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Balloon catheter device

Balloon catheter device description/claims

This application is a continuation of application Ser. No. 11/556,258 filed Nov. 3, 2006; which is a continuation of Ser. No. 11/182,874 filed Jul. 15, 2005; which is a continuation of application Ser. No. 10/300,056, now U.S. Pat. No. 6,923,827; which is a continuation of application Ser. No. 09/252,322 filed Feb. 18, 1999, now abandoned; which is a continuation of application Ser. No. 08/858,309 filed May 19, 1997, now U.S. Pat. No. 6,120,477; which is a continuation-in-part of application Ser. No. 08/673,635 filed Jun. 26, 1996, now U.S. Pat. No. 5,868,704; which is a continuation-in-part of application Ser. No. 08/532,905 filed Sep. 18, 1995, now U.S. Pat. No. 5,752,934.

The present invention relates to catheter balloons used in a variety of surgical procedures and to balloon covers for use with catheter balloons.

Balloon catheters of various forms are commonly employed in a number of surgical procedures. These devices comprise a thin catheter tube that can be guided through a body conduit of a patient such as a blood vessel and a distensible balloon located at the distal end of the catheter tube. Actuation of the balloon is accomplished through use of a fluid filled syringe or similar device that can inflate the balloon by filling it with fluid (e.g., water or saline solution) to a desired degree of expansion and then deflate the balloon by withdrawing the fluid back into the syringe.

In use, a physician will guide the balloon catheter into a desired position and then expand the balloon to accomplish the desired result (e.g., clear a blockage, or install or actuate some other device). Once the procedure is accomplished, the balloon is then deflated and withdrawn from the blood vessel.

There are two main forms of balloon catheter devices. Angioplasty catheters employ a balloon made of relatively strong but generally inelastic material (e.g., polyester) folded into a compact, small diameter cross section. These relatively stiff catheters are used to compact hard deposits in vessels. Due to the need for strength and stiffness, these devices are rated to high pressures, usually up to about 8 to 12 atmospheres depending on rated diameter. They tend to be self-limiting as to diameter in that they will normally distend up to the rated diameter and not distend appreciably beyond this diameter until rupture due to over-pressurization. While the inelastic material of the balloon is generally effective in compacting deposits, it tends to collapse unevenly upon deflation, leaving a flattened, wrinkled bag, substantially larger in cross section than the balloon was when it was originally installed. Because of their tendency to assume a flattened cross section upon inflation and subsequent deflation, their deflated maximum width tends to approximate a dimension corresponding to one-half of the rated diameter times pi. This enlarged, wrinkled bag may be difficult to remove, especially from small vessels. Further, because these balloons are made from inelastic materials, their time to complete deflation is inherently slower than elastic balloons.

By contrast, embolectomy catheters employ a soft, very elastic material (e.g., natural rubber latex) as the balloon. These catheters are employed to remove soft deposits, such as thrombus, where a soft and tacky material such as latex provides an effective extraction means. Latex and other highly elastic materials generally will expand continuously upon increased internal pressure until the material bursts. As a result, these catheters are generally rated by volume (e.g., 0.3 cc) in order to properly distend to a desired size. Although relatively weak, these catheters do have the advantage that they tend to readily return to their initial size and dimensions following inflation and subsequent deflation.

Some catheter balloons constructed of both elastomeric and non-elastomeric materials have been described previously. U.S. Pat. No. 4,706,670 describes a balloon dilatation catheter constructed of a shaft made of an elastomeric tube and reinforced with longitudinally inelastic filaments. This device incorporates a movable portion of the shaft to enable the offset of the reduction in length of the balloon portion as the balloon is inflated. The construction facilitates the inflation and deflation of the balloon.

While balloon catheters are widely employed, currently available devices experience a number of shortcomings. First, as has been noted, the strongest materials for balloon construction tend to be relatively inelastic. The flattening of catheter balloons made from inelastic materials that occurs upon inflation and subsequent deflation makes extraction and navigation of a deflated catheter somewhat difficult. Contrastly, highly elastic materials tend to have excellent recovery upon deflation, but are not particularly strong when inflated nor are they self-limiting to a maximum rated diameter regardless of increasing pressure. This severely limits the amount of pressure that can be applied with these devices. It is also somewhat difficult to control the inflated diameter of these devices.

Second, in instances where the catheter is used to deliver some other device into the conduit, it is particularly important that a smooth separation of the device and the catheter balloon occur without interfering with the placement of the device. Neither of the two catheter devices described above is ideal in these instances. A balloon that does not completely compact to its original size is prone to snag the device causing placement problems or even damage to the conduit or balloon. Similarly, the use of a balloon that is constructed of tacky material will likewise cause snagging problems and possible displacement of the device. Latex balloons are generally not used for device placement in that they are considered to have inadequate strength for such use. Accordingly, it is a primary purpose of the present invention to create a catheter balloon that is small and slippery for initial installation, strong for deployment, and returns to its compact size and dimensions for ease in removal and further navigation following deflation. It is also believed desirable to provide a catheter balloon that will remain close to its original compact pre-inflation size even after repeated cycles of inflation and deflation. Other primary purposes of the present invention are to strengthen elastic balloons, to provide them with distension limits and provide them with a lubricious outer surface. The term “deflation” herein is used to describe a condition subsequent to inflation. “Pre-inflation” is used to describe the condition prior to initial inflation.

