Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
2000-11-14
2002-12-10
Truong, Kevin T. (Department: 3731)
Surgery
Instruments
Internal pressure applicator
C623S001110
Reexamination Certificate
active
06491711
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the field of medical devices, and more particularly to a catheter balloon having a taper with a non-circular transverse cross section.
In percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter is advanced until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire, positioned within an inner lumen of an dilatation catheter, is first advanced out of the distal end of the guiding catheter into the patient's coronary artery 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 coronary anatomy, 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 one or more times to a predetermined size at relatively high pressures (e.g. greater than 8 atmospheres) so that the stenosis is compressed against the arterial wall and the wall expanded to open up the passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. Substantial, uncontrolled expansion of the balloon against the vessel wall can cause trauma to the vessel wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom.
In such angioplasty procedures, there may be restenosis of the artery, i.e. reformation of the arterial blockage, which necessitates either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate and to strengthen the dilated area, physicians frequently implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter, and the stent is left in place within the artery at the site of the dilated lesion.
In the design of catheter balloons, balloon characteristics such as strength, flexibility and compliance must be tailored to provide optimal performance for a particular application. Angioplasty balloons preferably have high strength for inflation at relatively high pressure, and high flexibility and softness for improved ability to track the tortuous anatomy and cross lesions. The balloon compliance is chosen so that the balloon will have a desired amount of expansion during inflation. Compliant balloons, for example balloons made from materials such as polyethylene, exhibit substantial stretching upon the application of tensile force. Noncompliant balloons, for example balloons made from materials such as PET, exhibit relatively little stretching during inflation, and therefore provide controlled radial growth in response to an increase in inflation pressure within the working pressure range.
In order to decrease the cross sectional profile of the balloon catheter to thereby facilitate advancement of the catheter within the patient's vasculature and across a stenosed region, balloons may be folded into a low profile configuration having balloon wings wrapped around the balloon prior to insertion into the patient. However, one difficulty has been after the balloon is inflated in the patient, the balloon tends to deflate to form a large flat wing or a bunched irregular shape. The resulting relatively large profile of the deflated balloon tends to complicate repositioning or removal of the balloon in the vasculature.
It would be a significant advance to provide a catheter balloon with improved refold upon deflation after inflation of the balloon.
SUMMARY OF THE INVENTION
The invention is directed to a balloon catheter including an elongated shaft and a balloon on a distal shaft section having a working section, and tapered sections having an inflated configuration with a non-circular transverse cross section (hereafter “non-circular tapers”). In one embodiment, the noncircular tapers are triangular, although alternative non-circular cross sectional designs may be used, such as lobed tapers. The non-circular tapers deflate to form two or more deflated wings along at least a section of the deflated balloon. The deflated wings provide a deflated balloon with a relatively low profile, which facilitates repositioning or removal of the balloon catheter within the patient's vasculature.
The balloon catheter of the invention generally comprises an elongated shaft having proximal and distal ends and at least an inflation lumen, and a balloon on a distal shaft section having an interior in fluid communication with the inflation lumen. The balloon has a working section which in a presently preferred embodiment has a cylindrical inflated configuration. The balloon working section or length is typically centrally located and is configured to inflate to perform a therapeutic or diagnostic medical procedure such as dilatation of a stenosis, deployment of a stent, or delivery of a medium. A proximal non-circular tapered section is proximal to the working section, and a distal non-circular tapered section is distal to the working section
The non-circular tapered section of the balloon has a plurality of side sections and cusps between adjacent side sections. The balloon deflates with a fold along the line of the each cusp, to thereby form a plurality of deflated wings. In a presently preferred embodiment, the tapered section has three cusps to thereby form three deflated wings. However, in alternative embodiments, the tapered section may have two cusps or more than three cusps, depending on the non-circular shape of the tapered section. A tapered section with three cusps, such as in a triangular cross section, is generally preferred over shapes with four or more cusps due to the lower volume and the smaller outer diameter provided by the tri-cusped tapered section.
The non-circular configuration of the tapers provides tapered sections having a reduced volume compared with conventional conical tapered sections. Preferably, the non-circular tapered section has an inflated inner volume which is not greater than about 75% of the inflated inner volume of a conventional conical tapered section. As a result, the balloon of the invention inflates and deflates faster than a balloon having a conical tapered section due to the reduced inner volume of the balloon of. the invention, and without reducing. the inflated outer diameter of the working section.
In one embodiment, the balloon includes a proximal conical tapered section between the working length and at least a portion of the proximal non-circular tapered section, and a distal conical tapered section between. the working length and at least a portion of the distal non-circular tapered section. The conical section preferably slopes away from the working length at a steeper angle than conventional conical tapered sections. The non-circular tapered sections preferably taper at the same angle than conventional conical tapered sections. However, the non-circular tapered sections may taper at a smaller angle than conventional tapers, i.e., a more gradual taper, which, due to the reduced volume of the non-circular configuration, will not: impact the inflation/deflation time of the balloon. The balloon of the invention is configured to minimize contact between the patient's vessel wall and the sections of the balloon beyond either end of the working length.
In one embodime
Advanced Cardiovascular Systems Inc.
Fulwider Patton Lee & Utecht LLP
Truong Kevin T.
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