High torque balloon catheter

A balloon catheter (2) comprises an outer sheath (3) housing an inner catheter (10). The inner catheter comprises an inner tubular member (30), a braided reinforcement layer (32), and a soft outer layer (34). The inner tubular member extends from a proximal end (15) of the inner catheter to a first distal location (22). The braided reinforcement layer extends from the proximal end to a second distal location (18), usually located proximal of the first distal location. The soft outer layer extends from the proximal end of the inner catheter to the tip (44) of the inner catheter. In this way, a catheter having a shaft region (16), a transition region (20), and a distal region (24), each with different strength and flexibility characteristics, can be used with the outer sheath. The balloon (8) is bonded to the distal ends of the outer sheath and the inner catheter and is inflated through the space defined therebetween.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to medical balloon catheters and 
methods for their fabrication. More particularly, the present relates to 
the construction of both large and small diameter, braid-reinforced 
balloon catheters having controlled flexibility, a soft distal tip and an 
elastomeric balloon at the tip for the partial or total occlusion of a 
vessel; the invention can be used for a wide variety of medical 
applications, such as interventional cardiological or neuroradiology 
procedures, but are particularly useful for intercranial selective 
catheterization. 
Medical catheters exist for a wide variety of purposes, including 
diagnosis, interventional therapy, drug delivery, drainage, perfusion, and 
the like. Catheters for each of these purposes can be introduced to 
numerous target sites within a patient's body by guiding the catheter 
through the vascular system, and a wide variety of specific catheter 
designs have been proposed for different uses. 
Of particular interest to the present invention, small diameter tubular 
access catheters are presently being used for diagnostic and 
interventional neurological techniques, such as the imaging and treatment 
of aneurysms, tumors, arteriovenous malformations/fistulas, and the like. 
The neurological vasculature places a number of requirements on the 
catheters which are to be employed. The primary requirement is size. The 
blood vessels in the brain are frequently as small as several millimeters, 
or less, requiring that the catheters have an outside diameter as small as 
one French (1 F; 0.33 millimeters). In addition to small size, the brain 
vasculature is highly tortuous, requiring that neurological catheters be 
very flexible, particularly at their distal ends, to pass through the 
regions of tortuosity. Difficulties in endovascular positioning, however, 
make it desirable to impart high tensile and column strength over at least 
the proximal portion of the catheter. Additionally, the blood vessels of 
the brain are relatively fragile, so it is desirable that the catheter 
have a soft, non-traumatic exterior to prevent injury. 
In an effort to meet at least some of these requirements, the 
small-diameter, variable flexibility catheters, such as Tracker.RTM. 
infusion catheters available from Target Therapeutics, Fremont, Calif., 
have been developed. Although generally successful, the Tracker.RTM. 
catheters suffer from certain deficiencies. In particular, to achieve high 
flexibility, tensile strength and catheter wall integrity have been 
compromised. The Tracker.RTM. catheters thus lack both column strength and 
hoop strength and have a tendency to kink and collapse when passing around 
small diameter bends. Directability and torqueability of the Tracker.RTM. 
catheters is also limited, and the most flexible distal regions of the 
catheter are subject to rupture and perforation. 
It would therefore be desirable to provide improved small diameter, 
flexible catheters suitable for introduction to very small blood vessels, 
particularly to the neurological vasculature. Such catheters should 
provide sufficient flexibility to permit access to the tortuous regions of 
the neurological vasculature, while retaining sufficient tensile, column, 
and hoop strengths to enhance resistance to kinking and collapse. The 
improved catheters should also have enhanced positioning characteristics, 
including pushability and torqueability. Additionally, it would be 
desirable to have an improved wall strength over a portion or all of the 
catheter wall to resist perforation and failure when introducing high 
pressure fluids and/or introducing thrombogenic coils and other devices 
through the catheter. 
