Patent Description:
In the prior art, in order to solve the problem of involvement of bifurcated vessels in a lesion site, a covered stent fenestrated technology is generally used, which can isolate the lesion vessels but also keep the bifurcated vessels clear. However, the technology still has the problems of difficult bifurcated port positioning, poor connection matching between branches and a main body, poor angle adaptability after placement of connection stent and the like, and how to effectively connect the branches and the main body to achieve an ideal effect of isolation and shunt is a research direction of this technology.

In-situ fenestrated technology of a covered stent is a technology that first inserts a complete coating main body, then introduces a physical puncture or laser breakdown to punch holes at branch positions, and finally introduces a connection stent. The technology is feasible in theory, but there are some problems in practice, such as debris falling off in the holes punching process, uncontrollability of the hole size, and possible thrombosis and the like during the fenestrated process.

In view of the above problems, the Chinese patent with the publication number of <CIT> proposes a fenestrated side branch covered stent, namely, a short branch <NUM> of transition segment is placed in a position to be opened in the main stent <NUM> in advance, and a polymer flexible segment <NUM> is used to connect the opening position at the adjacent opened position, so as to connect with the short branch. The method can be positioned through the short branch <NUM> of transition segment, and can be well connected through the polymer flexible segment <NUM>. Compared with a covered stent with only a short branch of rigid built-in transition segment, the covered stent can adjust the connection angle with the short branch within a certain range, such that the risk of endoleak caused by loose connection position can be effectively avoided.

However, due to the fact that the polymer flexible segment <NUM> lacks metal stent support and is placed in the covered stent, it may cause the risk of branch blood supply shortage due to branch closure under the impact of blood flow, which increases the burden of patients' self-healing. In addition, the polymer flexible segment <NUM> in the patent is completely fixed to the main body stent <NUM>, and when a branch stent is externally connected, an adjusted angle of the branch stent can be limited to a certain extent.

The Chinese patent application with the publication number of <CIT> provides an aorta fenestration stent, which opens a side window at a coating portion of a main stent without a metal framework and introduces a small stent <NUM> with a metal framework support into the inner wall of the side window, and the axis of the small stent <NUM> is parallel to the axis of the main stent <NUM>, and the small stent <NUM> serves to connect the main stent <NUM> and a branch stent <NUM>. The metal framework of the small stent <NUM> improves the radial support force of the small stent <NUM> and can effectively fix branch channels, but reduces the flexibility of the small stent <NUM>. When the branch stent <NUM> is introduced and connected with the small stent <NUM>, the branch stent <NUM> is easily restrained at the joint of being connected with the small stent <NUM>, especially for complex branch vessels having a large degree of bending. Moreover, the compatibility between the branch stent <NUM> and the small stent <NUM> is poor, which may lead to a risk of type endoleak. In addition, there is also the problem that the local stress in the connection section is too high and the branch vessels are pressed.

<CIT> discloses an endoluminal prosthesis with a branch lumen extending through an outer wall of a trunk lumen. The branch lumen is in fluid communication with the trunk lumen through anastomosis. The branch lumen is disposed longitudinally along and circumferentially about the prosthetic trunk.

<CIT> discloses a stent graft comprising a tubular main body with at least two fenestrations disposed adjacent to one another and each has a tube extending into the tubular body. The tubes are joined inside the tubular body into a larger tube to facilitate catheterization.

The object of the present invention is to provide a covered stent which can effectively fix an external branch stent and has good flexibility while also addressing the defects of the prior art.

According to the present invention a covered stent is provided as defined in claim <NUM>. The covered stent includes a tubular main stent and a connection stent disposed on the main stent. An opening is formed in a side wall of the main stent. The connection stent includes a fixed segment connected to the side wall of the main stent and a free segment connected to the fixed segment. Each of the fixed segment and the free segment includes a stent and a coating covering the surface of the sent. One end of the free segment distant from the fixed segment is connected to the edge of the opening, and a gap is formed between one side of the free segment near to the side wall of the main stent and the side wall of the main stent.

