Note: Descriptions are shown in the official language in which they were submitted.
WO 95/17918 2179635 PCTlOS94/14167
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INFUSION CATHETER WITH UNIFORPI DISTRIBUTION OF FLUIDS
BACKGROUND OF THE INVENTION
The present invention relates to infusion catheters for
delivery of therapeutic fluids to bodily passages, and
particularly to infusion catheters exhibiting uniform dis-
tribution of such therapeutic fluids along a length of the
catheter.
In certain medical conditions, it is advantageous to
deliver a therapeutic agent directly to a target region to
avoid medicating the entire body and to limit the amount of
therapeutic agent required for effective treatment. One
example of such a medical condition is an arterial thrombus,
or clot, which can be treated effectively by localized
application of such therapeutic fluids as those containing
tissue plasminogen activator, urokinase, or streptokinase.
Infusion catheters have been developed which can deliv-
er therapeutic fluids directly to affected bodily passages,
for example a thrombotic region of an artery. One type of
infusion catheter is a hollow tube, the distal end of which
has been pierced through its side wall to form multiple
openings, or ports, providing direct access to the exterior
for fluid flowing through a common central lumen. The ports
are disposed at several axial positions along the infusion
section to provide distribution of the therapeutic fluid
along a desired length of the bodily passage. However,
fluids flowing through a tube flow more readily from ports
offering the least flow resistance. The longer the flow
path followed by the fluid in the central lumen, the higher
the resistance and the higher the pressure drop (AP) in the
fluid. If the infusion section of this catheter is more
than a few centimeters long, the fluid flowing from each
port exhibits resistance and a OP proportional to the fluid
flow distance along the length of the central lumen. Thus,
the fluid flowing to the more distal ports experiences
higher AP than that flowing to the more proximal ports, and
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the fluid distribution is not uniform.
In another type of infusion catheter, the wall of
the infusion section includes several small axial lumens
each with a single opening or port to provide direct access
to the exterior of the catheter for fluid flowing through
each small lumen. The ports are disposed at different axial
lengths along the infusion section to provide distribution
to the desired length of the bodily passage. This design
offers some improvement in distribution, but the varying
lengths of the fluid flow paths still result in non-uniform
flow over the length of the infusion section. Also, in this
design the number of fluid delivery ports is limited by the
small circumference of the infusion section tube.
It would be desirable to have an infusion catheter
having an infusion section in which the resistance, or AP,
experienced by the fluid flowing to all the ports is
equalized or balanced to provide uniform distribution of
fluid along a desired length of a bodily passage. The
infusion catheter described herein was developed to address
that need.
SiJNIlMARY OF THE INVENTION
In a first aspect, the invention provides an
infusion catheter comprising an elongated catheter body
having a proximal end and a distal end and having an
infusion section at its distal end for delivery of
therapeutic fluid to bodily passages, said infusion section
having a proximal portion and a distal portion and
comprising: a first infusion catheter tube having a wall
delimiting a first lumen, said first tube wall having a
multiplicity of first ports therethrough; and a second
infusion catheter tube disposed within and concentric with
said first lumen, said second tube having a wall delimiting
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a second lumen, said second tube wall being uniformly spaced
apart from said first tube wall to provide an annular
passageway within said first lumen, the radial depth of said
annular passageway being sufficient to permit fluid flow
therewithin, said second tube wall having a multiplicity of
second ports therethrough; wherein each of said first ports
provides fluid communication between said annular passageway
and the exterior of said catheter and each of said second
ports provides fluid communication between said second lumen
and said annular passageway such that said therapeutic fluid
can flow from said second lumen through said second ports
into said annular passageway, flow within said annular
passageway, and flow from said annular passageway through
said first ports to said catheter exterior; and said first
ports and said second ports are positioned relative to one
another such that the average fluid flow distance in said
annular passageway between said second ports and said first
ports is smaller in said infusion section distal portion
than in said infusion section proximal portion to provide a
substantially uniform average flow rate of said therapeutic
fluid flowing from each of said first ports to said catheter
exterior along the length of said infusion section.
