DE3918736C2 - Plastic-coated metal mesh stents - Google Patents

Description

The invention relates to plastic-coated metal grids stents for permanent stretching of arterial constrictions.

After transluminal stretching of arterial stenoses with a Balloon catheter or completely closed after reopening In many cases, vessels cannot keep the lumen open be held as parts of the intima like a valve put in a closing position.

This leads to certain locations (e.g. the coronary arteries) to a critical situation requiring an emergency Bypass surgery with high risk required for the patient makes; in any case, however, it prevents the desired one Acute success.

Vascular endoprostheses, so-called Stents, experimented with a mesh of metal wires (usually in grid form) and either as self-expand active stents (Sigwart, U., Puel, J. Mirkovitch, V., Joffre, F., Kappenberger, L .: "Intravascular stents to prevent occlusion and restenosis after transluminal angioplasty ", New Engl. J. Med. 316, 701 (1987) and Palmaz, J.C., Richter, G.M., 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 on site and Place expanding (passive) stents (Strecker, E.P., Romaniuk, R., Schneider, B., Westphal, M., Zeitler, E., Wolf, H.R.D., Freudenberg, N .: Percutaneously implantable, balloon-expandable bare vascular prosthesis DMW 113 (1988), 538) and internal Support the jar open.  

Although these vascular endoprostheses consist of a blood and tissue ver inert material, e.g. B. gilded steel wire However, they show a not to be underestimated Thrombogenicity which, in order to avoid early occlusion, with high (potentially dangerous) doses of anticoagulant Medicines must be countered. After that, d. H. in a few weeks, the metal wires through the inner skin of the vessel, the endothelium, overgrown so that a smooth, relatively athrombogenic surface arises. Hope, the rate of recurrence through the deposit to be able to lower such vascular endoprostheses, however have not been confirmed so far (Mahler, F., Do, D., Triller, J., Thalmann, R., Walpoth, B .: History results after percutaneous Insertion of arterial endoprostheses (stents) into the leg arteries, VASA, Suppl. 23, 176-177 (1988). The problem appears in the Grid growth through tissue cells. Their Growth stimulated by the inserted stent it does not stop after the braid has been completely covered on, but goes on and can thus lead to a new one complete or partial occlusion of the vessel.

EP 0 150 608 discloses a valve device, in particular an artificial one Heart valve from a base body, which is also called a "stent" and leaf-shaped valve flaps, with all moving parts with a biocompatible material made of a synthetic polymer, which among other things can also be PTFE, are coated. On the one hand, this coating is intended to cover the surfaces smooth and on the other hand the frictional resistance and thus the abrasion of the outer Reduce surfaces. On the problem of stimulating tissue growth this writing is not received.  

In US 4,768,507 is a stent made of a coil spring material and a special one Device with which such a spiral spring in a comparatively thin vessel can be introduced disclosed. One problem with these spiral stents appears to be one Injury to the vessel wall when embedding it in the vessels, which is a Closure of the vessel caused by blood deposits within 24 hours To prevent this thrombosis, the spiral is coated with ULTI carbon (ultra low temperature isotropic carbon), such a casing directly can be applied to the spring material (steel or titanium alloys), or after previous coating with PTFE, which should act as a primer. The Problem of vascular overgrowth through cell formation stimulation over longer periods Periods are also not addressed in this document.

The object of the present invention was therefore to provide a vascular duo to develop prosthesis, which on the one hand is a constricted vessel permanently expanding; on the other hand does not have a thrombogenic effect prevents growth through tissue cells.

This task is surprisingly achieved by using an well-known metal mesh stent inside (and possibly outside) with a thin coating of polytetrafluoroethylene (PTFE or PTF) covered.

Polytetrafluoroethylene, a polymer of the formula - (CF ₂ -CF ₂ ) _n with n = 5000-100 000 is a well-known product which, due to its great chemical resistance, is widely used for a wide variety of coatings and linings in chemical apparatus engineering. For some time now, this material has also been used in medicine to coat prosthetic joints. For a long time, thin tubes made of PTFE have also been used with great success as vascular prostheses (bypasses). A special microporous structure ensures an organic growth of the ends with the vessels to be connected.

