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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for use in dilating
occluded blood vessels. The invention is particularly concerned with such
a method and apparatus wherein dilatation is achieved through means of a
balloon element which is initially inverted within the distal end of a
catheter and, in use, extruded through and expanded within the occlusion
being treated. The invention is intended for use in treating either
arterial or venous occlusions.
Prior art efforts for the treatment of occluded blood vessels have relied
primarily upon the employment of bypass vessels or some surgical technique
whereby the occlusion is physicially removed from the vessel being
treated. Another recent technique for treating occluded vessels relies
upon the insertion of some type of an instrument into the vessel to dilate
the occlusion through a stretching or compressing process. The present
invention is concerned with a technique of the latter type.
A principal problem with the employment of techniques wherein instruments
are inserted into the vessel to effect dilatation by compression or
stretching is that the instruments may damage the vessel and/or dislodge
material therefrom. Another problem with such techniques is that it has
been very difficult to place the instruments used therefor in highly
occluded or small diameter vessels. These problems have resulted primarily
from the construction and size of the instruments. In one such technique,
the instruments take the form of progressively larger catheters which are
successively forced through the vessel being treated. In another
technique, the instruments have taken the form of an inflatable catheter
which is forced into place within the occluded area to be treated and,
once in place, inflated. These prior catheters, although flexible, are
necessarily somewhat hard and inelastic, in order to enable the catheter
to be advanced large distances through the arterial or venous systems. The
inherent hardness of these catheters contribute to the problems of vessel
damage and material dislodgement mentioned previously.
SUMMARY OF THE INVENTION
The present invention relies on an apparatus and method wherein a highly
flexible balloon is inverted within the distal end of a flexible catheter
and everted from the catheter for extrusion through the occluded section
of the vessel to be treated. The balloon and catheter are so designed that
the balloon may symmetrically evert from the catheter and extrude through
the occlusion in anisotropic fashion in advance of substantial lateral
expansion of the balloon. Eversion of the balloon from the catheter is
effected through means of the application of internal fluid pressure to
the catheter. Once the balloon is in place within the occluded section of
the vessel, continued fluid pressure is applied to laterally expand the
balloon and dilate the occlusion. The process of laterally expanding the
balloon to dilate the occlusion may be pulsed by repeatedly increasing and
decreasing the fluid pressure within the catheter. In the preferred
embodiments, a cord element extends through the catheter and is connected
to the balloon to reinvert the balloon within the catheter after treatment
of the occlusion is complete.
A principal object of the invention is to provide an inflatable catheter
for use in dilating arterial or venous occlusions without injury to the
vessel being treated or dislodgment of material therefrom.
Another object is to provide an inflatable catheter for use in dilating
arterial or venous occlusions, such that a soft, inflatable dilating
portion is advanced through the occluded area in a gentle manner, with no
need to force a hard catheter through the occluded area prior to
dilatation.
Another and more specific object is to provide such a catheter wherein the
inflatable element is initially inverted within the end of the catheter
and, upon being placed in close proximity to the occlusion to be treated,
everted for extrusion through the occlusion in advance of substantial
lateral expansion.
Still another object of the invention is to provide such a catheter wherein
the inflatable element is evertable from the catheter in a symmetrical
fashion.
Yet another object of the invention is to provide such a catheter wherein a
mechanism is contained within the catheter for reinverting the inflatable
element after its expansion for dilatation purposes.
Another object related to the latter object is to provide such a mechanism
which assures that the inflatable element, or fragments thereof, cannot
separate from the catheter.
Another object is to provide such a catheter wherein the reinversion
mechanism includes a secondary catheter extending through the primary
catheter and the inflatable element to enable the taking of pressure
measurements or the making of injections without removal of the catheter
from the vessel being treated.
A further object of the invention is to provide an inflatable catheter
which enables the dilatation of select limited areas of the vessel being
treated.
A further specific object of the invention is to provide an inflatable
dilatation catheter wherein the catheter body may be of a diameter less
than the lumen of the vessel being treated and the inflatable element is
initially inverted within the distal end of the catheter.
