Vascular Implants
“Vascular implants, so-called stents, are utilized in the medicine to prevent or eliminate vascular restrictions. The implants may be inserted into a restricted vessel whereby the restricted vessel is widened. The vascular implants have, for example, the shape of net-like tubes or coil springs.”
“The experience with such vascular implants indicates that excessive growth of the adjacent cells results again in a restriction of the vessel particularly at the ends of the implants which results in reduced effectiveness of the implants. If a vascular implant is inserted into a human artery for the elimination of an arteriosclerotic stenosis, intimahyperplasia will occur within a year at the ends of the vascular implant and results in renewed stenosis. Upon infiltration of vessel systems with carcinoma cells, for example in the gall passage with a gall passage carcinoma, the vascular implant is rapidly overgrown by tumor cells.”
(Hehrlein and Fehsenfeld, US Patent 5,674,177, 10/7/1997)
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“Atherosclerotic vascular disease in the form of coronary artery and peripheral vascular disease is the largest cause of mortality in both the United States and Europe. Surgical mainstays of therapy for affected vessels include bypass grafting with autologous veins or arteries; however, adequate autologous vein is lacking in many patients. Prosthetic vascular grafts are therefore required.”
“Several materials are presently available for use as prosthetic vascular grafts and other surgical prostheses. These include polytetrafluoroethylene (PTFE) and Dacron. These two materials are rigid and when used as grafts create a compliance mismatch at the anastomosis. The primary patency rates of PTFE or Dacron grafts is 20 to 30% at 4 to 5 years. A further material which can be used as a vascular graft is polyurethane (PU). This material has the advantage that it is more elastic and therefore more similar to the blood vessel which it is to mimic. PU grafts are thus compliant grafts in the sense that they behave in a similar way to a natural blood vessel in the body. In particular, they flex more readily than PTFE or Dacron grafts when the site at which they are contained flexes.”
Recent US Patents
1/18/2011
7,872,068
Materials formable in situ within a medical device
Khosravi and Dreher of Incept, Massachusetts developed flowable precursors that form solid materials within an implanted medical device, for example an arterial prosthesis placed inside a natural blood vessel to treat an aneurysm. The precursor is a water soluble polymer precursor of at least about 10,000 molecular weight solubilized in a flowable aqueous solution. Functional groups on the polymer precursor undergo covalent bonding in situ to form a solid and nonbiodegradable material having a swellability less than about 20% v/v and a Young's modulus of at least about 100 kPa within about 30 seconds to about 30 minutes of initiating a chemical reaction of the functional groups to form the solid material. (RDC 8/5/2011)
10/26/2010
7,820,769
Polymer for use in conduits, medical devices and biomedical surface modification
Seifalian et al of UCL Biomedica, Great Britain have developed polyurethaneand silicone copolymers for implants especially coronary and vascular implants. The copolymers contain silsesquioxanes. (RDC 2/18/2011)