Patent Publication Number: US-2019175327-A1

Title: Luminal Stent and Luminal Stent System

Description:
TECHNICAL FIELD 
     This disclosure relates to the field of implantable medical devices, and more particularly relates to a lumen stent and a lumen stent system. 
     BACKGROUND ART 
     A lumen stent may be used to isolate an artery dissection or an arterial aneurysm in a vessel. If there is a branch vessel in a lesion region, at least two lumen stents are generally used in combination to prevent a main body lumen stent from blocking the blood supply of the branch vessel. 
     For example, referring to  FIGS. 1 and 2 , an artery dissection  10  is located in an aorta arch  11  and extends to a location adjacent to a left subclavian artery  12 . A main body lumen stent  13  may first be implanted into the aorta arch  11 , and then a branch lumen stent  14  is implanted into the left subclavian artery  12  through a side hole of the main body lumen stent  13 . The branch lumen stent  14  is also called a top hat stent because it is shaped like a top hat. The branch lumen stent  14  includes a tube body  141  and a border  142  surrounding an end opening of the tube body. The border  142  is basically perpendicular to the tube body  141  for abutting against the inner side wall of the main body lumen stent  13  to establish the blood supply between the aorta arch  11  and the left subclavian artery  12 , and is clamped to prevent the branch lumen stent from falling off in the left subclavian artery  12 , and to prevent the main body lumen stent  13  from moving under the impact of blood flow. 
     However, regardless of whether the side hole is formed on the side wall of the main body lumen stent  13  in vitro or in vivo to assemble the branch lumen stent  14 , it is inevitable that the side hole and the branch lumen will not be completely concentric, thus the side hole may not be completely filled by the tube wall after the branch lumen stent  14  is implanted, and a gap  13   a  appears. Further, when a main body lumen has an irregular shape, the border  142  of the branch lumen stent  14  will not be completely adhered to the inner wall of the main body lumen stent  13 . Moreover, continuous impact of the blood flow also may lead to the failure of the close connection of the branch lumen stent  14  and a connecting port of the main body lumen stent  13 , thereby forming a gap  13   b  between the border  142  of the branch lumen stent  14  and the inner side wall of the main body lumen stent  13 . The blood flow may enter a false lumen of the artery dissection  10  from the gap  13   b  through the gap  13   a , thus forming a blood flow leakage channel as shown by an arrow in  FIG. 2 , thereby causing type-III endoleak. 
     This type-III endoleak may occur in the thoracic aorta, the abdominal aorta or other lumens. Continuous inflow of the blood flow may cause continuous enlargement of the false lumen of the dissection or aneurysm cavity, and finally lead to serious consequence such as rupture of the false lumen or the aneurysm cavity. Therefore, it is particularly important to avoid the type-III endoleak. 
     SUMMARY OF THE INVENTION 
     The technical solution provides a lumen stent capable of preventing type-III endoleak, including a tube body and a skirt arranged on the tube body with the skirt surrounding the tube body. The skirt includes a flexible connecting section and a stent graft. The distal end of the flexible connecting section is sealed and connected with the outer surface of the tube body, and the proximal end of the flexible connecting section is connected with the distal end of the stent graft. The proximal end of the stent graft is suspended and provided with a first radial support structure. When the flexible connecting section is radially compressed, at least a portion of the first radial support structure bends away from the tube body. 
     An included angle between the flexible connecting section and the axial direction of the outer surface of the tube body is 5 to 80 degrees. The maximum length of the first radial support structure is less than or equal to the maximum perpendicular distance from the first radial support structure to the outer surface of the tube body. For example, the maximum perpendicular distance from the first radial support structure to the outer surface of the tube body is 6 to 40 mm, and the maximum length of the first radial support structure is 2 to 38 mm. 
     It is understood that the flexible connecting section has a connecting boundary connected with the tube body. The axial length of the flexible connecting section is required to be less than the length from the proximal end surface of the tube body to the connecting boundary. For example, the value of the difference between the length from the proximal end surface of the tube body to the connecting boundary and the axial length of the flexible connecting section is not more than 20 mm. 
     The stent graft may be a straight tube shape or a horn shape. Also, the circumferential surface of the stent graft is a concave curved surface along a direction from the connecting boundary towards the proximal end, namely the diameter is decreased progressively and then increased progressively. 
     The first radial support structure may be all covered by a coating membrane, or only a portion of the first radial support structure is covered by the coating membrane, namely a portion of the first radial support structure is exposed from the proximal end. 
     The flexible connecting section may only include the coating membrane. One end of the coating membrane is sealed and connected with the outer surface of the tube body, and the other end of the coating membrane is sealed and connected with the stent graft. Or, the flexible connecting section may further include at least one second radial support structure. The coating membrane covers the at least one second radial support structure. A distance between the first radial support structure and the adjacent second radial support structure is less than or equal to 2 mm. The first radial support structure and the adjacent second radial support structure are hooked and wound with each other, or are connected through a flexible wire. 
     In one specific implementation mode, an included angle between the stent graft and the axial direction of the tube body is greater than that between the flexible connecting section and the axial direction of the tube body. 
     In one specific implementation mode, the diameter of the flexible connecting section is increased progressively along a direction from the connecting boundary towards the proximal end. 
     In one specific implementation mode, in a natural state, the proximal end of the first radial support structure bends away from the tube body. 