2. Description of the Background Art 
U.S. Pat. No. 4,739,768, describes a catheter consisting of an inner layer 
and an outer layer, where the inner layer terminates proximally of the 
outer layer to form a relatively more flexible distal end. WO 91/17782 
describes a catheter having a braid-reinforced distal end with a low 
friction surface. WO 93/02733 describes a catheter having four regions of 
different stiffness. Braid and otherwise reinforced catheter structures 
are described in U.S. Pat. Nos. 3,416,531; 3,924,632; 4,425,919; 
4,586,923; 4,764,324; 4,817,613; 4,899,787; 5,045,072; 5,057,092; 
5,061,257; and EP 555 088. Catheters having soft tips are described in 
U.S. Pat. Nos. 4,636,346 and 5,078,702. A torque control catheter 
comprising stainless steel braid-reinforced polyethylene is described in 
Catalog 1982-84 "Radiology, Cardiology and Surgery," page 16, Cook Inc. 
The requirements and considerations for constructing catheters and other 
system components for intercranial selective catheterization are described 
in Rufenacht and Latchaw (1992) INTER. NEURORAD. 2:251-268. U.S. Pat. No. 
4,921,478 to Solano et al. shows a cerebral balloon catheter having an 
open central lumen and a specially shaped balloon. 
SUMMARY OF THE INVENTION 
A balloon catheter constructed in accordance with the principles of the 
present invention comprises an outer sheath, an inner catheter, an annular 
balloon mounted to and circumscribing the distal ends of the outer sheath 
and inner catheter, an inflation port at the proximal end of the outer 
sheath and an inflation passage as defined between the outer sheath and 
the inner catheter which fluidly couples the inflation port and the 
balloon. The outer sheath and inflation port are generally conventional. 
The balloon is usually made of an elastomeric (distensible) material, 
preferably of silicone rubber, and is preferably bonded to the tips of the 
outer sheath and the inner catheter. In some cases, it may be desirable to 
form the balloon from an inelastic (non-distensible) material, such as 
polyethylene pterephthalate, particularly if the balloon is to be used for 
dilation. 
The inner catheter includes a catheter body including an inner tubular 
member, a braided reinforcement layer disposed over the inner tubular 
member, and a soft outer layer formed over the braided reinforcement 
layer. The flexibility of the catheter body is controlled by selecting the 
relative lengths and mechanical characteristics of each of these 
components. The inner tubular member extends a first length with the 
braided reinforcement layer usually terminating proximally of the distal 
end of the inner tubular member, preferably by distance in the range from 
about 0 cm to 20 cm, more preferably from 1 cm to 10 cm, most preferably 
from 3 cm to 10 cm. The soft outer layer may terminate distally of the 
distal end of the inner tubular member, preferably by a distance in the 
range from about 0 cm to 10 cm, more preferably from 1 cm to 10 cm, and 
most preferably from 1 cm to 3 cm. In this way, up to three distinct 
regions of flexibility, tensile strength, column strength, and hoop 
strength may be provided. In addition or as an alternative to terminating 
the layers at different locations relative to each other, flexibility, 
tensile strength, column strength, and hoop strength may be varied by 
selectively controlling the mechanical characteristics of one or more of 
the individual layers. In particular, the pitch and other braid 
characteristics of the braided reinforcement layer may be varied to 
provide increased strength properties along the proximal portions of the 
catheter body and increased flexibility over the distal portion of the 
catheter body. The use of the braided reinforcement layer in the catheters 
of the present invention is particularly advantageous since it provides 
substantial tensile, column, and hoop strengths with minimum loss of 
flexibility. 
In the exemplary embodiment, a major portion of the catheter body extending 
from its proximal end to the termination of the braided reinforcement area 
is the least flexible, but has excellent torque transmission and hoop 
strength characteristics. The region of the catheter distal to the braid 
termination but proximal to the termination of the inner tubular member 
has enhanced flexibility while retaining adequate torqueability and hoop 
strength to permit guiding of the catheter over a guide wire and prevent 
kinking and collapse of the catheter lumen. The distal-most region of the 
catheter comprises only the soft outer layer and possesses the greatest 
flexibility with the minimum torqueability and hoop strength, and the 
catheters of the present invention are suitable for introduction to 
remote, tortuous regions of the brain vasculature. 
