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The present invention relates generally to catheter assemblies, and more
particularly to a catheter assembly for diagnostic use or for use in
removing an obstruction in a blood vessel, body channel or body cavity.
The American Heart Association has estimated that approximately four
million people in the United States suffer from arteriosclerotic coronary
artery disease. Many of these people are likely to suffer or die from a
myocardial infraction, commonly known as a heart attack. Heart attacks are
in fact the leading cause of death in the United States. Thrombosis in the
coronary artery beyond the arteriosclerotic constriction is the usual
cause of heart attacks. A procedure which can open arteriosclerotic
constrictions, thereby permitting the normal flow of blood to the heart,
may reduce the many deaths and disabilities caused by heart disease.
Constrictions in the coronary artery are caused by a build-up of plaque,
which may be "hard" or "soft". Plaque consists of calcium, fibrous and
fatty substances. If the plaque is of recent origin or "soft", that is, it
has a low concentration of calcium, a "Gruntzig" balloon catheter may be
used to clear the artery. The "Gruntzig" catheter is inserted into the
constricted area of the artery, and the balloon is inflated to expand and
compress the plaque, thereby opening the artery and permitting an
increased flow of blood through the artery. The "Gruntzig" balloon
catheter is described in the following article: "Nonoperative Dilatation
of Coronary-Artery Stenosis", A.R. Gruntzig, M.D., A. Senning, M.D., and
W.E. Siegenthaler, M.D., The New England Journal of Medicine, Vol. 301,
No. 2, July 12, 1979. See also U.S. Pat. No. 4,195,637, Gruntzig, et al.,
issued Apr. 1, 1980.
The "Gruntzig" technique, however, does not work where the constriction in
the artery is very tight, where the plaque is "old" and hard, or where the
plaque forming the constriction has a high concentration of calcium and
thus is very hard. It is estimated that the "Gruntzig" technique can be
successfully used on only about 5% of the patients suffering from
arteriosclerotic coronary disease.
Accordingly, the present invention is directed to a catheter assembly which
can remove (a) plaque, especially when hard, and (b) operate in a very
constricted area of an artery. The catheter assembly of the present
invention may also be used to remove obstructions from other blood vessels
and body channels or cavities, as well as to view a region of a blood
vessel or a non-vascular body channel.
The present invention also provides a catheter assembly which is able to
temporarily interrupt the flow of blood to an occluded or constricted
region while such region is treated or observed.
The catheter assembly of the present invention includes a first or outer
catheter having distal and proximal ends, and a second or inner catheter
which is positionable within the first catheter. The second catheter has a
smaller diameter than the first catheter, and preferably, the second
catheter is more flexible. The second catheter is positioned within the
first catheter so that the second catheter can be shifted or moved with
respect to the first catheter. Also, the distal end of the second catheter
is extendable past the distal end of the first catheter. Inflatable means
such as an expandable balloon is affixed to the outer surface of at least
one of the catheters near the distal end thereof. When inflated, the
balloon sealingly engages the interior walls of the blood vessel or the
like in which the catheter assembly is inserted. This is done to stop the
flow of blood into the area of the blood vessel in front of the distal end
of the second catheter and thus to facilitate visualization of the
obstructed or constricted region.
A plurality of optical fibers extend through a portion of the second
catheter and terminate at a point within the second catheter near its
distal end. Usually one bundle of optical fibers is used for illuminating
and another bundle of optical fibers is used for viewing the area in front
of the distal end of the second catheter.
Where the catheter assembly is to be used to remove an obstruction in a
blood vessel, such as plaque material in the coronary artery or a clot, a
special fiber capable of transmitting energy in the form of a laser beam
extends through a portion of the second catheter and terminates near the
distal end thereof. An appropriate lens may be attached to that end of the
"laser fiber" located at the distal end of the second catheter. The lens
focuses and intensifies the laser beam. In order to remove the
obstruction, the laser has to deliver to the target area power sufficient
to destroy, vaporize or soften the obstruction.
Additionally, one or more channels may be provided within the catheter
assembly for removal of combustion material generated during laser
irradiation and for flushing of body fluids trapped between an occlusion
and the adjacent catheter assembly. Suitable flushing fluids for this
purpose are saline solutions, Ringer's solution, and the like. These
channels may also be used to infuse a radio-opaque dye in the region.
Appropriate positioning means may also be provided within the catheter
assembly for positioning the laser fiber, and the viewing and illuminating
optical fibers relative to the central axis of the catheter assembly.