The stent of the free segment comprises a plurality of waveform rings, any two of the adjacent waveform rings being opposite in phase, and the crests and troughs of any two of the adjacent waveform ring being interlocked, and the crests or the troughs of at least two of the waveform rings at the fore and aft ends of the stent being connected to the coating of the free segment.

In addition, the present invention also provides an alternative covered stent as defined in claim <NUM>. The covered stent comprises a tubular main stent and a connection stent disposed on the main stent, an opening being formed in a side wall of the main stent, wherein the connection stent comprises a fixed segment connected to the side wall of the main stent and a free segment connected to the fixed segment, each of the fixed segment and the free segment comprising a stent and a coating covering the surface of the sent, one end of the free segment distant from the fixed segment being connected to the edge of the opening and a gap being formed between one side of the free segment near to the side wall of the main stent and the side wall of the main stent.

The stent of the free segment comprises a plurality of waveform rings, any two adjacent waveform rings being opposite in phase, and the crest or trough of one of the waveform rings being disposed on the trough or crest of the other waveform ring, and the crest or trough which being disposed on the other waveform ring being connected with the coating of the free segment.

Compared with a conventional fenestrated stent, the present covered stent can effectively solve the problem of the limitation of an adjusted angle of an external connection stent at the connection segment. Therefore, the covered stent can be suitable for various complicated and changeable branch vessel configurations, and has the advantages of good universality, simple structure and the like.

In addition, a corresponding number of the connection stents can be introduced depending on the number of branch vessels at a specific lesion site, and if there is no lesion at the branch vessel location, the connection stent serves only as a drainage to prevent a series of complications caused by the closure of the branch vessels; if branches involve a lesion, an external branch stent can be introduced at the branch fracture, which can be used in conjunction with the connection stent to play an isolation effect and achieve the purpose of treatment.

The present invention will now be further illustrated with reference to the accompanying drawings and embodiments, in which:.

The technical features of the present invention will be more clearly understood from the following detailed description of the specific embodiments with reference to the accompanying drawings.

The configurations shown in <FIG> are given as comparative examples and are not part of the present invention. As shown in <FIG> and <FIG>, a covered stent <NUM> includes a tubular main stent <NUM> and a connection stent <NUM> disposed on the main stent <NUM> and connected to the main stent <NUM>. An opening O is formed in a side wall of the main stent <NUM>. The connection stent <NUM> includes a fixed segment <NUM> connected to the side wall of the main stent <NUM> and a free segment <NUM> connected to the fixed segment <NUM>. One end of the free segment <NUM> distant from the fixed segment <NUM> is connected to the edge of the opening O, and a gap <NUM> is formed between one side of the free segment <NUM> near to the side wall of the main stent <NUM> and the side wall of the main stent <NUM>. The covered stent <NUM> has a radial expansion capability and may be compressed under the action of an external force and self-expand after the withdrawal of the external force or restore to the original shape and maintain the original shape by mechanical expansion, such as balloon expansion. Thus, after being implanted into a lumen, the covered stent <NUM> can be tightly attached to a wall of the lumen and may be fixed in the lumen through its radial support force, thereby playing the roles of reconstructing a blood flow channel and isolating the lesion.

