Implantable medical devices

Abstract

A medical device includes a balloon catheter having an expandable member, e.g., an inflatable balloon, at its distal end and a stent or other endoprosthesis. The stent is, for example, an apertured tubular member formed of a polymer and is assembled about the balloon. The stent has an initial diameter for delivery into the body and can be expanded to a larger diameter by inflating the balloon.

Description

TECHNICAL FIELD This invention relates to implantable medical devices and methods of delivering the same. BACKGROUND The body includes various passageways such as arteries, other blood vessels, and other body lumens. These passageways sometimes become occluded or weakened. For example, the passageways can be occluded by a tumor, restricted by plaque, or weakened by an aneurysm. When this occurs, the passageway can be reopened or reinforced, or even replaced, with a medical endoprosthesis. An endoprosthesis is typically a tubular member that is placed in a lumen in the body. Examples of endoprosthesis include stents and covered stents, sometimes called “stent-grafts”. An endoprosthesis can be delivered inside the body by a catheter that supports the endoprosthesis in a compacted or reduced-size form as the endoprosthesis is transported to a desired site. Upon reaching the site, the endoprosthesis is expanded, for example, so that it can contact the walls of the lumen. Prostate enl...

AI Technical Summary

Benefits of technology

In another aspect, a tubular endoprosthesis including a polymer body is provided and delivered into a body lumen. The endoprosthesis is expanded in the body lumen under conditions of expanding pressure and temperature so that the wall thickness of the polymer body is substantially maintained.

Embodiments may include one or more of the following advantages. A balloon expandable stent made of a polymer can be provided that maintains the integrity of the stent geometry on expansion and heating. Maintenance of stent geometry is desirable since geometry affects, for example, the resistance to compression in the body and a predictable geometry is important to avoid irregular surfaces, kinking, or extensions of material into the body lumen which can interfere with the flow of body fluid. The polymers can be elastomers that have melting or glass transitions at temperatures safe for use in the body and exhibit elastomeric properties at both the melted or glass transition stage and the solid or crystalline phase. The stent body exhibits high resistance to inward compressive forces when the polymer is in the solid or crystalline phase. The elastomeric nature of the polymer in the melted or glass state enhances the ability to maintain geometry as the stent is expanded. For example, the polymer exhibits minimal flow during expansion and the thickness of the stent remains substantially constant. Elastomeric properties in the crystalline or solid state enhance the ability to conform to torturous curvature in narrow body lumens. High compression resistance allows the stent to maintain the body lumen open and resist occluding forces such as elastic recoil or the growth of thrombus from the vessel wall.

The stent may be, for example, a coiled elongated element (for example, a rod, a tape or flattened tube) and the heating of the stent prior to removal allows the stent to be removed in a substantially uncoiled state. This method provides ease of removal, for example, for removing prostatic stents that have been inserted on an interim basis. The heating may be performed, for example, on a delivery tube.

Problems solved by technology

Benign prostate hyperplasia is uncomfortable because it makes urination difficult or impossible.

The condition is also dangerous because it can lead to infection of the bladder and kidneys.

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