The present invention is an improved balloon catheter device for use in a variety of surgical procedures. The balloon catheter device of the present invention comprises a catheter tube having a continuous lumen connected to an inflatable and deflatable balloon at one end of the catheter tube. The catheter tube may have additional lumens provided for other purposes. The balloon can have a burst strength equal to or greater than that of conventional PTA catheter balloons. The balloon also has a maximum inflation diameter in a similar fashion to conventional PTA catheter balloons. The inventive balloon offers the recovery characteristics of a latex balloon that when deflated is of about the same maximum diameter as it was prior to inflation. This allows the inventive balloon to be withdrawn following deflation more easily than conventional PTA balloons which assume a flattened, irregular cross section following deflation and so have a deflated maximum diameter much larger than the pre-inflation maximum diameter. The balloon also has a smooth and lubricious surface which also aids in insertion and withdrawal. The inventive balloon possesses all of the above attributes even when made in small sizes heretofore commercially unavailable in balloon catheters without a movable portion of the catheter shaft or some other form of mechanical assist. The present invention eliminates the need for a movable portion of the shaft and associated apparatuses to aid in balloon deflation.

The present invention is made from polytetrafluoroethylene (hereinafter PTFE) materials and elastomeric materials. The PTFE is preferably porous PTFE made as taught by U.S. Pat. Nos. 3,953,566 and 4,187,390, both of which are incorporated by reference herein. An additional optional construction step, longitudinally compressing a porous PTFE tube prior to addition of the elastomeric component, allows the balloon or balloon cover to sufficiently change in length to enable the construction of higher pressure balloons, again without the need for mechanical assist. Particularly small sizes (useful in applications involving small tortuous paths such as is present in brain, kidney, and liver procedures) can be achieved by decreasing the wall thickness of the balloon via impregnation of a porous PTFE tube with silicone adhesive, silicone elastomer, silicone dispersion, polyurethane or another suitable elastomeric material instead of using a separate elastomeric member. Impregnation involves at least partially filling the pores of the porous PTFE. The pores (void spaces) are considered to be the space or volume within the bulk volume of the porous PTFE material (i.e., within the overall length, width and thickness of the of the porous PTFE material) not occupied by PTFE material. The void spaces of the porous PTFE material from which the balloon is at least partially constructed may be substantially sealed in order that the balloon is liquid-tight at useful pressures by either the use of a separate tubular elastomeric substrate in laminated relationship with the porous PTFE, or by impregnation of the void spaces of the porous PTFE with elastomeric material, or by both methods. U.S. Pat. No. 5,519,172 teaches in detail the impregnation of porous PTFE with elastomers. In that this patent relates primarily to the construction of a jacket material for the protection of electrical conductors, the suitability of each of the various described materials for in vivo use as catheter balloon materials must be considered.

The balloon may be made from the materials described herein as a complete, stand-alone balloon or alternatively may be made as a cover for either conventional polyester PTA balloons or for latex embolectomy balloons. The use of the balloon cover of the present invention provides the covered balloon, regardless of type, with the best features of conventional PTA balloons and renders viable the use of elastic balloons for PTA procedures. That is to say, the covered balloon will have high burst strength, a predetermined maximum diameter, the ability to recover to substantially its pre-inflation size following deflation, and a lubricious exterior surface (unless it is desired to construct the balloon such that the elastomeric material is present on the outer surface of the balloon). The balloon cover substantially reduces the risk of rupture of an elastic balloon. Further, if rupture of the underlying balloon should occur, the presence of the balloon cover may serve to contain the fragments of the ruptured balloon. Still further, the inventive balloon and balloon cover can increase the rate of deflation of PTA balloons thereby reducing the time that the inflated balloon occludes the conduit in which it resides.

The present invention also enables the distension of a vessel and side branch or even a prosthesis within a vessel and its side branch without exerting significant force on the vessel or its branch. Further, it has been shown to be useful for flaring the ends of prostheses, thereby avoiding unwanted constrictions at the ends of the prostheses. Prostheses can slip along the length of prior art balloons during distension; the present invention not only reduces such slippage, it also can be used to create a larger diameter at the end of the graft than prior art materials.

The inventive balloon and balloon cover also maintain a substantially circular cross section during inflation and deflation in the absence of external constraint. Plus, the balloon and balloon cover can be designed to inflate at lower pressure in one portion of the length than another. This can be accomplished, for example, by altering the thickness of the elastomer content along the length of the balloon in order to increase the resistance to distension along the length of the balloon. Alternatively, the substrate tube may be constructed with varying wall thickness or varying amounts of helically-applied film may be applied along the tube length in order to achieve a similar effect.

The balloon catheter according to the present invention has opposing ends affixed to the catheter by opposing securing means. The balloon has a length measured between the opposing ends wherein the length preferably varies less than about ten percent, and more preferably less than about five percent, between when the balloon is in a deflated state and when the balloon is inflated to a pressure of eight atmospheres.

Balloons of the present invention can also be constructed to elute fluids at pressures exceeding the balloon inflation pressure. Such balloons could have utility in delivering drugs inside a vessel.

A catheter balloon of the present invention is anticipated to be particularly useful for various surgical vascular procedures, including graft delivery, graft distension, stent delivery, stent distension, and angioplasty. It may have additional utility for various other surgical procedures such as, for example, supporting skeletal muscle left ventricular assist devices during the healing and muscle conditioning period and as an intra-aortic balloon.

• Provisional Patent
• Utility Patent

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