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Claims  |
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Having described in detail various embodiments of my invention, what I
claim and desire to secure by letters patent in the U.S. Patent Office are
the following:
1. An electrode catheter system with temperature control adapted for making
radiofrequency heat lesions in a body and particularly the cardiac region
and having built-in thermocouple temperature sensor which can sense the
temperature of the heated body tissue, said electrode having the shape of
a elongated catheter with a distal end that is intended to be directed
into the bodily tissue, particularly near the cardiac region to be heated,
and a proximal end which is adapted to be connected to an external source
of radiofrequency energy and to an external thermocouple temperature
monitoring apparatus through a connection means, a portion of the
elongated catheter electrode that will be inserted into the body
comprising a flexible, tubular structure with an internal lumen and having
a longitudinally extending insulating material portion, said electrode
having at least one uninsulated conductive tip at its distal end from
which, when in use, radiofrequency current will flow to heat surrounding
tissue, said electrode having conductive means connecting said uninsulated
distal tip to said connection means located near said proximal end of said
electrode adapted for connection to an external source of radiofrequency
potential, and whereby said internal lumen can be used to insert stylet
means so that said catheter can be tunneled deep within the body through
blood vessels, whereby when in use, said uninsulated tip will be at said
radiofrequency potential, said electrode having a first metal element and
a second metal element, both metal elements running from said proximal end
to said distal end of said electrode, said two metal elements being the
two sides of a thermocouple pair, said two metal elements being embedded
within said longitudinally extending insulating material portion and
electrically insulated from each other over the length of said electrode
except at said distal end, the distal ends of said two metal elements
being electrically fused at said distal end of said electrode to form a
thermocouple junction in such a way that a portion of each of said distal
ends of said two metal elements and a portion of said fused junction are
part of an external surface of said uninsulated tip, the proximal ends of
said two metal elements near the proximal end of said electrode are so
adapted to be connected to an external thermocouple junction potential
measuring apparatus; whereby, when in use, said electrode is inserted into
the living body by inserting a stylet into said lumen means within said
catheter-shaped electrode, and thus said distal end of said electrode can
be worked into the proper position within the blood-carrying structure of
the living body, once in position so described, the radiofrequency
potential of said uninsulated tip of said electrode will cause a current
to flow in and thus heat up the tissue surrounding said uninsulated tip,
and said distal portions of said two metal elements and said portion of
thermocouple junction which are on the external surface of said
uninsulated tip will provide an intimate thermal contact with the heated
tissue adjacent to said external surface and thus a reliable measure of
the temperature of said adjacent tissue.
2. The electrode of claim 1 wherein said conductive means connecting said
uninsulated tip of said rf connection means, a portion of said uninsulated
conductive tip and one of said metal thermocouple elements are the same
continuous metal structure.
3. The electrode of claim 2 wherein said embedded two metal thermocouple
elements are insulated from external contacts from outside of the
electrode except at the distal tip and insulated from the internal lumen
of the electrode, such that when an insertion stylet is placed within the
lumen for insertion of the electrode within the body, said stylet will not
contact electrically or mechanically said two metal thermocopule elements.