     In one specific implementation mode, the proximal end of the first radial support structure is flush with the proximal end of the stent graft. 
     The technical solution further provides a lumen stent system, including the above-mentioned lumen stent and a main body lumen stent adapted for use with the lumen stent. The main body lumen stent is provided with a side hole. When the tube body passes through the side hole and the flexible connecting section is radially compressed by the main body lumen stent in the side hole, at least a portion of the first radial support structure bends away from the tube body so as to be adhered to the inner wall of the main body lumen stent. 
     According to the lumen stent and the lumen stent system which are provided by the present disclosure, which includes the first radial support structure which bends away from the tube body during compression of the flexible connecting section, the adhesion performance of the first radial support structure to the wall of the vessel or the inner wall of the main body lumen stent may be effectively improved, so as to prevent the occurrence of the type-III endoleak. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This disclosure will be further described below in combination with accompanying drawings and embodiments. In the drawings: 
         FIG. 1  is a structure schematic diagram of a lumen stent system of the prior art; 
         FIG. 2  is a partially enlarged view of  FIG. 1 ; 
         FIG. 3  is a schematic diagram of a main body lumen stent according to a first embodiment of the present disclosure; 
         FIG. 4  is a schematic diagram of a branch lumen stent according to the first embodiment of the present disclosure; 
         FIG. 5  is a schematic diagram of an axial section of the branch lumen stent in  FIG. 4 ; 
         FIGS. 6 to 10  are schematic diagrams showing the gradual release of the branch lumen stent in  FIG. 4  from a delivery sheath; 
         FIG. 11  is a schematic diagram of an axial section of a branch lumen stent according to a second embodiment of the present disclosure; 
         FIG. 12A  is a schematic diagram of a partial axial section of a branch lumen stent according to a third embodiment of the present disclosure; 
         FIG. 12B  is a schematic diagram of the branch lumen stent in  FIG. 12A  after implantation; 
         FIG. 13  is a schematic diagram of a partial axial section of a branch lumen stent according to a fourth embodiment of the present disclosure; 
         FIG. 14  is a schematic diagram of a skirt of a branch lumen stent according to a fifth embodiment of the present disclosure; 
         FIG. 15A  is a schematic diagram of a skirt of a branch lumen stent according to a sixth embodiment of the present disclosure; 
         FIG. 15B  is a partially enlarged view of  FIG. 15A ; 
         FIG. 16A  is a schematic diagram of first and second radial support structures of the branch lumen stent according to the sixth embodiment of the present disclosure; and 
         FIG. 16B  is a partially enlarged view of  FIG. 16A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     For a better understanding of technical features, objectives and effects of the present disclosure, specific implementation modes of the present disclosure will be described in detail in combination with the accompanying drawings. To facilitate the description, a lumen is described by using a vessel as an example. The vessel may be an aortic arch, or a thoracic aorta, or an abdominal aorta and the like. Those ordinarily skilled in the art should know that the vessel used for description herein is only used as an example, and not as a limitation to the present disclosure. The present disclosure is applicable to various other human lumens, such as a digestive tract lumen. Various improvements and transformations which are derived from the basis of the present disclosure shall all fall within the protective scope of the present disclosure. In addition, in the description of the vessel, a direction may be defined according to a blood flow direction. In the present disclosure, it is defined that blood flow flows from the proximal end to the distal end. Unless otherwise specified, radial support structures of the present disclosure refer to closed wave-shaped annuluses that are axially disposed along the stent graft as is conventional in the art. 
     First Embodiment 
     Referring to  FIG. 3  and  FIG. 4 , a lumen stent system according to the first embodiment of the present disclosure includes a main body lumen stent  2  and at least one branch lumen stent  3  used cooperatively with the main body lumen stent  2 . 
     The main body lumen stent  2  includes a tubular structure having an axial direction  1   a . The tubular structure may be used as a new fluid channel after the main body lumen stent  2  is implanted into a lumen. For example, the tubular structure may be used as a new blood flow channel after the main body lumen stent  2  is implanted into a vessel. The main body lumen stent  2  includes a radial support structure  21  and a coating membrane  22  covering the radial support structure  21 . The radial support structure  21  cooperates with the coating membrane  22  to form a side wall of the main body lumen stent  2 . At least one side hole  23  is formed in the side wall, and is adapted to be matched in shape and size with the branch lumen stent  3 , so that the branch lumen stent  3  may be combined with the main body lumen stent  2  through the side hole  23  and then implanted into a branch lumen. A radiopaque structure may be arranged at the periphery of the side hole  23 . For example, one coil of radiopaque metal wire may be adhered to the edge of the side hole  23 . 
     The radial support structure  21  may be made of various biocompatible materials including known materials used in manufacturing of an implantable medical device or a combination of various materials, such as 316L stainless steel, a cobalt-chromium-nickel-molybdenum-iron alloy, other cobalt alloys such as L605, tantalum, a nickel-titanium alloy (nitinol) or other biocompatible metals. The radial support structure  21  may be formed by winding a metal wire or cutting a metal tube, and may include a plurality of wave-shaped annuluses along the axial direction, such as multiple turns of Z-shaped waves, or include a helically wound structure, or include a mesh structure. The coating membrane  22  may be a PET (polyethylene terephthalate) membrane or a PTFE (polytetrafluoroethylene) membrane, which covers the radial support structure  21  by suturing or hot melting. 
