Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent combined with surgical delivery system
Reexamination Certificate
2001-01-29
2003-09-02
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent combined with surgical delivery system
C623S001360, C606S200000
Reexamination Certificate
active
06613076
ABSTRACT:
BACKGROUND OF THE INVENTION
Vascular restenosis is the pathological process whereby the vessels become clogged and which corresponds, in particular, to coronary disease. It is associated with the widening or thickening of the internal wall of the arteries which causes a narrowing of the vascular lumen and a reduction in the blood flow or rate. The same process is involved in arterial atheroscleroses, particularly cerebral ones or ones relating to the limbs, particularly the lower limbs.
These diseases can nowadays be treated by interventional cardiology instead of the older method of cardiac surgery. Interventional cardiology consists in introducing an angioplasty catheter into the femoral artery under local anesthetic. Under x-ray control, this catheter can be fitted at the site of the stenosis.
Several types of catheter are used to perform angioplasty, particularly balloon-type or PTCA (Percutaneous Transluminal Coronary Angioplasty) catheters; DCA or RCA (Directional or Rotational Coronary Atherectomy) catheters or LA (Laser Angioplasty) catheters.
These techniques are not very invasive which means that the length of the hospital stay can be reduced.
The major disadvantage is the level of restenosis after three months which is as high as 30 to 50%. In an attempt at avoiding a bypass, which would then often be inevitable, use is nowadays made of spacing implants or stents.
Numerous spacer or stent systems are already in use. These generally consist of a structure (mesh or spring) made of metal and capable of expanding into the shape of a hollow cylinder inside a vessel.
In theory, stents fitted after the angioplasty procedure at the site of the wall that is to be treated are supposed to reduce the level of restenosis after three months. The main reason for this is that the stents very markedly increase the diameter of the vascular lumen. The same degree of restenosis of the vessels will no longer be enough to clog the vessel for the same period after intervention and even beyond, because the initial diameter of the lumen is greater.
Restenosis is the result of various important factors including inflammatory reaction, the elasticity of the vascular walls, mural thrombosis or the proliferation of smooth muscle cells.
Certain recent clinical results obtained with stents have encouraged the belief that the actual level of restenosis has not fallen. Although, for the same period of time after intervention, clogging is avoided, it is possible that the stent is merely delaying the deadline. With the time scales being pushed back in the use of stents, an increasing level of late restenosis requiring reintervention is actually noted.
To face up to this threat the use of an active principle may be associated with the stents, for example by coating the stent with a view to avoiding restenosis through the combined mechanical action of the stent and pharmacological action of the product.
This approach runs into various difficulties including the very small surface area of the stent, which does not allow a great deal of active principle to be associated, or the locating of the product between the stent and the wall of the vessel which either does not correspond to the optimum zone for release or leads to its being taken away rapidly in the blood stream.
Another major difficulty with this solution is that there is no product which has truly been proven to be effective in preventing restenosis, particularly at local intravascular level.
The disappointing results ultimately achieved with stents could be explained by the fact that this mechanical device does not tackle the cause of the restenosis but simply seeks to avoid its consequences.
The various angioplasty techniques, PTCA, DCA, LA or, alternatively, ultrasound, are all traumatic revascularization techniques.
What is in fact involved is spacing the vascular tissues apart, removing plaques of atheroma which will be crushed, destroyed or removed to restore the path for the blood. The zone treated is therefore a zone containing lesions capable of giving rise to post-surgical adhesion phenomena, scarring and tissue formations which could explain the later restenosis.
There is also a risk of thrombosis in this zone after tissue lysis and dilatation.
Implanting a stent directly in contact with this lesion-containing surface could give rise to chronic inflammation phenomena and create aggregation problems. In addition, it is a foreign body placed in direct contact with the tissues on which it exerts permanent mechanical stress. These intravascular tissues are not very tolerant of foreign bodies.
Numerous factors may explain the problems of atherosclerosis after the fitting of a stent.
The risk of causing thrombosis and inflammation is increased by the use of any hollow structure with a non-smooth surface, whether this is in contact with the blood stream in the central flow or at its periphery.
Outside of the treatment of the large coronary blood vessels, there are, with improvements made to stents and vascular access techniques, increasing numbers of radiological applications for perivascular diseases.
All the tissue or cell phenomena are therefore magnified by the reduction in the lumen of the vessel, which increases the risk of restenosis.
Furthermore, it is more difficult to produce and make effective use of a stent in long and/or narrow vasculatures, with greater risks of failure. If the vasculature to be treated is not straight or if there is a branch, fitting a stent is also trickier, if not impossible.
Post-angioplasty restenosis may lead to further clogging which again means that all interventional cardiology treatments are once more to be envisioned. On the other hand, the post-operative reaction of tissue proliferation, if it takes place around a stent, will trap the stent and make it very complicated, if not impossible, depending on the size of the vessel, to resort to any treatment other than bypass surgery.
SUMMARY OF THE INVENTION
The present invention sets out to provide a device which avoids or limits the drawbacks of the prior art and which makes it possible to reduce the risks of stenosis or restenosis, particularly after angioplasty.
Another objective is to provide such a device which is very simple to manufacture and of low cost.
Another objective of the invention is to provide such a device which is easy to fit and fix to the desired site in the vasculature that is to be preserved.
Another objective of the invention is to produce such a device which can be removed far more easily than can a stent.
Another objective of the invention is to provide such a device which can deliver a significant amount of an active principle which is effective against stenosis or restenosis.
Yet another objective is to provide a device which is resolvable and can disappear by itself, after a certain length of time.
Yet another objective of the invention is to provide such a device which limits or eliminates mechanical action on the wall of the vessel.
Another objective of the invention is to provide such a device which can easily be manufactured in different sizes and, advantageously, allows one and the same device of a given size to be used for a relatively broad range of lumen diameters.
The subject of the present invention is a device that can be implanted in the vasculature, characterized in that it comprises an elongate intraluminal element capable, in a portion of the vascular lumen, of occupying a volume of this lumen without reducing the blood flow and without exerting appreciable mechanical action, and preferably without exerting any mechanical action, on the vascular wall, said element being associated with a means of fixing into the vascular lumen.
This device is preferably in the form of a rod, preferably solid and smooth or uniform in its longitudinal surface, of preferably constant diameter and cross section, one of the ends of which is free; the other end being either held by contact with the wall of the vessel or implanted in this wall by said fixing means; this being directly or via an associated anchoring zone.
The objectiv
Jackson Suzette J.
Societe de Conseils de Recherches et d'Applications Scienti
Willse David H.
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