Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2000-06-15
2004-03-09
Lazarus, Ira S. (Department: 3749)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S524000, C604S525000, C604S264000, C604S104000, C623S001110, C623S001130
Reexamination Certificate
active
06702802
ABSTRACT:
FIELD OF INVENTION
The invention relates to the field of intravascular delivery systems, and more particularly to balloon catheters for stent delivery in the intracranial vasculature, referred to herein as neurovasculature.
BACKGROUND OF THE INVENTION
In neurovascular angioplasty procedures a guiding catheter is advanced until the distal tip of the guiding catheter is just proximal to the origin of the intracranial arteries that lead to the target vascular site. A guidewire, positioned within an inner lumen of a dilatation catheter, is first advanced out of the distal end of the guiding catheter into the patient's intracranial vasculature until the distal end of the guidewire crosses a lesion to be dilated. Then the dilatation catheter, having an inflatable balloon on the distal portion thereof, is advanced into the patient's intracranial vasculature over the previously introduced guidewire until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with liquid saline or radiopaque contrast one or more times to a predetermined size at relatively high pressures (e.g. at least about 4-6 atmospheres) so that the lesion is dilated to restore vessel patency. However, damage to the vessel wall at and around the lesion can result from the expansion of the balloon against the vessel wall. After the balloon is finally deflated, blood flow resumes through the dilated vessel and the dilatation catheter can be removed therefrom.
In such neurological angioplasty procedures, there may be restenosis of the lesion due to acute or sub-acute (chronic) complications, such as vessel recoil, lesion dissection, intimal hyperplasia, or other factors. The resulting restenosis may in turn necessitate either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. In similar coronary angioplasty, the restenosis rate is reduced and the dilated area is strengthened by implanting an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. However, currently, this treatment modality is not available in neurovascular applications due primarily due to the inability to access the distal, highly tortuous anatomy of the neurovascular system with conventional stent delivery systems. Further details of stents and stent delivery systems for PTCA procedures can be found in U.S. Pat. No. 5,507,768 (Lau et al.), U.S. Pat. No. 5,458,615 (Klemm et al.), and U.S. Pat. No. 5,514,154 (Lau et al.), which are incorporated herein by reference in their entireties. Commonly used coronary stent delivery systems are too inflexible to track through the neuro anatomy. Furthermore, they tend to kink when bent into tight radius curves.
Therefore, what has been needed is a catheter and stent delivery system suitable for use in neurovascular applications. The present invention satisfies these and other needs.
SUMMARY OF THE INVENTION
The present invention is directed to a balloon catheter, such as a dilatation catheter and a stent delivery catheter with improved stiffness transition and specifically with no sudden changes in stiffness along the catheter length. In the balloon catheters of the invention alone or mounted with a stent, whether used for peripheral, coronary, or neurovascular applications, is important to reduce the significant bending stiffness changes (herein referred to as bending stiffness discontinuity) present along the length of the catheter. It should also be appreciated that although in describing features of the present invention, the features are directed primarily to a neurovascular stent delivery system, the invention is also applicable to coronary and peripheral stent delivery systems, as well as dilatation catheters for peripheral, neurological, coronary, and similar applications.
Having smooth transitions from one region to another along the length of the catheter, in particular, when a stent is located on the catheter, is of particular importance in neurovascular applications. The major design challenge for a Neurovascular Stent Delivery System (NSDS), in particular, has been in improving the ability to access the distal, highly tortuous anatomy of the neurovascular system. In order to meet this challenge, the present invention provides for a catheter and stent delivery system optimized for flexibility and kink-resistance. Improved flexibility allows the device to turn tight corners along the vasculature without applying large forces against the wall of the vessels, thus minimizing the surface friction between the catheter and the vessel. This allows more distal access, particularly in tortuous neurovascular anatomy.
The optimization of flexibility for the neurovascular stent delivery system may aggravate the kinking dynamic, as for example, bending stiffness discontinuities can be more pronounced as some softer catheter members are more likely to kink than stiffer members. Kinking of the catheter is also a common constraint to distal access. The kink creates a hinge point in the catheter so that the catheter can no longer navigate tight radius turns in the vasculature. Kinks often occur at the interface of two regions along the device having substantially different bending stiffness (i.e., have a discontinuity in the bending stiffness). Examples of such interfaces, include, but are not limited to: the proximal and distal ends of a stent disposed on a catheter, and areas adjacent the balloon seals and marker bands.
The stent delivery system of the present invention, in particular as adapted for neurovascular applications, has been optimized for flexibility and kink resistance. The kink resistance has been achieved by minimizing the differential in bending stiffness at the troublesome regions. The present invention includes various embodiments for minimizing the bending stiffness differential as well as increasing the overall flexibility of the catheter, including but not limited to one or more of the following: (1) the lengthening and softening of the catheter tip and the distal balloon seal while maintaining a low profile, (2) crimping the ends of the stent onto the marker bands, (3) locating stiffening sleeves on the inner member on or near the ends of the stent, (4) using a variable stiffness inner member, and (5) providing variable stiffness sheath on the catheter particularly over the stent; in order to reduce the stiffness differential among adjacent portions along the catheter.
In the practice of the present invention, the areas of low bending stiffness located immediately before or after an area of higher bending stiffness may be “built up” in stiffness to gradually transition the stiffness of that portion to an adjacent portion of higher value, thus providing a relatively smooth transition from one region to another.
In other words, the present catheter has more than one portion with different stiffness values, each portion comprising of components that gradually transition the stiffness of that portion to an adjacent portion, thus reducing the differential in bending stiffness in moving from one region to another, when the catheter is used alone or in combination with a stent in a stent delivery system.
The stent delivery system of the present invention includes a catheter having an elongated shaft with proximal and distal ends and an inner lumen extending therein. The system further includes an enlargable member mounted on a distal shaft section proximal to the distal end which is configured for supporting a deployable prosthetic device on a receiving portion thereon. The enlargable member has an interior in fluid communication with the inner lumen. Furthermore, a tubular member extends through the interior of the enlargable member.
In one embodiment, the stent delivery system further includes proximal and distal radiopaque markers disposed on a portion of the tubular member extending within the interior of the enlargable member. Preferably, a portion of each marker is within and a portion is outside the receiving po
Brown Peter S.
Chi David
Cryer Brett W.
Hancock David
Mirizzi Michael S.
Endovascular Technologies, Inc.
Fulwider Patton Lee & Utecht LLP
Lazarus Ira S.
Nguyen Camtu
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