CN113558833A

CN113558833A - Method for crimping stent and stent system

Info

Publication number: CN113558833A
Application number: CN202010350591.0A
Authority: CN
Inventors: 张万谦; 李海锋
Original assignee: Biotyx Medical Shenzhen Co Ltd
Current assignee: Biotyx Medical Shenzhen Co Ltd
Priority date: 2020-04-28
Filing date: 2020-04-28
Publication date: 2021-10-29
Anticipated expiration: 2040-04-28
Also published as: CN113558833B; WO2021218903A1

Abstract

The invention discloses a stent crimping method, which is used for crimping a stent on a balloon, wherein the stent is provided with an inner cavity and comprises the following steps: inserting the balloon into the inner cavity of the stent, placing the balloon and the stent into a press-holding cavity of a press-holding machine, blowing air into the balloon, and simultaneously reducing the inner diameter of the press-holding cavity to perform first press-holding on the stent; stopping blowing, exhausting air to the saccule, increasing the inner diameter of the pressing and holding cavity, stopping pressing and holding, keeping exhausting air to the saccule, and contracting the pressing and holding cavity again to press and hold the bracket for the second time. According to the crimping method of the stent, provided by the invention, the saccule is crimped for the second time, and the saccule is respectively subjected to air blowing and negative pressure pumping operations during the two-time crimping, so that the stent rods are uniformly distributed on the saccule, the contact area between the saccule and the stent is increased, and the removal force of the stent is increased.

Description

Method for crimping stent and stent system

Technical Field

The invention relates to the field of medical instruments, in particular to a stent crimping method and a stent system.

Background

Percutaneous transluminal angioplasty is the most effective way to treat diseases caused by vascular stenosis and insufficient blood supply (such as coronary heart disease) at present. When the stent is transported to the lesion site, the stent needs to be mounted on a delivery system. For the balloon expandable stent, after the balloon catheter is used to transport the stent to a diseased site, the balloon is filled to expand the stent pressed on the balloon, so as to achieve the purpose of supporting a blood vessel.

One key consideration in the performance of balloon expandable stents is the stent removal force, which is defined as the maximum force required to disengage the stent from the delivery system. The stent is carried on a delivery system through complex lesions (such as calcified lesions), sometimes some resistance is met, if the removal force is too low, the stent can easily slide on a balloon, so that the stent is not uniformly expanded or is incompletely expanded, and the effectiveness of the stent is influenced; or cause the stent to become detached from the delivery system, resulting in an embolism, myocardial infarction, or the like. Therefore, the removal force of the stent is an important index for evaluating the safety and effectiveness of the use of the stent system, and the larger this index value is, the better the other properties are satisfied.

There are three common directions to increase removal force. The first direction is to change the design of the stent, such as by surface treating the stent to increase the surface roughness of the material. However, in order to ensure the support performance of the stent, the wall thickness design of the stent usually needs to be changed, which brings a lot of evaluation work on clinical safety and effectiveness, and is time-consuming and labor-consuming. The second direction is to change the design of the balloon, such as modifying the surface of the balloon to improve the surface roughness of the balloon material. However, the processing technology of the balloon in the mode is extremely complex. The third is to optimize the process of the press-grip production, such as increasing the radial force value of the press-grip. However, the increase of the crimping radial force value has a bottleneck for different stent designs, the smaller the stent is crimped in the circumferential direction, the balloon is often reduced in size by means of the flap, the flap can make the surface of the balloon uneven, which can lead to that some places of the stent struts on the balloon are well embedded and some places are difficult to be embedded in the crimping process, the stent struts which are difficult to be embedded can slide relative to the surface of the balloon, so that the stent struts collide with each other to damage the coating, or the stent struts are overlapped.

Accordingly, there is a need for a method of crimping a stent that can greatly improve the removal force of the stent without increasing the complexity and difficulty of the process.

