Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2B410/714
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WIRE GUIDED LASER CATHETER
FIELD OF THE INVENTION
This invention relates to catheters and
techniques for delivering and applying laser energy
to a location within the human body.
BACKGROUND OF THE INVENTION
Although the theoeetical possibilities for the
medical use of laser energy have been recognized for
a long time, its practical use has been limited to
only a few types of procedures. Typically, the
procedures in which laser energy has been used for
treatment have been in readily exposed, easily
accessible portions of the body, such as the
patient's skin and eyes. While it has been
suggested for some time that laser energy might be
useful in the recanalization of obstructed blood
vessels to remove the obstruction from the blood
vessel, a satisfactory, practical system has not yet
been developed. A major obstacle in the development
of techniques for applying laser energy to blood
vessels has been in the problem of how to deliver
3~
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the laser beam precisely to the vascular site to be
treated and then, how to apply controllably the
laser beam so as to remove the biological material
causing the blockage without damaging or otherwise
adversely effecting the patient's vasculature. The
difficulties presented have been compounded further
by the dimensional limitations which must be imposed
on any catheter which is to be inserted into a blood
vessel, particularly narrow blood vessels such as
coronary arteries which may have lumens of the order
of 1.5 to 4.5 millimeters in diameter.
Among the difficulties is the manner of placing
and locating the distal end of the catheter so that
it is positioned properly with respect to the
obstruction. Prior proposals, which have included
the use of supplemental optical fibers to transmit
illuminating light into the blood vessel in
conjunction with other groups of fibers to permit
visual observation of the interior of the blood
vessel, are not practical because they are too large
and too stiff for use in narrow arteries. Another
difficulty which has been presented is that there
often may be materials such as blood, in the region
between the emission point of the laser beam at the
end of the fiber and the obstruction. Such material
may obstruct the optical path. The blood may become
charred at the distal emitting tip of the fiber
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which can result in overheating and destruction of
the optical fiber. Still another difficulty is that
such a catheter which is to be advanced to small,
distally located arteries must be very flexible to
be able to make sharp, short radius bends in order
to reach those arteries. The catheter also must
have a small diameter, yet must be capable of being
pushed and manipulated, from its proximal end,
without becoming bunched up or bent as it advances
within the patients blood vessels. A further, very
desirable feature of such a catheter is that it
should be capable of providing fluid communication
from the proximal to the distal end of the catheter,
to enable liquid infusion or to make pressure
measurements. The development of a practical
catheter which achieves the foregoing objects while
avoiding the above and other difficulties has proved
to be a substantial problem.
Although many laser catheters have been
proposed in the past, none has proved to be usable
to any practical degree. All suffer from one or
more of various difficulties. It is among the
general objects of the invention to provide a
practical and effective catheter system by which
laser energy can be delivered to selected sites in a
patient's blood vessels with precision and control.
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SUMMARY OF THE INVENTION
The catheter is capable of and is intended to
be used with a guide wire. A central lumen, which
receives the guide wire, extends fully through the
catheter and is open at the distal end of the
catheter. The catheter has a very small outer
diameter, of the order of 1.5 millimeters, and is
small enough to be advanced deeply into the
patient's more narrow blood vessels.
A plurality of optical fibers are contained
within the wall of the catheter. The distal end of
the catheter includes an optically transparent
cylindrical cap which covers and protects the distal
ends of the optical fibers. The cap has a central
aperture which defines the distal outlet aperture of
the lumen with the distal end of the cap defining an
annular, ring-like configuration about the
aperture. The distal ends of the optical fibers are
mounted securely with respect to the end cap so that
light emitted from the fibers passes through the
distal annular portion of the cap and is emitted
from the ring-shaped distal end face of the cap.
The proximal end of the catheter includes a
branch fitting from which extends a plurality of
tubes, there being one tube to receive the proximal
end of each optical fiber. The proximal end of the
each tube has a connector by which the optical
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fibers may be connected individually to a laser
light source. Each of the optical fibers is
independent of the other and each can be used and
controlled independently of the others should that
S be desired.