In a first particular aspect of the present invention, the inner tubular 
member is composed of a lubricious material, such as a fluorocarbon 
polymer, polyamide, a polyolefin, a polyimide, or the like, preferably 
being formed from polytetrafluoroethylene (PTFE). The use of such 
materials provides a very smooth surface for introducing devices and high 
velocity fluids through the lumen defined by the inner tubular member. The 
catheter of the present invention includes only a single transition from 
the inner tubular member to the contiguous lumen defined by the soft outer 
layer which extends beyond the distal termination of the inner tubular 
member. 
In a second preferred aspect of the present invention, the braided 
reinforcement layer is composed of a filament braid, preferably a 
stainless steel braid, which is annealed and transversely cut at its 
distal end to remove any protrusions, burrs, discontinuities, or the like, 
which may result from the termination of braiding. Such discontinuities in 
the braid at the distal end (or elsewhere) are unacceptable as they would 
expose the vasculature to trauma, even when covered by the soft outer 
layer. Previous catheter constructions have generally relied on covering 
braid terminations with a ring or other protective structure. The present 
invention minimizes the need for any additional structure at braid 
termination by use of the unique annealing and cutting process, as 
described in more detail hereinafter. However, it has been found useful to 
use a ring of PET heat shrink material to cover the braid terminations. 
In a third particular aspect of the present invention, the material of the 
soft outer layer has a hardness in the range from 30 A to 72 D, and is 
preferably selected from the group consisting of polyamide polyether block 
copolymer (Pebax.RTM.), polyurethane, silicone rubber, nylon, and the 
like. 
In a fourth particular aspect of the present invention, the inner catheter 
consists essentially of the inner tubular member, the braided 
reinforcement layer, and the soft outer layer, as described above, and is 
free from other structural components which would change the essential 
mechanical and structural characteristics of the catheter, particularly 
with regard to flexibility, torque transmission, and softness of the 
exterior. Such catheter bodies may, however, include other components 
which do not affect the essential mechanical and structural 
characteristics, such as proximal connectors, proximal housings, 
radiopaque markers, and the like. 
In a fifth particular aspect of the present invention, the inner catheter 
further comprises a less stiff reinforcement layer, typically a helically 
wound ribbon reinforcement layer, that extends distally from the braided 
reinforcement layer to provide a transition stiffness within the balloon 
that is less than that of the region comprising the braided reinforcement 
layer. Usually, the braided reinforcement layer will terminate from 2 cm 
to 20 cm proximally of the distal end of the inner catheter, more usually 
from 3 cm to 10 cm proximally of the distal end. 
In a sixth particular aspect of the present invention, the outer sheath 
comprises a reinforcement layer, preferably a helically wound ribbon 
reinforcement layer which, preferably, extends from the proximal end to 
the distal end thereof. The reinforcement layer inhibits collapse of the 
sheath and blockage of the inflation lumen that might otherwise occur 
during normal use. 
In a sixth particular aspect of the present invention, a soft, atraumatic 
distal tip is secured to the distal end of the inner catheter, with the 
tip extending distally of the balloon. The tip is preferably unreinforced, 
but may include a radiopaque marker. 
According to a method of the present invention, the inner catheter may be 
fabricated by providing an inner tubular member, preferably having the 
characteristics described above. A braid is formed over the inner tubular 
member from the proximal end to a location spaced proximally from the 
distal end of the inner tubular member by a distance in the range from 0 
cm to 10 cm, preferably from 1 cm to 10 cm, and more preferably from 1 cm 
to 3 cm. A soft outer layer is then formed over the resulting assembly 
from its proximal end and extending distally beyond the distal end thereof 
by a distance in the range from 0 cm to 10 cm (when extending distally 
beyond the inner tubular member). The soft outer layer further defines a 
distal lumen which is contiguous with the lumen of the inner tubular 
member. Preferably, each of the above-fabrication steps occurs while the 
inner tubular member is disposed over a mandrel which supports the inner 
tubular member and extends beyond the distal end of said member. 
