RU2234884C1 - Self-expansion endovascular stent (variants) - Google Patents

Abstract

FIELD: medicine, namely device used in roentgen -endovascular surgery for restoring changed zones of blood vessels or other hollow tubular organs.

SUBSTANCE: according to first variant of invention stent includes metallic wire bent to zigzag shape and forming cylindrical surface. Said wire is made of cobalt-iron-chrome-nickel alloy "Plastocryst-08" and it has rectangular cross section with rounded angles. Stent has at least one section whose zigzag shaped wire portions are directed along lengthwise axis of stent and they have camber directed inside stent. According to second variant stent is in the form of wire bent in zigzag shape and defining cylindrical surface. Wire is made of cobalt-iron-chrome-nickel alloy "Plastocryst-08" and it has rectangular cross section with rounded angles. Zigzag shaped portions of wire are in the form of rhombic members with rounded angles, large diagonal of rhomb is inclined by angle 0 - 90 degrees relative to lengthwise axis of stent.

EFFECT: enhanced biological compatibility, maximum adaptation of stent to walls of hollow organ.

14 cl, 16 dwg

Description

The invention relates to medical equipment, namely, devices used in endovascular surgery to restore altered portions of the lumen of blood vessels or other hollow tubular organs. Self-expanding endovascular stents made of metal wire are used to restore and maintain the lumen of the hollow organs with stenosis and vascular occlusion, with mechanical compression and tumor obstruction of the hollow organs.

A self-healing stent for vessels and hollow organs is known, made of nitinol wire in the form of a mesh cylindrical surface with rhombic cells, while the cells are made in the form of an unequal rhombus, a large diagonal of the rhombus is located along the longitudinal axis of the stent, and all cell elements form minimal angles with the axis blood flow, which preserves the laminar flow of blood in the vessel {patent of the Russian Federation No. 2121317, MKI ⁶ A 61 F 2/06, published 10.11.98}. At the ends of the stent, radiopaque marks are made, since the nitinol alloy has a low radiopacity. The stent made of nitinol wire of circular cross-section has good biological compatibility and minimal trauma. However, the rigidity of the nitinol wire is insufficient to effectively perform the function of restoring and maintaining the lumen of a vessel or hollow organ. In addition, nitinol is an expensive alloy, which affects the cost of manufactured stents.

The closest set of essential features to the claimed stent is a self-expanding endovascular stent made of a zigzag bent metal wire in the form of a cylindrical hollow body (US patent No. 5800456, MKI ⁶ A 61 M 29/00, published 01.09.98). The stent is made of round wire made of stainless steel. Round “eyes” are formed on the tops of the zigzags, some of which are sealed to form a ringlet. The zigzag blank is coiled into a tube; the thread connecting the structure is drawn through the “eyes”. The thread is also placed in a spiral. The length of straight sections in zigzags located at the ends of the stent varies from 9 to 17 mm. This gradually increasing length of the straight sections leads to the fact that the cross sections of the stent at the ends are perpendicular to its axis despite the spiral arrangement of the workpiece. The stent can be compressed along the axis and expands independently after installation in a blood vessel or other hollow organ, and it has a uniform expanding “stiffness” in length.

However, constant stiffness along the length is not always an advantage of the stent, especially in cases where the stent is placed in organs having a bend. In addition, stainless steel wire has a relatively low corrosion resistance and low biocompatibility.

The technical problem to which the claimed invention is directed is to increase the biocompatibility of the stent and the manufacture of the stent with variable stiffness along the length, which ensures maximum adaptation of the stent to the walls of a blood vessel or other hollow organ.

The indicated technical problem is solved in that a self-expanding endovascular stent made of a metal zigzag bent wire forming a cylindrical surface is made of a wire made of cobalt-iron-chromium-nickel alloy (Plastokrist-08) and has a rectangular cross section with smoothed corners, at least having a cross-sectional shape one cylindrical section in which the zigzags of the wire are directed along the longitudinal axis of the stent and have a deflection inside the stent (first option).

The number of sections of a cylindrical shape, slightly concave inward, in the stent can be from 1 to 10.

In the event that there are more than one sections in the stent, the sections are fastened with at least one fastener, which is a rectilinear strip with rectangular cross-section with smoothed corners, made of Plastokrist-08, ribbed from the outside of the stent.

The number of V - periods in one cylindrical section of the stent can be 6-8.

Due to the deflection of the zigzags inside the stent, the longitudinal profile of the section has a shape close to trapezoidal.