4. An electrode catheter system with temperature control adapted for making
radiofrequency heat lesions in a body and particularly the cardiac region
and having built-in thermocouple temperature sensor which can sense the
temperature of the heated body tissue, said electrode having the shape of
a elongated catheter with a distal end that is intended to be directed
into the bodily tissue, particularly near the cardiac region to be heated,
and a proximal end which is adapted to be connected to an external source
of radiofrequency energy and to an external thermocouple temperature
monitoring apparatus through a connection means, a portion of the
elongated catheter electrode that will be inserted into the body
comprising a flexible structure having a longitudinally extending
insulating material portion, said electrode having at least one
uninsulated conductive tip at its distal end from which, when in use,
radiofrequency current will flow to heat surrounding tissue, said
electrode having conductive means connecting said uninsulated distal tip
to said connection means located near said proximal end of said electrode
adapted for connection to an external source of radiofrequency potential,
and whereby said catheter can be tunneled deep within the body through
blood vessels, whereby when in use, said uninsulated tip will be at said
radiofrequency potential, said electrode having a first metal element and
a second metal element, both metal elements running from said proximal end
to said distal end of said electrode, said two metal elements being the
two sides of a thermocouple pair, said two metal elements being embedded
within said longitudinally extending insulating material portion and
electrically insulated from each other over the length of said electrode
except at said distal end, the distal ends of said two metal elements
being electrically fused at said distal end of said electrode to form a
thermocouple junction in such a way that a portion of each of said distal
ends of said two metal elements and a portion of said fused junction are
part of an external surface of said uninsulated tip, the proximal ends of
said two metal elements near the proximal end of said electrode are so
adapted to be connected to an external thermocouple junction potential
measuring apparatus; whereby, when in use, said electrode is inserted into
the living body, and thus said distal end of said electrode can be worked
into the proper position within the blood-carrying structures of the
living body, once in position so described, the radiofrequency potential
of said uninsulated tip of said electrode will cause a current to flow in
and thus heat up the tissue surrounding said uninsulated tip, and said
distal portions of said two metal elements and said portion of
thermocouple junction which are on the external surface of said
uninsulated tip will provide an intimate thermal contact with the heated
tissue adjacent to said external surface and thus a reliable measure of
the temperature of said adjacent tissue. |
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Claims |
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Description |
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BACKGROUND TO THE INVENTION
Radiofrequency lesioning electrodes have common application in
neurosurgery. Examples of previous designs are illustrated in the present
author's Pat. No. 4411266. Typically these electrodes consist of a
cylindrical shaft insulated primarily over its entire length, with the
exclusion of the exposed distal tip. Thermocouple or thermistor wires were
located internal to the longitudinal shaft of the electrode, and a
thermocouple of thermistor sensor is located at the electrode tip. Such
electrodes are extremely important in neurosurgery and have been used
effectively there.
The present invention is a new and unique electrode configuration involving
a catherter-type electrode for use in cardiology. In that field, an
objective is to destroy portions of the nerve-carrying cardiac tissue,
such as the Hiss bundle, in which irregular pulse sources are present.
Also in the case of cardiac infarction where disturbance of the normal
trigger patterns and flow of electricity in the cardiac tissue is altered,
radiofrequency heating or other heating methods for ablation of the
trouble zones is indicated. Flexible cardiac catheters are well know in
the field of cardiology. These catheters in some cases are insulated over
their entire length and are directed through openings in the veins in the
groin and work up to the cardiac region. Once there, the exposed metal tip
of the electrode can be directed to a desired portion of the cardiac wall,
and a pulse or continuous amount of radiofrequency energy can be delivered
so as to heat the desired tissue. Here, as in the neurosurgical context,
faithful reproduction of the tissue heating is important, and also rapid
response to tell the surgeon about immediate changes of tissue is also of
great importance.
Therefore, one object of this invention is to implement an embodiment of
the flexible cardiac catheter for the purpose of cardiac tissue ablation
by radiofrequency heating with ultra-fast faithful recording of
temperature in the affected tissue.
DESCRIPTION OF THE FIGURES
FIG. 1 shows a sectional view of one embodiment of the invention
representing a flexible cardiac catheter.
FIG. 2 shows a sectional view of the tip detail of the catheter showing the
construction of the thermal sensor at one of the electrode surfaces.
FIG. 3 shows a further embodiment of the electrode with a single
thermocouple wire joining to a surface region of the catheter electrode
tip.
DESCRIPTION OF THE INVENTION
Referring to FIG. 1, one sees the sectional view of a typical embodiment of
the cardiac type catheter electrode. The electrode will have an insulative
exterior 2, except for exposed tip regions 1A, 1B, and 1C. Other
independent tip exposures could also be present. In the case of 1A, it is
connected via a conductor indicated as 1 along the length of the catheter,
and that in turn can be connected via contact 1' to a voltage source 3.
Each of the surface electrodes 1A, 1B, and 1C can be independently
connected to similar contacts as 1', or they can be all connected
together. Typically such contacts in catheter electrodes can be used for
recording or stimulation, and thus would be independent. For the purpose
of illustration, we have focused on electrode surface 1A, which is
connected electrically through conductor 1 to pin 1'. On surface 1A, we
have connected the temperature-measuring conductor 5, which runs the
length of the catheter to a junction element (for example thermocouple)
with 5, which is designated as 5". The junction, therefore, consists of
the end element 5" of the thermocouple element 5 and the end element
surface 1A, which is electrically connected to 1. Elements 5 and 1 could,
for example, be dissimilar metals such as copper and constantan or
stainless steel and constantan to form a thermocouple junction. For
instance, the conductor 1 could be a stainless steel, flexible, braided
wire running the length of the catheter, and its end portion designated as
1' could attach to the surface element 1A, which could be a stainless
steel ring. 1', which is the end portion of conductor 1 could then join to
the end portion 5' of constantan element 5. This forms the junction 4. The
junction 4 is on the surface and the exterior portion of the ring 1A and
forms part of that external surface. Because of the dissimilar metals,
there is a potential difference generated at junction 4 which reflects
itself as a voltage difference between pins 1' and 5' which connect to
stainless steel conductor 1 and constantan conductor 5 respectively. These
contacts can then in turn be connected through a radiofrequency filter 8
to a thermometric measuring box circuitry 7 so that the temperature
precisely at the surface 1A or correspondingly at the junction 4 is
measured. Element 1 could be another material, such as copper, as long as
it is dissimilar from the material 5 of the second conductor so that the
thermocouple junction potential will be generated.