Disclosure of Invention

The crimping method of the bracket provided by the invention comprises the following steps:

inserting the balloon into the inner cavity of the stent, placing the balloon and the stent into a press-holding cavity of a press-holding machine, blowing air into the balloon, and simultaneously reducing the inner diameter of the press-holding cavity to perform first press-holding on the stent;

stopping blowing, exhausting air to the saccule, increasing the inner diameter of the pressing and holding cavity, stopping pressing and holding, keeping exhausting air to the saccule, and contracting the pressing and holding cavity again to press and hold the bracket for the second time.

In one embodiment, prior to inserting the balloon into the lumen of the stent, the method further comprises the step of flap folding the balloon.

In one embodiment, the method further comprises the step of pre-pressing the stent before inserting the balloon into the lumen of the stent and after the balloon is folded, so that the difference between the pre-pressed inner diameter of the stent after pre-pressing and the outer diameter of the balloon after folding is within ± 5%.

In an embodiment, after the stent is pre-pressed and before the stent is crimped for the first time, the method further includes the step of reducing the inner diameter of the crimping cavity, so that the inner diameter of the crimping cavity is smaller than the pre-pressed outer diameter of the stent by within 5%.

In one embodiment, the inflation pressure ranges from 50psi to 140psi when inflating the balloon.

In one embodiment, the stent comprises a metal stent or a metal composite stent.

In an embodiment, after the first pressing and the second pressing, the method further includes a step of maintaining the pressing radial force of the pressing machine for pressure maintaining.

The invention also provides a stent system which comprises a stent and a balloon, wherein the stent is pressed and held on the outer surface of the balloon, the stent comprises a plurality of stent units, each stent unit comprises a plurality of mutually connected stent rods, when the stent is pressed and held on the balloon, the stent rods are basically parallel to each other and are approximately uniformly distributed in the circumferential direction, and the balloon part protrudes out of the stent rods.

In one embodiment, the plurality of stent struts form pinch marks on the balloon surface.

In one embodiment, the stent also carries a therapeutic drug.

According to the crimping method of the stent, provided by the invention, the saccule is crimped for the second time, and the saccule is respectively subjected to air blowing and negative pressure pumping operations during the two-time crimping, so that the stent rods are uniformly distributed on the saccule, the contact area between the saccule and the stent is increased, and the removal force of the stent is increased. According to the stent system prepared by the method, when the stent is pressed and held on the balloon, the plurality of stent rods on the stent unit are basically parallel to each other and are uniformly distributed in the circumferential direction, and the balloon is partially protruded and is uniformly distributed between the plurality of stent rods, namely the stent rods are uniformly distributed on the outer surface of the balloon, so that the contact area between the balloon and the stent is increased, the removal force of the stent is increased, and the stability, effectiveness and safety of the stent are improved.

Drawings

FIG. 1 is a schematic partial structural view of a stent system of the present invention, including a stent and a balloon;

FIG. 2 is a schematic view of a portion of the stent shown in FIG. 1;

FIG. 3 is a cross-sectional structural schematic view of the stent system of FIG. 1;

fig. 4 to 6 are schematic structural changes of the stent and the balloon in the crimping process of the stent of embodiment 1 of the present invention;

FIGS. 7 to 8 are schematic views showing a partial structure and a cross-sectional structure of a stent crimped according to the crimping method of comparative example 1;

FIG. 9 is a graph comparing removal force of a stent crimped according to an embodiment of the present invention and a comparative crimping method;

fig. 10 is a graph comparing the maximum cross-sectional dimensions of a stent crimped according to an embodiment of the present invention and a comparative crimping method.

Detailed Description

In order to better understand the technical scheme and effective effect of the invention, the invention is further described with reference to specific embodiments.

