Surgery – Means for introducing or removing material from body for... – Material introduced into and removed from body through...
Reexamination Certificate
2000-04-07
2004-03-16
Hayes, Michael J. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Material introduced into and removed from body through...
C604S264000, C604S103000, C604S096010
Reexamination Certificate
active
06706010
ABSTRACT:
TECHNICAL FIELD
This invention relates to a balloon catheter used in percutaneous transluminal angioplasty (PTA) or percutaneous transluminal coronary angioplasty (PTCA), in which constricted areas or obstructions such as in the coronary artery, limb arteries, the renal artery, or peripheral vessels are treated by dilation, and to a method for manufacturing this balloon catheter, and more particularly relates to a balloon catheter with improved characteristics for the catheter shaft distal end portion, including the balloon, and to a method for manufacturing this balloon catheter.
BACKGROUND ART
A balloon catheter is generally made up of a catheter shaft and a vascular dilation balloon provided to the distal end portion of this catheter shaft. Angioplasty using a balloon catheter such as this is conducted by the following procedure. First, a guide wire is passed through the afflicted site (such as an obstruction), the balloon catheter is inserted along this guide wire until the balloon is at the afflicted site, and the balloon is inflated by supplying a suitably diluted contrast medium or the like to an inflation lumen. After this inflation, the balloon is depressurized and deflated, and the balloon catheter is taken out of the body.
A specific example of a conventional balloon catheter, and the problems encountered with it, will now be described.
FIG. 5
illustrates the cross sectional structure of a conventional balloon catheter at its distal end portion. In the figure,
80
is a catheter shaft,
81
is an inner tube,
82
is an outer tube,
83
is a balloon, and
84
is an X-ray impermeable marker. The proximal end
85
of the balloon
83
provided at the distal end portion of the catheter shaft
80
is joined to the distal end portion of the outer tube
82
, and the distal end
86
of the balloon
83
is joined in the proximity of the distal end portion of the inner tube
81
. When this balloon
83
is depressurized and deflated, it wraps up as shown in FIG.
6
. The following problems were encountered when a balloon catheter with a structure such as this was used at an afflicted site with a high degree of difficulty. When the surgeon applied force to the proximal end of the balloon catheter so as to align the balloon at a highly constricted site, the thin-walled balloon
83
deformed like a bellows (called “accordioning”), so the force applied to the proximal end was not sufficiently transmitted to the distal end, making it much more difficult for the catheter to pass through the afflicted site, and the balloon could not be accurately aligned with the constricted area. The cause of this was that the outer tube
82
and inner tube
81
were fixed to branched hubs, or the like, at the proximal end of the catheter, and were therefore securely restrained, and were weakly linked via just the thin-walled balloon
83
at the distal end portion, so the middle part between the distal end and proximal end portions was not restrained at all.
Balloon catheters with the structure illustrated in
FIG. 7
have been proposed in an effort to solve this problem (see, for example, Japanese Laid-Open Patent Applications H3-51059, H4-2363, and H5-137793). In the figure,
90
is a catheter shaft,
91
is an inner tube,
92
is an outer tube,
93
is a balloon, and
94
is an X-ray impermeable marker. Specifically, since the inner tube
91
was joined to the inner wall surface of the outer tube
92
in the proximity of the distal end portion of the outer tube
92
, and the outer tube
92
and the inner tube
91
were securely restrained by this joint
95
, the balloon
93
did not accordion even at difficult afflicted sites with severe constriction, and the pushing force applied by the surgeon was transmitted to the distal end portion. Nevertheless, the following problems were encountered with these balloon catheters.
In the positioning and inflation of the balloon at the afflicted site, the balloon extends radially and longitudinally due to the pressure applied by a pressurizing fluid, but the inner tube inside the balloon, that is, the inner tube located between the distal end portion proximity of the outer tube and the distal end portion proximity of the balloon, is stretched along with the longitudinal extension of the balloon. Then, when the dilation of the afflicted site is completed and the balloon is deflated, the balloon
93
returns to its original dimensions because it is made from a pressure-resistant type of material, but as shown in
FIG. 8
, the stretched inner tube
91
does not return to its original length, and instead slackens. The reason for this is that because the inner tube is usually made from a material selected for its ability to slide smoothly over the guide wire, it does not exhibit the elastic changes that the balloon does, and is instead prone to plastic deformation and is easily stretched. In this state, the position of the inner tube is shifted with respect to the folding creases in the balloon, and this makes it much more difficult to rewrap the balloon when it is deflated, resulting in winging, and if another attempt is made to pass the catheter through the constriction, the wings often snag and prevent the catheter from passing through. Specifically, once the balloon has been inflated, it passes through the afflicted site with more difficulty the second and subsequent times. This situation is illustrated in
FIGS. 9 and 10
. FIG.
9
(
a
) shows the state when the wings of the balloon
93
are wrapped in opposite directions around the inner tube
91
, and FIG.
9
(
b
) shows the state in which the wings
93
a
and
93
b
are not wrapped sufficiently and stick out. FIG.
10
(
a
) shows the state when the wings of the balloon
93
are wrapped in the same direction around the inner tube
91
, and FIG.
10
(
b
) shows the state in which the wings
93
a
and
93
b
are not wrapped sufficiently and stick out.
A problem that is common to both of the balloon catheters shown in
FIGS. 5 and 7
is that since the rigidity varies greatly in the outer tube distal end portion, this portion is prone to breakage when the balloon catheter is handled or when the guide wire is replaced. This is because the only things beyond the outer tube distal end portion are the slender inner tube and the thin-walled balloon, so discontinuity in the rigidity occurs.
Problems related to the very farthest point at the distal end portion of a conventional balloon catheter will now be described through reference to
FIGS. 21
to
26
.
FIG. 21
is an enlarged cross section illustrating the very farthest point at the distal end portion of a balloon catheter. In the figure,
100
is a balloon and
101
is an inner tube. The inner tube
101
goes through and sticks out from the distal end portion of the balloon
100
, and is bonded to the distal end-side bonded portion of this balloon by an adhesive agent layer
103
. The distal end portion of the inner tube
101
retains the tubular shape of the inner tube, and has an edge
104
at the most distal end portion. A problem with this edge
104
, however, was that it would snag when passing through the afflicted site in a blood vessel or through a curved section, making it difficult to pass the catheter through these areas.
In view of this, prior art has been proposed in which just the edge portion of the most distal end of the inner tube is removed, but at afflicted sites with a high degree of constriction, for instance, the difficulty of passing through the afflicted site or through curved sections has not been solved to satisfaction. Prior art in which the distal end tip of the balloon catheter is made flexible in order to improve this passage has been proposed in Japanese Laid-Open Patent Applications H2-271873 and H5-253304. Both of these disclose a structure in which the sleeve portion
111
(
121
) of the distal end portion of a balloon
110
(
120
) sticks out from an inner tube
112
(
122
) that forms a guide wire lumen (see
FIGS. 22 and 23
, which are simplified cross sections of the distal end tip). Here, in the example shown in
FIG. 22
,
Fukaya Kohei
Hashiba Masato
Maeda Hiromi
Miki Shogo
Nakano Ryoji
Armstrong Westerman & Hattori, LLP
Ghafoorian Roz
Hayes Michael J.
Kaneka Corporation
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