Patent Application
20080097300
The present invention provides a catheter balloon with the balloon material formed into micropleats distributed about the circumference of the balloon. The micropleats reduce the entry profile of the balloon and are formed to pull taut in an inflated state.
As shown in
The micropleats 8 are invaginated areas of folded balloon material 4 with at least one fold 5 or bend which forms a pocket 10 of balloon material. The pocket comprises an opening 11 and at least one side of the pocket and a bottom 12 of the pocket 10. The inside of the pocket is a cavity wherein the most distant part of the pocket is adjacent to the bottom of the pocket. The side 13 of the pocket runs from the balloon opening to the bottom of the pocket flanking the opening to the pocket. The opening 11 is ideally located opposite of the bottom 12 of the pocket. The micropleats 8 are distributed about the circumference of the balloon. The bottom of each micropleat pocket is oriented such that it is free of contact or overlap with any other portion of an adjacent micropleat. Each micropleat has at least one fold 5 which allows balloon material to be stored upon itself. While the micropleats are depicted as running longitudinally in the direction of the axis, helical orientations, S-shaped orientations and other configurations of micropleat distribution may be formed. In one embodiment, as shown in
The micropleats may be oriented in different ways. In one embodiment of the invention, as shown in
Multiple methods may be used in micropleating a balloon. As shown in
In one aspect, the average micropleat width is less than 1 mm, preferably less than 0.7 mm, independent of inflated/diameter balloon diameters.
A balloon may be micropleated by positioning the balloon to be packed or micropleated on a catheter shaft 14. Then, the balloon is heat set to the catheter shaft and a small diameter elastomeric tube 18, such as a silicone tube or other suitable material, is rolled over it (see
Of the types of balloon material suitable for the invention, a material comprising a fluoropolymer and a second polymer is preferred. A common fluoropolymer appropriate for the fluoropolymer component is PTFE or expanded PTFE (ePTFE); however other fibrous reinforcing, highly-oriented materials such as polyolefins, polyesters, polyamides may be used. Polymers suitable for use as second polymers include but are not limited to elastomers such as urethanes, aromatic and aliphatic polyurethanes, thermoplastic polyurethanes, polyester thermoplastics, styrene block copolymers, and silicones. Alternatively, a second fluoropolymer, such as PTFE, may be used for the second polymer. The above described methods enable the balloon profiles of the uninflated balloons to return to essentially the same profile after inflation and subsequent deflation. Essentially, the same profile means that the size of the profile does not change by more than (30%) after deflation as compared to its profile prior to inflation.
One composite film of the present invention comprises a porous reinforcing layer and a continuous polymer layer. The porous reinforcing polymer layer is preferably a thin, strong porous membrane that can be made in sheet form. The porous reinforcing polymer can be selected from a group of polymers including, but not limited to, olefin, PEEK, polyamide, polyurethane, polyester, polyethylene, and polytetrafluoroethylene. In a preferred embodiment, the porous reinforcing polymer is expanded polytetrafluoroethylene (ePTFE) may be made in accordance with the teachings of U.S. Pat. No. 5,476,589 or U.S. patent application Ser. No. 11/334,243 to Bacino incorporated herein by reference. In this preferred embodiment, the ePTFE membrane is anisotropic such that it is highly oriented in the one direction. An ePTFE membrane with a matrix tensile value in one direction of greater than 690 megapascals is preferred, and greater than 960 megapascals is even more preferred, and greater than 1,200 megapascals is most preferred. The exceptionally high matrix tensile value of ePTFE membrane allows the composite material to withstand very high hoop stress in the inflated balloon configuration. In addition, the high matrix tensile value of the ePTFE membrane makes it possible for very thin layers to be used which reduces the deflated balloon profile. A small profile is necessary for the balloon to be able to be positioned in small arteries or veins or orifices. In order for balloons to be positioned in some areas of the body, the balloon catheter must be able to move through a small bend radius, and a thinner walled tube is typically much more supple and capable of bending in this manner without creasing or causing damage to the wall of the vessel.