-flap-folding the balloon to form a multi-flap uniform balloon flap and to maintain the balloon in the flap-folded state;

sleeving the stent on the lining rod, placing the stent in a pressing and holding cavity of a pressing and holding machine, and pre-pressing the stent to ensure that the pre-pressed inner diameter of the stent is approximately equal to the size of a flap of the balloon;

taking out the stent, inserting the balloon with the flaps into the inner cavity of the stent after being pre-pressed, and realizing the primary assembly of the balloon and the stent;

-placing the balloon together with the stent in a crimping chamber of a crimping machine, reducing the inner diameter of the crimping chamber so that the inner diameter of the crimping chamber is slightly smaller than the pre-pressed outer diameter of the stent;

-setting the crimping radial force and the crimping speed, and connecting a pressurizing valve, setting the blowing pressure, blowing the balloon, while crimping the stent for the first time at a certain speed;

-maintaining the gripping radial force of the gripper machine after the gripping radial force reaches a set value, and performing short pressure maintaining;

closing the pressure valve, connecting the pressure valve, setting the air exhaust pressure, exhausting the balloon, increasing the inner diameter of the pressure-holding cavity, stopping the pressure-holding, setting the pressure-holding radial force again after the stent is stable in size and does not rebound, keeping the air exhaust, and performing the second pressure-holding on the stent;

increasing the inner diameter of the pressing and holding cavity of the pressing and holding machine, closing the pressure-pumping valve, and taking the stent and the saccule out of the pressing and holding cavity together to finish the pressing and holding of the stent.

The specifications of the stent and the balloon can be selected according to actual requirements, and correspondingly, the crimping parameters can be changed according to the specifications of the stent and the balloon. Generally, the balloon length needs to be greater than the stent length, and the longer the stent length, the greater the crimping radial force that needs to be set when crimped.

For example, the number of balloon wings formed behind the balloon flap of the present invention may be 2-10 flaps; the flap size (i.e., the maximum outer profile diameter behind the flap) of the balloon behind the flap ranges from 0.040 inch to 0.082 inch; the stent specification can be selected according to actual requirements, for example, the deployment specification of the stent (i.e. the expanded size of the stent under the nominal pressure of 8 atm) is that the diameter of the stent ranges from 2 mm to 10 mm, the length of the stent ranges from 8 mm to 118 mm, and the wall thickness of the stent ranges from 50 micrometers to 150 micrometers; the range of the radial force of the pressing and the holding can be 450N-2670N; the gripping speed is 0.01 inch/second to 0.001 inch/second; the blowing pressure range is optionally from 50psi to 140 psi; the range of the pumping pressure can be selected from-0.1 psi to-15 psi; the pressure maintaining time after one-time pressing can be 20 seconds to 60 seconds.

In addition, the radial force of the crimping, the speed of the crimping, and the dwell time after the crimping may be the same or different for the first crimping and the second crimping of the stent.

The stent of the present invention includes a metal stent or a metal composite stent such as an iron stent, a magnesium stent, a cobalt-chromium alloy stent, and the like. Wherein the metal coverage on the stent is between about 8% and 18%.

The balloon material of the present invention may comprise at least one of nylon 11, nylon 12, PEBAX7233, PEBAX7033, PEBAX6333, PEBAX5533, polyurethane, polyethylene terephthalate, or polyethylene, and the thickness of the balloon may range between about 0.005 mm and about 0.1 mm.

A partial structure of the stent system 100 provided by the present invention and prepared according to the above method is shown in FIG. 1. The stent system 100 includes a stent 10, a balloon 20, and a catheter assembly 30. Wherein both ends of the balloon 20 are fixedly connected with the catheter assembly 30; the stent 10 is crimped to the outer surface of the balloon 20, and the axial length of the balloon 20 is greater than the axial length of the stent 10. The part of the catheter assembly 30 covered by the balloon 20 is also provided with 2 developing structures 40, and the two developing structures 40 are located at two ends of the stent and are both arranged on the part of the catheter assembly 30 not covered by the stent 10, so as to indicate the position of the stent in the implantation process under a developing device and improve the accuracy of the implantation position of the stent.

As shown in fig. 1 and 2, the stent 10 includes a plurality of stent units 11 and connection units. The plurality of stent units 11 are arranged in the longitudinal direction of the stent 10 and connected by the connection unit. In some embodiments, the connection unit may include a first connection unit 13 and a second connection unit 14. The first connecting unit 13 includes an Ω structure, and may provide a certain margin and buffer for deformation of the bracket 10; the second connection unit 14 encloses a closed structure, which may also be filled with a developing substance 15.