Another tube extendiny from the proximal
fitting at the proxilnal end of the catheter is in
; communication with the proximal end of the central
lumen of the catheter and provides access for a
guide wire. The guide wire may be a very small
diameter, steerable guide wire, such as that
described in Canadian Patent 1,208,096, issued
July 22, 1986. The cross sectional dimensions
and shape of the guide wire and the catheter lumen
are such that when the guide wire is in place,
adequate flow area will remain within the lumen to
permit pressure measurements to be taken in the
blood vessel beyond the distal end of the catheter
and also to permit liquids to flow through the lumen.
In another aspect of the invention the catheter
is constructed as to be highly flexible so as to be
adapted to follow relatively short radius, sharply
curved paths along the patient's vasculature. The
catheter includes a composite wall construction
which includes an inner core, through which the
central lumen is formed, and an outer sheath. The
sheath is not secured to the core and is permitted
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to slide and shift longitudinally with respect to
the core when the catheter is bent. The core is
formed to include a plurality of flutes which extend
longitudinally along the outer surface of the core.
The flutes receive the individual optical fibers.
The fibers are retained within the flutes by the
surrounding sheath which, although not secured to
the core, is dimensioned to cover the flutes and
prevent the fibers from shifting out of their
respective flutes. The fibers are freely shiftable
longitudinally within the flutes. When the catheter
is bent, all of the longitudinally extending
components are free to shift to minimize resistance
to bending. In addition, the flexibility of the
composite catheter is enhanced further by forming
the core in an articulated configuration. The core
is formed to include reduced diameter peripheral
notches at spaced locations along the core shaft.
The notchecl sections are more flexible and enable
the catheter to be bent to very small radius
curves. The flexibility of the catheter may be
varied along its length by varying the longitudinal
spacing of the notches.
It is among the objects of the invention to
provide a small diameter guidable laser catheter
which is highly flexible and maneuverable.
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Also among the objects of the invention is to
provide a laser catheter which can be placed with
the use of a guide wire.
Another object of the invention is to provide a
laser catheter having a central lumen adapted to
receive a guide wire and in which the lumen provides
fluid communication from the proximal to the distal
end of the catheter to permit pressure measurement
and liquid flow while the guide wire is in place in
the lumen.
A further object of the invention is to provide
a laser catheter of the type described in which the
tip of the fibers are isolated to protect the fiber.
Another object of the invention is to provide a
laser catheter having a plurality of optical fibers
extending through the catheter, for delivery of
laser enerc3y, in which the individual fibers are
provided with separate connective fittings and in
which the transmission of energy through the fibers
is controllable independently of the others.
A further object of the invention is to provide
a catheter of the type described in which the
objects of the invention are achieved within the
context of a small outer diameter catheter, of the
order of 1.5 millimeters diameter.
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DESCRIPTION OF THE DRAWINGS
The foregoing and other objects and advantages
of the invention will be appreciated more fully from
the following further description thereof, with
reference to the accompanying drawings wherein:
FIG~ 1 is a fragmented illustration of the
catheter having a guide wire extending therethrough;
FIG~ 2 is an isometric illustration of the
distal portion of the catheter, broken away and
shown in quarter section (enlarged);
FIG~ 3 is a longitudinal section of the distal
region of the catheter;
FIG~ 4 is a lonyitudinal illustration of a
section of the main core shaft with the catheter
sheath removed to illustrate the articulated nature
of the core shaft; and
FIG~ 5 is an enlarged cross-sectional
illustration of the catheter as seen along the line
5-5 of FIGo 3 with the position of the guide wire
within the lumen illustrated in phantom;
FIG~ 6 is an end view of the distal end of the
catheter as seen along the line 6-6 of FIG~ 3;
FIG~ 7 is a diagrammatic side view of the
distal tip of the catheter illustrating the pattern
of light rays emitted from the distal end of the
catheter;
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g
FIGS. 7A, 7B and 7C are diagrammatic
illustrations of the beams emitted from the catheter
having four optical fibers as seen along the image
planes indicated at 7A-7A, 7B-7B and 7C-7C of FIG. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 illustrates the catheter, indicated
generally by the reference character 10, with a
guide wire, indicated generally at 12, extending
through the catheter. The guide wire 12 is shown
with its distal end 14 projecting out of the distal
end of the catheter 10 and with its proximal end 16
extending out of and being exposed at the proximal
end of the catheter 10. The catheter 10 has an
elongate main portion 18 which, by way of example
only, rnay be of the order of 160 centimeters long.