A further object of the invention is to provide an inflatable dilatation
catheter which may be extruded into place within an occluded section of
the vessel being treated without materially disturbing the occlusion and,
once in place, may be repeatedly laterally expanded and contracted to
subject the occlusion to pulsing dilatation.
The foregoing and other objects will become more apparent when viewed in
light of the following detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating an occluded vessel in the process
of being treated by a first embodiment of the invention, with parts of the
vessel broken away and shown in section;
FIG. 2 is an elevational cross-sectional view illustrating the catheter of
the first embodiment and a phantom line representation of a vessel to be
treated, as the catheter would appear when being directed to an occluded
section of the vessel;
FIG. 3 is a cross-sectional elevational view similar to FIG. 2,
illustrating the first embodiment catheter in association with a vessel
being treated, as the inflatable element appears when first extruded
through the occluded section of the vessel;
FIG. 4 is a cross-sectional elevational view, similar to FIG. 3,
illustrating the inflatable element, after it has expanded to dilate the
occlusion being treated;
FIG. 5 is a cross-sectional elevational view, similar to FIG. 4,
illustrating the inflatable element after completion of the dilatation
treatment and reinversion of the element into the catheter;
FIG. 6 is a cross-sectional elevational view of a second embodiment of the
catheter with solid lines showing the inflatable element in the inverted
condition and phantom lines showing the inflatable element in progressive
stages of eversion and lateral expansion;
FIG. 7 is a cross-sectional elevational view illustrating the catheter of a
third embodiment of the invention and a phantom line representation of a
vessel to be treated, as the catheter would appear when being directed to
the occluded section of the vessel;
FIG. 8 is a cross-sectional view, similar to FIG. 7, illustrating the third
embodiment catheter in association with a vessel being treated, as the
inflatable element appears when first extended through the occluded
section of the vessel;
FIG. 9 is a cross-sectional elevational view, similar to FIG. 8,
illustrating the third embodiment inflatable element after it has expanded
to dilate the occlusion being treated; and
FIG. 10 is a cross-sectional elevational view, similar to FIG. 9,
illustrating the third embodiment inflatable element after completion of
the dilatation treatment and reinversion of the element into the catheter.
DESCRIPTION OF THE FIRST EMBODIMENT
FIG. 1 illustrates a blood vessel 10 partially occluded by an occlusion 12.
As shown, the vessel takes the form of an artery and the occlusion is what
is commonly known as an arteriosclerotic plaque or atheroma. This is the
type of adhering occlusion with which the inventive apparatus and method
is expected to find primary application. It should be understood, however,
that the invention is applicable in treating other types of occluded
vessels wherein dilatation is desired. For example, the invention may be
used in treating occlusions resulting from fibromuscular-dysplasia in
veins.
The principal elements of the first embodiment apparatus shown in FIG. 1
comprise: a flexible generally inelastic catheter 14 fabricated of an
inert polymer material such as Dacron; a balloon element 16 fabricated of
a highly elastic resilient material, such as latex, said element having a
mouth portion (attachment shoulder) 18 peripherally secured to the distal
end of the catheter 14 and a body portion 20 initially inverted within the
catheter; a cord 22 extending through the catheter 14 and connected at one
end of the body portion 20 of the balloon element; a syringe 24 connected
to the proximate end of the catheter 14 through an intermediate tubular
coupling 26, said syringe having a cylinder 28 with a positive
displacement piston plunger 30 sealingly and slidably received therein,
which plunger has the proximate end of the cord 22 connected thereto; a
flexible reservoir 32 removably connected in fluid communication with the
interior of the coupling 26 through means of a tubular lateral extension
34 formed as part of the coupling; and a selectively operable shut-off
valve 36 interposed in the extension 34. The catheter may vary in length,
depending upon the application in which it is intended to be used, and
commonly measures up to 30 inches in length. Cross-sectional dimensions of
the catheter may vary, depending upon the application, and are generally
chosen so that the outside diameter of the catheter is equal to about
one-half the inner diameter of the nonoccluded lumen of the vessel being
treated. In one typical embodiment, the catheter and associated balloon
element have the following dimensions:
______________________________________
Catheter Body Dimensions
______________________________________
O.D.: .085 inches
I.D.: .060 inches
Length: Variable up to about 30 inches
______________________________________
______________________________________
Balloon Element Dimensions When
Detached from Catheter
______________________________________
Reduced Diameter Body O.D.:
.034 inches
Reduced Diameter Body I.D.:
.020 inches
Reduced Diameter Body
Thickness: .007 inches
Attachment Shoulder O.D.:
.14 inches
Attachment Shoulder
Thickness: .007 inches
Attachment Shoulder Length:
.26 inches
______________________________________
______________________________________
Attached Balloon Dimensions
______________________________________
Uninflated Inverted Length:
.20 inches
Inflated Length After
Eversion: .70 inches
Inflated O.D.: .16 inches
______________________________________
In the preferred embodiment, the length, wall thickness, and O.D. of the
balloon element are such that the element does not drag on the inner walls
of the catheter when the element is everted out of the catheter
symmetrically. The balloon element should ideally have a length no more
than about 25 times the I.D. of the catheter.
