BACKGROUND

[0001] The present invention relates generally to medical devices and particularly to a balloon catheter with integral extensions on the surface of the balloon for securing a dilation element.

[0002] Balloon catheters are widely used in the medical profession for various intraluminal procedures. One common procedure involving the use of a balloon catheter relates to angioplasty dilation of coronary or other arteries suffering from stenosis (i.e., a narrowing of the arterial lumen that restricts blood flow).

[0003] Although balloon catheters are used in many other procedures as well, vascular angioplasty using a balloon catheter has drawn particular attention from the medical community because of the growing number of people suffering from vascular problems associated with arterial stenosis. This has lead to an increased demand for medical procedures to treat such problems. The widespread frequency of vascular problems may be due to a number of societal changes, including the tendency of people to exercise less while eating greater quantities of unhealthy foods, in conjunction with the fact that people generally now have longer life spans than previous generations. Angioplasty procedures have become a popular alternative for treating arterial stenosis because angioplasty procedures are considerably less invasive than other alternatives. As an example, stenosis of the coronary arteries has traditionally been treated with bypass surgery. In general, bypass surgery involves splitting the chest bone to open the chest cavity and grafting a replacement vessel onto the heart to bypass the blocked, or stenosed, artery. However, coronary bypass surgery is a very invasive procedure that is risky and requires a long recovery time for the patient.

[0004] To address the increased need for vascular treatments, the medical community has turned to angioplasty procedures, in combination with stenting and other procedures, to avoid the problems associated with traditional open surgery. Typically, angioplasty procedures are performed using a balloon-tipped catheter that may or may not have a stent mounted on the balloon (also referred to as a stented catheter). The physician performs the angioplasty procedure by introducing the balloon catheter into a peripheral artery (commonly one of the leg arteries) and threading the catheter to the narrowed part of the artery to be treated. During this stage, the balloon is uninflated and collapsed onto the shaft of the catheter in order to present a low profile which may be passed through the vasculature. Once the balloon is positioned at the narrowed part of the artery, the balloon is expanded by pumping a mixture of saline and contrast solution through the catheter to the balloon. As a result, the balloon presses against the inner wall of the artery to dilate it. If a stent is mounted on the balloon, the balloon inflation also serves to expand the stent and implant it within the artery. After the artery is dilated, the balloon is deflated so that it once again collapses onto the shaft of the catheter. The balloon-tipped catheter is then retracted from the body. If a stent is mounted on the balloon of the catheter, the stent is left permanently implanted in its expanded state at the desired location in the artery to provide a support structure that prevents the artery from collapsing back to its pre-dilated condition. Alternatively, if the balloon catheter is not adapted for delivery of a stent, either a balloon-expandable stent or a self- expandable stent may be implanted in the dilated region in a follow-up procedure. Although the treatment of stenosed arteries is one common example where balloon catheters have been used, this is only one example of how balloon catheters may be used and many other uses are also possible.

[0005] One problem that may be encountered with conventional angioplasty techniques is the proper dilation of stenosed regions that are hardened and/or have become calcified. Stenosed regions may become hardened for a variety of reasons, such as the buildup of atherosclerotic plaque or other substances. Hardened regions of stenosis can be difficult to completely dilate using conventional balloons because hardened regions tend to resist the expansion pressures applied by conventional balloon catheters. One solution that has been offered for dilating hardened stenoses is special balloon catheters with dilation wires or beads that extend along the length of the balloon. The dilation wires and/or beads focus that dilation pressure of the balloon onto the narrower contact area between the dilation wire or bead and the vessel wall. As a result, the increased, focused pressure may crack and/or break up the hardened stenosis, thereby allowing the vessel lumen to be expanded. [0006] One approach that has been used to attach dilation wires and/or beads to a balloon is securing the wires and/or beads to the exterior surface of the balloon with adhesives. However, the use of adhesives to secure dilation wires and/or beads has several disadvantages. For example, there may be concern that the adhesive could detach from the balloon surface and allow the dilation wire and/or bead to break loose. This may be a particular concern when the adhesive is the only or the primary mechanism for securing the dilation wire and/or bead to the balloon surface. Detachment of the adhesive from the balloon surface can be a more serious problem when the balloon is made of a compliant or semi-compliant material, because the balloon material stretches as the balloon expands but the dilation wire and/or bead may not stretch during expansion or may stretch at a different rate.