The guide wire may be of the order ot 180
centimeter~s long, or more. As will be described in
further detail, the invention enables the catheter
to have I main portion 18 with an outer diameter of
the order of 1.5 millimeters. A branch fitting 20
is molded securely to the proximal end of the main
portion 18 of the catheter 10 and a plurality of
tubes 22 extend proximally from the fitting 20. The
tubes 22 are intended to carry optical fibers,
described below, each tube 22 being provided with a
single fiber and having a connector 24 at its
proximal end by which the fiber within each of the
tubes 22 may be connected to a source of laser light.
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The catheter 10 includes an additiohal flexible
tube 26 extending yroximally ~rom the fitting 20
which communicates with a lumen extending through
the catheter through which the guide wire 12 may be
passed. The tube 26 has a fittiny 28 on its
proximal end. Fitting 28 may be a Luer-Lok fitting
to enable the tube 26 to be easily and quickly
connected to liquid infusion devices and/or pressure
monitoring devices. The fitting 28 can be connected
to a conventional Y-fitting to permit the guide wire
12 to be controlled while also permitting liquid
infu~lon and pressure monltoring.
The maln portion 18 of the catheter 10 includes
an inner elongate core 30 which is surrounded by an
outer elongate sheath 32. As shown in ~urther
detail ln FIGS. 2-5 the inner core 30 ha~ a lumen 34
which extends centrally along and wit~lin the core
30. The lumen 34 may be circular in cross section
although in the preferred embodiment a non-circular
cross section is preerred, such as the four-lobed
shape shown in FIG. 5 having alternate lands 36 and
groove-like lobes 38. The lobes 38 cooperate with
the guide wire 12 which has a circular cross section
(illustrated in phantom in FIG. 5) to define an
enlarged cross sectional ~low area in the space
between the guide wire 12 and the inner,
lumen-de~ining surface of the core 34. The guide
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wire 12 and core lumen 34 are arranged to provide a
clearance within the lumen 34 to permit liquid to
flow and pressure measurements to be made through
the lumen 34 while the guide wire 12 is in place in
the lumen. The proximal tube 26 is connected within
the fitting 20 to the core 30 so that the lumen 34
is in communication with the lumen of the tube 26.
The core 30 also is provided with a plurality
of longitudinally extending circumferentially spaced
flutes 40. Each of the flutes 40 receives waveguide
means, such as an optical fiber 42 adapted to
transmit radiant energy, such as laser light. The
optical fibers 42 are not secured within the flutes
40 and are permitted to shift longitudinally within
the flutes as the catheter is bent. The distal ends
of the fibers 42 are secured within the distal
portion of the catheter, in a manner which will be
described. The proximal ends oE the fibers ~2 pass
through the fitting 20, extend through the flexible
tubes 22 and are secured at their proximal ends
within the optical connectors 24. The tubes 22 are
secured within the fitting 20 and the fitting is
formed to provide a smooth transition and passage
for the fibers 42 from the flutes 40 through the
fitting 20 into the tubes 22.
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The outer sheath 32 covers the core 30 and
fibers 42 and serves to retain the fibers 42 within
the flutes 40. Except for its connections to the
catheter at its proximal and distal ends, the sheath
32 also is not attached to the core 30 or to the
optical fibers 42. Thus, there are no points of
attachment along the length of the catheter between
the core 30, optical fibers 42 or sheath 32 which
enhances the high degree of flexibility of the
catheter by minimizing internal resistance to
bending of the catheter.
