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The present invention relates to catheters, cannulae, and the like. More
particularly, the present invention relates to catheters that are
steerable through body cavities and aimable at obstructions, organs, or
tissue within the body from a position external to the body.
Some attempts have been made in the past to provide catheters having distal
ends which, when inserted into a body, are manipulatable to advance the
catheter through body cavities. See for example, U.S. Pat. Nos. 3,674,014
and 3,773,034. The catheter disclosed in U.S. Pat. No. 3,674,014 includes
permanent magnets and employs a magnetic field to bend the distal end of
the catheter. The catheter disclosed in U.S. Pat. No. 3,773,034 includes
fluid conduits and employs a fluid to bend the distal end of the catheter.
Other controlled devices are disclosed in U.S. Pat. Nos. 3,605,725 and
4,176,662. However, these prior devices are quite difficult to control and
manipulate.
Some work has previously been done to produce a catheter which is readily
insertable while being effectively anchorable in a body cavity. See, for
example, U.S. Pat. Nos. 3,729,008 and 3,890,977. In U.S. Pat. No.
3,890,977 the distal end of the catheter is formed into a desired shape by
using a material exhibiting mechanical memory that is triggered by heat.
By heating the mechanical memory material, the distal end of the catheter
is shaped to anchor the catheter within the body. However, the change of
the shape of the distal end in these prior devices is limited to a single
direction.
Other devices are known for guiding a catheter to a particular location
within the body. See for example U.S. Pat. No. 3,043,309.
According to the present invention, a catheter has a distal end for ready
insertion into a body, a plurality of temperature-activated memory
elements in the distal end, each memory element assuming a first shape in
response to temperature and being moved to a second shape in response to a
force, means for coupling each memory element to at least one other memory
element, and control means for controlling the temperature of each memory
element from a position adjacent the proximal end of the catheter to
deflect the distal end of the catheter in a plurality of directions to
steer or aim it within the body.
One object of the present invention is to provide a steerable catheter,
cannula, and the like which is easy to operate and steerable in a
plurality of different directions within the body.
Another object of the present invention is to provide an aimable catheter,
cannula, and the like which is easy to operate and which can be aimed at
obstructions, organs, or tissues in a plurality of different directions
within the body.
Yet another object of the present invention is to provide a catheter,
cannula, and the like which is aimable to direct the course of fluid,
light, medical instruments or a laser beam within the body.
Various other features and advantages of the present invention will become
apparent in view of the following detailed description of embodiments
thereof representing the best mode of carrying out the invention as
presently perceived, which description should be considered in conjunction
with the accompanying drawings, in which:
FIG. 1 is a perspective view of a steerable and aimable catheter, cannula,
and the like embodying the present invention;
FIG. 2 is a longitudinal cross-sectional view, partly broken away, of a
body cavity and the distal end of the catheter, cannula, and the like
shown in FIG. 1;
FIG. 3 is a perspective view of an embodiment temperature-activated memory
element employed in the catheter, cannula, and the like showing its
different shapes;
FIG. 4 is a transverse cross-sectional view of the distal end of the
catheter, cannula, and the like embodying the present invention taken
generally along section lines 4--4 in FIG. 2;
FIG. 5 is a longitudinal cross-sectional view of a body cavity showing the
aimable feature of a catheter, cannula, and the like embodying the present
invention;
FIG. 6 is a transverse cross-sectional view of the embodiment of the
catheter, cannula, and the like shown in FIG. 5 taken generally along
section lines 6--6 of FIG. 5; and
FIG. 7 is a perspective view of an embodiment of a plurality of
temperature-activated memory elements employed in the distal end of the
catheter, cannula, and the like to deflect or move the distal end for
steering and aiming thereof.
A catheter 10 embodying the present invention is generally shown in FIG. 1.
Catheter 10 includes an elongated tubular member 12 having a proximal end
14 and a steerable and aimable distal end 16. In the illustrative
embodiment, the tubular member 12 is formed of plastic, Teflon, or
cross-linked kynar or polyethylene. As will become apparent in the
description of catheter 10, it is desirable that tubular member 12 be
formed of a material that is flexible, that can withstand heat, and which
provides electrical insulation.
As best shown in FIG. 2, the tubular member 12 can have a lumen 18 for the
passage of fluid from the proximal end 14 to the distal end 16 and vice
versa. Typically, the tubular member 12 includes one or more holes or
openings 19 through which fluids are either injected into or drained from
a body cavity. Some cannulae may have an open distal end 16 for insertion
and withdrawal of medical instruments.