In a specific embodiment of the first aspect, the
catheter infusion section further includes at least one
additional portion between the proximal portion and the
distal portion, and the first ports and the second ports are
positioned relative to one another so that the average fluid
flow distance between the second ports and the first ports
progressively decreases in the distal direction along the
length of the infusion section.
According to a second aspect, the invention
provides an infusion catheter comprising an elongated
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catheter body having a proximal end and a distal end and
having an infusion section at its distal end for delivery of
therapeutic fluid to bodily passages, said infusion section
having a proximal portion and a distal portion and
comprising: a first infusion catheter tube having a wall
delimiting a first lumen, said first tube wall having a
multiplicity of first ports therethrough; and a second
infusion catheter tube disposed within and concentric with
said first lumen, said second tube having a wall delimiting
a second lumen, said second tube wall being uniformly spaced
apart from said first tube wall to provide an annular
passageway within said first lumen, the radial depth of said
annular passageway being sufficient to permit fluid flow
therewithin, said second tube wall having a multiplicity of
second ports therethrough; wherein each of said first ports
provides fluid communication between said annular passageway
and the exterior of said catheter and each of said second
ports provides fluid communication between said second lumen
and said annular passageway such that said therapeutic fluid
can flow from said second lumen through said second ports
into said annular passageway, flow within said annular
passageway, and flow from said annular passageway through
said first ports to said catheter exterior; and the ratio of
the number of said second ports to the number of said first
ports is higher in said infusion section distal portion than
in said infusion section proximal portion to provide a
substantially uniform average flow rate of said therapeutic
fluid flowing from each of said first ports to said catheter
exterior along the length of said infusion section.
In a specific embodiment of the second aspect, the
first ports and second ports are positioned relative to one
another so that the average fluid flow distance in the
annular passageway between the second and first ports is
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smaller in the distal portion than in the proximal portion
of the catheter infusion section.
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BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention,
together with other objects, advantages, and capabilities
thereof, reference is made to the following Description and
appended Claims, together with the Drawings in which:
Figure 1 is an elevation view of an infusion catheter
in accordance with one embodiment of the present invention;
Figure 2 is a radial cross-sectional view of the infu-
sion section of the catheter of Figure 1, taken along the
line 2 - 2.
Figure 3 is a schematic representation in longitudinal
cross-section of a proximal portion of the infusion section
of the catheter of Figures 1 and 2;
Figure 4 is a schematic representation in longitudinal
cross-section of a distal portion of the infusion section of
the catheter of Figures 1 and 2;
Figure 5 is a schematic representation in longitudinal
cross-section of the infusion section of an infusion cathe-
ter in accordance with an alternate embodiment of the inven-
tion.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An exemplary embodiment of the infusion catheter in
accordance with the invention has an infusion section formed
from two cylindrical hollow tubes. A smaller tube is in-
serted concentrically into the lumen of a larger tube with
an annular space between the tube walls. Openings, holes,
or ports are provided in each tube for therapeutic fluid to
flow from the interior of each tube to its exterior. The
radial depth of the annular space is sufficient to permit
the fluid to flow between the tubes from the inner tube
ports to the outer tube ports. Thus therapeutic fluid
supplied to the lumen of the inner tube can flow into the
annular space between the tubes through the ports in the
inner tube, and from the annular space to the exterior of
the catheter through the ports in the outer tube.
. WO 95/17918 PCTlUS94114167
In such a catheter, the fluid flow rate at any position
along the length of the infusion section is proportional to
4P (described above). The AP, in turn, is affected not only
by (a) the distance traveled by the fluid through the cen-
5 tral lumen of the inner tube, but also by (b) the fluid flow
volume supplied to the annular space and (c) the fluid flow
distance through the annular space. Where the size of the
inner and outer ports is uniform, as is convenient for ease
of manufacture, the fluid flow volume through the annular
space is greatly affected by the number of inner ports
available for fluid flow relative to the number of outer
ports. Further, the fluid flow distance through the annular
space is influenced by the distance between adjacent inner
and outer ports. Thus, the flow rate from ports at differ-
ent axial positions along the infusion section can be regu-
lated by the relative number and positions of the ports in
the inner and outer tubes at that position.