The sheath 32 preferably is formed from a heat
shrinkable material, such as PTFE, and is heat
shrunk about the core 32, but not to a degree of
tightness which would impair the freedom of the
sheath and core to shift with respect to each other
when the catheter is bent. By way of exan~ple, the
core may have a diameter of the order of .046~ and
the sheath may have an inner diameter of about .050
and a wall thickness of about .003~, thus leaving a
very slight clearance between the core and sheath.
The flexibility of the catheter is enhanced
further by forming the core 30 so that it defines a
series of articulated segments. FIG. 4 illustrates
a portion of the core from which it may be seen that
the core is provided with a plurality of
longitudinally spaced, circumferential notches 44.
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The notches separate and define the core into a
plurality of serially arranged core segments 46
connected by smaller diameter and shorter connective
segments 48. The arrangement of articulated core
segments 46 increases the flexibility of the core 30
and, therefore, increases the flexibility of the
composite catheter. The connective segments 48 are
smaller in diameter and present less resistance to
bending so that a bending force applied to the
catheter will cause the core to bend at the
connective segments 48. The connective segments 48
may be spaced in equal distances along the length of
the catheter to provide a uniform degree of
flexibility for the catheter along its length.
However, if it is desired to vary the flexibility of
the catheter, at any location, that may be achieved
by varying the spacing of the connective seg~ents
48. By spacing the segments 48 closer to each
other, the resulting catheter segment will have a
higher degree of flexibility than where the spacing
is greater and in where the length of the core
segments 46 is laryer. For example, it may be
desirable to provide a catheter in which the distal
region is more flexible than the proximal portions
so as to permit the distal region to be bent into
sharper radius curves. Variations in the
flexibility of the catheter also may be achieved by
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varying the length of the connective segments 48 as
well as the core segments 46. By way of example, in
a catheter having the dimensions described above the
core segments 46 may be between about one to four
millimeters long and the connective segments may be
one-half to one millimeter in length.
The core 30 preferably is formed from a
material having a relatively low coefficient of
friction, such as PTFE, to reduce resistance of the
guide wire within the lumen 34. The guide wire
preferably is also coated with a low friction
material such as PTFE to further reduce friction
between the two.
The core 30 preferably is provided with
ra~iopaque stripes 35 which extend lengthwise of the
core. The stripes 35 may be formed by radiopaque
materials added to the resin from which the core is
extruded according to procedures well known in the
art. In the preferred embodiment a plurality of
radiopaque stripes 35 are formed between adjacent
flutes 40. The radiopaque stripes 35 preferably are
formed only on the outer surface of the core so that
the inner surface may remain defined completely by
the low friction material. It may be noted that the
radiopaque stripes are interrupted at the notches
44. The resulting stripe, however, presents a
sufficiently continuous radiopaque image as to be
effective in visualizing its position under
fluoroscopy.
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The distal ends of the optical fibers 42 are
secured together by a fiber holder 50 which is
secured to the fibers 40 at their distal ends. The
fiber holder 50 is contained within and also is
secured to an optically transparent distal cap 52
which is formed from an optical glass or crystalline
equivalent which is transmissive to the wavelength
of radiant energy with which the catheter is to be
used. The cap serves to isolate the fibers 40 from
the vascular environment and protects them from
exposure to biological material.
The fiber holder 50, shown also in FIG. 6,
preferably is formed from a radiopaque material,
such as stainless steel or a more radiopaque
material such as platinum. The fiber holder 50 is
cylindrical and is provided with a central aperture
54 which preferably is substantially about the same
size as the lumen 34 in the core 30. The central
aperture 54 may be circular or lobe shaped, although
a circular aperture 54 may be used in a catheter in
which the central lumen 34 is lobe shaped as shown
in FIG. 5. The fiber holder 50 is provided with a
plurality of longitudinally extending holes 56 which
extend through the wall of the holder 50 and
receive, in a snug fit, the distal ends of the
optical fibers 40. The distal face 58 of the
combined fibers 40 and fiber holder 50 is polished
flat to butt flush against an annular shoulder 60
formed in the optically transparent cap 52.