The braid is formed from stainless steel ribbon or other suitable material, 
typically as a one-over-one or two-over-two braid. After the braid is 
formed over the inner tubular member and the distal end terminated, the 
braid is translated distally to extend beyond the mandrel. The braid is 
then annealed, typically by heating, and the annealed braid filaments cut 
transversely to form a square-cut end which is free from protrusions, 
burrs and other discontinuities. The braid is then translated proximally 
back over the inner tubular member to the desired position space 
proximally from the distal end thereof. The soft outer layer is then 
formed over the braid and extending beyond the distal end of the inner 
tubular member on to the mandrel. Preferably, the soft outer layer is 
formed by first placing a preformed tube of the desired soft material over 
the assembly of the braid and inner tubular member and thereafter placing 
a heat shrink tube over the soft outer layer tubular material. The entire 
assembly is then heated to a temperature which melts the soft outer layer 
of material and which constricts the heat shrink tube over the assembly, 
thus applying pressure to the soft outer layer material. After cooling, 
the heat shrink tube can be cut from the catheter, and the distal end 
trimmed to a desired length. Optionally, a proximal connector can be 
attached to the proximal end of the catheter body. 
Other features and advantages of the invention will appear from the 
following description in which the preferred embodiments have been set 
forth in detail in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a simplified side view of a balloon catheter made 
according to the invention. Balloon catheter 2 includes an outer sheath 3 
made of, for example, Pebax.RTM., a polyamide polyether block copolymer, 
having a proximal end 4 and a distal end 5. An injection port assembly 6 
is mounted to proximal end 4 through a strain relief 7. An annular, 
elastomeric balloon 8 is secured to distal end 5 of outer sheath 3 and to 
an inner catheter 10 housed within outer sheath 3 as will be discussed in 
more detail below. Injection port assembly 6 includes a connector 14 
coupled to the proximal end 15 of inner catheter 10. The specific 
construction and materials of sheath 3, elastomeric balloon 8, and 
injection port assembly 6 are generally conventional. The specific 
construction of inner catheter 10 will now be discussed in detail. 
The present invention provides an improved construction for inner catheters 
of the type having an elongated catheter body with a central lumen 
extending from proximal end to a distal end thereof. See FIGS. 2 and 3. 
Such constructions are particularly useful for forming very small diameter 
catheters, having outside diameters of 4 mm (12 F) preferably below 2.67 
mm (8 F), and frequently as small as 1 mm (3 F), and below, such as those 
used in neurological diagnostic and interventional procedures. Such small 
catheters will also be useful for other procedures, such as gynecological 
procedures, cardiac procedures, general interventional radiology 
procedures, and the like, for access to the small vasculature as 
necessary. Constructions of the present invention, however, are not 
limited to such small diameter catheters, and will be useful for larger 
diameter catheters as well, such as vascular guiding catheters which may 
have outside diameters larger than 4 mm. 
Inner catheters according to the present invention will comprise a catheter 
body having dimensions and a geometry selected for the intended use. The 
catheter body will typically have a length in the range from about 40 cm 
to 200 cm, usually having a length in the range from about 60 cm to 175 
cm. The outside diameter of the catheter body will typically be in the 
range from about 0.33 mm (1 F) to 4 mm (12 F), usually being in the range 
from about 0.66 mm (2 F) to about 2.66 mm (8 F). The catheter body will 
define an inner lumen typically having a diameter in the range from about 
0.1 mm to 3.6 mm, usually being in the range from about 0.3 mm to 2.5 mm, 
with catheters having larger outside diameters usually having larger lumen 
diameters. For the preferred microcatheters of the present invention, the 
catheter body will have a length in the range from about 80 cm to 150 cm, 
an outside diameter in the range from about 0.66 mm to 1.75 mm, and an 
inside diameter in the range from about 0.375 mm to 1.07 mm. 
The catheter body will usually be straight along all or most of its length. 
By "straight" it is meant that the catheter body will assume a straight or 
linear configuration, when free from external bending forces. The catheter 
body, however, will be highly flexible so that it will be able to pass 
through the tortuous regions of a patient's vasculature, as described in 
more detail herein below. In some cases, the catheter bodies may have a 
shaped distal end including curves and bends which are selected to 
facilitate introduction and placement of the catheter (usually over a 
separate guide wire) in the vascular system. A particular geometry of 
curves and/or bends may be selected to accommodate the intended use of the 
catheter. 