The catheter assembly embodying the present invention may include fiber
optics for viewing and illuminating a body region, a fiber optic for
transmitting a laser beam to a region within the patient's body, or both
types of fiber optics, as desired. Alternatively, both types of fiber
optics may be omitted and the catheter assembly of the present invention
used to pretreat the plaque, occlusion or clot with a chemotherapeutic
substance. In this later embodiment, the catheter assembly could be guided
to the occlusion or clot by such means as fluoroscopy. Fluoroscopy could
also be used to guide the catheter assembly to the target area where the
assembly includes only a laser fiber optic.
The catheter assembly of the present invention will be described in more
detail hereinafter in conjunction with the drawings wherein:
FIG. 1A through 1C are schematic, side views, partly in section,
illustrating the positioning of the inner catheter within the outer
catheter of the catheter assembly of the present invention.
FIG. 2 is a schematic, sectional view of the catheter assembly of the
present invention.
FIG. 3 is a schematic, sectional view along the central axis of the inner
catheter of the catheter assembly of the present invention.
FIG. 4 is a schematic, sectional view of an alternative embodiment of the
catheter assembly of the present invention.
FIGS. 5 and 6 are schematic views, partly in section, of a positioning
means used with the catheter assembly of the present invention.
FIG. 7 is a schematic, sectional view along the central axis of the inner
catheter illustrating an alternative embodiment of the catheter assembly
of the present invention.
FIG. 8 is a schematic, side view of the catheter assembly of the present
invention wherein the inflatable means is affixed to the outer surface of
the outer catheter.
The present invention will be described in conjunction with its most
suitable use: the removal of plaque material from the coronary artery. The
catheter assembly of the present invention, however, can also be used to
remove occlusions, such as clots, in other arteries and veins. The present
invention is especially useful in very constricted areas of blood vessels
and for removing very hard material. Further, the catheter assembly could
be used where it is necessary to temporarily stop the flow of blood to
permit visual inspection and to achieve successful removal of an
occlusion. The catheter assembly could also be used without its associated
laser apparatus where it is simply desired to view an area of a blood
vessel, some non-vascular body channel, or the interior of an organ or
cavity. The present invention could also be used to remove obstructions
from non-vascular body channels; for example, it could be used to remove
bladder, kidney and gall stones.
Referring now to the drawings, in which like components are designated by
like reference numerals throughout the various figures, attention is first
directed to FIGS. 1A through 1C. FIGS. 1A through 1C show catheter
assembly 10 of the present invention positioned for use in removing plaque
92 from coronary artery 90. Catheter assembly 10 comprises a guide or
outer catheter 12 and a second or inner catheter 14. Guide catheter 12 has
been inserted into an arm, leg or other artery 96 to extend near orifice
94 of the coronary artery. The guide catheter is guided through such
artery to the orifice by procedures well known in the art, such as
fluoroscopy. Alternatively, catheter 12 may be an existing pre-formed
catheter or articulated endoscope, adapted as described herein.
Catheter 14 is positioned in coronary artery 90 by inserting it through
guide catheter 12. Catheter 12 guides catheter 14 from the point of
insertion, which is at the proximal end 12b of catheter 12, into coronary
artery 90. To facilitate movement of catheter 14 within guide catheter 12,
catheter 14 is more flexible than catheter 12. Catheter 14 also has a
smaller outside diameter than the guide catheter. The outside diameter of
catheter 12 is about 2.5 to 3.5 millimeters for use within the coronary
artery. For other blood vessels or body channels, the outside diameter of
catheter 12 may be selected accordingly. The outside diameter of catheter
14 is approximately 1.5 to 2.5 millimeters. In instances, where the
catheter assembly does not include optical fibers for viewing and
illuminating, the outside diameter of catheter 14 can be as small as about
1 to 2 millimeters.
In use, catheter 14 is inserted in and pushed through the guide catheter
until its distal end 14a extends beyond distal end 12a of the guide
catheter, see FIGS. 1A through 1C. Inflatable means 16, discussed in more
detail below, is affixed to inner catheter 14 at the distal end thereof.
The inflatable means is collapsed as the inner catheter moves through the
guide catheter, see FIGS. 1A and 1B. After distal end 14a of the inner
catheter has been positioned near plaque buildup 92 by such means as
fluoroscopy and the viewing and illuminating fiber optics, which are
discussed below, inflatable means 16 is inflated as shown in FIG. 1C.
Radio-opaque bands 56 may be located at distal end 14a so that the
position of distal end 14a and inflatable means 16 can be precisely
determined by use of the fluoroscope.
To illuminate stenotic obstruction 92, an optical fiber bundle comprising a
plurality of optical fibers 22 is provided within catheter 14, see FIGS. 2
and 3. Optical fibers 22 originate at an exterior intense viewing light
source, which is not illustrated, and extend from the proximal end 14b of
catheter 14 to a point within the catheter near its distal end 14a.