As shown in <FIG>, the connection stent <NUM> is integrally positioned inside the lumen of the main stent <NUM>, and the fixed segment <NUM> is fixed on an inner side wall of the main stent <NUM> and has a connection line L with the inner side wall of the main stent <NUM>. The proximal end of the free segment <NUM> is connected to the fixed segment <NUM>, and the distal end thereof is connected to the edge of the opening O through the inner and outer side walls of the main stent <NUM>. And a gap <NUM> is formed between one side of the free segment <NUM> near to the inner side wall of the main stent <NUM> and the inner side wall of the main stent <NUM>. In this embodiment, the center of the opening O falls on an extension line of the connection line L of the fixed segment <NUM> and the inner side wall of the main stent <NUM>. As shown in <FIG>, the center of an opening O' may also deviate from a connection line L' of the fixed segment <NUM> and the inner side wall of the main stent <NUM>. A part of the blood flowing into the lumen of the main stent <NUM> flows out of the opening O through the connection stent <NUM>, and the blood flowing out of the opening O is supplied the branch vessels via an external stent. The position of the center of the opening O with respect to the connection line L may not only control the flow rate of blood flowing through the connection stent <NUM> so as to achieve a blood pressure fine-tuning effect and match the flow rate of normal branch vessels, but also avoid implantation difficulty caused by overlap of the two connection stents <NUM> when the branch vessels are close to each other. Specifically, it can be set according to the actual condition of a patient, and in the end, the blood flow within the connection stent <NUM> may be guaranteed and the blood flow rate within the connection stent <NUM> may be controlled. It is to be noted that the opening O may be positioned between wave coils of the main stent <NUM> or on the wave coils of the main stent <NUM>. For example, when the opening O is connected to two branch stents, the opening O may be positioned on the wave coils of the main stent <NUM>, and the two branch stents are positioned on either side of the wave coil of the main stent <NUM>, respectively. When the opening O are positioned between the wave coils of the main stent, due to the fact that there are morphological differences in blank areas of the coating between the wave coils, the binding force to the branch stent <NUM> is different when the opening O is connected to the branch stent <NUM> at different positions, and the branch stent <NUM> shows different bending angles macroscopically, indicating that the flexibility of the branch stent <NUM> may be fine-adjusted by changing the position of the opening O. In the exemplary configurations shown in <FIG>, the number of the fixed segments <NUM> is equal to that of the free segments <NUM>. It should be noted that the number of the free segments <NUM> may be greater than the number of the fixed segments <NUM>, and at least one of the fixed segment <NUM> is connected to a plurality of the free segments <NUM>. This configuration may be used for branch openings with slow blood flow rate, more branches, and different orientations, and may be flexibly applied to main vessel lesions involving multiple branches. Specifically, as shown in <FIG>, there is provided one fixed segment <NUM> and two free segments <NUM> with an opening O1 and an opening O2, and the fixed segment <NUM> and the inner side wall of the main stent <NUM> have a connection line L1, and the opening O1 and the opening O2 are positioned at either side of an extension line of the connection line L1, respectively.

As shown in <FIG>, the connection stent <NUM> further includes an extension segment <NUM> which connects to one end of the free segment <NUM> distant from the fixed segment <NUM> and extends out of the main stent <NUM> (as shown in <FIG>) or is positioned inside the main stent (as shown in <FIG>). When the connection stent <NUM> is built-in as shown in <FIG>, the branch stent <NUM> may access the free segment <NUM> through the extension segment <NUM> and the opening of the main stent <NUM>, with the actual effect as shown in <FIG>, at which point if the diameter of the connection stent <NUM> is smaller or the length of the free segment <NUM> is shorter, the length of the extension segment <NUM> may be appropriately extended to increase an anchor area of the branch stent <NUM> to improve the anchoring force thereof; if a tumor cavity at the lesion site is smaller, the length of the extension segment <NUM> may be appropriately reduced, and the specific condition may be set according to the actual conditions of the patient. In another embodiment, when the connection stent <NUM> is externally provided, as shown in <FIG>, the branch stent <NUM> may access the free segment <NUM> through the fixed segment <NUM> and the joint between the fixed segment <NUM> and the free segment <NUM>, and the actual effect is as shown in <FIG>, at which point if the axial extension area of a tumor body is shorter, the length of the fixed segment <NUM> may be appropriately reduced, and the extension segment <NUM> only serves as a branch shunting, and the length of the extension segment <NUM> may be appropriately reduced, or the extension segment <NUM> may even be eliminated; if the volume of the tumor cavity is further reduced, the branch stent <NUM> may be directly passed through the connection stent <NUM>, with an effect shown in <FIG>, at which point the effect is similar to that of a chimney stent, and the specific condition may be set according to actual conditions of the patient. It should be noted that an angle of the connection port of the branch stent <NUM> at the opening of the free segment or the extension segment may be adjusted in the above two cases. In addition, the lengths of the fixed segment <NUM>, the free segment <NUM> and the extension segment <NUM> may be adjusted according to the design, which indicates that the design may be applied to various complex branch by-passes. With further reference to <FIG>, one end of the extension segment <NUM> distant from the free segment <NUM> is provided with a developing mark <NUM>, by which the end position of the connecting stent <NUM> may be accurately determined to facilitate a doctor to access the branch stent <NUM> on the connecting stent <NUM>. The number and shape of the developing mark <NUM> may be adjusted and designed according to actual conditions. The extension segment may have a variety of shapes, as shown in <FIG>, the extension segment <NUM> may be of a cylindrical shape with the same size at both ends (as shown in <FIG>), the extension segment <NUM> may also be of a truncated cone shape with different sizes at both ends (as shown in <FIG>), and the extension segment <NUM> may also be of an hourglass shape with the same size at both ends and gradually reducing from both ends to the middle position (as shown in <FIG>), and the extension segment <NUM> may also be of an angular shape in which the center lines of both ends are not in the same straight line (as shown in <FIG>). It will be appreciated that <FIG> are only an illustration of the shape of the extension segment <NUM> and are not a limitation of the present application, and that those skilled in the art may adjust the shape of the extension segment <NUM> according to actual conditions.

