DE10357281A1 - Degradable stent for blood vessel support made of magnesium material, comprises degradation-inhibiting biocompatible coating - Google Patents

Abstract

The stent (1) is at least partially provided with a degradation-inhibiting, biocompatible coating (3). The coating comprises magnesium fluoride as a main component, and may have different thickness or structural form in different areas of the stent.

Description

The The invention relates to a degradable designed in particular as a stent Vascular support off a magnesium material.

Suffer annually in Germany several hundred thousand people have a heart attack. This is a necrosis of a circumscribed heart muscle area due to severe circulatory disorders, which mostly caused by a constriction or the occlusion of a coronary vessel caused becomes. This is known as arteriosclerosis (arteriosclerosis) pathological change arterial vessels manifests itself Hardening, Thickening, loss of elasticity and clearing of the affected areas.

healthy Arteries are flexible. Due to poor diet, lack of exercise and not least by the natural Aging process, fatty acids, cholesterol and calcium salts accumulate in to the blood vessels. As a result, the arteries lose flexibility, thicken the vessel walls and narrow. The blood flow is increasingly hampered, resulting in a Lack of nutrients and oxygen leads. At the narrowed vessel walls can it as well come to coagulation processes. A resulting thrombus (Blood clot) can completely occlude the vessel, causing the heart muscle tissue dies and the infarction is initiated.

Around Reopen closed or closed vessels can, The affected vessel is often through a PTCA (percutaneous transluminal coronary angioplasty) with a subsequent Implantation of a stent provided. This is the ischemic (bleeding) event first by the expansion of a balloon introduced via a catheter. Plaques and thrombi are pushed into the vessel wall and the lumen is dilated. To keep open the extended diameter is often a Vessel-supporting implant (Stent) also over the catheter in the form of a thin, structured tube introduced and dilatation (dilation) takes place at the appropriate place through a stretchable balloon. The stent is enlarged by enlarging its Diameter without big change in length pressed against the vessel wall and ensures the required lumen cross section.

Often sets However, due to the foreign body used increased cell growth one. In the place, originally was narrowed, often form cell proliferations and thus again Vasoconstriction.

by virtue of In addition, the perforation of vessels has increased. This is usually associated with an acute pain for the patient who is at the Stretch arises, connected. In addition, the patients tachycardia and show a drop in blood pressure. For closing the perforation site It may be necessary to implant more stents, thereby the effort continues to rise.

To the implantation of the vascular support must be Patient because of the very high risk of thrombosis, which prevails in the stent, drugs for dilution of the blood, such as drugs for inhibition the platelet aggregation.

It are already generic vascular props a magnesium-lithium alloy known to be within less Dissolve months. Such Magnesium stents are advantageous because the vascular supporting function only temporarily for a few Weeks is required, however, the subsequent removal of a once implanted stent is generally excluded. magnesium is particularly suitable for the stent insert, because it is easy to handle, no own toxic effect and controlled by the nature of the alloy can be how fast the stent dissolves. In addition, such can be Stents also coat with active ingredients that block the vaso-occlusive growth of the connective tissue. For children deleted about that addition to the prior art problem of conventional stents, that these become too small due to the growth of the blood vessels after some time are.

It are still also vascular props with different coatings known. For example, experiments taken with the vascular support Coat gold to achieve a lower restenosis rate. Furthermore, stents are known for this purpose, with phosphorylcholine or coated with heparin.

Furthermore is experimented with radioactive stents, so by local Radiotherapy - over one radioactive wire portion or by radioactivity directly over a Stent placed - the To reduce restenosis rate.

Farther Stents are also known whose surface is coated with medication is. After stent implantation, these drugs are released to prevent a renewed narrowing of the vessels. Besides that is It is also known to use stents with an antiproliferative substance coat and thus the possibility to restrict the proliferation of smooth muscle cell.

Of the Invention has for its object to provide a way, a adapted to the medical healing process dissolution process to realize the vascular support.

These Task is according to the invention with a Device according to the features of claim 1. The dependent claims concern particularly expedient further education the invention.

According to the invention is thus a degradable vascular support a magnesium material provided, at least in sections with a delaying the degradation, biocompatible coating is equipped. This allows the resolution process the vascular support in time be adjusted so that the vascular support the healing process optimally support especially the support function only fulfilled as long as how this is necessary or meaningful from a medical point of view. The coating can be applied in a suitable thickness. Therefore, a adapted to the patient, individual course of the support function and the start of degradation. The mechanical Properties of the base material of the vascular support remain during the support phase unchanged and the degradation protective layer dissolves steadily but very slowly and evenly on. To the resolution the protective layer begins the actual degradation, the Implant loses its mechanical properties and completely absorbed becomes.

there proves to be particularly promising if the coating as a material material component magnesium fluoride. This is done on the uncoated surface of the structured stent the coating applied to the degradation control on the transformation of course existing superficial mixed oxide layer is based on a mixed fluoride layer. Main component of this layer is in particular magnesium fluoride and the minor constituents exist from the fluorides of the alloying elements contained in the base material. The coating is, for example, by dipping in fluoride-containing Media with or without electrolytic support with a coverage strength up to to a few microns applied.

The Coating can be used in different areas of the vascular support homogeneous thickness and minimal roughness, thereby providing a constant resolution process in the support phase is achieved, through which an optimized adaptation to the desired medical requirements is ensured. On the other hand proves It turns out to be especially practical if the coating is in different areas the vascular support one has different thickness and / or texture. hereby becomes a local different dissolution process achieved by a further optimized adaptation to the desired medical properties is achieved.

there proves to be particularly practical if the coating in different areas a different thickness and / or Composition, by which one over the time course the degradation targeted change stability reached the vascular support becomes. As a result, the function maintenance is set such that an individual adaptation to problem statement and medical history can be realized.

Especially In this case, the coating deviates so differently in different areas executed that due to the degradation a flexibility of the initially immovable vascular support is realized so the support function optimal for the healing progress and thereby from medical View desirable Adjust the degree of stress on the vessel to be able to.

A Another particularly promising embodiment is thereby reached even if the coating has a structuring, so that due to the different degradation properties recesses and / or perforations of the vascular support arise. As a result, the production cost can be significantly reduced by the desired Breakthroughs of the vascular support only through the dissolution process arise. The insertion of the stent into the vessel is thereby facilitated and cell proliferations diminished. The removal of the during the dissolution process released hydrogen gas is thereby also improved.

there It turns out to be particularly practical if the coating accordingly the degradation of the outer dimensions determined by the degradation deviated in different areas. hereby let yourself in a simple way, for example, a shortening of the length or reduction of the outer diameter to reach.

A individual adaptation to the patient is also achieved if the coating corresponds to the expected rate of healing is applied. This will be done first a prognosis of the expected healing progress in dependence created the diagnosis, so as to the nature, strength and distribution of the coating optimally determine and adapt.

Especially Promising is also an embodiment in which the Layer executed in such a way is that while a first degradation period initially no or only one very slight change the mechanical properties of the vascular support occurs while in a second degradation period following the first degradation period In particular, the mechanical properties change constantly. hereby becomes a history not yet attainable in medical practice achieved the degradation that allows it, from medical Viewpoint to optimally depict the optimal requirement profile and thus the Significantly increase healing success. It takes place during the first degradation period a steady and slow degradation of the Coating takes place, which by the solution of the coating material causal brought becomes. While During this first period of degradation, endothelialization takes place (New formation of the vessel wall with Endothelial cells) and thus the ingrowth of the implant, wherein the mechanical properties are preserved and the implant its support function 100% fulfilled. After endothelialization, the second degradation period begins, with the main body of the implant slowly dissolves and reabsorbed. Here, the stent steadily loses its strength and the vessel can support the function take over again independently.

there is it particularly favorable if during the second degradation period the strength steadily decreases and thereby the vascular support, for example while the first degradation period a substantially constant strength that has during decreases the second degradation period.

A another particularly profitable modification of the present invention is also achieved by the vascular support around its longitudinal axis spirally deformable executed is. This achieves optimum dilatation. Come as a stent basic body while, for example, spiral rollable and in particular form-fitting in the functional position definable shapes in question.

Farther proves to be particularly useful when the vascular support a laser-structured, tubular body is constructed so as to be optimal for the respective conditions of use to achieve an adapted structure. The plastic deformation zones are thereby burdened only with very low degrees of deformation. In particular the vascular support in such a way executed that after the expansion of the implant no or only a very small rebound (Recoil) occurs and the dilatation does not lead to any appreciable shortening of the Stents leads.

The Invention leaves different embodiments to. To further clarify its basic principle is one of them shown in the drawing and will be described below. These shows in

1 a partially sectioned side view of a vascular support according to the invention.

2 a schematic representation of a spirally deformable around its longitudinal axis vascular support.

1 shows a particularly designed as a stent degradable vascular support 1 which consists of a fine-grained and biocompatible magnesium alloy. On a smooth surface 2 the structured vascular support 1 is a biocompatible coating to control the degradation 3 applied. This coating 3 is based on the transformation of the surface 2 existing mixed oxide layer in a Mischfluoridschicht and can for example by dipping in fluoride-containing media with or without electrolytic support with a, for example, in various areas of the vascular support 1 different layer thickness d of <3 microns are applied. In particular, the coating can 3 be equipped with a structuring such that due to the different degradation properties over the time course of the degradation individual perforations 4 the vascular support 1 arise. The degradation of the vascular support 1 This leads to the fact that foreign bodies decompose biocompatible and the affected arterial area can take over its function again completely and autonomously after the dismantling. After resorption of the vascular support 1 is therefore no longer expected to foreign body reactions.

2 shows a schematic representation of a about its longitudinal axis 5 spirally deformable vascular support 6 , Due to this basic structure of the vascular support 6 the plastic deformation zones are only loaded with very low degrees of deformation. In its not shown functional position of the vascular support 6 snap individual projections 7 savings in appropriate 8th the vascular support 6 a form-fitting, so that a return movement is largely excluded even under the influence of external forces.

Claims (12)

A degradable vascular support, especially designed as a stent ( 1 . 6 ) of a magnesium material, characterized in that the vascular support ( 1 . 6 ) at least in sections with a degradation-delaying biocompatible coating ( 3 ) Is provided. Vascular support according to claim 1, characterized in that the coating ( 3 ) as a material material component magnesium fluoride. Vascular support according to claims 1 or 2, characterized in that the coating ( 3 ) in different areas of the vascular support ( 1 . 6 ) has a different thickness (d) and / or texture. Vascular support according to at least one of the preceding claims, characterized in that the coating ( 1 . 6 ) has a different thickness (d) and / or composition in different regions, through which a change in the stability of the vascular support directed over the time course of the degradation ( 1 . 6 ) is achieved. Vascular support according to at least one of the preceding claims, characterized in that the coating ( 3 ) is performed in different areas so deviant that due to the degradation of a flexibility of the initially immovable vascular support ( 1 . 6 ) is realized. Vascular support according to at least one of the preceding claims, characterized in that the coating ( 3 ) has a structuring such that due to the deviating degradation properties over the time course of the degradation recesses and / or openings ( 4 ) of the vascular support ( 1 ) arise. Vascular support according to at least one of the preceding claims, characterized in that the coating ( 3 ) is applied differently in different areas according to the desired change in the outer dimensions. Vascular support according to at least one of the preceding claims, characterized in that the coating ( 3 ) is applied according to the expected healing progress. Vascular support according to at least one of the preceding claims, characterized in that the coating ( 3 ) is designed in such a way that during a first degradation period initially no or only a very slight change in the mechanical properties of the vascular support ( 1 . 6 ), while in one of the first degradation period following the second degradation period, the mechanical properties in particular change continuously. Vascular support after Claim 9, characterized in that during the second degradation period the strength decreases steadily. Vascular support according to at least one of the preceding claims, characterized in that the vascular support ( 6 ) about its longitudinal axis ( 5 ) is designed spirally deformable. Vascular support according to at least one of the preceding claims, characterized in that the vascular support ( 1 ) is constructed from a laser-structured, tubular body.