Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
2000-07-10
2003-01-14
Walberg, Teresa (Department: 3742)
Surgery
Instruments
Internal pressure applicator
C604S103050, C604S103060, C604S103080
Reexamination Certificate
active
06506202
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a system which can be used when an interventional procedure is being performed in a stenosed or occluded region of a blood vessel to substantially retain the unexpanded axial dimension of an expandable interventional instrument upon expansion thereof. The system of the present invention is particularly useful when performing stenting procedures in critical vessels, such as the carotid arteries.
A variety of non-surgical interventional procedures have been developed over the years for opening stenosed or occluded blood vessels in a patient caused by the build up of plaque or other substances on the walls of the blood vessel. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient's arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the blood vessel.
Another procedure is laser angioplasty which utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which a cutting blade is rotated to shave the deposited plaque from the arterial wall. A vacuum catheter is usually used to capture the shaved plaque or thrombus from the blood stream during this procedure.
In another widely practiced procedure, the stenosis can be treated by placing an expandable interventional instrument such as an expandable stent into the stenosed region to hold open and sometimes expand the segment of blood vessel or other arterial lumen. Stents are particularly useful in the treatment or repair of blood vessels after a stenosis has been compressed by percutaneous transluminal coronary angioplasty (PTCA), percutaneous transluminal angioplasty (PTA) or removal by atherectomy or other means. Stents are usually delivered in a compressed condition to the target site, and then are deployed at the target location into an expanded condition to support the vessel and help maintain it in an open position.
Prior art stents typically fall into two general categories of construction. The first type of stent is expandable upon application of a controlled force, often through the inflation of an expandable member such as an expandable balloon in a dilatation catheter which, upon inflation of the balloon or other expansion means, expands the compressed stent to a larger diameter to be left in place within the artery at the target site. The second type of stent is a self-expanding stent formed from, for example, shape memory metals or super-elastic nickel-titanum (NiTi) alloys, which will automatically expand from a compressed state when the stent is advanced out of the distal end of the delivery catheter into the body lumen. Such stents manufactured from expandable heat sensitive materials allow for phase transformations of the material to occur, resulting in the expansion and contraction of the stent.
Stent delivery systems typically include a balloon catheter, a stent which is mounted on the balloon, and a delivery sheath which surrounds the stent-delivery catheter. Initial angioplastic dilation of the lesion produces a residual lumen large enough to accept the stent delivery system. The guiding catheter used to perform the initial dilation is typically left in place in the patient and reused during the stent implantation procedure. The stent-delivery catheter is routed through the guiding catheter to a position in which its distal end is disposed substantially coextensively with the distal end of the guiding catheter and immediately proximate of previously expanded lesion.
Once properly positioned relative to the guiding catheter, the stent-carrying catheter is extended from the distal end of the gliding catheter until the stent spans the previously dilated lesion. The delivery sheath which is slidable relative to the delivery catheter, balloon and stent, is then withdrawn into the guiding catheter to expose the balloon and stent. The delivery catheter is then supplied with a pressurized fluid, which expands the balloon and associated stent to a desired diameter sufficient to exceed the elastic limit of the stent. The stent thus comes in contact with, and permanently supports, the wall of the vessel. The delivery catheter balloon is then deflated and the delivery catheter and guiding catheter are withdrawn, leaving the expanded stent supporting the vessel lumen.
The above stent delivery procedure, if successful, avoids the necessity of major surgical operations. It is desirable to position the undeployed stent near the middle of the length of the affected area, such that upon radial expansion for deployment thereof, it will be positioned so as to precisely treat the entire affected area. However, for balloon-expandable stents, the expansion characteristics of the balloon may result in changes in the unexpanded axial dimension of the stent, constituting the unexpanded length thereof, upon radial expansion, which may cause stent lengthening or shortening from the initial length of the stent in its unexpanded condition. Stent lengthening may adversely affect healthy tissue, while stent shortening may fail to treat the entire affected area. Stent shortening may result from inadequate adhesion between the stent and the balloon as the balloon is being inflated. When a balloon is inflated, it grows axially. However, a stent crimped on the balloon usually shortens as the balloon inflates. This contradictory phenomenon of axial balloon growth and stent shortening may occur due to the loss of friction contact between the stent and the balloon during deployment. Stent shortening may still occur even when the stent is crimped with a heat and pressure process, which improves stent retention through mechanical interlocks formed between the balloon and stent. This process does not always, however, prevent the stent from decoupling during deployment.
The above problems may arise from the expansion characteristics of the expandable balloon used to expand and deploy the stent. The expandable balloon may be manufactured from a single layer of material such as polyurethane, having strong adhesion characteristics such that balloon axial growth may cause the stent to grow beyond its stated length, which could adversely affect healthy tissue extending beyond the affected area. Further, a condition known as “dog boning” may arise whereby the ends of the expandable balloon may expand initially while the middle portion of the stent remains unexpanded. As the ends of the balloon expand, they may tend to push the struts of the stent inward causing shortening of the stent and preventing treatment to the entire affected area.
What has been needed is a reliable system and method for delivering an expandable interventional device for treating stenosis in blood vessels which treat precisely the length of the lesion constituting the entire affected area, and which do not adversely affect surrounding healthy tissue. The system and method should be capable of expanding the expandable interventional device while retaining the unexpanded length thereof to allow the precise placement of the stent over the lesion to be treated. The system and method should be relatively easy for a physician to use. Moreover, such a system should be relatively easy to deploy and remove from the patient's vasculature. The inventions disclosed herein satisfy these and other needs.
SUMMARY OF INVENTION
The present invention provides a system and method for treating an entire affected area in a blood vessel during the performance of a therapeutic interventional procedure, such as a balloon angioplast
Dutta Debashis
Wang Chicheng
Advanced Cardiovascular Systems Inc.
Dahbour Fadi H.
Fulwider Patton Lee & Utecht LLP
Walberg Teresa
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