In another preferred embodiment, the ePTFE membrane is relatively mechanically homogeneous. The mechanically balanced ePTFE membrane can increase the maximum hoop stress that the composite film made therefrom can withstand.
The continuous polymer layer of the present invention is coated onto at least one side of the porous reinforcing polymer. The continuous polymer layer is preferably an elastomer, such as, but not limited to, aromatic and aliphatic polyurethanes including copolymers, styrene block copolymers, silicones, preferably thermoplastic silicones, fluoro-silicones, fluoroelastomers, THV and latex. In one embodiment of the present invention, the continuous polymer layer is coated onto only one side of the porous reinforcing polymer. The continuous polymer layer is coated onto both sides of the porous reinforcing polymer. In a preferred embodiment, the continuous polymer layer is imbibed into the porous reinforcing polymer and the imbibed polymer fills the pores of the porous reinforcing polymer.
The continuous polymer layer can be applied to the porous reinforcing polymer through any number of conventional methods including, but not limited to, lamination, transfer roll coating, wire-wound bar coating, reverse roll coating, and solution coating or solution imbibing. In a preferred embodiment, the continuous polymer layer is solution imbibed into the porous reinforcing polymer. In this embodiment, the continuous polymer layer is dissolved in a suitable solvent and coated onto and throughout the porous reinforcing polymer using a wire-wound rod process. The coated porous reinforcing polymer is then passed through a solvent oven and the solvent is removed leaving a continuous polymer layer coated onto and throughout the porous reinforcing polymer. In some cases, such as when silicone is used as the continuous polymer layer, the coated porous reinforcing polymer may not require the removal of solvent. In another embodiment, the continuous polymer layer is coated onto at least one side of the porous reinforcing polymer and maintained in a “green” state where it can be subsequently cured. For example, an ultraviolet light (UV) curable urethane may be used as the continuous polymer layer and coated onto the porous reinforcing polymer. The composite film comprising the porous reinforcing polymer and the UV curable urethane continuous polymer layer can then be wrapped to form at least one layer of the balloon and subsequently exposed to UV light and cured. A ply is a number of layers applied in a wrapping event. A layer is a single layer of composite film wrapped around the balloon.
While particular embodiments of the present invention have been illustrated and described herein, the present invention should not be limited to such illustrations and descriptions. It should be apparent that changes and modifications may be incorporated and embodied as part of the present invention within the scope of the following claims.
The following examples are intended to illustrate the present invention. These examples are in no way intended to limit the present invention or depart from the spirit of the invention described above.
The balloon portion of a balloon catheter of the present invention comprising micropleats distributed about the circumference of the balloon was made by inflating a 50 mm section of platinum cured silicone tubing (part # 30400, Saint-Gobain Performance Plastics, Taunton, Mass.) using a Balloon Development Station Model 210A (Beahm Designs, Campbell, Calif.) and a dispensing tip (part #: 5121-1-B, EFD, Inc., East Providence, R.I.). One end of the tube was attached to the dispensing tip with a touhy borst (part #: 80369, Qosina, Edgewood, N.Y.). The silicone tube was inflated to approximately 275 kPa. Once fully inflated, the pressure was quickly lowered to about 130 kPa keeping the tube inflated. While the silicone tube was still inflated, a 1.5 mm PTFE covered mandrel (New England Precision Grinding, Inc., Holliston, Mass.) was inserted into the tube approximately 100 mm. The tube was deflated and enough hand tension was applied to keep the length constant and under strain while it deflated and compressed onto the mandrel. The tube was cut rolled onto itself about 100 mm in length such that it formed a toroid and removed from the dispensing tip.
The wrapped balloon of this example was comprised of balloon material laid in longitudinal passes about the lumen of the balloon. A longitudinal pass is comprised of one or more layers of material which are laid at similar angles in relation to the longitudinal axis of the balloon. A longitudinal pass comprises a distinctive layer or series of layers of material which are wound or wrapped to form a region or area distinct from surrounding or adjoining parts. It is important to note that a pass may span the entire length of the balloon or in certain instances, such as non-distending regions, the pass may span only a partial length of the balloon.