The rack unit 11 includes a plurality of rack bars 12 and a connector 16. The proximal end of any one of the stent struts 12 is connected to the proximal end of an adjacent one of the stent struts 12 by one of the connectors 16, and the distal end of any one of the stent struts 12 is connected to the distal end of another adjacent one of the stent struts by another of the connectors 16, so that the stent unit 11 forms a closed structure in the circumferential direction.

As shown in fig. 2 and 3, when the stent 10 is crimped on the balloon 20, the plurality of stent struts 12 are substantially parallel to each other, and the plurality of stent struts 12 are substantially uniformly distributed in the circumferential direction, and the balloon 20 partially protrudes between the plurality of stent struts 12, so that the balloon 20 is not only in contact with the inner surfaces of the stent struts 12, but also in contact with the side surfaces of the stent struts 12, thereby increasing the contact area between the balloon 20 and the stent 10, increasing the friction force therebetween, and improving the stent removal force. Still further, the stent struts 12 may also form pinch marks on the surface of the balloon 20, thereby stabilizing the shape of the portion of the balloon 20 protruding between the stent struts 12.

In some embodiments, the surface of the stent 10 may also carry a therapeutic drug, such as sirolimus (sirolimus), everolimus (everolimus), Paclitaxel (Paclitaxel), and the like.

Specific examples and comparative examples will be set forth below to further illustrate the crimping method of the stent of the present invention and the effects thereof. The following embodiments and comparative examples are given for a stent having a crimped gauge of 3.5X8.0 (i.e., a stent having a deployment gauge of about 3.5 mm outer diameter and about 8 mm length).

Example 1

With reference to fig. 4 to 6, the crimping method of the stent of the present embodiment includes the following steps:

s1, carrying out flap folding on the balloon 20 to enable the balloon 20 to form three-flap uniform balloon wings 21 and keep the balloon 20 in a flap state;

step S1 is to perform the folding of the balloon 20, especially to perform the folding to make the balloon form multi-flap uniform balloon wings 21, so as to ensure the overall contour of the balloon flaps to be uniform, and to ensure that the subsequent stent can be pressed to a smaller size, so that the stent can be delivered to the lesion site by using a smaller delivery sheath. Meanwhile, the balloon which is always kept in the uniform flap state can ensure that the balloon has uniform acting force on the stent and the stent has better expansion uniformity when the stent is expanded. When the balloon is folded, the number of balloon wings can be 2-10 petals, preferably 3-5 petals. The balloon flap size of this embodiment after uniform folding of the balloon 20 is about 0.046 inches (about 1.1684 mm).

S2, sleeving the stent 10 on a lining rod, sleeving a layer of PTFE film for protecting the stent 10 from being scratched outside the stent 10, putting the PTFE film into a pressing and holding cavity of a pressing and holding machine, and pre-pressing the stent 10 to enable the pre-pressed inner diameter of the stent 10 to be approximately equal to the size of a flap of the balloon 30;

in step S2, the cut stent is pre-compressed, so that the inner diameter and the outer diameter of the stent 10 can be reduced appropriately, the gap between the stent 10 and the balloon 20 is reduced during subsequent crimping, and the pre-compressed inner diameter of the stent can be approximately equal to the size of the flap of the balloon, thereby avoiding the relative movement between the stent and the flap when the stent is crimped. For the supports with different specifications, the prepressing sizes are different, so the force applied during prepressing is also different. In this embodiment, the flap size of the flap rear balloon is about 0.046 inches, so a 50psi air cylinder is used to drive the press to pre-press the stent, the pre-pressed inner diameter of the pre-pressed stent 10 is about 0.048 inches, and the pre-pressed outer diameter is about 0.056 inches. It should be understood that the balloon 20 is inserted into the inner cavity of the stent 10 subsequently, so that the pre-pressed inner diameter of the stent is slightly larger than the size of the flap of the balloon, and the "approximately equal" in the invention means that the gap between the stent and the balloon is small, and the stent and the balloon cannot easily move relatively when not being pulled by external force; or may be understood as having a difference between the inner diameter of the stent and the outer diameter of the balloon within ± 5%.