According to the invention, either a dispersion of PTF is one Corresponding stent sintered around from a metal grid or a very thin film peeled off from a block of PTF from the inside inserted into the stent and heated to 370-380 ° C and / or connected to the stent using pressure. If necessary, another film can be placed around the outside of the stent be placed to complete containment of the metal to reach. The film can optionally also form a tube to be sewn.

This way the thrombogenicity leads to early occlusion and lead to the tractability that the latex closures the vascular endoprosthesis avoided.

Since the metal of the stent is no longer with the blood and the Tissue comes into contact, the braid can be made out of relative inexpensive steel wire, preferably a stainless steel, exist, of course also tissue compatible metals sufficient hardness such as titanium or precious metals can be used can.

The stents according to the invention are in the usual way over a catheter inserted into the vessel into the narrowed area brought in. So that the stent can pass through the vessel it should be compressed around the catheter beforehand if possible only at the site of action through your own resilience or with the help of a Balloon catheter to be expanded to the required width.  

The preformed final width starts at about 2 mm through knife, larger diameter of z. B. 3-12 mm allow Use in other vascular areas (e.g. leg, pelvic or Renal arteries, aorta, carotid arteries, coronary arteries, etc.).

While the well-known, consisting only of a metal grid Stents are stretchable and squeeze or through Allow longitudinal elongation to narrow in cross section is the fiction appropriate PTFE coating not or only very little stretch. The necessary reduction in cross-section when inserting into the vessel is therefore preferably by one or more longitudinal folds reached and the original cross section by stretching with reached a balloon catheter, the fold being unfolded. Alternatively, with a helical metal insert Cross-sectional narrowing are generated by twisting. The However, the invention is not intended to cover these embodiments be limited.

The necessary flexibility of the stent is due to the PTFE over train not affected; this is for insertion in the vessel bends important.

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

Fig. 1 shows a conventional metal mesh stent.

Fig. 2 shows a metal mesh stent with PFTE inner lining.

Fig. 3 shows a metal mesh stent with an inner lining in a 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 of tantalum or a noble metal, for example, a hose (1), the wire mesh (2) is compressed for introduction into a vessel or in the length can be pulled so that the cross section of the stent is reduced. After insertion into the vessel, the stent can then be expanded again to the vessel diameter.

Fig. 2 shows a corresponding metal grid stent ( 1 ) in cross section, the metal wire mesh ( 2 ) being indicated by thick and thin circumferential lines. The inside of the stent is lined with a PTFE layer ( 3 ), a distance from the wire mesh ( 2 ) being indicated for technical reasons, but in use the tube and mesh are close together.

In Fig. 3 a corresponding stent ( 1 ) made of tantalum wire ( 2 ) with an inner lining made of PTFE ( 3 ) is shown in a compressed state, which is indicated by the fact that the metal wire mesh almost touch. To compensate for the reduced circumference, the PTFE inner tube is shown with an additional fold ( 4 ), which, as shown in FIG. 2, lies flat against the metal grid when the stent is expanded.

In FIG. 4, a further metal mesh stent (1) is shown with an inner tube (3) and an outer jacket (5). Depending on the method of manufacture, these two PTFE sleeves are connected to one another between the wire meshes ( 2 ).

Claims (8)

1. Metal lattice stents for permanent expansion of arterial constrictions, characterized in that they are covered on the inside with a thin coating of polytetrafluoroethylene. 2. Metal mesh stents according to claim 1, characterized in that inner and Are covered with polytetrafluoroethylene on the outside. 3. Metal grid stents according to claim 1, characterized in that the coating as Foil is formed. 4. Metal mesh stents according to one of claims 1-3, characterized in that the Cross section of the stent is changeable over a longitudinal fold. 5. metal grid stents according to any one of claims 1-4, characterized in that the Cross section is changeable via a longitudinal twist. 6. A method for producing metal lattice stents according to claims 1-5, characterized characterized in that the coating is sintered onto the metal grid or as a hose sewn on or around the same. 7. The method according to claim 6, characterized in that two films around the Metal grids are sintered together. 8. The method according to claim 6, characterized in that a polytetrafluor ethylene dispersion applied to the metal grid and to a coating is sintered together.