     Through the radial support structure  21 , the main body lumen stent  2  has a radial expandability, may be compressed under an external force, and restores to an initial shape through self-expansion or mechanical expansion (such as balloon dilatation expansion) and maintains the initial shape after the external force is withdrawn, so that after being implanted into the lumen, the main body lumen stent  2  can be secured within the lumen by its radial support against the lumen wall. It should be noted that unless otherwise specified in the following description, the initial shape of the lumen stent after radial deployment is described. Through the coating membrane  22 , the main body lumen stent  2  may isolate a lesion region of the lumen. For example, the main body lumen stent  2  may isolate an artery dissection or an arterial aneurysm after being implanted into an artery vessel. 
     Referring to  FIG. 4 , the branch lumen stent  3  includes a tube body  31  and a skirt  32  arranged outside the tube body  31  in a manner where the skirt  32  surrounds the tube body  31 . The tube body  31  includes a tubular structure having an axial direction  1   b . The tubular structure may be used as a new fluid channel after the branch lumen stent  3  is implanted into a lumen. For example, the tubular structure may be used as a new blood flow channel after the branch lumen stent  3  is implanted into a vessel. The tube body  31  includes a radial support structure (not shown in the figure) arranged on the tube body and a coating membrane covering the radial support structure. The radial support structure cooperates with the coating membrane to form a side wall of the tube body  31 . The same or similar radial support structure and coating membrane for the above-described main body lumen support  2  can be used, and will not be described herein. Through the radial support structure, the tube body  31  has a radial expandability, may be compressed under an external force, and restores to an initial shape through self-expansion or mechanical expansion (such as balloon dilatation expansion) and maintains the initial shape after the external force is withdrawn, so that after being implanted into a main body lumen, the tube body  31  can be secured within the lumen by its radial support against the lumen wall. Through the coating membrane, the tube body  31  may isolate a lesion region of the lumen. For example, the tube body  31  may isolate an artery dissection or an arterial aneurysm after the branch lumen stent  3  is implanted into an artery vessel. 
     The tube body  31  is divided into a first section  311  and a second section  312  along the axial direction, with the connecting boundary  31   a  of the tubular body  31  and the skirt  32  defining a boundary. The first section  311  is located on one side of the proximal end of the second section  312 , namely the first section  311  extends from the connecting boundary  31   a  to a proximal-end opening end  31   b  of the tube body  31 , and the second section  312  extends from the connecting boundary  31   a  to a distal-end opening end  31   c  of the tube body  31 . It should be noted that the first section  311  and the second section  312  are only distinguished for facilitating the description, but does not represent that the tube body  31  is separated and disconnected at the above-mentioned connecting boundary  31   a . The tube body  31  may be of a uniform integrated structure. 
     The skirt  32  includes stent graft  321  and a flexible connecting section  322  along the axial direction. The stent graft  321  is located on one side of the proximal end of the flexible connecting section  322 . The stent graft  321  is substantially cylindrical and includes a first radial support structure  323  having a plurality of Z-shaped waves arranged along its circumferential direction. The wave heights of the plurality of Z-shaped waves may be equal or unequal. The stent graft  321  is suspended to form an opening  30 . When a radial compression force is applied to the flexible connecting section  322 , the flexible connecting section  322  would be radially compressed, and the opening end of the membrane-coated stent graft  321  will bend relative to the flexible connecting section  322  towards a direction away from the axial direction  1   b . The skirt  32  includes a coating membrane  324 . The coating membrane  324  seals and connects the connecting section  322  to the outer surface of the tube body  31 . 
     Still referring to  FIGS. 4 and 5 , the flexible connecting section  322  includes the coating membrane  324  adjacent to the connecting boundary between the tube body  31  and the skirt  32 . The coating membrane  324  may be a PET membrane or a PTFE membrane, which can seal and connect the flexible connecting section  322  to the outer surface of the side wall of the tube body  31  by suturing or hot melting. For example, the coating membrane  324  of the flexible connecting section  322  may be hot-melted together with the outer surface of the tube body  31  to achieve a sealed connection. Those ordinarily skilled in the art can select a proper sealing method as required, so that no more details will be described here. The coating membrane  324  may cover part of, or the whole of, the first radial support structure  323 , or the first radial support structure  323  may be located in the middle region of the coating membrane  324 . In the present embodiment, the flexible connecting section  322  is composed of the coating membrane  324  which may cover the first radial support structure  323  by hot melting or suturing. The coating membrane  324  is made of a flexible material, so that the stent graft  321  and the flexible connecting section  322  may be connected together in a bendable manner through the coating membrane  324 . 
     The closed end of the flexible connecting section  322  is sealed and coupled to the tube body  31 , and the other end of the flexible connecting section  322  radiates outwardly in the direction of the distal end towards the proximal end to form an approximately conical structure, namely the diameter of the flexible connecting section  322  increases progressively from the connecting boundary  31   a  to its opening end. An included angle α between the flexible connecting section  322  and the axial direction  1   c  of the outer surface of the tube body  31  is 5 to 80 degrees, or 5 to 60 degrees. The axial direction  1   c  of the outer surface of the tube body  31  is an axial direction along the contour of the outer surface. In the present embodiment, the tube body  31  is a straight tube, so that the axial direction  1   c  of the outer surface is parallel to the axial direction  1   b  of the tubular structure. If the tube body  31  is a conical tube, the axial direction  1   c  of the outer surface and the axial direction  1   b  generally form an acute included angle. 