Because of these opposing forces between the balloon material and the dilation wire and/or bead, the adhesive may crack or lose its adherence to the balloon surface. Moreover, even in the case of non-compliant balloons, detachment of the adhesive may be a concern because physicians are particularly adverse to any possible risk of intravascular device failures. Thus, a mechanism for more securely attaching dilation wires and/or beads to a balloon surface would be desirable.

[0007] In addition, the use of adhesives in a manufacturing setting is

disadvantageous. Applying adhesives during the manufacturing process is typically a manually intensive task and time consuming. Maintaining cleanliness standards is also more difficult with the presence of adhesives, since adhesives are generally messy. The use of adhesives also requires extra fixturing to temporarily secure the parts being adhered while the adhesive cures.

[0008] Accordingly, the inventor believes it would be desirable to provide a balloon catheter with a mechanism that is integral with the balloon for securing a dilation wire and/or bead to the balloon surface.

SUMMARY

[0009] A balloon catheter is described that has an integral tubular extension along the length of the balloon for securing a dilation element to the balloon. The balloon may be made from an extruded parison with the tubular extensions integrally extruded with the parison. The dilation elements may be installed into the tubular extensions after the parison is extruded. The balloon may be formed by blow molding the parison.

[0010] The invention may include any of the following aspects in various combinations and may also include any other aspect described below in the written description or in the attached drawings.

[0011] A method of forming a balloon for a balloon catheter, comprising:

extruding a parison having a uniform shape along an entire length thereof, the parison comprising a central opening and a longitudinal tubular extension extending from an exterior surface of the parison, the tubular extension defining a longitudinal cavity bounded circumferentially and longitudinally by a wall of the tubular extension; disposing a dilation element into the longitudinal cavity of the tubular extension through an end opening thereof; and

heating the parison inside a mold and pressurizing the central opening, the parison thereby expanding against the mold, wherein an outer portion of the wall is compressed against the mold, and the dilation element extends along a length of a working diameter of the balloon.

[0012] The method wherein the mold comprises a clearance cavity receiving the tubular extension along a working diameter portion.

[0013] The method wherein the mold comprises a clearance cavity at least partially receiving the tubular extension along a neck region, the clearance cavity in the neck region thereby indexing the parison to the clearance cavity along the working diameter portion.

[0014] The method further comprising disposing heat shrink tubing over the tubular extension along the neck region after the heating and pressurizing, the tubular extension along the neck region thereby being substantially reformed into the exterior surface of the parison.

[0015] The method further comprising stretching the parison while the parison is heated after the dilation element is disposed into the tubular extension and before the parison is pressurized, the tubular extension thereby shrinking diametrically against the dilation element.

[0016] The method wherein the mold does not comprise any clearance cavities receiving the tubular extension along a tapered region extending to a neck region, the tubular extension thereby being compressed against the mold and substantially closing the longitudinal cavity along the tapered region.

[0017] The method wherein a first outer width across the tubular extension between the longitudinal cavity and the exterior surface of the parison is less than a second outer width across the tubular extension across the longitudinal cavity, the first outer width isolating the tubular extension during the heating and pressurizing to minimize reshaping of the tubular extension during the heating and pressurizing.

[0018] The method wherein the dilation element is entirely sealed within the tubular extension, the tubular extension being characterized by not comprising any lateral openings through the wall of the tubular extension.

[0019] The method wherein the dilation element comprises a round cross-section.