The catheter described herein balances the fluid flow
rate (a) by providing a smaller ratio of inner ports to
outer ports in the proximal portion than in the distal
portion, and/or (b) by providing a shorter average flow
distance between the more distal inner and outer ports than
between the more proximal inner and outer ports. Fluid
traveling a longer distance within the central lumen of the
catheter to reach the inner tube ports at the distal portion
of the infusion section experiences a higher AP and slower
fluid flow in the central lumen. The slower fluid flow can
be compensated for by providing a higher ratio of inner
ports to outer ports in the distal portion to increase the
fluid volume supplied to the annular space. Alternatively
or concurrently, the higher AP in the distal portion central
lumen can be compensated for by allowing the fluid to travel
a shorter average distance in the distal portion annular
space than in that of the proximal portion, and experience a
lower AP in the annular space before exiting the catheter.
This may be accomplished by shortening the average fluid
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flow distance between adjacent inner and outer ports. Thus
the fluid flow rate from different regions of the infusion
section can be more uniform than in prior art catheters.
The description below of various illustrative embodi-
ments shown in the Drawings is not intended to limit the
scope of the present invention, but merely to be illustra-
tive and representative thereof.
Referring now to Figure 1, infusion catheter 10 in-
cludes elongated catheter body 12 having proximal end 14 and
distal end 16. Infusion section 18 is provided at distal
end 16 for delivery of therapeutic fluids to a thrombotic
region of an artery (not shown). Infusion section 18 in-
cludes proximal portion 20 and distal portion 22. Guidewire
24 is threaded axially through catheter body 12 and infusion
section 18, and is of sufficient length to extend proximally
beyond fitting 26 and distally beyond distal tip 28 of
distal end 16. Fitting 26 includes fluid inlet 30 for
delivery of therapeutic fluid from, e.g., a syringe (not
shown) to the catheter.
Figure 2 is a radial cross-section of infusion section
18 of catheter 10, taken along line 2 - 2 of Figure 1.
Infusion section 18 includes outer tube 32 having tube wall
34 enclosing lumen 36. Infusion section 18 also includes
inner tube 38 disposed within lumen 36 to be concentric with
tube 32. Inner tube 38 has wall 40 enclosing central lumen
42 through which guidewire 24 passes. Tubes 32 and 38 are
spaced apart by uniform radial distance 44 to form annular
space or passageway 46 extending longitudinally between tube
32 and tube 38.
Tube 32 has four longitudinal rows of ports 50 perfo-
rating wall 34. Tube 38 has two longitudinal rows of ports
48 perforating wall 40. In the embodiment shown in Figure
2, each of the rows of ports 48 is disposed between two of
the,rows of ports 50. However, in other embodiments the
rows of ports may be otherwise disposed. Also, the number
of rows of ports present in the inner and outer tubes may be
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different from one another, as shown, or may be the same.
Alternatively, each row of inner ports may be aligned with a
row of outer ports. As may be seen in Figure 2, fluid
communication exists between central lumen 42, annular
passageway 46, and the exterior of infusion section 18 via
ports 50 and 48.
Figures 3 and 4 schematically illustrate longitudinal
cross-sections of portions of infusion section 18, showing
the relative disposition of ports 48 and 50 in the proximal
and distal portions, respectively, of infusion section 18.
(For purposes of illustration, ports 48 are shown rotated
45 about the axis, not shown, of infusion section 18.)