The material and relative thicknesses of the balloon element are chosen so
that expansion of the balloon element out of the end of the catheter takes
place in anisotropic fashion with the element first everting out of the
catheter in advance of substantial lateral expansion and then, after
eversion, laterally expanding in response to the continued exertion of
fluid pressure internally of the catheter. Once everted out of the
catheter, the balloon element is designed to laterally expand to an
outside diameter equal to or greater than the I.D. of the nonoccluded
vessel treated. Although such characteristics may be achieved through the
employment of an elastomeric balloon element such as that of the foregoing
example, it is anticipated that similar characteristics may be achieved by
fabricating the balloon element of a folded generally inelastic flexible
material, such as polyvinyl chloride, which is adapted to first evert to
an extended condition and then unfold to a laterally expanded condition.
The cord 22 should be flexible and generally inelastic and of such a length
that it will not restrict eversion of the balloon element 16 as it is
moved from the inverted condition shown in FIG. 2 to the extended
condition shown in FIG. 3. To permit such unrestricted extension of the
balloon element, the cord is ideally provided with a slack portion, as
shown in the cylinder 28 illustrated in FIG. 2. The cord should also,
however, be of such a length that retraction of the plunger 30 beyond a
predetermined limit functions to reinvert the balloon element within the
distal end of the catheter, as shown in FIG. 5.
The catheter 14, syringe 24 and reservoir 32 contain an incompressible
fluid F. Preferably, this fluid is radiopaque in order to facilitate the
radiographic monitoring of the position of the catheter and progress of
the dilatation procedure. The valve 36 provides means whereby this fluid
may be selectively captured between the balloon element 16 and the piston
30 (i.e., when the valve is closed) or permitted to charge into and out of
the reservoir 32 (i.e., when the valve 36 is open). In either condition,
however, the reservoir 32 assures that the catheter 14 is always filled
with fluid. Prior to the dilatation procedure, both the catheter and the
reservoir are purged of air and filled with fluid. The reservoir is
detached from the catheter, both portions are separately filled, and the
reservoir and catheter are reattached. With the valve in the open
condition, as it would be in the FIG. 4 condition, the piston plunger 30
may be retracted to tension the cord 22 and, thus, draw the balloon
element 16 into the reinverted condition within the catheter. With the
valve 36 closed, the piston plunger 30 may be compressed to subject the
catheter 14 to internal pressure and, thus, evert the balloon element out
of the end of the catheter, as shown in FIG. 3. In the preferred mode of
operation, the piston plunger 30 is depressed to a predetermined degree
prior to closing of the valve 36 to provide for carefully controlled
expansion of the balloon element by depression of the plunger and assure
that the cord 22 is slack throughout eversion of the balloon element out
of the catheter. Suitable indicia may be provided on the syringe 24 to
index the point of plunger travel at which the valve 36 should be closed.
The preferred construction also includes a shoulder 37 on the plunger 30
for abutment with the end of the cylinder 28 to limit inward movement of
the plunger.