The stated technical problem is also solved by the fact that a self-expanding endovascular stent made of a metal zigzag bent wire forming a cylindrical body is made of a wire made of cobalt-iron-chromium-nickel alloy “Plastokrist-08” and having a rectangular cross section with smoothed corners, and in the form of zigzags a rhombic shape with smoothed corners, and the large diagonal of the rhombus is directed at an angle of 0-90 ° to the longitudinal axis of the stent (second option).

For the manufacture of a stent according to the first embodiment, a blank of zigzag bent wire is wrapped around the mandrel, the ends are connected and the resulting section is slightly bent inward. For the manufacture of a multi-section stent, sections are connected by one or two rectilinear strips ribbed from the outside of the stent.

The stent according to the second embodiment is formed by continuous winding of a wire curved into elements of a rhombic shape on a mandrel.

The Plastokrist-08 alloy contains 30.0-32.0 wt.% Cobalt, 26.4-32.9 wt.% Iron, 20.0-22.0 wt.% Chromium, 17.0-19.0 wt.% nickel, as well as up to 0.05 wt.% manganese, up to 0.4 wt.% carbon, up to 0.05 wt.% aluminum, not more than 0.05 wt.% silicon and not more than 0.05 wt. .% titanium (Ukrainian patent No. 24523, MKI ⁶ A 61 K 6/04, published 10/30/98, Bulletin No. 5). It was used for the manufacture of solid cast fixed and removable dentures.

To manufacture self-expanding endovascular stents, the Plastokrist-08 alloy has not yet been used.

We conducted comparative tests of a wire with a diameter of 0.3 mm made of Plastokrist-08 and a wire of the same diameter made of stainless steel grade 316Z and from an alloy of nitinol. The test results are presented in the table.

As can be seen from the table, “Plastokrist-0.8” possesses high corrosion resistance, biocompatibility and X-ray contrast with high physical and mechanical properties.

The thickness of the wire from which the claimed stents were made can be in the range from 30 to 200 microns (0.03 - 0.20 mm); width - in the range from 75 to 390 microns (0.075 - 0.390 mm).

The diameter of the stents in the expanded state can be from 5 to 25 mm. For installation inside the hollow organs using a delivery device, the inventive stents can be compressed to a diameter not exceeding 6-7 times the wire width for the first embodiment and 4-5 times for the second embodiment.

The length of the stent according to the first embodiment can be 3-60 mm. The minimum length of the stent in the second embodiment is limited by the size of the small diagonal of the element of the rhombic shape; the stent according to the second embodiment can be made arbitrarily long.

The inventive stents can be coated with a shell made of a thin biaxially oriented film of polytetrafluoroethylene or copolymers of tetrafluoroethylene with hexafluoropropylene or tetrafluoroethylene with perfluorovinyl propyl ether with a comonomer content of not more than 2%. The film is obtained as described in the patent of the Russian Federation No. 2117459, MKI ⁶ A 61 F 2/02, published on 08.20.2002, Bulletin No. 23.

The sheath may cover the outer or outer and inner surfaces of the stent. The shell covering the inner surface of the stent can be made of 1-3 layers of polymer material. The shell covering the outer surface of the stent can be made of 1-6 layers of polymer material.

The polytetrafluoroethylene film has a structure characterized by two interconnected interpenetrating matrices: a polymer matrix in the form of nodes connected by fibrils, and a void space matrix, and these elements form a three-dimensional network. The shells can be made of a material having a volume fraction of void space of 1 to 35%, a specific surface of the void space of 0.5 to 20 μm ² / μm ³ , an average distance between voids in a volume of 0.5 to 15 μm and an average chord volumetric from 0.1 to 10 μm, or from a material having a volume fraction of void space of 25 to 94%, a specific surface space of voids of 0.1 to 9.0 μm ² / μm ³ , the average distance between voids in a volume of 1 , 5 to 50 microns and an average chord volume from 0.4 to 30 microns. The best result is shown by a shell made of a material having a volume fraction of void space of 45 to 94%, a specific surface space of voids of 0.1 to 0.6 μm ² / μm ³ , an average distance between voids in a volume of 5 to 45 μm, and volumetric chord from 5 to 30 microns.

The specified polymer material in the form of a film with a thickness of from 0.005 mm to 0.25 mm is formed in the form of a single cover covering the stent. In the case where the stent has both an inner and an outer sheath, they are sintered together in the spaces between the bends of the wire forming the walls.

The invention is illustrated by the drawings shown in figures 1-16.

Figure 1 presents the workpiece from a zigzag bent wire.

Figure 2 presents the cross section of the wire from which the inventive stents are formed.

