tip having passages is positioned within the body.
A fluid flow is directed through the catheter. The fluid flow is
passed through the passages in the catheter tip in a radial
direction. A fluid layer is formed around the catheter tip to
maintain biological materials at a distance from the catheter tip
and minimize contact of the catheter tip with the biological
materials.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of an ablation catheter and
tip.
FIG. 2 is a fragmentary enlarged section view of the catheter tip
having a bulbous configuration.
FIG. 3 is a fragmentary enlarged section view of the catheter tip
having a spherical configuration.
FIG. 4 is a fragmentary enlarged section view of a catheter tip
having an extended rectangular shape.
FIG. 5 is a fragmentary enlarged section view of a catheter tip
having a rectangular shape showing the electrical conduit.
FIG. 6 is a fragmentary enlarged section view of a solid catheter
tip having a multiplicity of discreet passages.
FIG. 7 is a fragmentary enlarged section view of a solid catheter
tip having a passage extending the length of the catheter tip.
FIG. 8 is a cross section view of the catheter tip showing axial
channels extending the length of the catheter tip.
FIG. 9 is a cross section view of the catheter tip showing a
multiplicity of radially directed channels encircling the catheter
tip.
FIG. 10 is a fragmentary enlarged section view of a catheter tip
made of a ceramic insulating material having monitoring
members.
FIG. 11 is a fragmentary enlarged section view of a catheter having
ring electrodes which have path means.
FIG. 12 is a fragmentary enlarged section view of an alternative
embodiment of a catheter having a large central lumen and a smaller
lumen.
FIG. 13 is a cross section view taken along line 13--13 of FIG.
12.
FIG. 14 is an enlarged fragmentary sectional view of a portion of
the catheter tip and ring electrodes shown in FIGS. 2-5, 10, and
11.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a catheter having a fluid perfused or
insulated tip. Fluid passes through the tip structure, forming a
fluid protective layer around the exterior surface of the tip
structure. The fluid which permeates and surrounds the tip
structure minimizes the amount of the biological material which
comes in contact with the catheter tip structure, as well as cools
the tip structure. The cooling fluid prevents a rise in the
resistance (impedance) of the tissue to energy transfer from an
ablation energy source, and maximizes the potential energy transfer
to the tissue in communication with the catheter tip. As a result,
a larger lesion size in the tissue is produced.
Referring to FIG. 1, a side elevational view of catheter 20 is
shown having catheter body 22, a handle 24, and a tip structure 26.
Catheter body 22 may be of varying lengths, the length being
determined by the application for catheter 20. Catheter body 22 is
preferably made of a flexible, durable material, including
thermoplastics such as nylon, in which a braiding is embedded.
Preferably, catheter body 22 includes a large central lumen 28,
such as a three French (F) lumen in a four F to twelve F,
preferably eight F catheter 20. Catheter body 22 may contain a
plurality of ring electrodes 30 which surround the exterior surface
of catheter body 22 at selected distances from the distal end 32
proximate tip structure 26.
As shown in FIG. 1, handle 24 is positioned on the proximal end 34
of catheter body 22. Handle 24 may contain multiple ports, such as
ports 36, 38. Port 36 may be utilized, in this embodiment, for
electrical connections between electrophysiological monitoring
equipment and electrical potential sites of the tissue. Electrical
connection means 40, exiting through port 36, is positioned between
and connects tip structure 26 and the electrophysiological
monitoring equipment. Port 36 is in communication with central
lumen 28 of catheter body 22 and may also be used for the
introduction and passage of devices 42 through catheter 20. Port
38, in this embodiment, is connected to a fluid source means and is
also in fluid communication with central lumen 28 of catheter 20.
Port 38 may be used for the entry of a fluid into catheter 20.
Additional ports may be included on handle 24 which are in
communication with central lumen 28. Port 36 may, for example,
contain electrical connection means 40, and an additional port may
contain device 42.
Referring to FIG. 1, tip structure 26 is located at the distal end
32 of catheter body 22. Tip structure 26 may range from four (4) to
twelve (12) French catheter tips. Tip structure 26 includes an
attachable electrode which can be used for monitoring electrical
potentials of the tissue, measuring cardiac signals, and mapping to
locate the tissue to be ablated. In addition, the tip structure may
include monitoring means for measuring, monitoring, and adjusting
the rate of fluid flow through tip 26 relative to biological
parameters, such as tip and tissue temperature.