     The length of the flexible connecting section  322  is less than that of the first section  311  of the tube body  31 , and is equal to a length from the connecting boundary  31   a  to the bendable connecting boundary between the stent graft  321  and the flexible connecting section  322  along the axial direction of the outer surface of the flexible connecting section  322 , and the length of the first section  311  is equal to a length from the connecting boundary  31   a  to the proximal-end opening  31   b  of the tube body  31  along the axial direction of the outer surface of the tube body  31 . The value of the difference between the length of the flexible connecting section  322  and the length of the first section  311  of the tube body  31  is not more than 20 mm, for example, the difference value is 5 to 10 mm. 
     The first radial support structure  323  may be distributed on a portion of the stent graft  321 , namely the maximum length of the first radial support structure  323  is smaller than the length of the stent graft  321  along the axial direction. The first radial support structure  323  also may be distributed over the whole stent graft  321 , namely the maximum length of the first radial support structure  323  is equal to the length of the stent graft  321  along the axial direction. In the present embodiment, the first radial support structure  323  is distributed over the whole stent graft  321 , and the proximal end of the first radial support structure is flush with the proximal end of the stent graft. The first radial support structure  323  has a radial expandability, may be compressed under an external force, and restores to an initial shape through self-expansion and maintains its initial shape after the external force is withdrawn. The first radial support structure  323  may be made of various biocompatible materials including known materials used in manufacturing of the implantable medical device or a combination of various materials, such as 316L stainless steel, cobalt-chromium-nickel-molybdenum-iron alloy, other cobalt alloys such as L605, tantalum, nickel-titanium alloy (nitinol) or other biocompatible metals. The first radial support structure  323  may include a plurality of wave-shaped annuluses along the axial direction, such as Z-shaped waves, or include a helically wound structure, or include a mesh structure. 
     The first radial support structure  323  may be formed by winding a metal wire having a diameter of 0.15 to 0.4 mm, or may be formed by cutting a metal tube. A wire diameter of a cut metal rod forming the first radial support structure  323  is 0.15 to 0.4 mm. In the present embodiment, the first radial support structure  323  is formed by winding a nickel-titanium alloy, and the diameter of the metal wire is 0.2 mm. 
     Along the direction of the opening  30  of the skirt  32 , namely along the direction from the distal end to the proximal end, an included angle between the first radial support structure  323  and the axial direction  1   b  of the tube body  31  is more than or equal to 0 degree and less than 180 degrees, namely the orientation of the first radial support structure  323  is basically parallel to the axial direction  1   b  of the tube body  31 , or turns outwardly relative to the axial direction  1   b  of the tube body  31 ; for example, turns perpendicularly outwardly relative to the axial direction  1   b  of the tube body  31 . In the present embodiment, the orientations of the stent graft  321  and the first radial support structure  323  are basically parallel to the axial direction  1   b  of the tube body  31 . 
     The stent graft  321  has the first radial support structure  323  having the above orientation, which favorably enables the flexible connecting section  322  to actuate the opening end of the stent graft  321  to automatically bend outwardly relative to the flexible connecting section  322  in a radially compressed state, so as to form an approximately perpendicular border relative to the axial direction  1   b  of the tube body  31  after the first radial support structure  323  bends. In other words, after implantation, the flexible connecting section  322  actuates the stent graft  321  to bend under the radial compression of the delivery sheath or the branch lumen, so that the first radial support structure  323  is approximately perpendicular relative to the axial direction  1   b  of the tube body  31  so as to be adhered to the inner tube wall of the main body lumen stent  2 . If the included angle between the first radial support structure  323  and the axial direction  1   b  of the tube body  31  is more than or equal to 0 degree and less than 90 degrees, the stent graft  321  (namely the first radial support structure  323 ) relatively turns outwardly (bends along a clockwise direction in the axial section in  FIGS. 4 and 5 ) under the radial compression of the flexible connecting section  322 , so that the first radial support structure  323  may be approximately perpendicular relative to the axial direction  1   b  of the tube body  31 . If the included angle between the first radial support structure  323  and the axial direction  1   b  of the tube body  31  is more than 90 degrees and less than 180 degrees, the stent graft  321  (namely the first radial support structure  323 ) relatively turns inwardly (bends along an anticlockwise direction in the axial section in  FIGS. 4 and 5 ) under the radial compression of the flexible connecting section  322 , so that the first radial support structure  323  may be approximately perpendicular relative to the axial direction  1   b  of the tube body  31 . If the included angle between the first radial support structure  323  and the axial direction  1   b  of the tube body  31  is approximately equal to 90 degrees, the first radial support structure  323  may be approximately perpendicular relative to the axial direction  1   b  of the tube body  31  in an initial state under the radial compression of the flexible connecting section  322 . 
     The maximum length of the first radial support structure  323  is less than or equal to the maximum perpendicular distance from the first radial support structure  323  to the outer surface of the tube body  31 . It is understood that when the wave heights of waveform units included in the first radial support structure  323  are unequal, the maximum length is the corresponding maximum wave height in all the waveform units. When the first radial support structure  323  includes a plurality of waveform units having equal wave heights, its maximum length is equal to a length from the distal end portion of the first radial support structure  323  to the proximal end portion of the first radial support structure  323  along the axial direction of the outer surface of the first radial support structure  323 . The maximum length is 2 to 40 mm, for example 2 to 30 mm. The perpendicular distance from the first radial support structure  323  to the outer surface of the tube body  31  is related to the orientation of the first radial support structure  323 . The first radial support structure  323  is basically parallel to the outer surface of the tube body  31  or turns outwardly relative to the outer surface of the tube body  31 , so that the perpendicular distance from the edge of the proximal end (opening end) of the first radial support structure  323  to the outer surface of the tube body  31  is generally selected as the maximum perpendicular distance which is 6 to 40 mm, for example 6 to 30 mm. 
