Patent Application
20080127707
The present invention relates generally to intraluminal devices, and more particularly relates to apparatus and methods for diametrically reducing the size of these devices, such as a stent, stent-graft, graft or vena cava filter, for percutaneous transluminal delivery thereof.
A number of vascular diagnostic and interventional medical procedures are now performed translumenally. For example, a catheter is introduced into the vascular system at a convenient access location and guided through the vascular system to a target location using established techniques. Such procedures require vascular access, which is usually established during the well-known Seldinger technique. Vascular access is generally provided through an introducer sheath that is positioned to extend from outside the patient body, through a puncture in the femoral artery for example, and into the vascular lumen. Catheters or other medical devices are advanced into the patient's vasculature through the introducer sheath, and procedures such as balloon angioplasty, stent placement, etc. are performed.
In particular, stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well known. A stent is a generally cylindrical prosthesis introduced, via a catheter, into a lumen of a body vessel in a configuration having a generally reduced diameter for transport and delivery, and then expanded to a diameter of the target vessel when deployed. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.
Balloon expandable stents are well known and widely available in a variety of designs and configurations. Balloon expandable stents are crimped to their reduced diameter about the delivery catheter, then maneuvered to the deployment site and expanded to the vessel diameter by fluid inflation of a balloon positioned between the stent and the delivery catheter. One example of a stent is described in US Patent Application having Publication No. 2004/0093073, published May 13, 2004, the content of which is incorporated herein by reference.
During advancement of the stent through a body vessel to a deployment site, the crimped stent must capable of securely maintaining its axial position on the delivery catheter. That is, the crimped stent must not translocate proximally or distally during advancement, and especially must not dislodge from the catheter. Stents that are not properly crimped, secured or retained to the delivery catheter may slip and will either be lost, be deployed in the wrong location or only be partially deployed. Moreover, the stent must be crimped in such a way as to minimize or prevent distortion of the stent, and thereby, minimize or prevent abrasion and/or trauma to the vessel walls. Additionally, if a stent has been coated with a beneficial agent, care must be taken when crimping the stent onto the delivery device so that the coating is not disturbed or removed from the stent during the crimping process.
In the past, crimping has been performed by hand, often resulting in an undesirable application of uneven radial crimping forces to the stent. Such a stent must either be discarded or re-crimped. Stents that have been crimped multiple times can suffer from fatigue and may be scored or otherwise marked, increasing the risk of thrombosis. In fact, a poorly crimped stent can also damage the underlying balloon.
In addition to hand crimping of stents, automated crimping machines have been developed, wherein the automated crimping machines provide a more consistent crimp radial force during the crimping process or consistent profile. In addition to providing consistent crimping forces, many other crimping parameters can be closely controlled through the use of computer controls or mechanical controls. Typically, an automated crimping machine and related crimping methods include a crimp head comprising a plurality of segments aligned to defined a cylindrical-shaped cavity that is reduced in diameter in an iris-type displacement, uniformly compressing the stent. Typical of such designs are described in U.S. Pat. No. 6,629,350 to Motsenbocker.
While these designs are suitable to uniformly the crimp stents, the iris-type movement generally involves a rolling motion where the blades slide tangentially across an exterior or outer surface of the stent. Such sliding contact with the outer surface of some stents may be problematic, such as for example drug coated stents. Accordingly, it is desirable to provide a crimping apparatus that minimizes damage to the outer surface of the stent during the crimping process.
The present invention provides an apparatus and methods for mechanically crimping a generally tubular stent from a first diameter to a reduced second diameter. A stent crimping assembly is provided that includes a set of two or more blade devices each having a proximal portion, a downstream distal portion, and a respective edge wall extending from the proximal portion to the distal portion. Each respective edge wall is oriented relative to one another, in a respective crimp position, to collectively define an elongated conical-shaped crimp aperture. Further, each edge wall tapers inwardly along a common longitudinal axis from the respective blade proximal portion toward the distal portion. The conical-shaped crimp aperture at the respective proximal portion of each blade is formed for receipt of at least a portion of the stent in the first diameter. The crimping assembly further includes a drive assembly associated with each blade device and configured to independently displace each blade edge wall in a manner substantially along a respective predetermined first path from the respective crimp position to a respective retracted position, oriented a predetermined incremental distance from the crimp position in a respective proximal direction.
In one specific embodiment, a transverse cross-sectional dimension of each respective edge wall is circular sector-shaped such that the collective transverse cross-sectional dimension of the opposed two or more blades, in the crimp position, is substantially circular shaped. Each respective edge walls, in the crimp position, is configured to cooperate with an adjacent edge wall to form a substantially continuous circular surface to define a substantially continuous crimp aperture.