As shown in FIGS. 2 and 3, a plurality of temperature-activated memory
elements 20 are incorporated into the distal end 16 of the tubular member
12. It may be desirable to isolate the memory elements 20 from the body
cavity. The temperature-activated memory elements 20 preferably exhibit a
memory characteristic in response to temperature changes. The elements 20
may be wires or flat strips such as shown in FIG. 3. In the illustrative
embodiment, the temperature-activated memory elements 20 are formed of a
mechanical memory metal such as a nickel titanium alloy. While a nickel
titanium alloy is desirable, other metal elements having a memory
characteristic related to temperature could be used without departing from
the scope of the invention. Such metal elements should have a high
resistance to electric current so that heat is produced when current is
passed therethrough.
As shown in FIG. 3, the elements 20 have a proximal end 22 and a distal end
24. Each element 20 has a first shape represented by the broken lines in
FIG. 3 and a second shape represented by the solid lines in FIG. 3.
Illustratively, the first shape is an arcuate shape, and the second shape
is a straight shape. It will be appreciated that the first shape could be
any shape.
Each temperature-activated memory element 20 is originally annealed into
its first or preset shape (represented by the broken lines in FIG. 3).
Memory elements 20 are cooled and straightened to their second shape
(represented by the solid lines in FIG. 3) before incorporation into the
distal end 16 of the tubular member 12. When the elements 20 are again
heated to a predetermined transitional temperature they return to their
first or preset shape. By applying an opposing force to an element 20 that
has assumed its preset shape it can be moved to its second shape
(represented by the solid lines in FIG. 3). In the illustrative
embodiment, the predetermined transitional temperature is any temperature
above body temperature. For example, the predetermined transitional
temperature may be in the range of 100.degree. to 150.degree. F.
The elements 20 can either be directly incorporated into the distal end 16
of the tubular member 12 or can be carried on an electrically insulative
core 50. As will be discussed later, each memory element 20 must be
coupled to at least one other memory element 20 so that when one of the
memory elements is heated it applies a force to the other memory element
20.
The catheter 10 further includes an electronic control system 30 for
controlling current flow to vary the temperature of each
temperature-activated memory element 20 from a position external to the
body so as to deflect the distal end 16 of the tubular member 12 in a
plurality of different directions corresponding to the first shapes of the
elements 20. The control system 30 includes a power supply source 32 which
may be either AC or DC. The system 30 also includes a control device 34
which, in the illustrative embodiment, is similar to a "joystick" control,
tactile membrane switch, or ball controller. It will be appreciated that
various types of control devices 34 may be employed without departing from
the scope of the present invention.
The power supply source 32 is coupled through control device 34 to the
tubular member 12 by cable 36 and a coupling device 38. Further, the
temperature-activated memory elements 20 are electrically connected to the
control device 34 through cable 36 and coupling 38 by electrical wires 40
which are attached to the proximal ends 22 of elements 20 by conventional
means 42 such as soldering or crimping. Return or ground wires 44 are
attached to the distal ends 24 of elements 20 by conventional means such
as soldering or crimping 46. Return or ground wires 44 may be combined
into a single ground cable 48 as shown in FIG. 2. In the embodiment
illustrated in FIG. 2, the temperature-activated memory elements 20 are
carried on the exterior of the core 50 and ground wire 48 runs through the
interior of the core 50. Core 50 couples each memory element 20 to at
least one other memory element 20 so that when a memory element 20 assumes
its first shape in response to heat it applies a force to the other memory
element 20 coupled thereto. Other mounting arrangements could be used for
incorporating the memory elements 20 into the distal end 16 of the tubular
member 12 without departing from the scope of the present invention.
In operation, the distal end 16 of the tubular member 12 is inserted into a
body cavity 60 such as a blood vessel while memory elements 20 are
straight and at a temperature below the transitional temperature. At this
stage, each memory element 20 in its second shape for ready insertion of
the distal end 16 into the body cavity 60. The tubular member 12 is pushed
through cavity 60 until it reaches a desired branch 62 or 64 extending
from the cavity 60. Control device 34 is manipulated to apply an
electrical voltage or current to one or more of the memory elements 20.
Because of the high resistance of memory elements 20, heat is generated.
When a memory element reaches its predetermined transitional temperature
(i.e., a predetermined temperature above body temperature) the memory
element 20 assumes its first shape (as shown by the broken lines in FIG.