S3, taking out the stent 10 from the crimping cavity of the crimping machine, inserting the saccule 20 with the flap into the inner cavity of the stent 10 after being pre-pressed, and realizing the primary assembly of the saccule 20 and the stent 10;

as shown in fig. 4, the circumferential distance between the stent struts 12 is greater before crimping. After the balloon 20 is inserted into the inner cavity of the stent 10, basically each stent rod 12 can contact with the balloon wings 21, and the balloon wings 21 are uniformly distributed, and the tail ends of the balloon wings 21 are just positioned at the gap between the two stent rods 12. In addition, before inserting the balloon into the stent, it is necessary to peel off the film outside the stent and observe whether the stent is intact in appearance or not and whether there is damage such as scratches or the like.

S4, placing the saccule 20 and the stent 10 into a pressing and holding cavity of a pressing and holding machine, and reducing the inner diameter of the pressing and holding cavity to ensure that the inner diameter of the pressing and holding cavity is less than the prepressing outer diameter of the stent 10 by within 5 percent;

before formal pressure holding, the inner diameter of the pressure holding cavity is reduced to a position slightly smaller than the prepressing outer diameter of the support 10, the distance between the inner wall of the pressure holding cavity and the support 10 is reduced, and the situation that the support is expanded by a saccule and then a support rod deforms or even the support fails when the saccule is inflated in the subsequent pressure holding process can be avoided as much as possible. In this embodiment, the pre-stressed outer diameter of the stent 10 is about 0.056 inches, so the crimping cavity in step S4 can be reduced to 0.055 inches.

S5, setting the squeezing radial force of the squeezing machine to be 944N and the squeezing speed to be 0.001 inch/second; connecting a pressurizing valve, setting the air blowing pressure to be 30psi, starting to blow the balloon 20, and then starting to press and hold the bracket 20 for the first time;

as shown in fig. 5, when the related parameters are set to start crimping, the balloon 20 is inflated due to the inflation, so as to generate an opposite force (i.e. a force opposite to the radial force of crimping) for resisting the deformation of the stent 10, and especially, the balloon wings 21 on the side close to the inner surface of the stent 10 initially form bulges for resisting the deformation of the stent struts 12 at the parts not blocked by the stent struts 12, so that the stent struts 12 can be uniformly distributed in the circumferential direction all the time in the first crimping process without deviation or overlapping. In addition, because the inflated balloon 20 can generate a reverse force resisting the deformation of the stent 10, the pressing and holding radial force of the stent 10 and the balloon 20 reaching the compression limit is improved, so that the stent and the balloon are compressed more tightly, and the stent removing force is higher.

S6, continuously pressing and holding until the pressing and holding radial force reaches a set value of 944N, keeping the pressing and holding radial force of the pressing and holding machine, and keeping the pressure for a short time, wherein the pressure keeping time is 30 seconds;

in step S6, after the crimping radial force of the crimping machine reaches the set value, the crimping cavity of the crimping machine is still maintained in the crimping state, the stent is held in the crimping state, the shape of the stent is further consolidated, the crimping shape of the stent is stabilized, and the clamping marks on the balloon wings generated by the limiting and blocking of the stent rods are further stabilized. If the clamping radial force set value is reached, the clamping is released, at the moment, the clamping shape of the stent is unstable, and after the inner diameter of the clamping cavity is increased, the stent can rebound rapidly and even break away from the surface of the balloon, so that the clamping fails.