     The maximum length of the first radial support structure  323  is less than or equal to the maximum perpendicular distance from the first radial support structure  323  to the outer surface of the tube body  31 , so that the flexible connecting section  322  in the radially compressed state easily actuates the opening end (namely the first radial support structure  323 ) of the stent graft  321  to bend relative to the flexible connecting section  322  towards a direction away from the axial direction  1   b , thereby increasing the automatic bending success rate of the stent graft  321  and also improving the possibility that the first radial support structure  323  is perpendicular to the axial direction  1   b  of the tube body  31 . The maximum length of the first radial support structure  323  is set to be 2 to 38 mm to ensure that the first radial support structure  323  has sufficient length to be adhered to the inner wall of the main body lumen stent  2  and also to avoid the first radial support structure  323  overlapping with adjacent side hole that will affect the implantation of the other branch lumen stents. Accordingly, the maximum perpendicular distance from the first radial support structure  323  to the outer surface of the tube body  31  is 6 to 40 mm. 
     In addition, when the opening end of the stent graft  321  is driven to bend under the radial compression of the flexible connecting section  322 , the flexible connecting section  322  is basically adhered to the outer surface of the tube body  31 , namely basically adhered to the outer surface of the first section  311  of the tube body  31 . At this moment, the length of the flexible connecting section  322  is set to be less than that of the first section  311 , so that at least a portion of the first section  311  of the tube body  31  is exposed relative to the skirt  32  after the stent graft  321  bends. After implantation, the proximal-end opening end  31   b  extends into the lumen of the main body lumen stent  2 , and the exposed portion is located in the lumen of the main body lumen stent  2 , so as to ensure that the blood flow in the main body lumen stent  2  may enter the branch lumen stent  3  through the proximal-end opening end  31   b , thereby establishing blood flow of a branch lumen and preventing the main body lumen stent from moving. Meanwhile, the value of the difference between the length of the flexible connecting section  322  and the length of the first section  311  of the tube body  31  is set to be not more than 20 mm, which ensures that blood flows smoothly into the branch lumen stent  3 , and blood turbulence or eddy currents are not caused in the main lumen stent  2 , thereby minimizing the risk of thrombosis. 
     An implantation process of the lumen stent system of the present disclosure will be described below by taking the re-establishment of the blood supply between the aortic arch  11  and the left subclavian artery  12  from the aortic arch  11  as an example. It should be known that the following description is only used as an example instead of a limitation to the present disclosure. The lumen stent system of the present disclosure may also be applicable to other vessels. For example, the lumen stent system of the present disclosure may be adopted to reestablish the blood supply between an abdominal aorta and a renal artery from the abdominal aorta, and no more descriptions will be provided here. 
     Referring to  FIG. 6 , during the implantation of the lumen stent system of the present disclosure, the main body lumen stent  2  is first implanted into a main body lumen (for example the aortic arch  11 ) using any proper technique, and the side hole  23  of the main body lumen stent  2  is aligned with the opening of a branch lumen (for example the left subclavian artery  12 ) from the main body lumen. Then, a delivery sheath  40  pre-loaded with the branch lumen stent  3  is delivered into the lumen of the main body lumen stent  2  from the left subclavian artery  12  through the side hole  23  of the main body lumen stent  2 , and at this moment, the branch lumen stent  3  is radially compressed within the sheath  40 . 
     Referring to  FIG. 7 , the sheath  40  is withdrawn along the direction of the arrow to release the branch lumen stent  3 , namely the branch lumen stent  3  is released step by step from its proximal end to distal end. For the skirt  32 , the stent graft  321  is first released in the main body lumen stent  2 . The stent graft  321  released from the sheath  40  is self-expanded to its initial shape and maintains its initial shape through the radial expansion capability of the first radial support structure  323 . Similarly, the tube body  31  released in the main body lumen stent  2  is also self-expanded to its initial shape and maintains its initial shape through its radial support structure. 
     Referring to  FIG. 8 , the sheath  40  is continuously withdrawn until the stent graft  321  is completely released from the sheath  40 , while at least a portion of the flexible connecting section  322  remains within the sheath  40 . In other words, during the releasing process, after the stent graft  321  is completely released, the flexible connecting section  322  is still in a radially compressed state. Under the radial compression of the flexible connecting section  322 , the released stent graft  321  bends relative to the flexible connecting section  322  and turns outwardly to enable the first radial support structure  323  of the stent graft  321  to be approximately perpendicular to the axial direction  1   b  of the tube body  31 . As the length of the flexible connecting section  322  is greater than that of the first section  311  of the tube body  31 , at least a portion of the tube body  31  is exposed relative to the skirt  32  after the stent graft  321  bends. 
     Referring to  FIG. 9 , after the stent graft  321  is completely released, the sheath  40  and the lumen stent system are moved together along the direction of the arrow during continuous withdrawal of the sheath  40  along the arrow in the Figure till the stent graft  321  is adhered to the inner side wall of the main body lumen stent  2 , and then the sheath  40  may be pulled properly to enable the stent graft  321  to be more closely adhered to the inner side wall of the main body lumen stent  2 . 
