Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
1998-10-14
2001-01-23
Bockelman, Mark (Department: 3763)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
C623S017120, C606S108000, C604S021000, C604S103020, C604S522000
Reexamination Certificate
active
06176871
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to devices for intraluminal implantation of polymeric materials in a human or animal patient and methods for delivering such materials.
BACKGROUND OF THE INVENTION
The application of polymeric materials to body tissues of human or animal patients is becoming increasingly important in medicine. Among the proposed uses of such materials are the alteration of tissue; the creation or preservation of lumens, channels or reservoirs for the passage or collection of fluids; the creation of matrices for the growth of tissue; the control of undesirable tissue growth; the delivery of therapeutic agents to a tissue surface; the ability to join a tissue surface to another tissue or an artificial implant; the ability to isolate or protect tissue or lesions to enable or mediate healing; and the ability to mediate the rate of substances or energy passing into, out of, or through tissue.
Although it has been recognized that the use of polymeric materials in vivo may offer significant therapeutic effects, to date such applications have met many limitations. For example, the methods for applying such polymers to tissue surfaces often require the use of pressures heat or electrical energy exceeding limits of tolerability at the tissue site. Likewise various chemical effects associated with such polymers have been found to be physiologically unacceptable.
Numerous methods for reshaping polymeric materials in vivo are known in the prior art. In particular, U.S. Pat. No. 5,213,580 and International Publication WO 90/01969, both to Slepian et al., the entire disclosures of which are incorporated herein by reference, describe methods in which polymers having melting points slightly above physiological temperatures are implanted into a patient and in which such polymers are melted via contact with heated fluids and shaped using mechanical force provided by a balloon catheter. Unfortunately, many of the methods known in the art suffer from the need to use energy levels beyond those which are physiologically tolerable, or from the inability to sufficiently control the shape change and/or temperature of the polymeric material.
Typically, the primary limitation in prior art methods for the delivery of energy to an implanted device is the inability to direct the energy specifically to the device, while minimizing energy delivery to body tissue. For example, it is known in the prior art that polymeric devices such as stents may be delivered to specific locations in vivo using a balloon catheter. Such stents may be heated at the site by filling the balloon with a heated fluid. In that method, heat is conducted from the fluid in the balloon, through the balloon material, and into the stent. Since conduction is a relatively slow process and the balloon has a relative large thermal mass, energy is transferred not only to the stent, but also to the surrounding body tissues and fluids. The result is that undesired amounts of heat are transferred into the surrounding body tissues and fluids.
Accordingly, a need exists for apparatus for implanting polymeric materials in vivo that avoids the problems associated with the prior art. A need also exists for methods for delivering and reshaping materials in vivo which allow a physician to safely and easily introduce the material into a patient, configure the material as desired, and deposit the material at a desired location for at least a therapeutically desirable period of time. A further need exists for materials and methods for reshaping such materials in vivo that offer the ability to reshape the materials while minimizing the amount of energy that is transferred to surrounding tissues and physiological fluids.
SUMMARY OF THE INVENTION
The present invention pertains to apparatus and methods for the delivery of polymeric material in vivo, and more particularly to the implantation of polymeric material into tissue lumens of human or animal patients. More particularly the invention relates to methods for photothermoforming a polymeric article in vivo, that is, modifying the shape of a polymeric article in vivo by using light to selectively heat the article to a temperature at which it is fluent, molding the article into a desired conformation, and allowing the article to become non-fluent in the desired conformation. Material from which the article is made is selected such that it is moldable at a temperature at which substantial damage to adjacent or proximate tissue does not occur.
Heating is achieved by irradiating, or illuminating the article with light of a wavelength or within a wavelength range at which the polymeric material readily absorbs, or at which adjacent tissue or body fluids do not significantly absorb. According to one aspect of the invention, the article is irradiated at a wavelength or within a wavelength range at which the polymeric material readily absorbs and at which adjacent tissue or fluids do not significantly absorb. This is achieved by providing polymeric material that relatively strongly absorbs the radiation provided, or by loading the polymeric material with a chromophore that readily absorbs the radiation. It is preferred that the light used to thermoform the polymer be of a wavelength that is not readily absorbed by body tissues or fluids, thereby minimizing the amount of light absorbed by, and heat generated in, the tissue or fluid in the region of the thermoforming. According to one aspect of the invention visible or near-infrared light is provided locally to the polymeric material by an optical tip assembly on a delivery device.
The resulting shaped article provides a therapeutic benefit by acting, in one embodiment, as a stent to maintain patency through a blood vessel. Numerous other therapeutic shapes are contemplated as well.
According to one embodiment, the polymeric material has a chromophore such as a dye or pigment compounded therein. The chromophore is selected, in conjunction with a particular light source, to absorb light that is produced by the light source. The absorbed light is converted to thermal energy which acts to heat the polymer. According to one aspect of the invention, the chromophore is thermochromic. As an alternative to compounding the polymer with a chromophore, polymers that naturally absorb the wavelength spectrum of the light produced by the source may be used. The natural absorption spectrum of the material may result from the polymer in its native state, or alternatively, by the incorporation of one or more chromophores into the polymeric backbone or side-chains. In each case, however, it is necessary that the polymer satisfies other selection criteria such as biocompatibility and moldability.
By selecting a chromophore, or polymeric material, having maximum absorption characteristics at or near a particular wavelength or spectral range, in conjunction with a light source that emits at or near the particular wavelength or spectral range, the polymer is provided with the ability to be efficiently heated via light absorption. In this way, selective heating of the polymer with minimal heating of surrounding body tissues and fluids may be achieved.
Broadly, the apparatus comprises a catheter having a shaping element positioned near its distal end. The polymeric material is positioned adjacent or near the shaping element, illuminated by light delivered by the catheter and thus heated to render it fluent, and molded by the shaping element into contact with a tissue lumen.
In one embodiment, the apparatus comprises a balloon dilatation catheter having an associated optical tip assembly. The polymeric material is positioned on the balloon, preferably in the form of a tube or sleeve which surrounds the balloon. The optical tip assembly serves to direct light to the polymeric material. The light may be provided from an external source. Upon absorption of the light, the polymeric material is heated to a temperature at which it becomes moldable. Inflation of the balloon causes the moldable polymeric material to expand outwardly, thereby pressing the polymer into cont
Berrigan Kevin M.
Campbell Patrick K.
Coury Arthur J.
Herman Stephen J.
Hubbell Jeffrey A.
Bockelman Mark
Focal, Inc.
Wolf Greenfield & Sacks P.C.
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