3), thereby deflecting or moving the distal end 16 of tubular member 12
into one of the desired branch cavities 62 or 64. Once the distal end 16
is in the branch 62 or 64, power can be removed from the memory element 20
to allow it to cool. While the memory element 20 is at a temperature above
its predetermined transitional temperature it remains relatively stiff in
its first shape. When the memory element 20 cools to a temperature below
its predetermined transitional temperature it becomes soft or pliable in
its first shape. After cooling, a voltage or current is applied to another
memory element 20 coupled to the cooled memory element 20 still in its
first shape. When the other memory element 20 reaches its predetermined
transitional temperature, it begins to assume its first shape and in doing
so applies a force to the memory element 20 coupled thereto to move it to
its second shape (as shown by the solid lines in FIG. 3). The catheter
tubular member 12 can continue to be pushed through the branch 62 or 64
until it is again desirable to turn or bend the catheter 10.
As illustrated in FIG. 4, four temperature-activated memory elements 20 may
be carried on the exterior of core 50. In the illustrative embodiment,
pairs of the memory elements 20 are shown diametrically opposed to each
other so that opposed elements 20 apply forces to each other when they are
heated. Thus, the distal end 16 may be deflected in at least four
different directions by applying an electrical current or voltage to one
of the memory elements 20. It will be appreciated that more or less than
four memory elements 20 may be utilized without departing from the scope
of the present invention. However, it should be noted that at least two
memory elements 20 are required. Further, it may be desirable to apply an
electrical voltage or current to more than one of the memory elements 20
simultaneously to increase the number of directions in which the distal
end 16 of the tubular member 12 may be deflected. The control system 30
may include means for regulating the application of current or voltage
applied to the memory elements 20 to allow virtually an unlimited number
of directions in which the distal end 16 may be deflected for the purpose
of steering the catheter tubular member 10 through body cavities. It will
be appreciated that a large number of wire memory elements could be
incorporated into the distal end 16 and a voltage or current applied to
one or more of the wires to deflect the distal end 16 in a desired
direction.
Another application for a catheter 70 embodying the present invention is
shown in FIGS. 5 and 6. Reference numerals from FIGS. 1-4 have been
applied to the catheter 70 shown in FIGS. 5 and 6 where the same or
similar parts are being used. Catheter 70 includes a tubular member 72
having a distal end 76. The distal end 76 includes a plurality of
temperature-activated memory elements 20 of the type previously described.
The same or similar control system may be employed in connection with the
catheter 70 in a body cavity 80 for the purpose of aiming the distal end
76 at an obstruction, organ, or tissue 82 within the cavity 80. The
catheter 70 may be anchored in the cavity 80 by a balloon 78. Once the
catheter 70 is anchored, the distal end 76 is aimed in one of a plurality
of directions to establish a course for the injection of fluid or a laser
beam at the organ or tissue 82.
As shown in FIG. 6, a core 90 formed of insulative material passes through
tubular member 72. Memory elements 20 are carried on the core 90 between
the core 90 and the tubular member 72. Core 90 serves to couple each
memory element 20 to at least one other memory element 20 in the manner
and for the purpose previously described. The hollow core 90 may include a
first tube 92 for carrying a fluid from the proximal end of the catheter
70 to the distal end 76. A return tube 94 may be included for extracting
fluid. It will be appreciated that either passage 92 or 94 may be used for
inserting a medical instrument into the cavity 80. Core 90 may also
include a transparent member 95 providing a lens for observing the
obstruction, organ, or tissue 82 and a bundle of fiber-optic lines 96 for
transmitting light or a laser beam to the distal end 76. Thus, in the
embodiment illustrated in FIGS. 5 and 6, catheter 70 has a distal end 76
which is aimable in a plurality of directions in accordance with the
present invention for the purpose of establishing a course for the
injection of fluid, light, or a laser beam at an obstruction, organ, or
tissue 82.
Another embodiment of an arrangement for the memory elements 20 is shown in
FIG. 7. The memory element arrangement 100 includes a plurality of memory
elements 20 coupled at their distal ends 24 by a thermally and
electrically insulative ring 102. Various materials, such as plastic, may
be used to construct the ring 102. Ground wires from each memory element
20 are channeled through a common ground wire conduit 44. Ring 102 serves
to couple the memory elements 20 to each other and performs a function
similar to cores 50 and 90. This arrangement facilitates the mounting of
the memory elements 20 in the distal end 16, 76 of the catheters 10, 70,
respectively.
While illustrative embodiments and uses of catheters, cannulae, and the
like embodying the present invention have been shown and described, it
will be appreciated that various modifications may be made to the
illustrative embodiments without departing from the scope of the present
invention.
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