It will also be appreciated that the surface of the extension segment <NUM> may be further provided with a self-expanding or ball-expanding metal framework, and the length of the extension segment <NUM> may be adjusted according to actual needs.

As shown in <FIG>, in another exemplary configuration, not part of the invention, the connection stent <NUM> is integrally positioned outside a lumen of the main stent <NUM>, the fixed segment <NUM> is fixed on an outer side wall of the main stent <NUM>, one end of the free segment <NUM> is connected to the fixed segment <NUM> and the other end is connected to the edge of an opening O of the main stent <NUM>, and a gap <NUM> is formed between one side of the free segment <NUM> near to the outer side wall of the main stent <NUM> and the outer side wall of the main stent <NUM>. In addition, the opening direction of the connection stent <NUM> is adjustable.

Each of the fixed segment <NUM> and the free segment <NUM> includes a stent and a coating covering the surface of the sent. The stent of the fixed segment <NUM> can effectively exert radial and axial support, and one side of the fixed segment <NUM> is integrally connected with a side wall of the main stent <NUM>, thereby stabilizing a channel of the fixed segment <NUM>, preventing the channel of the fixed segment <NUM> from closing under the impact pressure of blood flow. In the assembly state, the length a of the coating of one side of the free segment <NUM> distant from the side wall of the main stent <NUM> is greater than the shortest vertical distance b from the proximal end to the distal end of the coating (as shown in <FIG>), and a gap is formed between wave coils of the stent of the free segment <NUM>. This configuration not only enables the free segment <NUM> to be axially stretched, but also provides radial support for the coating of the free segment <NUM> to avoid the channel closure of the free segment <NUM>. In addition, when an external branch stent is provided, the proximal end of the external branch stent is in the free segment <NUM>, and due to the fact that a gap <NUM> is formed between one side of the free segment <NUM> near to the main stent <NUM> and the side wall of the main stent <NUM>, when an angle of the external branch stent needs to be adjusted, the gap <NUM> between the free segment <NUM> and the main stent <NUM> may provide space for the angle adjustment of the external branch stent. In one of the embodiments, the diameter of the free segment <NUM> is greater than the diameter of the fixed segment <NUM>. After the branch stent is introduced into the free segment <NUM>, by increasing the diameter of the free segment <NUM>, the blood flow cross-section of the branch stent may be increased under the condition that the blood flow of the main stent <NUM> remains unchanged. Further, when the diameter of the branch stent is large, it may be well matched with the branch stent without affecting the diameter of a sheath required by the main stent <NUM>, so as to reduce the occurrence of endoleak.