[0020] The method wherein the dilation element comprises a non-round cross- section.

[0021] The method wherein the dilation element is entirely sealed within the tubular extension, the tubular extension being characterized by not comprising any lateral openings through the wall of the tubular extension, the mold comprising a clearance cavity receiving the tubular extension along a working diameter portion, and further comprising stretching the parison while the parison is heated after the dilation element is disposed into the tubular extension and before the parison is pressurized, the tubular extension thereby shrinking diametrically against the dilation element.

[0022] The method wherein the mold does not comprise any clearance cavities receiving the tubular extension along a tapered region extending to a neck region, the tubular extension thereby being compressed against the mold and substantially closing the longitudinal cavity along the tapered region, and the mold comprising a clearance cavity at least partially receiving the tubular extension along the neck region, the clearance cavity in the neck region thereby indexing the parison to the clearance cavity along the working diameter portion.

[0023] The method further comprising disposing heat shrink tubing over the tubular extension along the neck region after the heating and pressurizing, the tubular extension along the neck region thereby being substantially reformed into the exterior surface of the parison, wherein a first outer width across the tubular extension between the longitudinal cavity and the exterior surface of the parison is less than a second outer width across the tubular extension across the longitudinal cavity, the first outer width isolating the tubular extension during the heating and pressurizing to minimize reshaping of the tubular extension during the heating and pressurizing, and the dilation element comprising a round cross-section.

[0024] A balloon catheter, comprising:

a balloon mounted on a catheter, the balloon configured to expand from a deflated state to an expanded state;

an integral longitudinal tubular extension disposed along a working diameter length of an exterior surface of the balloon, wherein the tubular extension comprises a longitudinal cavity bounded by a wall of the tubular extension; and

a dilation element disposed within the longitudinal cavity, wherein opposing ends of the dilation element are longitudinally restrained by compressed portions of the tubular extension adjacent the opposing ends.

[0025] The balloon catheter wherein a first outer width across the tubular extension between the longitudinal cavity and the exterior surface of the balloon is less than a second outer width across the tubular extension across the longitudinal cavity.

[0026] The balloon catheter wherein the dilation element is diametrically squeezed by the wall of the longitudinal extension.

[0027] The balloon catheter wherein the dilation element extends substantially the entire length of the working diameter length of the balloon.

[0028] The balloon catheter wherein the dilation element is entirely sealed within the tubular extension, the tubular extension being characterized by not comprising any lateral openings through the wall of the tubular extension.

[0029] The balloon catheter wherein the dilation element is diametrically squeezed by the wall of the longitudinal extension, and the dilation element extends substantially the entire length of the working diameter length of the balloon.

[0030] The balloon catheter wherein the dilation element is entirely sealed within the tubular extension, the tubular extension being characterized by not comprising any lateral openings through the wall of the tubular extension. BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0031] The invention may be more fully understood by reading the following description in conjunction with the drawings, in which:

Figure 1 is a perspective view of an extruded parison;

Figure 2 is a perspective view of different dilation elements;

Figure 3 is a perspective view of dilation elements being disposed within the tubular extensions;

Figure 4 is a side view of the parison being stretched;

Figure 5 is a side view of the parison in a mold;

Figure 6 is a side view of the parison in the mold and being stretched;

Figure 7 is an end view of a working diameter piece of the mold;

Figure 8 is a side view of a balloon catheter with the dilation elements; and

Figure 9 is a cross-sectional view of the dilation element disposed within the tubular extension.

DETAILED DESCRIPTION

[0032] Referring now to the figures, and particularly to Figure 1 , an extruded parison 10 is shown. The extruded parison 10 may be continuously extruded through a mold from a polymer material, such as nylon. Thus, each of the structures of the extruded parison 10 are integral with each other and extend along the entire length of the extruded parison 10. The extruded parison 10 may have a central opening 12 that is used for blow molding the parison 10 as described below. The central opening 12 will form the inner lumens of the neck regions 68, which are attached to a catheter 66, and will also form the interior of the balloon 64, which allows the balloon 64 to expand from a deflated state to an expanded state.