In Fig.3 presents a cylindrical section of the stent made of the workpiece shown in Fig.1.

Figure 4 presents the stent, consisting of several cylindrical sections.

Figure 5 presents a rectilinear strip of rectangular cross section with one ribbed surface, used as a fastener for the multi-section stent shown in figure 4.

Figure 6 presents the workpiece from a zigzag bent into elements of a rhombic type of wire (the direction of the zigzags along the axis of the stent).

Figure 7 presents a fragment of the frontal element of the rhombic type.

On Fig presents a profile of a fragment of the frontal element shown in Fig.7.

Figure 9 presents the workpiece zigzag bent into elements of a rhombic type wire with a zigzag direction at an angle of 90 ° to the axis of the stent.

Figure 10 shows the workpiece zigzag bent into elements of a rhombic type of wire with the direction of the zigzags to the axis of the stent at an angle α equal to 0 ° <α <90 °.

FIG. 11 shows a stent formed from the blank of FIG. 6.

On Fig presents a stent formed from the workpiece shown in Fig.9.

On Fig presents a stent formed from the workpiece shown in figure 10.

On Fig presents a stent having an outer shell of polytetrafluoroethylene.

On Fig presents a stent having an outer and inner shell of polytetrafluoroethylene.

On Fig a) b) presents fragments of the outer and inner shells of polytetrafluoroethylene sintered around stent elements made of round wire (a) and the inventive section (b).

From a zigzag bent wire (Fig. 1) made of Plastokrist-0.8, having a rectangular cross-section with a rectangular angle with smoothed corners (Fig. 2), a cylindrical section is formed (Fig. 3). Zigzags of the wire are directed along the axis of the stent and have a deflection inside the stent, as shown in Fig.3. The deflection gives the frontal profile of the stent a trapezoidal shape. A stent may include 1-10 sections. In the event that the stent includes two or more sections, they are fastened with straight stripes made of Plastokrist-0.8 alloy. Figure 4 presents the stent, which includes 6 sections of a zigzag bent wire 1. The sections are fastened with two fasteners made in the form of rectilinear strips, ribbed on one side (figure 5). The extreme sections of the stent (Fig. 4) have variable radial stiffness with decreasing it to the ends of the stent (the first version of the self-expanding endovascular stent).

According to the second variant of the inventive stent, a wire from the Plastokrist-08 alloy having a rectangular cross section with smooth angles (FIG. 2) is curved in zigzags in the form of rhombic elements with smooth corners (FIGS. 6, 7, 8). The stent in the form of a cylindrical body (11-13) is formed from a zigzag bent wire. In this case, the large diagonal of the rhombus can be directed along the longitudinal axis of the stent, across the longitudinal axis of the stent or at an acute angle to the longitudinal axis of the stent (tilt angle 0 ° -90 °).

If the large diagonal of the rhombic element is directed along the axis of the stent (Fig.6), the formed stent has the form shown in Fig.11. This stent has maximum longitudinal stiffness and minimum torsional stiffness.

In the case where the large diagonal of the rhombic element is directed at an angle of 90 ° to the longitudinal axis of the stent, as shown in Fig. 9, the stent shown in Fig. 12 is formed. This stent has maximum compression stiffness and minimum stiffness along the axis.

If the large diagonal of the rhombic element is directed at an acute angle to the longitudinal axis of the stent, as shown in Fig. 10, the formed stent has the form shown in Fig. 13. Such a stent has the most flexible design and easily bends in different planes.

FIG. 14 shows a stent 1 coated externally with a shell 2 formed of 1-6 layers of a biaxially oriented film of polytetrafluoroethylene or a copolymer of tetrafluoroethylene with hexafluoropropylene or perfluorovinyl propyl ether containing not more than 2% comonomer. The shell has a structure characterized by two interconnected interpenetrating matrices, a polymer matrix in the form of nodes connected by fibrils, and a void space matrix, and these two matrices are connected into a three-dimensional network.

In Fig. 15, the stent 1 is provided with an outer shell 2 and an inner shell 3 made of 1-3 layers of a biaxially oriented film of the same polymer. In this case, the outer sheath 2 is sintered with the inner sheath 3 in the spaces between the bends of the wire.

On Fig shows that with a rectangular cross-section of the wire forming the inventive stent (fig.16b), the contact area of the outer and inner polymer shells is larger than would be the contact area if the stent was formed from a wire of circular cross section (figa) the diameter of which is equal to the width of the wire from which the claimed stent is formed. The increase in the contact area of the shells prevents their unwanted separation during operation.