Arrows 52 in Figures 3 and 4 schematically illustrate the
direction of flow of the therapeutic fluid within central
lumen 42, through ports 48 into passageway 46, along pas-
sageway 46, and through ports 50 to the exterior of the
catheter. For clarity, guidewire 24 is not shown in Figures
3 and 4.
As may be seen by a comparison of Figures 3 and 4, the
number and spacing of outer tube ports 50 is the same in the
proximal portion 20 and distal portion 22 of infusion sec-
tion 18. However, the number of inner tube ports 48 in
distal portion 22 is twice that in proximal portion 20, and
the longitudinal spacing between inner tube ports 48 is
reduced by half. This results in a greater volume of fluid
flowing to each outer port 50 in distal portion 22 than in
proximal portion 20. Also, arrows 52 show that, although
the spacing between inner ports 48 is less, the average
longitudinal distance traveled between adjacent inner and
outer ports remains about the same. Thus in infusion cathe-
ter 10 of Figures 1 - 4, it is largely the difference in the
ratios of the number of inner ports 48 to the number of
outer ports 50 in the proximal and distal portions which
balances the average flow rate of therapeutic fluid flowing
to the catheter exterior along the length of infusion sec-
tion 18.
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Figure 5 schematically represents a longitudinal cross-
section of a portion of infusion section 60 in accordance
with another embodiment of the invention. In Figure 5, like
features to those shown in Figures 1 - 4 are indicated by
the same reference numerals. Figure 5 shows the relative
disposition of ports 48 and 50 in proximal portion 20,
middle portion 62, and distal portion 22 of infusion section
18. (For purposes of illustration, ports 48 are shown rotat-
ed 45 about the axis, not shown, of infusion section 60 in
a similar manner to the illustration of infusion section 18
of Figures 3 and 4.) As in Figures 3 and 4, arrows 52
schematically illustrate the direction of flow of the thera-
peutic fluid within central lumen 42, through ports 48 into
passageway 46, along annular passageway 46, and through
ports 50 to the exterior of the catheter. Also as in Fig-
ures 3 and 4, guidewire 24 is not shown.
In infusion section 60, outer tube 32 has four longitu-
dinal rows of ports 50 perforating wall 34. Inner tube 38
has two longitudinal rows of ports 48 perforating wall 40.
In the embodiment shown in Figure 5, each of the rows of
ports 48 is disposed between two of the rows of ports 50,
similarly to the arrangement shown for infusion section 18
in Figure 2. (As mentioned above, ports 48 are shown rotat-
ed 45 about the axis of infusion section 60.) However, in
other embodiments the rows of ports may be otherwise dis-
posed. Also, the number of rows of ports present in the
inner and outer tubes may be different from one another, as
shown, or may be the same. Alternatively, each row of inner
ports may be aligned with a row of outer ports.
The number and spacing of outer tube ports 50 is the
same in the proximal portion 20, middle portion 62, and
distal portion 22 of infusion section 18. However, the
number of inner tube ports 48 in middle portion 62 is great-
er than that in proximal portion 20, and the longitudinal
spacing between inner tube ports 48 is reduced. This re-
sults in a greater volume of fluid flowing to each outer
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port 50 in middle portion 62 than in proximal portion 20.
Also, unlike the catheter of Figures 1 - 4, arrows 52 in
Figure 5 show that the average longitudinal distance trav-
eled between adjacent inner and outer ports is less in
middle portion 62 than in proximal portion 20, and still
less in distal portion 22. The number of inner tube ports
48 in distal portion 22, however, is the same as that in
middle portion 62.
Thus in infusion catheter 60 of Figure 5, two flow
balancing mechanisms are in effect. Both of these mecha-
nisms depend on providing concentric tubes 32 and 38 in
infusion section 60 and on the relative placement of ports
48 and 50 in these tubes. The first flow balancing mecha-
nism is the same as that described for infusion section 18
of Figures 1- 4. That is, the difference in the ratios of
the number of inner ports 48 to the number of outer ports 50
in the proximal and middle portions of infusion section 60
tends to balance the average volume of therapeutic fluid
flowing to the catheter exterior from proximal portion 20
and middle portion 62.