The catheter body will usually include at least two, and more usually three 
distinct regions, with each region having a different construction 
resulting in different mechanical properties. A shaft region extends from 
the proximal end of the catheter body to a location spaced within 20 cm of 
the distal end of the catheter body, usually from 2 cm to 6 cm of the 
distal end. The shaft region will have the maximum reinforcement of the 
catheter body (including all three layers), thus having most column 
strength and hoop strength but the least flexibility. A transition region 
is located immediately on the distal side of the shaft region and extends 
to a location spaced within 10 cm of the distal end of the catheter body, 
usually from 1 cm to 3 cm of the distal end. The transition region will 
have an intermediate level reinforcement (including the inner tubular 
member and the soft outer layer, but lacking the braided reinforcement 
layer) together with intermediate levels of column strength, hoop 
strength, and flexibility. A distal region extends distally from the 
transition region, and is composed of a soft, unreinforced material. The 
distal region will generally be relatively short, typically having a 
length in the range from about 1 cm to 3 cm, and will have the greatest 
flexibility of the three regions of the catheter body. 
In a first alternate embodiment, the braided reinforcement layer terminates 
at the distal end of the inner tubular member, with the soft outer layer 
extending distally from 1 cm to 10 cm, preferably from 1 to 3 cm. In a 
second alternate embodiment, the outer soft layer terminates at the distal 
end of the inner tubular member, with the braided reinforcement layer 
terminating proximally of both the outer layer and tubular member by a 
distance in the range from 1 cm to 10 cm, preferably from 1 cm to 3 cm. In 
both these embodiments, the catheter has two distinct regions with 
different mechanical properties. 
As a consequence of the preferred fabrication technique, as described in 
more detail below, the diameters of the transition region and the distal 
region of the catheter body may be somewhat smaller than that of the shaft 
region. While such a decrease in geometry in the distal direction may be 
advantageous, is not essential for the catheters of the present invention. 
Thus, the present invention includes both catheters having uniform 
diameters along their entire length and catheters having diameters which 
decrease in the distal direction. 
In a preferred construction, the catheter body of the present invention 
will consist essentially of three structural components. The first 
component is an inner tubular member which defines the inner lumen and 
provides a lubricious surface to receive the fluid or device which is to 
be introduced to a target location within the vasculature or other body 
lumen. Typically, the inner tubular member will be a sleeve formed from a 
single material, preferably a lubricious polymer, such as a fluorocarbon 
(e.g., polytetrafluoroethylene (PTFE)), a polyamide (e.g., nylon), a 
polyolefin, a polyimide, or the like. It would also be possible to form 
the inner tubular members as a laminate structure comprising a 
non-lubricious outer layer and an inner lubricious layer or coating. 
The second structural component of the catheter body is a braided 
reinforcement layer comprising braided filaments formed directly over the 
inner tubular member using conventional braiding techniques. The braid 
filaments will have a very small cross-sectional area while possessing 
sufficient tensile strength to undergo the braiding process. Preferably, 
the braid filaments will be composed of stainless steel, a shape memory 
alloy (e.g., Nitinol.RTM.), polymeric fibers, or the like. Particularly 
preferred are stainless steel filaments having a rectangular cross-section 
with a width in the range from 0.001 inch to 0.01 inch, preferably being 
about 0.0025 to 0.005 inch, and a thickness in the range from 0.0002 inch 
to 0.002 inch, preferably being about 0.0005 to 0.001 inch. Such small 
filaments can be formed over the inner tubular member in a conventional 
one-over-one or two-over-two braid pattern, with the machine being 
carefully adjusted to avoid excessive tensile forces on the filaments. 