As shown in FIGS. 2-5, the overall shape of tip structure 26 may
have a variety of configurations. The various configurations may be
machined into the material comprising tip structure 26. Preferably,
the shape of tip structure 26 permits catheter 20 to proceed
readily through the vein or artery into which catheter 20 may be
inserted. The shape of tip structure 26 is determined by the
application for which catheter 20 is designed. For example, FIG. 2
is a fragmentary enlarged section view of tip structure 26 having
wall portions 27 which extend beyond the diameter D of catheter
portions proximal to the tip. For example, a bulbous or dumbbell
configuration, as shown in FIG. 2, may be useful in situations
requiring access to pathway ablations which lie on top of a valve
or other relatively inaccessible site. FIG. 3 illustrates a
fragmentary enlarged section view of tip structure 26 which has a
spherical or rounded configuration which may be advantageous, for
example, in situations involving cardiac pathways underneath a
valve. FIG. 4 and FIG. 5 illustrate fragmentary enlarged section
views of tip structure 26 which vary in the length of tip structure
26. Tip structure 26 shown in FIG. 4 may be useful in applications
which lie along the myocardial wall, and tip structure 26
illustrated in FIG. 5 may be particularly advantageous for uses
such as electrophysiological mapping.
Tip structure 26 may comprise a variety of materials. Preferably,
the material used for tip structure 26 in the different embodiments
may include a plurality of apertures or path means which are either
randomly or discreetly formed in or spaced throughout tip structure
26. The diameter of the path means is substantially smaller than
the overall diameter of tip structure 26. The diameter dimensions
of the path means in the different embodiments discussed below may
vary, and may include microporous structures.
As illustrated in FIGS. 2-5, tip structure 26 is preferably made of
a sintered metal which contains a plurality of randomly formed
through-passages or path means 48 in tip structure 26. Generally,
to create the sintered metal for tip structure 26, spherical
particles, such as finely pulverized metal powders, are mixed with
alloying elements. This blend is subjected to pressure under high
temperature conditions in a controlled reducing atmosphere to a
temperature near the melting point of the base metal to sinter the
blend. During sintering (heating), metallurgical bonds are formed
between the particles within the blend at the point of contact. The
interstitial spaces between the points of contact are
preserved.
Paths means 48 and tip structure 26 comprise interstitial spaces
structures which are randomly positioned, are of varying sizes, and
are interconnected in a random manner with other interstitial
spaces in tip structure 26 to provide fluid communication between
central lumen 28 of catheter 20 and the exterior surface 50 of tip
structure 26. Path means 48 are generally five to twenty microns in
diameter, although this may vary. The metal material utilized for
tip structure 26 should conduct heat well, have the ability to
monitor electrical potentials from a tissue, and be economical to
fabricate, such as stainless steel or platinum.
Alternatively, as shown in FIG. 6, tip structure 26 may comprise a
solid metal material. FIG. 6 is a fragmentary enlarged section view
of catheter body 22 connected to tip structure 26. Tip structure 26
in this embodiment comprises a solid metal, such as stainless steel
or platinum, having a multiplicity of specifically formed apertures
or path means 52 within tip structure 26 which provide fluid
communication between central lumen 28 of catheter 20 and the
exterior surface 50 of tip structure 26 for the passage of a fluid.
Position of path means 52 are designed to provide a continuous
layer of fluid over the exterior surface 50 of tip structure 26.
Preferably, the apertures of path means 52 have a diameter less
than five hundred microns, although this may vary. The metal
material utilized for tip structure 26 shown in FIG. 6 should
conduct heat, as well as have the ability to monitor electrical
potentials from a tissue.
FIG. 7 is a fragmentary enlarged section view illustrating catheter
body 22 attached to tip structure 26. Tip structure 26, in this
embodiment, is preferably made of a solid metal material which
conducts heat well, and has the ability to monitor and measure
electrical potentials of a tissue, such as stainless steel or
platinum. Alternatively, tip structure 26 may comprise a dense
ceramic material. As shown in FIG. 7, a single orifice, channel or
through path means 54 is formed through the length L of tip
structure 26. Path means 54 is in fluid communication with central
lumen 28 of catheter 20. Preferably, the aperture of path means 54
has a diameter less than five hundred microns, although this may
vary.