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The cap 52 is cylindrical and has the same
outer diameter as the sheath 32 so that they may
define a smooth and continuous consistent outer
diameter. The cap 52 has an enlarged bore 62 formed
in its proximal end. The bore terminates at and
defines the internal shoulder 60 and a smaller
diameter central aperture 64 is formed in the distal
end of the cap 52. The central aperture 64 may be
the same diameter as the aperture 54 in the fiber
holder 50 to provide a smooth and continuous passage
which opens at the distal tip of the catheter.
However, the central aperture 64 may be somewhat
narrower than the lumen 34 as long as sufficient
clearance is provided about the guide wire so as not
to adversely interfere with fluid flow and pressure
measurement. Some restriction in the flow area can
be tolerated at the distal tip as long as the
restriction extends over a relatively short length~
as would be the case if the openings 64 and 54
presented somewhat of a narrowed or partly
restricted flow area.
The cap 52 is secured, as by an epoxy adhesive,
to the fiber holder 50 and also to that portion of
the core 30 and the fibers 42 which are disposed
within the proximal end of the cap 52. The distal
end of the sheath 32 is simply butted against the
proximal end of the cap 52 and need not be
adhesively connected to the cap 52.
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By way of example the cap 52 may be formed from
a pair of Pyrex brand glass cylinders which are
fusable to each other. l'hus, the cap 50 may be
formed from an elongate relatively large diameter
Pyrex glass sleeve and a relatively short, smaller
diameter Pyrex glass sleeve, the smaller sleeve
fitting within and being fused to one end of the
outer sleeve. The end where the two sleeves are
joined defines the relatively thick walled distal
segment 72. The faces 60, 74 may be polished so as
to be optically flat. The foregoing arrangement
serves to position securely the distal ends of the
fibers 42 and in a manner which completely protects
and isolateq the flbers 42 from expoQure to and
contact with biological material.
In order to maximize the flexibility of the
catheter it is preferred to use relatively few
optical fibers. The beam pattern elnitte~ by the
catheter preferably should diverye to deEine a
diameter slightly beyond the end of the catheter
which is just slightly greater than the diameter of
the catheter so that the hole formed through the
biological material by the laser energy will be
large enough to permit the catheter to be passed
through it. Moreover, it is peeferred to accomplish
that with a relatively few number of optical fibers
so as not to impair the high degree of catheter
* a trade mark of Corning Glass Works
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flexibility which is preferred. A catheter having a
very small diameter, of the order of 1.5 millimeters
can achieve these objectives using an arrangement of
four optical fibers equiangularly spaced about the
central axis of the catheter. It should be
understood, howevee, that the advantages of the
invention can be achieved using somewhat more, or
possibly even fewee than four optical fibers,
although it is preferred to maintain the number at
the minimum required in order to form the desired
beam pattern.
FIG. 7 illustrates, diagramatically, the beam
pattern of a pair of diametrally opposed fibers.
The beam as defined by l/e2 radius is suggested by
the ray lines 70 in FIG. 7. ~he beam from each
individual fiber 42 is emitted from the distal face
of the fiber 42 and enters the distal segment 72 of
the cap 52 through the face defining the shoulder
60. The beam is divergent and, in the illustrative
embodiment, may have a half angle of the order of
between about 6 to 16 , depending on the numerical
aperture of the fiber. The diverying beam from each
of the fibers 42 exits from the distal emission face
74 at the end of the cap 52. FIGS. 7A, 7B and 7C
illustrate the beam pattern, in cross section, as
seen along the image planes 7A, 7B and 7C in FIG.
7. At the emission face 74 of the cap 52 the beams,
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in the illustrative embodiment, are still separate.