The third structural component of the catheter body is a soft outer layer 
which is formed over the braided reinforcement layer and which extends 
distally of the distal end of the tubular member. The soft outer layer 
will cover the entire assembly of both the inner tubular member and the 
braided reinforcement layer, creating the three distinct regions discussed 
above in connection with the exemplary embodiment. The shaft region will 
include all three structural components, i.e., the inner tubular member, 
the braided reinforcement layer formed over the inner tubular member, and 
the soft outer layer formed over the braided reinforcement layer. The 
transition region will include both the inner tubular member and the soft 
outer layer, but will free from the braided reinforcement layer. In this 
way, the flexibility of the transition region is significantly improved, 
although the strength characteristics are reduced somewhat when compared 
to the shaft region. The distal region will consist only of the soft outer 
layer. The soft outer layer will be formed so that it defines a distal 
lumen which is contiguous with the central lumen defined by the inner 
tubular member. Alternate embodiments lacking either of the two distal 
regions have been described above. 
The soft outer layer can be composed of a variety of materials, preferably 
being composed of a soft thermoplastic material having a hardness in the 
range from 30 A to 72 D. Exemplary materials include polyamide polyether 
block copolymer (Pebax.RTM.), polyurethanes, silicone rubbers, nylons, 
polyethylenes, fluoronated hydrocarbon polymers, and the like. 
Referring now to FIGS. 2 and 3, an inner catheter 10 constructed in 
accordance with the principles of the present invention includes a 
catheter body 12. The catheter body 12 includes a shaft region 16 which 
extends from the proximal end 15 to a distal termination location, 
indicated by broken line 18. The transition region 20 extends from the 
termination 18 of the shaft region to a second termination location 
indicated by broken line 22. A distal region 24 extends from the 
termination 22 of the transition region 20 to a distal end 26 of the 
catheter body 12. The transition region 20 will thus have a length D.sub.1 
in the range from 0 cm to 10 cm, preferably from 1 cm to 10 cm, and more 
preferably from 1 cm to 3 cm and the distal region 24 will have a length 
D.sub.2 in the range from 0 cm to 10 cm, preferably from 1 cm to 10 cm, 
and more preferably from 1 cm to 3 cm, as shown in FIG. 2. 
The catheter body 12 includes an inner tubular member 30, typically 
comprising a PTFE tube. Braid structure 32 is then formed over the inner 
tubular member 30 from the proximal end thereof to near the termination 
location 18. The braid structure 32 will be square cut, as described in 
more detail hereinafter, so that it terminates cleanly at the desired 
termination location and is free from protrusions, burrs, and other 
discontinuities which could expose the patient to injury. A soft outer 
layer 34 extends from the proximal end of catheter body 16 to the distal 
end 26, covering both the inner tubular member 30 and the reinforcement 
braid 34. 
According to a preferred fabrication method, the catheter body 12 may be 
formed by placing a selected length of PTFE or other tubing over an 
elongate mandrel. Usually, the mandrel will be coated with PTFE to 
facilitate introduction and removal of the mandrel to and from the 
structure being formed. The assembly of the inner tubular member 30 over 
the mandrel is then introduced to a braiding machine, such as those 
available from Steeger, Germany; Wardwel, Mass.; and other commercial 
suppliers, where a conventional one-over-one or two-over-two braid pattern 
is formed. The pic and other characteristics of the braid will be selected 
to provide the desired stretch and flexibility for the shaft region. 
Usually, the pic will be in the range from 20 to 150 pics/inch, preferably 
from 60 to 100 pics/inch, and the pic may be constant over the entire 
length of the braided reinforcement layer or may be varied to increase 
flexibility at or near the distal end of the shaft region. In particular, 
the braid characteristics such as the pic, cross-sectional area, material 
strength, and the like, may be varied to provide increased flexibility at 
the distal end of the catheter body, typically over the distal 1 cm to 60 
cm of the catheter body, usually over at least 5 cm, and more usually from 
10 cm to 60 cm. The increased flexibility may be constant over the distal 
end, or may be progressive (i.e., becoming increasingly flexible near the 
distal end). The use of such non-uniform braid characteristics to enhance 
flexibility at the distal end of the catheter body is particularly useful 
when the inner tubular member, reinforcement layer, and soft outer layer 
are terminated within 1 cm of each other. 