FIGS. 8 and 9 illustrate alternative cross section embodiments of
tip structure 26 shown in FIG. 7. FIG. 8 illustrates tip structure
26 having a plurality of grooves or directional channels 56 which
extend in an axial direction along the length L of tip structure
26. Interconnecting channels may extend radially between channels
56 to aid in the fluid distribution over tip structure 26. FIG. 9
illustrates a plurality of annular grooves or directional channels
58 which encircle tip structure 26 in a radial manner. As shown in
FIG. 9, channels 60 extend between path means 54 and channels 58 to
direct the fluid flow through central lumen 28 and path means 54 to
the exterior surface 50 of tip structure 26. In these embodiments,
channels 56, 58 are designed to communicate with path means 54 to
provide a continuous, evenly distributed fluid protective layer
over substantially the entire exterior surface 50 of metallic tip
structure 26.
Referring to FIG. 10, an alternative embodiment of tip structure 26
is shown. FIG. 10 is a fragmentary enlarged section view of
catheter body 22 attached to tip structure 26. Tip structure 26, in
this embodiment, preferably comprises a ceramic insulating material
which includes randomly formed path means 61. Path means 61 are
generally five to twenty microns in diameter, although this may
vary. Path means 61 are in fluid communication with central lumen
28 of catheter 20. In addition, tip 26 includes at least one
monitoring member 62 positioned throughout tip structure 26.
Member(s) 62 may be of varying shapes and dimensions. Preferably,
members 62 are made of a conductive material suitable for
monitoring electrical activity and for application of electrical
energy to a biological tissue, such as stainless steel or platinum.
Tip structure 26, in this embodiment, may contain axial or radial
directional channels on exterior surface 50 of tip structure
26.
As shown in FIGS. 1 and 11, ring electrodes 30 may be attached to
catheter body 22. Ring electrodes 30 are connected to the
monitoring equipment by electrical connection means 64 through port
36 in handle 24. Electrical connection means 64 are attached to
ring electrodes 30, by, for example, soldering or other suitable
mechanical means. Ring electrodes 30 may be made of a material
which has path means similar to path means 48, 52, 60 as described
above with reference to tip structure 26 in FIGS. 2-5 and 10, and
is preferably a sintered metal material. A plurality of ring
electrodes 30 may be positioned at distal end 32 of catheter 20.
Ring electrodes 30 may be used for electrophysiological monitoring
and mapping, as well as for ablation. Fluid passes from central
lumen 28 through path means 48, 52, 61 in ring electrodes 30 to
form a fluid protective layer around the exterior surface 66 of
ring electrodes 30.
FIG. 14 illustrates an enlarged fragmentary section view of a
portion of catheter tip structure 26 and/or ring electrodes 30
shown in FIGS. 2-5, 10, and 11. Substantially spherical particles
84, preferably biologically compatible metal particles, are
positioned and arranged so as to form and create numerous
interconnected, omnidirectional, tortuous path means 48, 52, and 61
(only 48 shown) through tip structure 26. Fluid flows through these
tortuous path means 48, 52, 61 in the varied tip structure
configurations to the exterior surface 50 of tip structure 26 or
exterior surface 66 of ring electrodes 30 to uniformly and evenly
distribute the fluid around tip structure 26. Substantially all
path means 48, 52, 61 at surface 50 of tip structure 26 or surface
66 of ring electrodes 30 is connected through the tortuous paths to
central lumen 28.
The fluid introduced through port 38, or an additional port, of
catheter 20 is preferably a biologically compatible fluid, and may
be in a gaseous or liquid state. For example, the fluid may
comprise carbon dioxide, nitrogen, helium, water, and/or saline.
Fluid enters through, for example, port 38 and is passed though
central lumen 28 of catheter body 22. The fluid perfuses tip
structure 26 and/or ring electrodes 30 through the path means in
tip structure 26 and/or ring electrodes 30, and creates a fluid
protective layer surrounding exterior surface 50 of tip structure
26 or exterior surface 66 of electrodes 30, thereby minimizing
contact of tip structure 26 or electrodes 30 with biological
material, such as blood. The rate of fluid flow through central
lumen 28 of catheter 20 may vary and range from 0.1 ml/min. to 40
ml/min. Fluid flow through catheter 20 may be adjusted by a fluid
infusion pump, if the fluid is liquid, or by pressure, if the fluid
is a gas. The fluid flow is regulated by the infusion pump for the
liquid fluid, or by a needle valve if a gas, so as to maintain an
optimal disbursing flow over tip structure 26 and/or ring
electrodes 30 and maintain a desired tip temperature. Preferably,
the protective layer of fluid covers all or substantially all of
the surface area of tip structure 26 and is between about 0.001 mm
and one (1) mm, and more preferably, about 0.01 mm. in thickness,
although this may vary depending on the application, and may vary
in thickness during a given procedure.