[0033] The extruded parison 10 also includes a tubular extension 14 on the exterior surface 16 that extends longitudinally along the length of the extruded parison 10. The tubular extension 14 has a wall 18 that defines the circumferential boundary of a longitudinal cavity 22 in the tubular extension 14. An opening 20 that communicates with the longitudinal cavity 22 may be provided at each end of the tubular extension 14. The cross-sectional shape of the longitudinal cavity 22 preferably matches the cross-sectional shape of the dilation element 28 described below. In order to allow the dilation element 28 to be inserted into the longitudinal cavity 22, the size of the longitudinal cavity 22 is initially slightly larger than the dilation element 28. The exterior shape of the tubular extension 14 also preferably matches the cross-sectional shape of the dilation element 28. Thus, the thickness of the circumferential wall of the tubular extension 14 may be generally uniform.

Preferably, there are no lateral openings through the wall 18 of the tubular

extension 14 so that the longitudinal cavity 22 is completely sealed by the wall 18 from the outside except for the openings 20 at the ends of the tubular extension 14. The outer width across the tubular extension 14 may also be narrower between the bottom of the longitudinal cavity 22 and the exterior surface 16 of the parison 10 than it is across the longitudinal cavity 22. In other words, the tubular extension 14 may have a narrowed neck 36 below the longitudinal cavity 22. As described further below, the narrowed neck 36 may be useful to isolate the tubular extension 14 during the blow molding process.

[0034] As shown in Figure 2, a dilation element 28 may also be provided. The dilation element 28 is preferably made from a different material than the extruded parison 10. For example, the dilation element 28 may be made of a metal to provide hardness and strength to the dilation element 28. The dilation element 28 may be a solid wire, a coiled wire, a continuous wire with regions of reduced cross-sectional area, or may be multiple longitudinally spaced apart wires within a single tubular extension 14. The cross-sectional shape of the dilation element 28 may be modified as desired. For example, the cross-sectional shape of the dilation element 28 may be round like dilation element 28A in Figure 2 or non-round like dilation

elements 28B-D in Figure 2. As shown, dilation element 28B has a rectangular cross-sectional shape. Dilation element 28C has a half-round cross-sectional shape. Dilation element 28D has a triangular cross-sectional shape. Preferably, the length of the dilation element 28 is significantly longer than the width of the dilation element 28 with a ratio of at least 10:1 or 50:1 . Accordingly, the shape of the dilation element 28 may be designed for the particular application and may have a blade shape, bead shape or any other suitable shape for focusing pressure along a discrete longitudinal region.

[0035] As shown in Figure 3, after the parison 10 has been extruded, the dilation element 28 is disposed within the tubular extension 14 of the extruded parison 10. Specifically, one end of the dilation element 28 may be inserted through an end opening 20 of the longitudinal cavity 22 and slid through the tubular extension 14. If additional securement of the dilation element 28 is desired, adhesive may be applied within the longitudinal cavities 22 to bond the dilation element 28 to the tubular extension 14. However, it is preferred that no adhesive is used to bond the dilation element 28, since this would add extra cost and difficulty in manufacturing the balloon catheter 72. Although it is preferable for the dilation elements 28 to extend substantially the entire length of the working diameter region 74 of the balloon 64, it is also possible to use shorter dilation elements 28 that extend along only part of the length of the working diameter 74 of the balloon 64. In addition, while a single length of the dilation element 28 may be used along the length of the balloon 64, multiple dilation element sections 28 may also be used to provide flexibility to the finished balloon catheter 72. Although the multiple dilation element sections 28 may be separate from each other, multiple dilation element sections 28 may also be connected together with thin portions to provide flexibility while still providing an element that extends substantially the entire length of the working diameter region 74.