S7, closing the pressure valve, connecting the pressure valve, setting the air exhaust pressure to-12 psi, exhausting the balloon, increasing the inner diameter of the pressure holding cavity, stopping pressure holding for about 5 seconds, setting the pressure holding radial force of the pressure holding machine to be 944N and the pressure holding speed to be 0.001 inch/second again after the size of the support is stable and does not rebound, keeping air exhaust, and performing secondary pressure holding on the support;

in step S7, the pressurizing valve is closed to stop the operation of inflating the balloon 20, the balloon 20 is evacuated to extract the remaining gas in the balloon, and the inner diameter of the pressure-holding cavity is increased to prevent the balloon from being inflated to deform the stent after the pressure-holding of the pressure-holding cavity is released. Meanwhile, the inner diameter of the pressing and holding cavity is increased, the pressing and holding is stopped, the bracket is pressed and held again after being stabilized in size, air is always pumped into the saccule in the pressing and holding process, and the air in the saccule can not resist the pressing and holding of the pressing and holding cavity on the saccule. When the stent is pressed and held for the second time, the gas in the saccule is completely pumped out, so that the stent can be compressed to a smaller size. At this time, because the bulges between the stent rods are formed on the balloon at the first pressing, and the stable clamping marks are formed on the balloon wings, the balloon material on the stent of the stent rod is not changed in position or the clamping marks on the balloon wings disappear by air suction at the second pressing.

S8, keeping the pressing radial force of the pressing machine after the pressing radial force reaches a set value, and keeping the pressure for 30 seconds;

similar to step S6, the pressure maintaining purpose of step S8 is to further strengthen the shape of the stent and stabilize the crimped shape of the stent.

And S9, increasing the inner diameter of a pressing and holding cavity of the pressing and holding machine, stopping pressing and holding, closing the pressure-pumping valve, taking the stent and the saccule out of the pressing and holding cavity together, and finishing pressing and holding of the stent.

As shown in FIG. 6, the circumferential distance between the stent struts 12 on the stent after completing two crimping operations is smaller, and the diameter of the stent 10 is also smaller. Compared with the balloon wings 21 when the pressing is started, the bulges formed on the balloon wings 21 are more obvious after the pressing is finished, and even can be positioned on the same outer contour line with the support rod 12. Therefore, according to the stent after being pressed and held by the embodiment, the stent rods are uniformly distributed in the circumferential direction, so that the uniform stress of the stent during expansion is ensured, and the stent is good in unfolding shape; and the bulges formed on the saccule can increase the contact area between the stent and the saccule, so that the removal force of the stent is increased, and the bulges can also form physical resistance to increase the resistance to relative movement of the stent rod.

It should be understood that the crimping machine used for pre-pressing the stent may be the same as or different from the crimping machine used for the first crimping and the second crimping, and when the crimping machine is attached with a film covering system, the film covering operation of the stent before pre-pressing or crimping is not needed. The squeezing time and the squeezing speed in step S5 and step S7 may be the same or different, and the holding pressure time in step S6 and step S8 may be the same or different.

Example 2

The crimping method of the stent of the present embodiment is substantially the same as that of embodiment 1, except that the first crimping in step S5 in the present embodiment is performed with a blowing pressure that is set to be 140psi higher than that of embodiment 1. In the embodiment, the larger air-blowing pressure is set, so that the reverse force generated by the balloon and resisting the deformation of the stent is larger when the balloon is pressed for the first time, the pressing and holding radial force of the stent and the balloon reaching the compression limit is also improved, and finally the removal force of the stent is improved. Meanwhile, the blowing pressure is higher, the more balloon materials are blown into the space between the support rods to form the protrusions, the protrusions are closer to the outer contour lines of the support rods, the less balloon materials are located on the inner side of the support, and therefore the maximum section size of the support is smaller.

In order to better embody the advantages and superiority of the squeezing method of the present invention, some comparative examples are listed below to compare with the above examples.

Comparative example 1

This comparative example employed two squeeze grips with neither air blowing nor air extraction during the squeeze grip.

