| 摘要 |
Disclosed is an improved system and method to selectively promote tissue ingrowth on, or adjacent to, an implantable medical device. In one embodiment, at least one surface of the housing of a medical device is in contact with a first portion of a porous PTFE having a pore size adapted to prevent substantially all tissue in-growth. This first portion, or layer, of porous PTFE material is further in contact at predetermined locations with an additional porous PTFE layer having a pore size adapted to selectively promote tissue in-growth only at the predetermined locations. Each of the PTFE layers may be formed of porous PTFE tubing or tape. Alternatively, the two layers may comprise a single composite structure that has a more porous material exposed on a first surface, and a less porous, more dense, material on a second surface. Another embodiment of the invention involves forming the layers of PTFE into a removable member that is adjacent to at least one surface of the implantable medical device. The removable member may take the form of a sleeve that surrounds a portion of a the medical device and is adapted to remain in the body during an extraction process. For example, during the removal of a lead, the sleeve remains within the body and is capable of receiving a replacement lead, making it unnecessary to disturb tissue in-growth attached to the sleeve.
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