Temperature sensing means 47 may be incorporated into tip structure
26 for sensing and measuring the temperature of tip structure 26
and for sensing and measuring the temperature of the biological
tissue in contact with tip structure 26 as shown in FIG. 3 and FIG.
4. Temperature sensing means 47 may be incorporated in any of the
tip structure embodiments shown in FIGS. 2-10. The temperature
sensing means generally comprises at least one temperature sensor,
such as a thermocouple or thermistor. In addition, temperature
sensing means 47 may be utilized as a feedback system to adjust the
flow rate of the biologically compatible fluid to maintain the
temperature of the tip structure at a particular temperature within
a designated range of temperatures, such as 40.degree. C. to
95.degree. C. Also, temperature sensing means 47 may be used as a
feedback system to adjust the flow rate of the biologically
compatible fluid so as to maintain the temperature of the
biological tissue in contact with tip structure 26 at a particular
temperature within a designated range of temperatures, such as
40.degree. C. to 95.degree. C. The temperature of the tissue or tip
structure 26 is controlled by the temperature of the fluid, the
distribution of the fluid relative to internal and external
surfaces to the tip structure, the energy applied to the catheter,
and the fluid flow rate.
Catheter 20 may include ablation means within tip structure 26.
Preferably, the ablation means may be a wire connected to an RF
energy source, although other types of electrical energy may be
utilized, including microwave, ultrasound, and direct current.
Alternatively, the ablation means may include optical fibers for
delivery of laser energy. The ablation means may be connected to an
energy source through port 36, or an additional port.
As shown in FIG. 1, device 42 may be passed through central lumen
28 of catheter 20. Device 42 may include, for example, a guidewire
for ease of entry of catheter 20 into the heart or vascular system;
a diagnostic device, such as an optical pressure sensor; a suction
catheter for biopsy of biological material near the distal tip; an
endoscope for direct viewing of the biological material in the
vicinity of the distal tip of the catheter; or other devices.
FIG. 12 and FIG. 13 illustrate another embodiment of catheter 20. A
central lumen 74 extends the length of catheter 20. Distal end 76
of catheter 20 may include a smaller diameter lumen 78 relative to
lumen 74 positioned substantially parallel and adjacent to central
lumen 74. Lumen 74 permits the introduction of a device, such as
described above regarding device 42, through the center of catheter
20, as well as the passage of the fluid. Lumen 78 may be connected
to port 38, and may also be used to direct the fluid to tip
structure 26, such that the fluid passes through path means 48, 52,
54, 61 in tip structure 26, as discussed above in relation to FIGS.
2-10. Non-permeable layer 82, such as a plastic liner layer, may be
positioned between lumen 74 and lumen 78 to ensure that the fluid
in lumen 78 is directed through passages or path means 48, 52, 54,
61 in tip structure 26 to the exterior surface 50 of tip structure
26. Ring electrodes may also be used in this embodiment to direct
fluid to the exterior surface of tip structure 26 and catheter
20.
In operation, catheter body 22 of catheter 20 is percutaneously
inserted into the body. Catheter 20 may be articulable for ease of
insertion into the body. Catheter body 22 is positioned in the
heart or vascular system. Tip structure 26, as an electrode, may be
utilized to measure electrical potentials of the tissue and provide
information regarding cardiac signal measurement. Electrical
connection means 40 extends from tip structure 26, through port 36,
and is connected to monitoring equipment. Tip structure 26 may be
utilized to map, monitor, and measure the cardiac signals and
electrical potentials of the tissue, and locate arrhthymogenic
sites.
A biologically compatible fluid is introduced through port 38. The
fluid passes through a central lumen of catheter body 22 and is
directed to tip structure 26. The fluid passes through tip
structure 26 and/or ring electrodes 30 through path means 48, 52,
54, 61, in a manner determined by the embodiment of tip structure
26 used. The fluid perfuses tip structure 26 and forms a fluid
protective layer around exterior surface 50 of tip structure 26
and/or exterior surface 66 of ring electrodes 30. The fluid layer
formed around catheter tip structure 26 and/or ring electrodes 30
maintains biological materials, such as blood, at a distance from
catheter tip structure 26, thereby minimizing contact of catheter
tip structure 26 with the biological material, as well as cooling
tip structure 26. Since there is a consistent, controlled buffer
layer between the biological material and catheter tip structure
26, the coagulation of biological fluids on catheter tip structure
26 is reduced and the impedance or resistance to energy transfer of
the tissue in communication with catheter tip structure 26 is
regulated and minimized.