The method specifically comprises the following steps:

s4, setting the press-holding radial force of the press-holding machine to be 674N and the press-holding speed to be 0.001 inch/second, and starting to press and hold the bracket 20 for the first time;

s5, continuously pressing until the pressing radial force reaches a set value 674N, keeping the pressing radial force of the pressing machine, and keeping the pressure for a short time for 30 seconds;

s6, increasing the inner diameter of the crimping cavity, stopping crimping for about 5 seconds, setting the crimping radial force of the crimping machine to be 674N and the crimping speed to be 0.001 inch/second again after the size of the stent is stable and does not rebound, and performing secondary crimping on the stent;

s7, keeping the pressing radial force of the pressing machine after the pressing radial force reaches a set value, and keeping the pressure for 30 seconds;

and S8, increasing the inner diameter of the pressing and holding cavity of the pressing and holding machine to stop pressing and holding, and taking the stent and the saccule out of the pressing and holding cavity together to finish pressing and holding of the stent.

Although steps S1 to S3 in this comparative example are the same as steps S1 to S3 in example 1, since the balloon is not inflated in the first crimping, even if the balloon is uniformly flapped, uniform distribution of the stent struts in the circumferential direction after crimping cannot be ensured. The size difference exists near the ends of the balloon wings, simply because the outer profile behind the balloon flaps is not regularly rounded. As shown in fig. 7 and 8, according to the stent crimped according to comparative example 1, because the first crimping is not performed with air blowing, no protrusion for blocking the deformation and displacement of the stent rod is formed on the balloon wing, so that the stent rod has more or less position shift towards the balloon end, which causes the stent rod 12 to be unevenly distributed in the circumferential direction, and the stent rod may even overlap when the stent is implanted subsequently.

It should be noted that the step of reducing the inner diameter of the crimping cavity is omitted prior to crimping, since the balloon is not inflated when crimping of the present example.

Comparative example 2

This comparative example differs from comparative example 1 only in that a larger gripping radial force was used for the two-time gripping, and the same gripping radial force of 944N as that of example 1 described above was used for the two-time gripping.

Compared to comparative example 1, the stent removal force after crimping according to the method of comparative example 2 is greater than that of comparative example 1, and the maximum cross-sectional dimension of the stent is smaller than that of comparative example 1, because a greater crimping radial force is used.

Comparative example 3

The comparison example adopts the operation of one-time pressing and air blowing during pressing, and air is pumped after the pressing is finished without carrying out the second pressing. The method specifically comprises the following steps:

s5, setting the squeezing radial force of the squeezing machine to be 944N and the squeezing speed to be 0.001 inch/second; connecting a pressurizing valve, setting the air blowing pressure to be 30psi, starting to blow the balloon 20, and then starting to press and hold the bracket 20;

s7, closing the pressure valve, connecting the pressure valve, setting the air exhaust pressure to-12 psi, exhausting the balloon, then increasing the inner diameter of the pressure holding cavity, stopping the pressure holding for about 5 seconds until the size of the support is stable and does not rebound;

and S8, increasing the inner diameter of a pressure holding cavity of the pressure holding machine to stop pressing, closing the pressure-pumping valve, and taking the stent and the saccule out of the pressure holding cavity to finish pressing and holding of the stent.

The present comparative example is different from example 1 only in that only air suction is performed at step S7, but the stent is not crimped for the second time. So that the clamping marks on the balloon wings are shallower, and the maximum cross-sectional dimension of the stent after being crimped is larger.

Comparative example 4

The comparative example adopts the operation of blowing air during the first pressing and not pumping air during the second pressing. The only difference from example 1 is step S7, step S7 of this comparative example is:

s7, closing the pressurizing valve, increasing the inner diameter of the crimping cavity to stop crimping for about 5 seconds, setting the crimping radial force of the crimping machine to be 944N and the crimping speed to be 0.001 inch/second again after the stent is stable in size and does not rebound, and performing secondary crimping on the stent;

the only difference compared to comparative example 2 is that step S7 does not provide suction during the second crimping, so the residual gas in the balloon still generates a certain degree of counter force against the stent compression during the second crimping. Thus, the clamping marks on the balloon wings are shallower, and the maximum cross-sectional dimension of the stent after being crimped is larger.

In contrast to comparative example 3, the second crimping was performed without evacuating the balloon, which increased the removal force of the stent to some extent while slightly decreasing the maximum cross-sectional size of the stent.