[0036] As shown in Figure 4, it may be preferable to initially stretch a portion 42 of the parison 10 after installing the dilation elements 28 into the tubular extensions 14 of the parison 10. The initial stretching process may be achieved by heating one end 42 of the parison 10 without heating the middle 44 of the parison 10. The heated end 42 of the parison 10 may be pulled to stretch it without causing the middle portion 44 to be stretched. The other end 42 may then be heated and stretched in a similar manner. The initial stretching step may be helpful to define the region of the balloon 64 that will form the expanded balloon 64 after blow molding. The initial stretching step also may help determine the proper longitudinal positioning of the dilation elements 28 within the tubular extensions 14. Alternatively, if the parison 10 is stretched prior to inserting the dilation elements 28, it is preferable that the initial stretching does not significantly change the size of the longitudinal cavities 22 or the end openings 20 so that the dilation elements 28 can be inserted without excessive difficulty.

[0037] As shown in Figure 5, the parison 10 may then be positioned within a mold 46 for blow molding. While the mold 46 may take various forms, a three-piece mold 46 may be desirable. The three-piece mold 46 may be split in two places 48 at the transition between the tapered regions 50 and the working diameter 52. The parison 10 may be inserted into the mold 46 by separating one or more of the pieces of the mold 46 and inserting one end 42 of the parison 10 through one of the neck regions 54 in the mold 46. The working diameter piece 56 and/or the other neck piece 58 may then be slid over the other end 42 of the parison 10.

[0038] As shown in Figure 6, the parison 10 is preferably heated and stretched with the dilation elements 28 installed without pressurizing the center opening 12 prior to the blow molding. This is done by heating at least the middle portion 44 of the parison 10 and pulling on the ends 42 of the parison 10. Although a larger portion of the parison 10 may be heated, it may be desirable to only heat the portion of the parison 10 where the dilation elements 28 are installed and a small length beyond the ends of the dilation elements 28. The stretching of the middle portion 44 of the parison 10 causes the longitudinal cavities 22 to shrink in size and squeeze against the dilation elements 28. This locks the dilation elements 28 into the tubular extensions 14. The portions of the tubular extension 14 that extend past the ends of the dilation elements 28 may also be partially closed, i.e., compressed, by the stretching step. This can also result in longitudinally securing the dilation

elements 28 within the tubular extensions 14.

[0039] As shown in Figure 7, the mold 46 may also have longitudinal clearance cavities 60 along the working diameter 52 that receive the tubular extensions 14 and dilation elements 28. If desired, the working diameter clearance cavity 60 may be sized so that the tubular extension 14 does not significantly contact the mold 46 during blow molding to avoid changing the shape of the tubular extension 14.

Alternatively, the working diameter clearance cavity 60 can be sized to contact the tubular extension 14 during blow molding to cause the tubular extension 14 to be reformed into the final desired shape during blow molding. Preferably, the tapered regions 50 of the mold 46 do not have any clearance cavities to receive the tubular extension 14. As a result, when the parison 10 is blow molded, the tubular extensions 14 are compressed against the tapered regions 50 of the mold 46 and are closed and either mostly or entirely reformed into the wall of the finished balloon 64. Similarly, the clearance cavities 60 along the working diameter 52 may be omitted near the ends of the working diameter 52 to compress the tubular extensions 14 adjacent the ends of the dilation elements 28. The neck regions 54 of the mold 46 may or may not have clearance cavities for the tubular extension 14. However, it may be desirable to provide clearance cavities 62 that partially receive the tubular extensions 14 in order to index and align the parison 10 to the mold 46. The neck region clearance cavities 62 may be sized so that they partially reshape the tubular extensions 14 during blow molding to partially reform the tubular extensions 14 into the neck regions 68 of the balloon 64. Once the parison 10 has been indexed to the mold 46 so that the tubular extensions 14 are aligned with the clearance cavities 60, 62, the parison 10 is blow molded in the mold by heating the parison 10 and pressurizing the center opening 12. This causes the parison 10 to circumferentially stretch and expand outward against the walls of the mold 46. If it is desirable to minimize reforming and stretching of the tubular extensions 14 during blow molding, narrowed necks 36 as described above may be used to isolate the tubular extensions 14 from the main body of the parison 10 during blow molding.