In using the first embodiment catheter to practice the method of the
present invention, an incision is first made in the vessel to one side of
the occlusion to be treated and then the distal end of the catheter 14 is
introduced into the vessel through the incision. The catheter is then fed
through the vessel to position the distal end thereof proximate one end of
the occlusion, as shown in FIGS. 1 and 2. At or prior to this time, the
position of the plunger 30 is adjusted and the valve 36 is closed. With
the catheter so positioned and the plunger so conditioned, the next step
is to apply pressure to the plunger, as shown in FIG. 3, to subject the
catheter to internal fluid pressure and evert the body portion of the
balloon element therefrom for extrusion through the occlusion 12. In the
preferred mode, during such eversion, the balloon element extends axially
without substantial lateral expansion. Once the balloon element has
extruded through the occlusion 12, the application of continued fluid to
the catheter through the plunger 30 functions to laterally expand the
balloon element as shown in FIG. 4 and, thus, dilate the occlusion. Such
expansion and dilatation may be pulsed by moving the plunger 30 in and
out. Throughout the placement and dilatation process, the progress of the
treatment may be radiographically monitored. The extent of stretching
during the dilatation process as a result of lateral expansion of the
balloon may vary somewhat, depending upon the circumstances involved.
Ideally, the balloon is expanded so as to have an outside diameter equal
to or slightly greater then the internal diameter of the nonoccluded
vessel.
Once the dilatation is complete, the valve 36 is opened and the plunger 30
is retracted, as shown in FIG. 5, to tension the cord 22 and, thus,
reinvert the balloon element within the catheter. At this point, the
catheter may be removed from the vessel, and the incision through which
the catheter was introduced may be closed. It is also possible, depending
upon the circumstances involved, that the catheter may be moved into a
further section of the occlusion being treated, or on to a successive
occlusion prior to removal of the catheter. In such a case, the balloon
element would be everted and re-expanded, as shown in FIGS. 2, 3 and 4 for
each successive dilatation treatment and, ultimately, the balloon element
would be reinverted and the catheter removed from the vessel.
DESCRIPTION OF THE SECOND EMBODIMENT
The embodiment of FIG. 6 corresponds to that of the first embodiment, with
the exception that the balloon element, designated 16a, is not provided
with a cord to draw it back into the reinverted condition within the
catheter, designated 14a. Other than this difference, the structure and
mode of operation of the embodiment shown in FIG. 6 would be identical to
that of the first embodiment described in the foregoing discussion with
respect to FIGS. 1 to 5. With the FIG. 6 embodiment, reinversion is
achieved through means of the vacuum created within the catheter 14a by
retraction of the plunger of the syringe (not illustrated) associated with
the catheter 14a. It is also possible that the FIG. 6 balloon element
might be permitted to remain in the extended, but uninflated, condition
during the course of removal of the catheter 14a after a dilatation
treatment. Once the catheter 14a is removed from the vessel being treated,
external means could be used to assist in reinversion of the balloon
element.
DESCRIPTION OF THE THIRD EMBODIMENT
The principal difference between the third embodiment, illustrated in FIGS.
7 to 10, and the first embodiment described in the foregoing discussion
with respect to FIGS. 1 to 5 is that the third embodiment employs an
annular balloon element 16b in place of the closed bulbous element 16, and
a tubular cord element in the form of a flexible catheter 22b in place of
the simple cord 22. The purpose of these differences is to provide a
passage (i.e., the passage through the catheter 22b and the annular
balloon element 16b) through which pressure within the vessel being
treated may be measured, or injections into the vessel may be made. For
the latter purpose, the plunger 30b (see FIG. 7) is provided with a
passage through which the catheter 22b extends and a syringe 38 is
connected to the proximate end of the catheter 22b.
The vessel and occlusion depicted in FIGS. 7 to 10 correspond to those of
FIGS. 1 to 5 and, accordingly, are designated by the numerals 10 and 12,
respectively. The elements of the third embodiment catheter and inflating
mechanism which correspond to those of the first embodiment are designated
in FIGS. 7 to 10 by numerals corresponding to those used in FIGS. 1 to 5,
as follows: catheter 14; syringe 24; tubular coupling 26; cylinder 28;
flexible reservoir 32; tubular lateral extension 34; and, shut-off valve
36.