At the plane 7B-7B the beams have further diverged
and have begun to overlap. At the plane indicated
at 7C-7C the beams have overlapped and define an
envelope 73 having an outer diameter which is
slightly greater than the diameter of the catheter.
Preferably the beams 70 have overlapped to merge and
fill in a continuous pattern within a distance from
the distal face 74 which is approximally equal to
the outer diameter of the catheter, about 1.5
millimeters in the illustrative embodiment. The
length of the distal segment 72 preferably is
determined so that the distance between the distal
face 74 of the cap 52 and the substantially
filled-in image plane is as desired.
In another aspect of the invention the optics
at the distal end of the catheter are arranged to
minimize re-reflection. In that regard it should be
understood that some of the light emitted from the
catheter may be re-reflected by the biological
material within the blood vessel. Additionally,
light in the infrared portion of the spectrum may be
radiated from biological material which is heated by
the absorption of radiant energy. Re-reflection is
undesirable because the re-reflected light and
emitted IR radiation may be absorbed by the optical
fiber and other components at the distal end and may
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cause them to overheat and possibly be destroyed.
In order to protect the device from re-reflection
and from emitted IR radiation the distal face 58 of
the fiber holder 50 and the distal ends of the
fibers 42 are highly polished to provide a
reflective surface. Light which is reflected or
emitted from the biological tissue back toward the
catheter will be re-reflected by the face 58 and
thereby returned toward the biological material.
Additionally, it is preferred to provide an
anti-reflection coating on the proximally facing
shoulder surface 60 of the cap to maximize
transmission of light distally through the surface
60.
The catheter may be used in a number of
protocols depending on the preference of the
physcian and the vascular anatomy to be treated.
For example, the catheter 10 may be preassembled
with the guide wire 12 extending through the
catheter, with the distal tip of the guide wire
retracted in the distal end of the catheter. The
combined catheter and guide wire then may be
advanced together through a previously placed guide
catheter which will have been placed so that its
distal tip will be at the entry to a coronary artery
to be treated. The distal end of the combined
catheter and guide wire then may be advanced
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slightly into the coronary artery and then the guide
wire may be advanced, alone, through the artery.
The guide wire 12 may be manipulated to advance
selectively into the arterial branch where the
stenosis to be treated is located. Once the guide
wire has been placed, the catheter can be advanced
over the guide wire and will follow the guide wire
to bring the distal end of the catheter to the
intended site. The positioning of the guide wire
and the catheter may be monitored fluoroscopically.
Additionally radiopaque dye may be injected through
the catheter lumen 34 at any tirne during the
procedure when it is desired to visualize
fluoroscopically the coronary anatomy.
Liquids, such as radiopaque dye, may be
injected at any time even while the guide wire is in
place. Flushing liquids, such as saline also can be
delivered and liquid and debris can be aspirated
through the catheter. Similarly, arterial pressure
measurements may be taken at any time even while the
guide wire is in place. The catheter is advanceable
easily over the guide wire and is highly flexible so
as to be capable of following any curve or bend in
the guide wire necessary to follow the contour of
the patient's vasculature. Once the catheter has
been advanced to the desired location laser energy
may be applied through the optical fibers and
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delivered to the site to be treated. The laser
energy may be applied simultaneously through all of
the optical fibers 42 or it may be applied
selectively through the individual fibers.
Thus, the invention provides a catheter and
system for delivering laser energy to remote and
difficult to reach regions of a patient's
vasculature. The invention enables a laser catheter
to be placed with the aid of a guide wire and is
constructed to be highly flexible so as to be
capable of making sharp, small radius bends. The
system enables pressure measurement and liquid
infusion without requiring withdrawal of the guide
wire. Moreover, these and other advantages are
achieved within a very small diameter catheter.
It should be understood, however, that the
foregoing description of the invention is intended
merely to be illustrative thereof and that other
embodiments and modifications may be apparent to
those skilled in the art without departing from its
spirit.
Having thus described the invention what we
desire to claim and secure by lettees patent is:
