DE3918736C2 - Plastic coated metal mesh stents - Google Patents

Description

The invention relates to plastic-coated metal mesh stents for the permanent elongation of arterial narrowing.

After transluminal expansion of arterial stenosis with a balloon catheter or by re-opening completely blocked blood vessels, the lumen in many cases can not be kept permanently open, since parts of the intima lay like a valve occlusive inside.

This results in certain locations (. Eg coronary arteries) to a critical situation that requires an emergency even bypass surgery at high risk for the patient; but in any case it prevents the targeted acute success.

For several years, experimented with vascular endoprostheses, so-called stents (usually in grid form) are made of a mesh of metal wires and either selbstexpan rocketing (active) stent (Sigwart, U., Puel, J. Mirkovitch, V., Joffre, .. F., Kappenberger, L .: "Intravascular stents to prevent restenosis and occlusion after transluminal angioplasty," New Engl J Med 316, 701 (1987) and Palmaz JC, judges, GM, Noeldge, G. et al: intraluminal stents in atherosclerotic iliuc artery stenoses. Preliminary report of an multicenter study, Radiology 168 (1988), 727) or with the balloon catheter in place aufzudehnende (passive) stents (Strecker, EP, Romaniuk, R., Schneider, B. , Westphal, M. Zeitler, E., Wolf, HRD, Freudenberg, N .: percutaneously implantable aufdehn by balloon bare vascular prosthesis DMW 113 (1988), there are 538) and as inner support hold open the vessel.

Although these vascular endoprostheses from a blood and tissue sealing träglichen material, eg. However, for example, gold-plated steel wire are prepared, they have a not to be underestimated thrombogenicity, which, in order to prevent premature closures, with high (potentially hazardous) doses must be countered of anticoagulant drugs. Thereafter, ie within a few weeks, the metal wires are overgrown by the vessel inner skin, the endothelium so that a smooth, relatively athrombogeneous surface. The hope of being able to reduce the rate of relapses by the deposit of such vascular endoprostheses, has come up so far not confirmed (Mahler, F., Do, D., trills, J., Thalmann, R., Walpoth, B .: History results after percutaneous insert arterial prostheses (stents) in the leg arteries, VASA, Suppl. 23, 176-177 (1988). the problem seems to be in the intergrowth of the grating by tissue cells. Their growth, which was stimulated by the inserted stent hears namely, not after complete casing of the braid, but rather goes on and can thereby lead to a complete or partial re-occlusion of the vessel.

EP 0150608 discloses a valve device, particularly an artificial heart valve of a base body, is which is also called a "stent" and sheet-shaped valve flaps, wherein all the moving parts with a biocompatible material of a synthetic polymer, which may be, inter alia, PTFE, coated are. This coating on the one hand smooth the surfaces and on the other hand reduce the frictional resistance and the abrasion of the outer surfaces. On the issue of stimulation of tissue growth, it is not a font.

In US 4,768,507 a stent made of a coil spring material, and a special device with which such a spiral spring can be introduced in a comparatively thin vessel is disclosed. One problem with this spiral stents appears to be an injury to the vessel wall when embedding into the vessels to be, which causes occlusion of the vessel within 24 hours by blood deposits To this thrombosis to prevent the spiral is clothed with ULTI carbon (ultra low temperature isotropic carbon) , such a casing may be applied directly on the spring material (steel or titanium alloys), or by prior coating with PTFE, which is to act as a primer. The problem of Zuwachsens of vessels by stimulating cell formation over extended periods is not addressed in this document.

It is an object of the present invention to develop a Gefäßendo prosthesis, on the one hand widening a narrowed vessel permanently; on the other hand does not affect thrombogenic and an intergrowth prevented by tissue cells.

This object is surprisingly solved by the inside a per se known metal mesh stent (and possibly exterior) clothed with a thin coating of polytetrafluoroethylene (PTFE or PTF).

Polytetrafluoroethylene, a polymer of the formula - (CF ₂ -CF _{2) n} with n = 5000-100000 is a known product, which is used because of its high chemical resistance on a large scale for a variety of coatings and linings in chemical apparatus. For some time, this material is also medical application for coating prosthetic joints. Has long thin tubes made of PTFE with great success as vascular prostheses (grafts) are used. A special microporous structure provides for an organic coalescence of the ends to be joined vessels.

According to the invention either herumgesintert a dispersion of PTF to a corresponding stent of metal grid or a very thin, peeled by a block of PTF film from the inside inserted into the stent and with heating up to 370-380 ° C and / or under application of pressure with connected to the stent. Optionally, a further film from the outside can be placed around the stent to achieve a complete enclosure of the metal. The film can also be sewn into a tube, if appropriate.

In this way, the thrombogenicity, which can lead to early closures and Durchwachsbarkeit which causes the late closures of vascular endoprostheses avoided.

Since the metal of the stent is thus no longer comes into contact with the blood and the tissue web of relatively inexpensive steel wire may, preferably a stainless steel, wherein, of course, also tissue-compatible metals sufficient hardness such as titanium or noble metals may be used.

The stents according to the invention are introduced in a conventional manner through a catheter introduced into the vessel in the restricted site. Thus, the stent can thereby pass through the vessel, it must be previously compressed as far as possible around the catheter to be extended only at the site of action by its own resilience or by using a balloon catheter to the required size.

The preformed final length starts at about 2 mm diameter larger diameters of z. B. 3-12 mm enable use in other vascular regions (z. B. leg, pelvic or renal arteries, aorta, carotid arteries, coronary arteries, etc.).

While the known, consisting only of a metal mesh stents are expandable and compress or constrict blank by longitudinal expansion in cross-section, the fiction, modern PTFE coating is not or only very slightly extensible. The necessary cross-sectional reduction during insertion into the vessel is thus preferably accomplished by one or more longitudinal folds and the original cross-section achieved by expansion with a balloon catheter, where the fold is expanded. Alternatively, the cross-sectional constriction can be produced by twisting in a helical metal insert. However, the invention is not limited to these embodiments.

The flexibility of the stent is affected by the PTFE About not train; this is for insertion into vessel bends important.

In the following figures, the invention is explained in more detail, without that this should be limited thereby.

Fig. 1 shows a conventional metal mesh stent.

Fig. 2 shows a metal mesh stent with PTFE liner.

Fig. 3 shows a metal mesh stent having inner liner in the compressed state.

Fig. 4 shows a metal mesh stent having interior and exterior coating of PTFE.

In detail, the FIG. 1 shows a conventional metal mesh stent, being knitted from thin wires, which can consist, for example, tantalum or a noble metal, a hose (1), the wire mesh (2) is compressed or for introduction into a vessel in the length can be drawn so that the cross section of the stent is reduced. After introduction into the vessel, the stent may then be expanded to the vessel diameter again.

Fig. 2 shows a corresponding metal mesh stent (1) in cross-section, the metal wire mesh (2) are indicated by thick and thin circumferential lines. The stent is lined with a PTFE-layer (3), from sign reasons, a distance from the wire mesh (2) is indicated, are in use, and hose mesh but close to each other.

In Fig. 3 a corresponding stent (1) made of tantalum wire (2) is shown with an inner lining of PTFE (3) in the compressed state, which is indicated by the fact that the metal wire meshes are almost touching. The PTFE tube is ready to compensate for the reduced circumference with an additional fold (4) which is applied to upon expansion of the stent, as shown in Fig. 2, straight to the metal grid.

In FIG. 4, a further metal mesh stent (1) with an inner tube (3) and an outer jacket (5) is reproduced. Depending on the production, both of these cases PTFE between the wire mesh (2) are connected together.

Claims (8)

1. a metal stent for permanent elongation of arterial constrictions, characterized in that they are covered over on the inside with a thin coating of polytetrafluoroethylene.

2. a metal stent according to claim 1, characterized in that inner and outer surfaces are clothed with polytetrafluoroethylene.

3. a metal stent according to claim 1, characterized in that the coating is formed as a film.

4. a metal stent according to any one of claims 1-3, characterized in that the cross section of the stent is changeable by a longitudinal fold.

5. a metal stent according to any one of claims 1-4, characterized in that the cross-section through a longitudinal twisting is variable.

6. A process for preparing a metal stent according to claim 1-5, characterized in that the coating is sintered onto the metal mesh or is sewn as a tube on or about the same.

7. The method according to claim 6, characterized in that two films are sintered to each other by the metal mesh around.

8. The method according to claim 6, characterized in that a polytetrafluoro ethylene dispersion applied to the metal grid and is sintered together to form a coating.