The mouth portion (attachment shoulder) of the element 16b is designated
18b and the body portion of the element 16b is designated 20b. In the
preferred construction, the balloon element 16b is fabricated of latex.
The inner catheter 22b to which the balloon element 16b is connected may
be fabricated of any suitable material, such as Dacron or polyvinyl
chloride. Ideally, the material from which the catheter 22b is fabricated
is flexible and generally inelastic.
Like the balloon element 16, the annular balloon element 16b is fabricated
so that it may evert out of the end of the catheter 14 in anisotropic
fashion, with the balloon element first everting out of the catheter in
advance of substantial lateral expansion and then, upon eversion, being
laterally expansible in response to the continued exertion of fluid
pressure internally of the catheter 14. The catheter 22b serves a function
similar to the cord 22 and should be flexible and generally inelastic and
of such a length that it will not restrict eversion of the balloon element
16b out of the catheter 14. To permit such unrestricted extension of the
element 16b, the catheter 22b is ideally provided with a slack portion, as
shown in the cylinder 28 in FIG. 7. The catheter 22b should also, however,
be of such a length that retraction of the plunger 30b beyond a
predetermined limit functions to reinvert the element 16b within the
distal end of the catheter 14, as shown in FIG. 10.
The third embodiment catheter 14, syringe 24 and reservoir 32 contain an
incompressible fluid F and operate, in cooperation with the valve 36, in
the same manner described in the foregoing discussion with respect to the
first embodiment. A stop shoulder 37b, corresponding to the aforedescribed
shoulder 37, is provided on the plunger 30b to limit inward movement of
the plunger relative to the cylinder 28.
The third embodiment catheter is used to practice the method of the
invention in essentially the same manner described in the foregoing
discussion with respect to the first embodiment. During this use, an
incision is first made in the vessel to one side of the occlusion to be
treated and then the distal end of the catheter 14 is introduced into the
vessel through the incision. The catheter is then advanced through the
vessel to a position proximate one end of the occlusion and, once so
positioned, the plunger 30b is used to first evert the element 16b out of
the catheter 14 and through the occlusion and then to expand the element
16b laterally to dilate the occlusion. As in the first embodiment
catheter, the element 16b is extruded through the occlusion in advance of
substantial lateral expansion of the element. Expansion of the element for
dilatation purposes may be pulsed by moving the plunger 30b in and out and
the progress of dilatation may be radiographically monitored. The extent
of stretching during the dilatation process may vary somewhat, depending
upon the circumstances involved. Generally, the element 16 b is expanded
so as to have an outside diameter equal to or slightly greater than the
internal diameter of the nonoccluded section of the vessel being treated.
FIGS. 7, 8, 9 and 10 show the successive steps in practicing the invention.
In FIG. 7, the catheter is shown as it would appear when being directed to
the situs of the occlusion. FIG. 8 shows the catheter as it would appear
when the element 16b is initially expanded for extrusion through the
occlusion. From this figure, it will be seen that the catheter 22b is
drawn through the occlusion with the element 16b and, thus, provides a
passage through the element 16b. FIG. 9 shows the element 16b as it would
appear when inflated to dilate the occlusion 12. In FIG. 10, the catheter
is shown in the condition it would assume when the valve 36 is opened and
the plunger 30b is retracted to tension the catheter 22b and, thus,
reinvert the element 16b within the catheter 14. With the element 16b so
reinverted, the catheter may be moved to another situs within the vessel
for further dilatation treatment, or removed from the vessel.
The lumen of the catheter 22b provides means whereby injections or pressure
measurement can be made while the third embodiment catheter 14 is in place
in a vessel. Such injections or measurements can be made at any time as
the lumen of the catheter 22b remains open at all times.
CONCLUSION
Although preferred embodiments of the invention have been illustrated and
described, it should be understood that the invention is not intended to
be limited to the specifics of these embodiments, but rather is defined by
the accompanying claims.
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