We have described the electrical and geometric configuration for only the
electrical surface element 1A. Typically, the cardiac catheters have more
surface elements, such as 1B and 1C and so on. Between them are insulative
rings designated as 2' and 2" in the figure. Each of the electrical
surfaces could have such surface thermocouple junctions, and there could
be pairs of thermocouple connectors at the proximal end of the catheter,
such as 1' and 5' for the surface 1A.
FIG. 2 shows more detail in the section view of another embodiment to the
invention. Here we see the surface elements 1A, 1B, and 1C with insulative
portions 2, 2', and 2" as before. Now in this geometry there are two
thermometric independent conductors 5A and 5B which are run inside of the
catheter and, of course, insulated from each other over the entire length,
except for the junction point 4 where they meet at the surface of the
electrical contact 1A. There may be yet another conductor 1, not shown,
which runs the entire length of the catheter and provides the voltage V
from a source 3 as shown in FIG. 1. In this configuration, the two
thermometric connections 5A and 5B could be copper and constantan, and
still they meet at the surface to give a faithful, fast-acting
thermocouple readout just where you want it, namely at the surface of the
electrical contact 1A.
FIG. 3 shows the type of geometry which was illustrated in FIG. 1, only in
a bit more detail. Here we only have one surface electrode for
illustration designated as 1". It is connected to a conductive element
which runs the length of the catheter designated as 1. This could be a
helical, stainless steel, or other metal, coil helix that goes the entire
length of the catheter and ends up terminating on surface 1', and in fact
being integral with 1'. Alternatively, it could be a separate conductive
wire that is buried within the insulation 2 and runs the length of the
catheter structure and makes electrical contact with surface area 1". The
thermometric conductor 5 is insulated by insulation 9 and runs the length
of the catheter to terminate at the junction 4 at the surface of the
electrode 1A. This is a simplified kind of thermocouple junction, as it
involves only one thermometric carrier 5. This carrier could be, for
example, constantan, and the entire electrical conveyance 1 could be
stainless steel, making a stainless steel and constantan junction. The
simplicity of this geometry in FIG. 3 is ideal for rugged and
easily-configured tip. It would require only one thermometric line 5 in a
helical or otherwise simplified catheter with a single electrical
conductor 1. Of course, this geometry could be devised with multiple
electrodes; each one of the electrode contacts could have thermometric
reading.
One of the important features of this construction beyond its simplicity of
fabrication is the fact that it gives faithful and rapid temperature
reading just where you want it; namely, the place where you are making the
temperature reading in the tissue. Because the electrical junction, for
example in FIG. 3, designated as 4, is exactly at the surface of the
electrical surface 1A means that you have no thermal mass effects at the
tip, and the temperature that you read is precisely the temperature of the
adjacent tissue outside of the electrode. In the cardiac application, the
electrode surface will be used for heating via radiofrequency current
which emanates from the surface as produced by the voltage source 3 in
FIG. 1. The burst of energy from the radiofrequency source may be rapid,
and the heating also very rapid. Thus you want extremely rapid temperature
measurement to prevent unwanted damage to tissue or unfaithful recording
of temperature in a critical temperature region. One of the reasons why
the construction, as shown in this invention, is so important is that it
gives you the best possible thermometric reading just where you want it at
the surface of the electrode. It is also important to note that the
thermocouple junctions can be extremely small yet rugged in construction,
meaning that they have very little thermal mass and thus will not affect
the temperature reading of the tissue which you wish to measure.
There are many other orientations, configurations, and embodiments of this
general concept. In particular, the thermocouple or temperature measuring
conductor 5 could be embed | | |