In a particular aspect of the fabrication technique of the present 
invention, the braid is formed over a length which is slightly greater 
than that desired in the final construction. After forming the braid, the 
braid will be slipped distally over the inner tubular member so that it 
extends beyond both the inner tubular member and the mandrel. The 
stainless steel braid material will then be heat annealed, typically by 
exposure to a flame or resistance heater, and will thereafter be 
transversely cut to provide a clean, square-cut distal end. After being 
cut, the braid is then pulled proximally back over the mandrel and the 
inner tubular member 30, so that the distal termination 18 of the braid 
lies at the desired location. 
The soft outer layer 34 is then formed over the assembly of the inner 
tubular member 30 and the braid 32 by placing a thermoplastic tube, 
typically a Pebax.RTM. tube, over the entire assembly so that a distal end 
of the tube extends distally of the distal end of inner tubular member 30. 
A heat shrink tube, such as a polyethylene or fluoropolymer tube, is then 
placed over the soft thermoplastic, and the entire assembly placed in an 
oven and heated to a temperature sufficient to melt the thermoplastic and 
constrict the heat shrink tube over the melted thermoplastic. In this way, 
the thermoplastic material is able to impregnate the braid 32 and is 
constricted over the mandrel to form a contiguous lumen, as best 
illustrated in FIG. 3. By carefully choosing the mandrel diameter to match 
that of the inner diameter of tubular member 30, a very smooth transition 
between the lumen of inner tubular member 30 and that defined by the soft 
outer layer 26 can be obtained. 
After cooling, the heat shrink tube can be cut from the catheter body 
assembly. The distal end of a soft outer layer can then be cut to its 
desired final length. The proximal connector 14 can then be attached to 
the proximal end of the catheter body 12, although the connector is not an 
essential part of the present invention. 
Inner catheter 10 can be further modified by providing radiopaque markers 
at one or more locations along its length. Such radiopaque markers can 
comprise metal rings, or can be defined by impregnating the soft polymeric 
layer with appropriate radiopaque dyes. The provision of radiopaque 
markers is well known in the art and does not form a part of the present 
invention. 
Balloon 8 is bonded distal end 5 of sheath 3. Distal end 5 is a necked-down 
region to reduce outside diameter after annular end 42 of balloon is 
attached. Balloon 8 is mounted to outer sheath end 5 using an adhesive 
such as an RTV silicone adhesive, for example Loctite 5140 or Nusil 
Technology R-1140, or a UV curing adhesive. As shown in FIG. 3, the tip 44 
body 12 extends beyond the distal end of sleeve 40; the distal annular 
edge 46 of elastomeric balloon 8 is bonded to tip 44 using the same or a 
similar adhesive as used with end 42. 
Injection port assembly 6 includes an injection port 48 fluidly coupled to 
an inflation passageway 50 defined between outer sheath 3 and inner 
catheter 10. An inflation medium, such as air, contrast fluid, saline, 
etc., can be injected through port 48, into passageway 50 and out through 
an annular exit opening 52 defined between distal end 5 of sheath 3 and 
distal region 24 of catheter body 12. Doing so causes balloon 8 to expand 
to either partially or totally occlude the particular vessel within which 
the balloon has been placed. Total occlusion of the vessel can be desired 
for, for example, diagnostic purposes or to permit injection of saline to 
promote successful use of endoscopic devices. Partial occlusion can be 
useful when injecting particles, tissue adhesives or coils, when placing 
detached balloons and when conducting diagnostic procedures and other 
therapeutic procedures. 
Balloons having minimum and maximum diameters from about 4 to 14 mm can be 
used with inner catheter/outer sheath sizes from about 3.2 F/5.5 F to 
about 7 F/9.5 F. Balloons having minimum and maximum diameters from about 
2 to 7 mm can be used with inner catheter/outer sheath sizes from about 1 
F/3 F to about 3.2 F/6.5 F. 