In order to further improve the flexibility of the free segment <NUM>, the present invention further improves the stent structure of the free segment <NUM>, as illustrated particularly by the following embodiments:
First however, an exemplary configuration, not part of the invention, is presented. As shown in <FIG>, a stent <NUM> of a free segment <NUM> includes a plurality of waveform rings <NUM> spaced along its axis, and the waveform phases of the plurality of the waveform rings <NUM> are the same. The waveform phases of the plurality of the waveform rings may also be opposite. As shown in <FIG>, the plurality of the waveform rings <NUM> are connected to the coating of the free segment <NUM> only at positions of crests and/or troughs thereof by sutures or band-shaped coating <NUM>. The advantages of being connected to the coating only at the positions of the crests and/or troughs are that the channel closure of the free segment may be avoided and the flexibility of the free segment <NUM> is maintained to a maximum extent due to the fact that the number of connection points between the stent <NUM> and the coating is minimized, and when the free segment is axially compressed, the coating may be compressed to a maximum extent and its shape is changed more freely. Not all the crests and the troughs are connected to the coating, and several crests and/or troughs may be selectively connected to the coating. The plurality of the waveform rings <NUM> are spaced apart and have the same waveform phase. When subjected to an axial compressive force, the crest of one of the waveform rings <NUM> may extend into the middle of the two troughs of the waveform rings adjacent thereto, thereby improving the flexibility of the free segment <NUM>.

<FIG> shows an alternative embodiment according to the present invention. As shown in <FIG>, a stent <NUM> of a free segment <NUM> includes a plurality of waveform rings <NUM>, and the waveform phases of two adjacent waveform rings <NUM> are opposite, and crests and troughs of the two adjacent waveform rings <NUM> are interlocked. The interlocking arrangement mentioned in the present application refers to the structure as shown in <FIG>. The wire forming the crest portion of a second waveform ring <NUM> in <FIG> passes over the wire forming the trough portion of a first waveform ring <NUM> in <FIG>, and then comes out from under the wire forming the trough portion. The number of fixing points may be reduced by connecting the two adjacent waveform rings through the interlocking structure rather than through sutures, and the interlocking structure allows for axial expansion and fine-tuning between the two adjacent waveform rings <NUM> so as to be conveniently mated with various complicated external branch stents and improve the flexibility of the free segment <NUM>. In addition, by setting the number and the spacing of the waveform rings, and adjusting the wire diameter, the wave number and the height of the waveform rings, the radial support may be controlled and the axial local fine-tuning may be achieved.

In addition, when the waveform rings <NUM> of the stent <NUM> is relatively small in number, the crests or troughs of the two waveform rings <NUM> at the fore and aft ends of the stent may be fixed only by the sutures or the band-shaped coating; as shown in <FIG>, when the free segment <NUM> is longer, with the increasing of the waveform rings <NUM> of the stent <NUM>, there might be a risk that the waveform rings in the middle part may be tilted away from the coating if only the crests or troughs of the two waveform rings <NUM> at the fore and aft ends of the stent are fixed, therefore, it is advisable to select one or more of the waveform rings between the two waveform rings <NUM> at the fore and aft ends of the stent and fix the crests or troughs thereof to the coating by sutures.

As shown in <FIG>, in another embodiment, on the basis that any two adjacent waveform rings in the previous embodiment are interlocked, a stent <NUM> of a free segment in this embodiment includes a first waveform ring <NUM>, a second waveform ring <NUM>, and a third waveform ring <NUM> positioned between the first waveform ring <NUM> and the second waveform ring <NUM>. The third waveform ring <NUM> has an unequal height waveform. Wherein, the third waveform ring <NUM> includes a plurality of first crests 1263a near to the first waveform ring <NUM> and a plurality of second crests 1263b distant from the first waveform ring <NUM>, and the first crests 1263a and the second crests 1263b are spaced circumferentially along the third waveform ring <NUM>. And the apices of all the first crests 1263a fall on a plane perpendicular to the axis of the third waveform ring <NUM>, and the apices of all the second crests 1263b fall on another plane perpendicular to the axis of the third waveform ring <NUM>. All apices of the troughs of the third waveform ring <NUM> fall on the same plane perpendicular to its axis. In this embodiment, a second crest 1263b is provided between any two adjacent first crests 1263a, as shown in <FIG>, two second crests 1263b' may further be provided between any two adjacent first crests 1263a'. That is, the wave height of the third waveform ring <NUM> varies periodically. Further, the first crest 1263a interlocks with the trough of the first waveform ring <NUM>, and the trough of the third waveform ring <NUM> interlocks with the crest of the second waveform ring <NUM>. The third waveform ring <NUM> has more wave numbers than the first waveform ring <NUM> and the second waveform ring <NUM> adjacent thereto, and while using the interlock structure to improve the flexibility, more wave numbers increase the contact area between the stent and the coating, so that the adhesiveness is better.