Optical fibers 22 are used to illuminate the area in front of the distal
end of catheter 14.
Catheter 14 further includes an optical fiber bundle 20 consisting of a
plurality of optical fibers for viewing the area in front of distal end
14a. Bundle 20 is connected to an appropriate eyepiece, which is not
illustrated, and extends from the proximal end 14b of catheter 14 to
terminate at a point within the catheter near distal end 14a. If desired,
a protective transparent shield may be provided over the distal end of
bundle 20. Viewing bundle 20 forms an image that is produced and viewed by
conventional means as in a medical endoscope. Bundle 20, which is offset
from central axis 17 of catheter 14, collects light through a tilted lens
32. Lens 32 permits observation of the central portion of the artery, the
surrounding area, and the occlusion.
A laser-beam transmitting fiber 26 for transmission of laser energy from a
laser source 34 is also carried by catheter 14. Laser-transmitting fiber
26 extends from proximal end 14b of catheter 14 to a point inwardly of but
near the distal end of catheter 14. Fiber 26 is preferably located along
the central axis of catheter 14, and may also be covered by a transparent
shield if desired.
Laser 34 is coupled to laser-transmitting fiber 26 by a lens 36, which is
either placed between the laser and the laser-transmitting fiber, as
illustrated, or which is incorporated into the optical fiber. The exterior
surface of laser transmitting fiber 26 is coated with an anti-reflective
coating for the laser wavelength of interest. A shutter 38 between laser
34 and lens 36 permits control of laser irradiation. Endoscopes used in
conjunction with lasers for the performance of surgery are discussed in
U.S. Pat. No. 3,858,577, issued Jan. 7, 1975, Bass, et al., and U.S. Pat.
No. 4,146,019, issued Mar.27, 1979, Bass, et al. The disclosures in these
two patents are hereby incorporated by reference.
Laser 34 has to deliver to the target area sufficient power at the
predetermined wavelength to destroy, vaporize or soften plaque material
92. The laser beam should be conducted through optical fiber 26 with as
little power loss as feasible. Additionally, the laser should interact
with the plaque material rather than with the surrounding normal tissue of
the artery or any infrared liquid that may be present. Several types of
lasers can be used, for example, argon-ion, carbon dioxide, and Neodynium
YAG lasers. Lasers having a wavelength capable of destroying or softening
plaque but without adverse effect on blood cells or tissue are preferred.
For lasers of certain wavelengths, for instance, carbon dioxide lasers,
some laser-transmitting guide other than an optical fiber might have to be
used.
To achieve the high intensities required for destruction of plaque material
92, the laser is focused by a short-focal length lens 28. Lens 28 is
either spaced from the end of optical fiber 26, or, as shown, affixed to
the end of optical fiber 26. Lens 28 may comprise a plurality of lenses.
The laser will destroy blood cells present and may produce blood clotting
in the area of the targeted occlusion. Clotting in the occluded coronary
artery would further compromise blood flow to the heart. Thus, laser
surgery in the coronary artery requires that blood flow to the targeted
occlusion be stopped. Catheter assembly 10 includes an inflatable or
expandable balloon 16 for temporarily stopping the flow of blood into the
area in front of the distal end of catheter 14. Blood flow in the coronary
artery, however, cannot be interrupted for more than 12 to 15 seconds
without endangering the patient's life. By temporarily interrupting the
flow of blood, blood can be excluded from the region, the obstructed or
constricted area can be viewed, and the obstruction can be successfully
removed. The region in front of the distal end of catheter 14 can also be
flushed with a solution, such as Ringer's or saline, to dilute any blood
present in that region. Perhaps, a gas such as carbon dioxide could also
be injected into this region to expand the artery, and to clear blood from
the ends of the optical fibers.
Inflatable balloon 16 is circumferentially affixed about the exterior
surface of catheter 14, and is located near the distal end of catheter 14.
Prior to opening shutter 38, balloon 16 is inflated to sealingly engage
the interior walls of coronary artery 90, thereby stopping the flow of
blood into the area of targeted occlusion 92, see FIG. 1C. The laser will
vaporize the occlusion within a time period of less than one second
depending upon the type and power of laser used. Afterwards, balloon 16
may be deflated to permit blood flow through the coronary artery, or if
time permits, catheter 14 may be extended further to remove or soften an
additional section of plaque before the flow of blood is restored.
As balloon 16 only has to stop the flow of blood and not expand the artery,
the balloon can be inflated by lower pressures and be constructed of less
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