Although not shown in the figures, it is preferred to secure inner catheter 
10 to outer sheath 3 at several places, typically three, in addition to 
their distal ends (through balloon 8) and their proximal ends (through 
injection port assembly 16). This can be accomplished by staking outer 
sheath 3 against inner catheter at several positions in a manner not to 
seal off passageway 50. Alternatively, outer layer 34 can be made with 
raised buttons or beads of material extending from the outer surface of 
outer layer 34; after assembly, sheath 3 can be heat sealed to outer layer 
34 of inner catheter 10 at the beads or buttons, again while maintaining 
free fluid flow along passageway 50. 
Outer sheath 3 can be further modified for particular uses. For example, 
small perfusion ports or holes can be formed near distal end 5 to 
facilitate liquid perfusion, e.g., drug delivery, using catheter 2. 
Coatings such as hydrophilic, anti-thrombogenic, low-friction, 
hydrophobic, and other, coatings can be placed over the outer surface of 
the outer sheath 3 to enhance its use for particular applications. 
Additionally, distal end 5 can be formed into a desired geometry. 
One specific treatment the present invention is especially suited for is 
treating aneurysms. An aneurysm is the thinning of a wall of a blood 
vessel; if the blood vessel is within the brain and the thin wall bursts, 
a stroke can result. One way to prevent bursting of the vessel is to halt 
the flow of blood just upstream of the aneurysm. However, before doing so, 
it is best to determine what the effects of the blockage will be. That is, 
will blockage of the vessel create more problems than it solves by, for 
example, causing the patient to lose his or her eyesight or the ability to 
walk. In the past, blood vessels were temporarily occluded by the 
insertion of a balloon at a distal end of a catheter. If the effects were 
acceptable, the balloon catheter would be removed and a therapeutic 
catheter would be inserted in its place. Some type of occlusion mechanism, 
typically tissue adhesives or a physical obstruction, would typically be 
inserted to occlude the vessel and thus prevent the stroke. However, 
balloon catheter 2 provides for both the occlusion of the vessel by 
elastomeric balloon 8 and an open inner passageway through inner catheter 
10 for carrying out the appropriate therapy. Therefore, there is no need 
to switch catheters with the present invention. 
An alternative embodiment 100 of the balloon catheter of the present 
invention is illustrated in FIG. 4. Balloon catheter 100 comprises an 
inner catheter 102, an outer sheath 104, and a balloon 106. Portions of 
the catheter 100 proximal to those illustrated may be identical to 
catheter 2 illustrated in FIG. 1. 
The inner catheter 102 comprises inner tubular member 108 and a soft outer 
layer 110, both of which elements are constructed similarly to those found 
in catheter 2. Inner catheter 102, in contrast to the prior described 
embodiments, includes a first reinforcement layer 112 and a second 
reinforcement layer 114, where the first reinforcement layer provides 
greater stiffness or column strength than does the second reinforcement 
layer 114. Preferably, the first reinforcement layer will be formed as a 
braided ribbon structure, generally as for the reinforcement layer in 
previously described embodiments. The second reinforcement layer 112, in 
contrast, will preferably be a helically wound ribbon, where the 
individual turns of the ribbon are axially spaced-apart by a short 
distance to enhance flexibility. Usually, the ribbon of the second 
reinforcement layer 114 will be a stainless steel ribbon. Also, the second 
reinforcement layer 114 will usually extend fully to the distal end 120 of 
the inner catheter 102. 
The outer sheath 104 will preferably be reinforced, typically by a 
helically wound ribbon, such as a stainless steel ribbon having 
cross-sectional dimensions of about 0.001 inch by 0.005 inch. The sheath 
104 will typically be composed of pebax. 
The balloon is preferably an elastomeric balloon typically composed of a 
urethane-based material. Such a balloon will be highly compliant. As 
illustrated in FIG. 4, the balloon 106 will be attached at its proximal 
end to the distal end of the sheath 104 and at its distal end to the 
distal end of the catheter 102. 
In the preferred embodiment, a separate, soft distal tip 122 will be 
attached to the distal end of the inner catheter 102. Usually, a 
radiopaque marker, such as the marker ring 124, will be embedded within 
the soft tip 122. 
Although the foregoing invention has been described in detail for purposes 
of clarity of understanding, it will be obvious that certain modifications 
may be practiced within the scope of the appended claims.