     Referring to  FIG. 10 , the branch lumen stent  3  is completely released from its proximal end to distal end, and the second section  312  and a portion of the first section  311  of the tube body  31  are implanted into the left subclavian artery  12 . Furthermore, the branch lumen stent  3  may be stably located in the left subclavian artery  12  through the radial expansion capability of the tube body  31 . The other portion of the second section  312  extends into the lumen of the main body lumen stent  2  through the side hole  23  of the main body lumen stent  2  to allow blood to enter the branch lumen stent  3 . The flexible connecting section  322  of the skirt  32  and the tube body  31  are together radially compressed by the left subclavian artery  12 . Under this radial compression, the stent graft  321  still bends relative to the flexible connecting section  322  and is closely adhered to the inner wall of the main body lumen stent  2  in the lumen of the main body lumen stent  2 . 
     The stent graft  321  of the skirt  32  is equivalent to a brim of a traditional top hat stent, which may reduce the impact of the blood flow on their combined positions after the stent graft  321  is adhered to the inner wall of the main body lumen stent  2  such that the tube body  31  may maintain its radial support shape to avoid deformation such as wrinkling, introversion and collapse, thereby preventing the blood that flows into the lumen from being blocked to prevent formation of type-III endoleak, and also reducing movement of the main body lumen stent  2  under the impact of the blood flow. Furthermore, on the side hole  23  of the main body lumen stent  2 , a semi-closed gap is formed between the stent graft  321  of the skirt  32  and the tube body  31 , and the blood flowing into the gap may be used as a filling material for occluding a type-III endoleak channel to prevent the blood from flowing into a aneurysm or a dissection  10 . Moreover, the stent graft  321  used as the brim of the top hat stent that is separated from the tube body  31  is used as a blood flow inlet of the branch lumen stent  3 , so that the blood flow inlet is not affected by conditions such as the shape of the side hole  23 , whether the side hole  23  is concentric with the opening of the branch lumen or not, and the deformation or failure of the brim. 
     It should be noted that the branch lumen stent  3  may be also used independently in addition to cooperative use with the main body lumen stent  2 . In other words, only the branch lumen stent  3  is implanted into the branch lumen (for example the left subclavian artery  12 ), namely the second section  312  and a portion of the first section  311  of its tube body  31  are implanted into the branch lumen, and the branch lumen stent  3  is stably located in the branch lumen through the radial expansion capacity of the tube body  31 . The other portion of the second section  312  extends into the lumen of the main body lumen through the opening of the main body lumen (for example the aortic arch  11 ) to facilitate blood flow into the branch lumen stent  3 . The flexible connecting section  322  of the skirt  32  and the tube body  31  are radially compressed by the branch lumen together. Under this radial compression, the opening end of the stent graft  321  still bends relative to the flexible connecting section  322  and is closely adhered to the inner wall of the main body lumen in the lumen of the main body lumen. 
     Second Embodiment 
     Referring to  FIG. 11 , a difference from the first embodiment is that according to a branch lumen stent  4  of the second embodiment, along an opening direction of a skirt  42 , namely along a direction from the distal end to the proximal end, an included angle between a stent graft  421  (namely a first radial support structure not shown in the figure) and an axial direction  4   b  of a tube body  41  is an acute angle, for example 60 degrees. Namely, in an initial state, the orientation of the stent graft  421  turns outwardly relative to the axial direction  1   b  of the tube body to form a horn shape. Furthermore, the included angle between the stent graft  421  and the axial direction  4   b  is greater than that between a flexible connecting section  422  and the axial direction  4   b . The tube body  41  is the same as or similar to the tube body  31  in the first embodiment, so that no more details will be described. 
     By adopting this arrangement, the maximum perpendicular distance H41 from the stent graft  421  to the outer surface (namely the axial direction  4   c  of the outer surface) of the tube body  41  may be correspondingly increased. To this end, under the condition that the included angle α between the flexible connecting section  422  and the axial direction of the outer surface of the tube body  41  is relatively small, the maximum perpendicular distance H41 is also greater than the maximum length L41 of the first radial support structure. If the included angle α between the flexible connecting section  422  and the axial direction  4   b  is smaller, the branch lumen stent is released more successfully, and the force needed for pulling the sheath during release is smaller. 
     Third Embodiment 
     Referring to  FIGS. 12A and 12B , a difference from the first embodiment is that the edge, namely the proximal end portion, of the suspended end (namely the first radial support structure that is not shown in the Figure) of a stent graft  521  of a skirt  52  of a branch lumen stent  5  according to the third embodiment is everted in a natural state. A tube body  51  is the same as or similar to the tube body  31  in the first embodiment, so no more details will be described. After the branch lumen stent  5  is implanted, and when the stent graft  521  (the first radial support structure not shown in the figure) bends relative to a flexible connecting section  522 , the outwardly turned edge may improve the adherence performance between the edge of the stent graft  521  and the inner wall of the main body lumen stent  2  so as to avoid formation of a leakage channel between the stent graft  521  and the inner wall of the main body lumen stent  2 . 