The rectangular profile of the wire from which the inventive stent is made, in addition, allows you to increase the inner diameter of the stent with the same external diameter, which helps to normalize blood flow. Variable stiffness along the length of the stent contributes to its adaptation to the walls of the blood vessel, which reduces the likelihood of impaired hemodynamics.

In addition, the high modulus of elasticity of the Plastokrist-08 alloy provides structural strength; Its high corrosion resistance and biocompatibility.

The x-ray contrast is greater than that of nitinol, which allows the use of stents without additional x-ray contrast marks.

The inventive stent (both options) passed clinical trials at the Center for Cardiovascular Surgery of the Central Military Clinical Hospital named after A.A. Vishnevsky with x-ray endovascular prosthetics in the treatment of abdominal aortic aneurysm.

The inventive endovascular stents were implanted in 6 sick patients aged 73 to 82 years by arteriological method through the femoral artery under local anesthesia. In this case, a conductor system (introducer) with a diameter of 24F was used. Four patients had infrarenal type II abdominal aortic aneurysms; in one patient operated on five years earlier for type II abdominal aortic aneurysm, a false aneurysm of the proximal anastomosis of the linear aortic explant was observed; in another patient, the proximal cone of the nitinol stent established three years earlier was observed.

When installing the claimed stents, there were no intraoperative complications. In the postoperative period (observation from 4 months to 2 years), complications were also not observed.

Claims (14)

1. Self-expanding endovascular stent made of a metal zigzag bent wire forming a cylindrical surface, characterized in that it is made of a wire made of cobalt-iron-chromium-nickel alloy "Plastokrist-08" and having a rectangular cross section with smooth angles, moreover the stent has the shape of at least one section in which the zigzags of the wire are directed along the longitudinal axis of the stent and have a deflection inward of the stent. 2. The self-expanding endovascular stent according to claim 1, characterized in that it includes 2-10 sections in which the zigzags of the wire are directed along the longitudinal axis of the stent and have a deflection inside the stent. 3. The self-expanding endovascular stent according to claim 2, characterized in that the sections are fastened with at least one fastener made of Plastokrist-08 alloy in the form of a rectilinear strip of rectangular cross section ribbed from the outside of the stent. 4. The self-expanding endovascular stent according to claim 1, characterized in that it is coated with a sheath made of polytetrafluoroethylene or copolymers of tetrafluoroethylene with hexafluoropropylene or tetrafluoroethylene with perfluorovinyl propyl ether with a comonomer content of not more than 2%, the structure of which is characterized by two interconnected matrices, namely, matrices polymer in the form of nodes connected by fibrils and a matrix of the space of voids, and these elements are connected in a three-dimensional network. 5. The self-expanding endovascular stent according to claim 4, characterized in that the sheath is made covering the outer surface of the stent. 6. The self-expanding endovascular stent according to claim 4, characterized in that the sheath is made covering the inner and outer surfaces of the stent. 7. The self-expanding endovascular stent according to claim 4, characterized in that the membrane is multilayer. 8. The self-expanding endovascular stent according to claim 6, characterized in that the shells covering the outer and inner surfaces of the stent are sintered together in the spaces between the bends of the wire forming the stent. 9. Self-expanding endovascular stent made of a metal zigzag bent wire forming a cylindrical surface, characterized in that it is made of a wire made of cobalt-iron-chromium-nickel alloy “Plastokrist-08” and having a rectangular cross section with smooth angles, and zigzags are made in the form of elements of a rhombic shape with smoothed corners, and the large diagonal of the rhombus is directed at an angle of 0-90 ° to the longitudinal axis of the stent. 10. The self-expanding endovascular stent according to claim 9, characterized in that it is coated with a sheath made of polytetrafluoroethylene or copolymers of tetrafluoroethylene with hexafluoropropylene or tetrafluoroethylene with perfluorovinyl propyl ether with a comonomer content of not more than 2%, the structure of which is characterized by two interconnected matrices, namely, matrices polymer in the form of nodes connected by fibrils and a matrix of the space of voids, and these elements are connected in a three-dimensional network. 11. The self-expanding endovascular stent of claim 10, wherein the sheath is made covering the outer surface of the stent. 12. The self-expanding endovascular stent of claim 10, wherein the sheath is made covering the inner and outer surfaces of the stent. 13. The self-expanding endovascular stent of claim 10, characterized in that the membrane is multilayer. 14. The self-expanding endovascular stent according to claim 12, characterized in that the shells covering the inner and outer surfaces of the stent are sintered together in the spaces between the bends of the wire forming the stent.

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