Figures 9 to 10 visually illustrate the various embodiments described above and the effect of the comparative ratio on the stent removal force and the maximum cross-sectional dimension. As can be seen from fig. 9, increasing the gripping radial force may increase the removal force somewhat; the bracket is pressed for the second time, and the removal force of the bracket can be increased and the maximum section size of the bracket can be reduced by pumping air during pressing; increasing the blowing pressure can greatly enhance the removal force of the stent and also can reduce the maximum cross-sectional dimension of the stent.

The removal force of the stent can be tested by the following test method, which complies with the standards ASTM F2394-07 and YY/T0807.

Specifically, before testing, a lining wire is adopted to penetrate through a wire guide cavity, two adhesive tapes are used for oppositely adhering, a bracket part of the bracket system is fixed between the two adhesive tapes, and the length of about 1 mm reserved at the two ends of the bracket is not contacted with the adhesive surface of the adhesive tape; and clamping the fixed sample on a tensile machine for traction, wherein during clamping, a lower clamp of the tensile machine clamps the near end of the bracket system (namely the near end of the catheter component), and an upper clamp of the tensile machine clamps the adhesive tape far away from the bracket system. The test was started with the sample held upright and in the position right in the middle of the jig. The test can be stopped when a peak in the pulling force on the test display occurs, i.e. the maximum removal force of the stent.

In conclusion, in the pressing and holding method of the stent, the stent is pressed and held twice, the balloon is inflated during the first pressing and held, and the balloon is exhausted during the second pressing and held, so that the post-pressing and holding frame rods are uniformly distributed in the circumferential direction, the removal force of the stent is increased, the stress of the stent rods is uniform during the subsequent implantation, and the shape of the stent is good after the implantation; and the maximum section size of the stent can be reduced, so that a smaller delivery sheath can be used for delivering the stent, and the injury caused by a sheath tube in the implantation process is reduced.

It should be understood that the above-mentioned embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention, and that several variations and modifications can be made without departing from the spirit of the present invention. The protection scope of the invention is subject to the claims.

Claims

1. A method of crimping a stent to a balloon, the stent having an inner lumen, comprising the steps of:

2. The method of crimping a stent according to claim 1, further comprising the step of flap-folding the balloon prior to inserting the balloon into the lumen of the stent.

3. The method of crimping a stent according to claim 2, wherein the step of pre-compressing the stent is further included after the balloon is flapped before the balloon is inserted into the lumen of the stent, so that a difference between a pre-compressed inner diameter of the stent after pre-compressing and an outer diameter of the balloon after the balloon is flapped is within ± 5%.

4. The stent crimping method according to claim 3, further comprising a step of reducing an inner diameter of the crimping cavity after the stent is pre-compressed and before the stent is crimped for the first time, so that the inner diameter of the crimping cavity is within 5% smaller than a pre-compressed outer diameter of the stent.

5. The method of crimping a stent according to claim 1, wherein the balloon is inflated to an inflation pressure in a range of 50-140 psi.

6. The method of crimping a stent according to any one of claims 1 to 5, wherein the stent comprises a metal stent or a metal composite stent.

7. The stent crimping method according to any one of claims 1 to 5, characterized by further comprising a step of maintaining a crimping radial force of the crimping machine for pressure holding after the first crimping and the second crimping are performed, respectively.

8. A stent system prepared according to the method of claim 1, the stent system comprising a stent and a balloon, the stent being crimped on an outer surface of the balloon, the stent comprising a plurality of stent units, the stent units comprising a plurality of interconnected stent struts, wherein the plurality of stent struts are substantially parallel to each other and are substantially uniformly distributed in a circumferential direction when the stent is crimped on the balloon, and wherein portions of the balloon protrude between the plurality of stent struts.

9. The stent system according to claim 8 wherein the plurality of stent struts pinch the balloon surface.

10. The stent system of claim 8, wherein the stent further comprises a therapeutic drug loaded thereon.