     Fourth Embodiment 
     Referring to  FIG. 13 , a difference from the first embodiment is that a stent graft  621  (namely a first radial support structure that us not shown in the Figure) of a skirt  62  of a branch lumen stent  6  according to the fourth embodiment is a concave curved surface, namely the diameter of the stent graft  621  is decreased progressively and then increased progressively according to a direction from a connecting boundary to the proximal end. After the branch lumen stent  6  is implanted, and when the stent graft  621  bends relative to a flexible connecting section  622 , the concave curved surface may improve the adherence performance between the stent graft  621  and the inner wall of the main body lumen stent  2  so as to avoid formation of a leakage channel between the stent graft  621  and the inner wall of the main body lumen stent  2 . The length L61 of the first radial support structure in the concave curved surface is equal to a length L61 of a connecting line between the proximal end portion and the distal end portion of the first radial support structure, and the maximum perpendicular distance from the first radial support structure to the outer surface of the tube body  61  is equal to a perpendicular distance H61 from the proximal end portion of the first radial support structure to the outer surface of the tube body  61 , and still maintains the requirement that H61&gt;L61. The tube body  61  is the same as or similar to the tube body  31  in the first embodiment, so no more details will be described. 
     Fifth Embodiment 
     Referring to  FIG. 14 , a difference from the first embodiment is that a flexible connecting section  722  of a skirt  72  of a branch lumen stent according to the fifth embodiment includes a second radial support structure  725  arranged along its circumferential direction. The second radial support structure  725  may be distributed on a portion of the flexible connecting section  722 , namely the maximum length of the second radial support structure  725  is less than the length of the flexible connecting section  722  along the axial direction. The second radial support structure  725  also may be distributed over the entire flexible connecting section  722 , namely the maximum length of the second radial support structure  725  is equal to the length of the flexible connecting section  722  along the axial direction. The second radial support structure  725  has a radial expansion capability, may be compressed under an external force, and restores to an initial shape through self-expansion and maintains the initial shape after the external force is withdrawn. The second radial support structure  725  may be made of various biocompatible materials including known materials used in manufacturing of the implantable medical device or a combination of various materials, such as 316L stainless steel, cobalt-chromium-nickel-molybdenum-iron alloy, other cobalt alloys such as L605, tantalum, nickel-titanium alloy (nitinol) or other biocompatible metals. The second radial support structure  725  may include a plurality of wave-shaped annuluses along the axial direction, such as Z-shaped waves, or include a helically wound structure, or include a mesh structure. 
     After the stent of the present embodiment is implanted into a branch lumen, similarly, the flexible connecting section  722  and the tube body (not shown in the Figure) are radially compressed together by the branch lumen. The flexible connecting section  722  improves its adhesion to the wall of the branch lumen through the radial expansion capacity of the second radial support structure  725 , thereby ensuring the smoothness of the gap between the flexible connecting section  722  and the tube body, so that blood can flow smoothly into the gap, and the sealing property is improved. Furthermore, the blood flow may be promoted to form a vortex under the action of pressure to change the direction, thereby facilitating the flow of the blood into the tube body. 
     The second radial support structure  725  may be formed by winding a metal wire having a diameter that less than that of a metal wire that is used to wind a first radial support structure  723 , or less than a wire diameter of a metal rod formed by cutting to form the first radial support structure  723 . Alternatively, the second radial support structure  725  may be formed by cutting a metal tube, and the wire diameter of the cut metal rod is less than the diameter of the metal wire that winds the first radial support structure  723 , or less than that of the metal rod formed by cutting to form the first radial support structure  723 . For example, if the second radial support structure  725  is formed by winding the metal wire, the diameter of the metal wire is 0.15 to 0.4 mm. Or, if the second radial support structure  725  is formed by cutting a metal tube, the wire diameter of the metal rod forming the second radial support structure  725  is 0.15 to 0.4 mm. The second radial support structure  725  has a relatively small wire diameter or rod diameter so as to reduce a friction force with the sheath, thereby reducing the release force of a delivery system. Furthermore, after implantation, the expansion force generated by the second radial support structure  725  also may be reduced. For example, the expansion force generated by the second radial support structure  725  on an opening of the branch lumen and/or main body lumen stent may be reduced. 
     In the present embodiment, the second radial support structure  725  is distributed on a portion of the flexible connecting section  722 , includes a second wave-shaped annulus which is a ring of Z-shaped waves, and is formed by winding a nickel-titanium alloy. The diameter of the metal wire is 0.1 mm. The first radial support structure  723  is basically distributed on the entire membrane-coated stent  721 , includes a first wave-shaped annulus which is a ring of Z-shaped waves, and is formed by winding a nickel-titanium alloy. The diameter of the metal wire is 0.2 mm. Compared with the radial support force of other radial support structures, the radial support force of the Z-shaped waves is relatively high. 
     The waveform number of the first wave-shaped annulus is less than or equal to that of the second wave-shaped annulus. For example, the waveform number of the first wave-shaped annulus may be 5 to 12, and the waveform number of the second wave-shaped annulus may be twice that of the first wave-shaped annulus. Due to the arrangement of the waveform numbers, under the radial compression, the second wave-shaped annulus drives the first wave-shaped annulus more easily to bend and turn over towards a direction away from a first main body axial direction, and the adherence performance of the first wave-shaped annulus may be also guaranteed. 
     A coating membrane  724  of the skirt  72  covers both the first radial support structure  723  and the second radial support structure  725 . The coating membrane  724  may be a PET membrane or a PTFE membrane, which may cover the first radial support structure  723  and the second radial support structure  725  after hot melting or suturing. 