The second flow balancing mechanism involves the aver-
age longitudinal distance travelled by the therapeutic fluid
in annular passageway 46 and the effect this distance has on
the AP. As described above, the average longitudinal fluid
flow distance decreases in the distal direction along the
length of infusion section 62. Thus, in this mechanism, the
progressively lower AP in passageway 46 from proximal por-
tion 20 to distal portion 22 of infusion section 60 tends to
offset the progressively higher GP along the length of
central lumen 42. In short, in infusion section 60 both
mechanisms are acting to provide a more uniform fluid flow
between proximal portion 20 and middle portion 62, but the
fluid flow between middle portion 62 and,distal portion 22
is balanced principally by only a single mechanism.
In the embodiments shown in Figures 1- 5, the spacing
of outer tube ports 50 is uniform along the length of the
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infusion section while that of inner tube ports 48 varies to
produce the flow balancing effects described above. In
other embodiments, however, the outer tube port spacing may
vary and the inner tube port spacing be uniform. Alterna-
5 tively, the spacing of both the outer and inner tube ports
may be varied along the length of the infusion section.
Similarly, in the infusion sections illustrated, the ports
are round and uniform in diameter along each tube and be-
tween the two tubes. Alternative embodiments, however, may
10 have square, oval, rectangular, or other shaped ports, and
their size need not be uniform along the length of each tube
or.uniform for the two tubes.
The infusion section of the catheters described above
may be assembled using known techniques. Typically, the
catheter body includes two concentric tubes, an outer cathe-
ter body tube providing the outer tube and being unitary
therewith, and an inner catheter body tube providing the
inner tube and being unitary therewith. Alternatively, a
single, unitary tube may provide both a single-tube catheter
body and either the outer tube or the inner tube of the
infusion section, the other infusion section tube being
bonded thereto by known means. Also alternatively, the
inner and outer tubes may each be bonded to a separate
catheter body tube. The central, fluid delivery lumen of
the catheter body is in fluid communication with the central
lumen of the inner tube (but not with the annular passage-
way). The tubing of the body and the infusion section may
be fabricated from a polymer, e.g., a polyamide, or other
flexible material conventional for infusion catheters, using
an extruder or other conventional means. Both the inner and
outer tubes of the infusion section are perforated to form
the above-described ports, using such conventional means as
a drill or laser. A conventional inlet fitting may be
provided in the proximal end of the catheter body for deliv-
ery of therapeutic fluid to the catheter from, e.g., a
syringe.
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Typically, in operation a conventional guidewire, as
24, is manipulated, using known techniques, through the
bodily passages of a patient to reach the region needing
treatment. The infusion catheter described above, including
the novel infusion section, as 18 or 60, is then threaded
onto the guidewire and manipulated into position with the
infusion section adjacent the region needing treatment. A
syringe or other known fluid medication providing device is
used to provide therapeutic fluid under pressure to inlet
30, catheter body 12, and central lumen 42 of the infusion
section. The fluid flows through central lumen 42, through
inner tube ports 48, through annular passageway 46, and
through outer tube ports 50, as described above, to deliver
the therapeutic fluid to the treated region of the bodily
passage. One or both of the fluid balancing mechanisms
described above operates to provide a more uniform distribu-
tion of therapeutic fluid along the length of the infusion
section than has been possible with prior art infusion
catheters.
The invention described herein presents to the art
novel, improved infusion catheters having the advantage of
more uniform application of therapeutic fluids along the
length of the infusion section. The improved fluid flow
from the distal end of the infusion section can also enable
the use of longer length infusion sections without the
problems of non-uniform flow associated with prior art
infusion catheters.
While there has been shown and described what are at
present considered the preferred embodiments of the inven-
tion, it will be apparent to those skilled in the art that
modifications and changes can be made therein without de-
parting from the scope of the present invention as defined
by the appended Claims.