<FIG> show another alternative embodiment of waveform rings according to the invention.

As shown in <FIG>, a stent <NUM> of a free segment in this embodiment still includes a plurality of waveform rings <NUM>, the waveform phases of any two adjacent waveform rings being opposite. Different from the previous embodiment, the crest or trough of one of any two adjacent waveform rings <NUM> is disposed on the trough or crest of the other waveform ring and is connected to the coating. <FIG> shows that the crest of the second waveform ring <NUM> is disposed on the trough of the first waveform ring <NUM> and is connected to the coating by the sutures.

As shown in <FIG>, in a circular area centered on a fixed point DI, four additional fixed points D2, D3, D4 and D5 are distributed. When the waveform where the fixed points D1, D2 and D3 are located is compressed in the free segment, the motion of the waveform is limited only by the above five fixed points, the waveform may move within the wave height range of the waveform where the fixed points D1, D4 and D5 are located. Therefore, the flexibility is better than that of the above-described embodiments.

<FIG> is a schematic diagram showing the effect of the covered stent <NUM> applied to the aortic arch <NUM> and its branches <NUM>,<NUM> and <NUM>, and the renal artery <NUM> and its branches <NUM> and <NUM>. If there is no lesion in the branch vessels (e.g., <NUM> and <NUM>), the connection stent <NUM> serves only as a drainage to prevent series of complications caused by the closure of the branch vessels; if the branches involve in a lesion (e.g., <NUM>, <NUM>, and <NUM>), an external branch stent may be introduced at the branch fracture (an external stent <NUM> is introduced in a branch <NUM> as shown in <FIG>) and used in conjunction with the connection stent <NUM> to play an isolation effect and achieve the purpose of treatment.

Claim 1:
A covered stent suitable for fixing an external branch stent comprising a tubular main stent (<NUM>) and a connection stent (<NUM>) disposed on the main stent (<NUM>), an opening (O) being formed in a side wall of the main stent (<NUM>), wherein the connection stent (<NUM>) comprises a fixed segment (<NUM>) connected to the side wall of the main stent (<NUM>) and a free segment (<NUM>) connected to the fixed segment (<NUM>), each of the fixed segment (<NUM>) and the free segment (<NUM>) comprising a stent and a coating covering the surface of the sent, one end of the free segment (<NUM>) distant from the fixed segment (<NUM>) being connected to the edge of the opening (O) and a gap (<NUM>) being formed between one side of the free segment (<NUM>) near to the side wall of the main stent (<NUM>) and the side wall of the main stent (<NUM>),
characterized in that the stent (<NUM>) of the free segment (<NUM>) comprises a plurality of waveform rings (<NUM>), any two of the adjacent waveform rings (<NUM>) being opposite in phase, and the crests and troughs of any two of the adjacent waveform rings (<NUM>) being interlocked, and the crests or the troughs of at least two of the waveform rings (<NUM>) at the fore and aft ends of the stent being connected to the coating of the free segment (<NUM>),
wherein the plurality of the waveform rings comprise a first waveform ring (<NUM>), a second waveform ring (<NUM>) spaced apart from the first waveform ring, and a third waveform ring (<NUM>) provided between the first waveform ring and the second waveform ring and connected to the first waveform ring and the second waveform ring, the third waveform ring having an unequal height waveform,
wherein an apex of the crest of the third waveform ring comprises a first crest (1263a) near to the first waveform ring and a second crest (1263b) distant from the first waveform ring, and the first crest and the second crest being spaced circumferentially along the third waveform ring (<NUM>) and falling on two planes perpendicular to an axis of the third waveform ring, respectively, and the apex of the trough of the third waveform ring (<NUM>) falling on the same plane perpendicular to the axis of the third waveform ring,
the crest near to the first waveform ring (<NUM>) being interlocked with the trough of the first waveform ring, and the trough of the third waveform ring (<NUM>) being interlocked with the crest of the second waveform ring (<NUM>).