[0040] As shown in Figure 8, after the parison 10 has been blow molded, the balloon 64 is cooled and removed from the mold 46. The balloon 64 is then mounted onto a catheter 66 by inserting the catheter 66 through the inner lumens of the neck regions 68 of the balloon 64. Preferably, the catheter 66 is bonded and sealed to the neck regions 68 of the catheter 66 by melt bonding. This may be accomplished by disposing heat shrink tubing 70 over the neck regions 68 of the balloon 64. The heat shrink tubing 70, neck regions 68 and catheter 66 are then heated. The heat softens the neck regions 68 and the catheter 66 and causes the heat shrink tubing 70 to shrink and squeeze the neck regions 68 and catheter 66 together. As a result, the neck regions 68 and catheter 66 melt together and adhere to each other when the heat shrink tubing 70, neck regions 68 and catheter 66 cool. In addition, the tubular extensions 14 are substantially reformed into the exterior surface of the neck regions 68 of the balloon 64 by the pressure of the heat shrink tubing 70 and the softening caused by the heat. This provides a smooth attachment between the catheter 66 and the balloon 64 without any significant remnant of the tubular extensions 14 in the neck regions 68.

[0041] As shown in Figure 9, the dilation element 28 is squeezed within the longitudinal cavity 22 of the tubular extension 14 after the balloon 64 has been blow molded. Thus, the blow molding process shrinks the tubular extension 14 around the dilation elements 28 to provide a tight fit between the dilation element 28 and the tubular extension 14. Preferably, the size of the tubular extension 14 is designed to provide an interference fit with the dilation element 28 after the balloon 64 has been blow molded. For example, with a round dilation element 28 having a diameter of 0.010", the initial thickness of the wall 18 of the tubular extension 14 may be about 0.0045", and the thickness of the wall 18 after blow molding the balloon 64 may be about 0.0025". Preferable ranges for the dilation element 28 and the tubular extension 14 are between about 0.005" and about 0.015" for the diameter of the dilation element 28, between about 0.002" and about 0.010" for the initial thickness of the wall 18, and between about 0.001 " and about 0.006" for the thickness of the wall 18 after blow molding the balloon 64. The initial clearance between the dilation element 28 and the longitudinal cavity 22 is preferably as small as possible to allow the dilation element 28 to be smoothly inserted into the longitudinal cavity 22. As described above, the narrowed neck 36 of the tubular extension 14 may help to minimize reforming of the tubular extension 14 during blow molding. Although the dilation element 28 need not extend the entire length of the balloon 64 or the working diameter 74 of the balloon 64, it is preferable for the dilation element 28 to extend substantially the entire length of the working diameter 74 of the balloon 64 with the tubular extension 14 being at least partially compressed adjacent opposing ends of the dilation element 28 to longitudinally restrain the dilation element 28. Although a portion of the dilation element 28 may extend past the working diameter 74 of the balloon 64, it may be preferable for the dilation element 28 to extend only along the working diameter 74. It is also preferable for the tubular extension 14 to not have any lateral openings through the wall 18 of the tubular extension 14 so that the dilation element 28 is completely sealed within the longitudinal cavity 22 after blow molding and is not exposed to the outside of the tubular extension 14.

[0042] While preferred embodiments of the invention have been described, it should be understood that the invention is not so limited, and modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein. Furthermore, the advantages described above are not necessarily the only advantages of the invention, and it is not necessarily expected that all of the described advantages will be achieved with every embodiment of the invention.