     The shortest distance between the first radial support structure  723  and the second radial support structure  725  is less than or equal to 2 mm, namely the shortest distance between the adjacent first wave-shaped annulus and second wave-shaped annulus is less than or equal to 2 mm. The shortest distance is a distance between a connecting line of all peaks of the first wave-shaped annulus and a connecting line of all valleys of the adjacent second wave-shaped annulus. In the present embodiment, referring to  FIG. 14 , the shortest length of the coating membrane length is equal to the shortest coating membrane gap L7 between one valley of the first wave-shaped annulus and the peak of the closest second wave-shaped annulus. Therefore, when radially compressed, the second radial support structure  725  may effectively assist the first radial support structure  723  to bend. If the shortest length of the coating membrane length between the first radial support structure  723  and the second radial support structure  725  is too long, it is difficult to transmit a radial compression force from the second radial support structure  725  to the first radial support structure  723 , which is unfavorable for driving the first radial support structure  723  to bend. 
     Sixth Embodiment 
     A difference from the fifth embodiment is that a coating membrane or no coating membrane is arranged between a first radial support structure and a second radial support structure of a branch lumen stent according to the sixth embodiment. The bendable connection between a stent graft and a flexible connecting section is implemented through the bendable connection between the first radial support structure and the second radial support structure. 
     Referring to  FIGS. 15A and 15B , in one specific implementation mode of the sixth embodiment, the first radial support structure  823  and the second radial support structure  825  are hooked and wound together, or are hung together. No coating membrane is arranged between the first radial support structure  823  and the second radial support structure  825 , and the coating membrane  824  only covers a portion of the second radial support structure  825  and is sealed and connected with a tube body. Under the radial compression, the second radial support structure  825  may directly transmit a force to the first radial support structure  823 , so that the first radial support structure  823  bends and turns over relative to the second radial support structure  825  more easily. To facilitate the implantation, a radiopaque apparatus may be arranged on the second radial support structure  825  to observe whether or not the first radial support structure  823  bends and turns over. The first radial support structure  823  includes at least a first wave-shaped annulus which may be a ring of Z-shaped waves. The second radial support structure  825  includes at least a second wave-shaped annulus which may be a ring of Z-shaped waves. 
     Referring to an enlarged region  8 A, the first wave-shaped annulus and the adjacent second wave-shaped annulus are hooked and wound together, namely the peak of one wave-shaped annulus is hung with the valley of the other wave-shaped annulus. Similarly, the waveform number of the first wave-shaped annulus is less than or equal to that of the second wave-shaped annulus. For example, the waveform number of the first wave-shaped annulus is equal to that of the second wave-shaped annulus in the Figure. 
     Referring to  FIGS. 16A and 16B , in another specific implementation mode of the sixth embodiment, a first radial support structure  833  and a second radial support structure  835  are connected through a flexible piece  836 , and no coating membrane is arranged between them. The flexible piece  836  includes a biocompatible metal wire and/or macromolecular wire. For example, the metal wire may be a nickel-titanium alloy wire, and the macromolecular wire may be a PET suture or an ePTFE suture or other proper medical grade sutures. The flexible piece  836  may include a silk thread, or various silk threads used cooperatively. Referring to an enlarged region  8 B, one end of the flexible piece is fixedly connected with the first radial support structure  833 , and the other end of the flexible piece is connected with the second radial support structure  835 . Similarly, the shortest distance between the first radial support structure  833  and the second radial support structure  835  along a skirt is less than or equal to 2 mm. Namely, a distance between one valley of the first wave-shaped annulus and one peak of the closest second wave-shaped annulus is less than or equal to 2 mm. Or, the length of the flexible piece also may be set to be less than or equal to 2 mm. Therefore, when radially compressed, the second radial support structure  835  may effectively assist the first radial support structure  833  to bend. 
     In conclusion, the stent graft of the skirt of the branch lumen stent according to the present disclosure includes a first radial support structure, and the first radial support structure is bendably connected to the flexible connecting section, so that during implantation and after implantation, under radial compression of the flexible connecting section, the first radial support structure bends relative to the flexible connecting section. The first radial support structure acts as the brim of the traditional top hat stent, which may be adhered to the inner wall of the main body lumen stent to reduce the impact of the blood flow to their combined positions so as to enable the tube body to maintain its radial support shape and avoid the deformation such as wrinkling, introversion and collapse, thereby avoiding resistance to the blood flowing into the lumen and preventing the formation of type-III endoleak. Meanwhile, the brim also may reduce the movement of the main body lumen stent under the impact of the blood flow. 
     Further, on the side hole of the main body lumen stent, a semi-closed gap is formed between the stent graft of the skirt and the tube body, and blood which flows into the gap may be used as the filling material for occluding the type-III endoleak channel to prevent the formation of the leakage channels between the tube body and the wall of the branch lumen as well as between the tube body and the opening of the branch lumen, thereby preventing the blood from flowing into the aneurysm or the dissection. 
     Further, the stent graft used as the brim of the top hat stent is separated from the tube body  31  used as the blood flow inlet of the branch lumen stent, so that the function of the blood flow inlet is not affected by the shape of the side hole of the main body lumen stent, whether the side hole is concentric with the opening of the branch lumen or not, and the deformation or failure of the brim. This ensures smooth blood flow into the branch lumen stent.