Patent Application
20070235899
The present invention generally relates to intravascular stent delivery and deployment catheters, and more particularly to a stent deployment device that is equipped with retention members for retaining a stent on a balloon during insertion and/or retraction of the stent.
In a typical percutaneous transluminal coronary angioplasty (PTCA) procedure, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient. The guide catheter is advanced through a vessel until the distal end thereof is at a desired location in the vasculature. A guide wire and a dilatation catheter having a flexible and expandable balloon on the distal end thereof are introduced into the guiding catheter with the guidewire sliding through the dilatation catheter. The guide wire is first advanced out of the guiding catheter into the patient's coronary vasculature, and the dilatation catheter is then advanced over the previously advanced guide wire until the dilatation balloon is properly positioned across the lesion. Once in position, the preformed balloon is inflated to a predetermined size with a liquid or gas at relatively high pressure (e.g. about ten to twelve atmospheres) to radially compress the arthrosclerotic plaque in the lesion against the inside of the artery wall and thereby dilate the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation catheter may be withdrawn from the patient's vasculature and blood flow resumed through the dilated artery.
Restenosis may occur in an artery following PTCA or other angioplasty procedure. Restenosis is a re-narrowing of the treated coronary artery that is related to the development of neo-intimal hyperplasia within the artery in response to mechanical intervention within a vascular structure. To prevent restenosis and strengthen the treated vascular area, an intravascular prosthesis generally referred to as a stent may be implanted for maintaining vascular patency inside the artery at the lesion. The stent is mounted in a pre-deployment or compressed state around a deflated balloon, and the balloon/stent assembly is maneuvered through a patient's vasculature to the site of a target lesion. The stent is then expanded to a larger diameter for implantation in the vasculature. The stent effectively overcomes the natural tendency of the vessel walls of some patients to close back down, thereby maintaining a normal flow of blood through the vessel that would not be possible if the stent was not in place.
One type of expandable stent that is delivered on a balloon catheter is a metallic steel cylinder having a number of openings in its circumference. The array of openings in the stent produces scaffolding when the device is expanded. The metallic steel cylinder is compressed onto an exterior surface of a non-expanded balloon that is attached to a catheter distal end region. Unfortunately, the stent is not always sufficiently secured to the balloon to ensure that the stent will properly stay in place while advancing the stent to and through a target lesion. Additionally, the outer surface of the delivery device may be uneven because the stent generally extends radially outwardly beyond the balloon exterior surface. Thus, the stent may contact a vessel wall and be displaced as the catheter negotiates a narrow vessel.
For example, the guide catheter may be inserted through the abdominal aorta to a point just beyond the ostium from which the right coronary artery and the left main artery diverge. Blockages or lesions may form in smaller coronary vessels, and there may be occasions when the balloon/stent catheter cannot be properly positioned within the target area due to the constriction of a vessel. Even if predilatation is performed prior to stent engagement, vascular spasms and/or re-closure of the vessel may occur and create difficulty when aligning the balloon/stent assembly. In addition, a lesion may be heavily calcified, requiring a high insertion pressure, which may result in unwanted displacement of the compressed stent.
Accordingly, it is desirable to provide a low profile stent delivery and deployment apparatus that includes features for improving the retention force acting on a compressed stent that is formed around a balloon. In addition, it is desirable to provide efficient and effective methods for manufacturing and using such a deployment apparatus. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
A method is provided for constructing stent retention features on a pre-formed stent deployment balloon. The pre-formed balloon is folded into a folded configuration for subsequently retaining an undeployed stent. The balloon is then inserted in the folded configuration into at least one sheath defining a pattern of openings. The balloon is then heated and pressurized to force exterior portions of the balloon into the openings and thereby form protruding stent retention features as part of the balloon. According to another embodiment, a stent is then crimped around the balloon in the folded configuration.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
The shaft 14 defines one or more passages or lumens extending therethrough, at least one of which is an inflation lumen that is connected to and in fluid communication with both the balloon and the hub for the purpose of selectively inflating and deflating the balloon.
The stent 22 is an expandable device made from a biocompatible material such as stainless steel, or a cobalt chromium alloy, or a bioabsorbable material and may be sized and configured as suitable for its intended placement, function, and so forth. The stent 22 depicted in the drawings is a cylindrical metal mesh having an initially crimped configuration, which may be forcibly expanded by the balloon 12 to a deployed configuration. In the crimped configuration, the stent has a smaller outer diameter than in the deployed configuration. When deployed in a body passageway, the stent 22 may be designed to press radially outward against a passageway wall to prevent the passageway from closing.
The balloon 12 includes substantially hemispherical-shaped dimples 28 protruding outwardly to frictionally engage with the stent 22. Consequently, the dimples 28 are formed in the balloon's expandable portion 25 on which the stent 22 is supported, and not on the distal or proximal end portions 27a and 27b. The dimples 28 are formed in a pattern on the overlapping pleats 32, the pattern being determined by an arrangement of holes in a mold as will be subsequently described in detail. Turning briefly to
As previously discussed, the balloon 12 may not provide a sufficient friction force on the stent 22 to ensure that the stent 22 will properly stay in place while being advanced to and through a target lesion. The stent 22 may have a larger outer diameter than the balloon 12, imparting an uneven surface to the overall balloon region. Thus, the stent 22 may contact a vessel wall and be displaced as the catheter negotiates a narrow vessel. The protruding dimples 28 formed on the balloon 12 create a sufficiently strong friction force on the stent 22 to maintain its placement through a patient's tortuous vasculature. Dimensions such as the overall width and height for the dimples 28 will vary depending on factors that may include the stent dimensions, the type of procedure for which the stent 22 will be employed, the balloon material, and the balloon configuration with respect to the stent 22.
Turning now to
Some prior art dimple forming methods attempt to include incorporate dimples or other stent retention features while the balloon itself is being initially molded or otherwise formed. This results in dimples being formed over many regions that will eventually be covered by overlapping folds or pleats in the balloon. In contrast, the present method includes folding and otherwise arranging the balloon 12 to the configuration it will ultimately resemble while retaining the un-deployed stent 22. After folding the balloon, dimples will be formed only in those outwardly exposed areas of the folds or pleats 32 that will contact the stent 22. Thus, dimples are not folded onto other dimples according to the present method, but non-dimpled regions are folded onto non-dimpled regions, and dimples are only formed on non-overlapping balloon regions.
In an exemplary embodiment, the balloon 12 is also configured for dimple formation by attaching the balloon 12 to the shaft distal end 18. More particularly, the balloon 12 is attached in the manner depicted in
After configuring the balloon 12, a sheath is placed around the balloon's expandable portion 25 as step 52.
There are numerous dimple patterns that may be formed in the balloon 12 by arranging the array of holes 34 in the sheath 30 as desired. Further, the holes 34 need not be round. For example, instead of forming hemispherical dimples on the balloon 12, it may be desirable to form elongate ribs along the balloon folds 32 instead of hemispherical dimples. The holes 34 in such an embodiment would be elongate openings. As previously discussed, the balloon 12 depicted in
Once the balloon 12 is inserted into a sheath, the coupled sheath and balloon are placed into a heating block as step 54.
In an exemplary embodiment, the balloon 12 is attached to the shaft distal end 18 as depicted in
As step 58, the constructed balloon 12 is coupled to the stent 22 by sliding the stent 22 onto the balloon's expandable portion 25. The stent 22 engages at least with the dimples 28 on the balloon 12 and is thereby longitudinally retained in position and prevented from slipping when the catheter 14 advances through a passageway such as a patient's vasculature.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.