Once the site has been located by the monitoring of the
electrophysiological signals of the tissue, the ablative energy is
activated. As a result of the fluid protective layer, the transfer
of electrical energy to the tissue is enhanced. Increased
destruction of cardiac tissue also results from tip structure
cooling since larger and deeper lesions in the cardiac tissue are
achieved than have been previously possible.
The flow rate of the fluid over exterior surface 50 of tip
structure 26 or exterior surface 66 of ring electrodes 30 may be
accomplished in a controlled manner so that a thin fluid film is
formed around exterior surface 50, 66 of tip structure 26 and ring
electrodes 30. The maintenance of a controlled, stable, uniform
fluid film along substantially the entire exterior surface of tip
26 and ring electrodes 30 may be accomplished by using the various
embodiments of tip structure 26 described above having a
multiplicity of passages or path means 48, 52, 54, 61. Path means
48, 52, 54, 61 permits an even, consistent distribution of minute
quantities of a biologically compatible fluid over substantially
the entire tip exterior surface 50 or ring electrodes exterior
surface 66. The fluid can be pumped through tip structure 26, or
heat generated by the electrical or ablation process can be used to
expand the fluid and create a movement of fluid to the exterior
surface 50, 66 of tip structure 26 or ring electrodes 30. This
movement of fluid provides a buffer or protective insulating layer
between the exterior surface of tip structure 26 and the biological
material, such as blood, thereby reducing the coagulation of
biological materials on tip structure 26. In addition, the movement
of fluid over and around tip structure 26 may be aided by passages
or channels 56, 58 on exterior surface 50 of tip structure 26.
Cooling of tip structure 26 increases the lesion size produced by
the ablation means since the point of maximum tissue temperature is
likely moved away from tip structure 26, which allows for an
altered tissue heat profile, as further described below.
A control system may be included for controlling and regulating the
electrical potentials and temperatures in a manner that allows for
determination of the ablation effects in the tissue. It is possible
to control the distribution of tissue heating by controlling the
temperature of tip structure 26 and the radiofrequency voltage, or
other energy used, applied between tip structure 26 and a reference
electrode on the surface of the body. The voltage may be set to
achieve a desired electrical field strength, and the temperature of
tip structure 26 may be set to provide a desired temperature
distribution of the tissue. The temperature distribution will then
determine the size of the lesion, i.e., the denatured protein
dimensions in the myocardium.
The fluid flow rate can be regulated relative to biological
parameters, such as tissue temperature, by the temperature sensing
means. For instance, if the temperature of the tissue increases,
the fluid flow rate can be increased by the regulation of the fluid
infusion pump or gas needle valve. If the tissue temperature
adjacent tip structure 26 is not high enough, the fluid flow rate
can be decreased. This permits power to be set independently of
temperature. It is significant to note that it is normally not
necessary to remove the introduced fluid from the body.
Another advantage of the fluid layer buffering the surface area of
tip structure 26 and/or ring electrodes 30 is that the fluid layer
also cools the tissue adjacent tip structure 26 during ablation. In
addition, the fluid aids in maintaining the cardiac tissue adjacent
tip structure 26 in a cooler and potentially more conductive state,
which permits more electricity or ablative energy to enter the
tissue. As a result, larger lesions are produced because a larger
voltage can be applied, producing a larger electric field without
producing excessive temperatures and coagulum formation at the
tip/tissue interface. In addition, the greater the pressure of the
fluid, the more biological products are kept from the field of
influence of, or area surrounding, tip structure 26.
It is also possible to generate reversible affects of ablation by
use of a cooling fluid down the central lumen 28 of catheter 20 and
tip structure 26, or by use of a low temperature controlled or
elevational heating. An area in the heart tissue is quenched with a
cold or icy fluid to produce a tissue temperature of 0.degree. C.
to 30.degree. C., or heated with electrical energy with closed loop
temperature controls as described above to produce tissue
temperatures ranging from 40.degree. C. to 48.degree. C. Those cool
and warm temperatures slow the conduction of signals and
temporarily and reversibly eliminate the conduction pathways. This
technique may be advantageously used to see the affect on the
tissue before the tissue is permanently affected. The heart tissue
gradually heats or cools back to normal. This technique is also
advantageous since no catheter exchange would be required.
* * * * *