A layer is considered to be one strand, strip or thickness of balloon material which may be wrapped, folded, laid or weaved over, around, beside or under another strand, strip or thickness of balloon material.
While it is clear that a longitudinal pass may span the entire length of the balloon at a single wrap angle, a longitudinal pass may also comprise a wrapping event in which the wrapping angles may be changed during the continuous longitudinal wrapping, so that in this type of wrapping pattern a single pass may include two or more wrap angles.
The 4 mm diameter x 40 mm long balloon was mounted to a 0.36 mm diameter stainless steel hypotube (Creganna Medical Devices, Parkmore West Galway, Ireland) that had been helically wrapped with approximately three layers of an ePTFE/eFEP film composite as described. The balloon was attached and sealed to the catheter shaft by wrapping an approximately 5 mm wide ePTFE/eFEP film circumferentially around the balloon approximately five times. One band was wrapped on each end of the balloon and was centered over the end of the balloon and the catheter such that it made a seal by contacting both the hypotube shaft and the balloon.
The rolled silicone tube, with an approximately 20 mm long unrolled tail, was removed from the mandrel and then unrolled onto the fully deflated balloon mounted to the catheter shaft described above. The silicone tube was unrolled over the mounted composite balloon such that the end of the unrolled silicone tube protruded just beyond the end of the composite balloon and made a seal on the catheter shaft. The silicone tube was inflated through the tail using the dispensing tip and the Balloon Development Station Model 210A to about 130 kPa such that its inner diameter was approximately 4.5 mm. Once the silicone tube was fully inflated, the balloon catheter was inflated to 4 mm diameter using approximately 130 kPa using a separate Balloon Development Station Model 210A and a touhy borst.
The silicone tube was then fully deflated ensuring that there was no change in axial length of the tube. With the axial length of the silicone tube fixed, the balloon was deflated such that the silicone tube applied both a normal compressive force and a tangential shear force against the composite balloon. This shear force was exerted from the decreasing circumference of the inner diameter of the silicone tube and the surface friction between the two surfaces. These combined forces formed a multiplicity of evenly distributed longitudinal micropleats around the circumference of the balloon.
After disconnecting both the balloon catheter and the silicone tube from the inflation devices, the assembly was swaged, or radial compressed, using a heated swaging machine set to 550 kPa and 150° C. for 30 seconds. The entire length of the balloon was swaged to heat set the micropleats. The silicone tube was then removed by inflating it to 130 kPa air pressure and unrolling it off of the balloon catheter. This process produced a balloon with tightly packed longitudinal micropleats attached and sealed to a catheter.
A 4 mm balloon was folded in accordance with Example 1 above. The balloon was marked in an uninflated state with two parallel rows, each row having 11 linear marked points. The marked points on the first row were directly above and in line with corresponding marked points on the second row, so that the points lined up to form eleven columns. Upon inflation pressure, the marked points in each row radially expanded with the balloon wall and showed a relative equidistant spacing between adjacent marked points. Thus, the rows on the inflated balloon maintained the linear marked points in rows of analogous orientation to the initial marked rows on the uninflated balloon. Additionally, the second row of linear marked points maintained linear rows of analogous orientation to the initial marked rows, and equidistant vertical spacing between the two parallel rows was observed analogous to the initial orientation of the marked points on the uninflated balloon. It was observed that the balloon inflated with radial concentric symmetry.
A similar set of markings was conducted on a balloon described in Example 2, with four rows of 11 marked points each oriented to form parallel rows and columns. Upon inflation pressure, the marked points in each row radially expanded with the balloon wall and showed a relative equidistant spacing between adjacent marked points in the corresponding row. Similarly, the columns, radially expanded with the balloon wall and showed a relative equidistant spacing between adjacent marked points in the corresponding columns, and maintained a parallel orientation between the columns and the rows. Thus, both the rows and columns of the inflated balloon maintained the linear marked points in analogous orientation to the initial marked rows on the uninflated balloon, again demonstrating radial symmetry upon inflation.