After each blade device has sequentially displaced from the respective crimp position to the respective retracted position, the drive assembly is configured to displace the respective edge walls along respective predetermined second paths, as a unit, from the respective retracted position back to the crimp position. This movement displaces the stent substantially along the common longitudinal axis, relative to the crimping assembly, in a direction toward the respective distal portions.
In yet another arrangement, each respective first and second path of each respective edge wall is contained in a respective plane extending through the common longitudinal axis.
The respective predetermined first path each of each blade edge wall from the respective crimp position to the retracted position is substantially linear, in one embodiment, while each respective predetermined first path is tapered radially outwardly away the common longitudinal axis. In yet another configuration, the respective predetermined first path each of each blade edge wall from the respective crimp position to the retracted position is substantially non-linear, initially extending in a direction radially away from the common longitudinal axis.
In another aspect of the present invention, a stent crimping assembly is provided for crimping a stent from a first diameter to a reduced second diameter. The crimping assembly includes a set of two or more blade devices each having a first end, a second end, and a respective edge wall in opposed relationship to one another. Each respective edge wall tapers inwardly from the respective one ends to the respective second ends, relative to a common longitudinal axis of an elongated crimp aperture collectively defined by the opposed edge walls in a respective crimp position. Each respective one ends collectively defining a receiving port into the crimp aperture formed for receipt of at least a portion of the stent in the first diameter. A respective drive assembly, associated with each blade device, is configured to sequentially displace each blade substantially along a respective predetermined path from the respective crimp position to a respective retracted position. At this location, the blade device is oriented a predetermined incremental amount substantially along the common longitudinal axis of the crimp aperture and in a relative direction toward the respective one ends, sequentially diametrically reducing at least a portion of the stent from the first diameter to the reduced second diameter.
In one specific arrangement, after each blade device has sequentially displaced from the respective crimp position to the respective retracted position, each respective drive assembly is configured displace the respective blade devices substantially along the common longitudinal axis, as a unit, from the respective retracted position back to the crimp position. This unitary embodiment, the stent is displaced, relative to the crimping assembly, in the direction toward the respective second ends. Each respective drive assembly is configured to displace each respective blade device, from the respective crimp position to the respective retracted position, along the predetermined path in a direction radially away from the common longitudinal axis.
The assembly of the present invention has other objects and features of advantage which will be more readily apparent from the following description of the best mode of carrying out the invention and the appended claims, when taken in conjunction with the accompanying drawing, in which:
While the present invention will be described with reference to a few specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications to the present invention can be made to the preferred embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims. It will be noted here that for a better understanding, like components are designated by like reference numerals throughout the various figures.
Referring now to
A drive assembly 30, associated with each blade device 22, 22′, 22″, . . . 22n, is configured to independently displace each respective blade edge wall 26, 26′, 26″, . . . 26n in a manner substantially along a respective predetermined first path P1 (e.g.,
Once each blade device 22, 22′, 22″, . . . 22n has independently displaced from the respective crimp position to the respective retracted position (i.e.,
This cycling of the blade devices 22, 22′, 22″, . . . 22n sequentially along the respective predetermined first path P1 (e.g.,
Referring back to
The housing plates of the polygonal-shaped housing assembly are configured to define an interior space 36, and further adapted to support each blade main assembly 35 in a manner positioning the respective blade devices 22, 22′, 22″, . . . 22n within the interior space 36. Moreover, the housing plates 33, 33′, 33″, . . . 33n facilitate orientation of the devices blade in opposed cooperative relationship to one another, radially about the common longitudinal axis 27, to collectively define the crimp aperture 28.
Referring now to
Due to the identical or substantially identical nature of each opposed blade main assembly, only one blade main assembly 35 of the four blade main assemblies 35, 35′, 35″, 35′″ (shown in the Figures) will be detailed for reasons of clarity. Hence, as best illustrated in
In one specific embodiment, the drive device 37 is provided by a voice coil or solenoid device capable of selective reciprocal substantially linear displacement along a respective longitudinal axis thereof (i.e., in a direction of arrow 42 in
Applying a conventional linear tracking system, such as the elongated rail 40 upstanding from the support table 38 and a corresponding slider carriage 43 (
A blade spacer 46 may be provided between the blade device 22 and the slider carriage 43 that is deployed to orient the blade device 22 relative to the remaining opposed blade devices 22′, 22″, 22′″ and the common longitudinal axis 27 of crimp aperture 28. Each blade spacer 46 includes a carriage mount flange 48; a blade mount flange 50 and an extension arm 51 extending between the carriage mount flange and the blade mount flange 50.
Accordingly, as will be described in the collective operation of this specific embodiment below, due to the substantially linear reciprocal movement of the single drive device 37, the respective predetermined first path P1 (e.g.,
It will be appreciated, however, that while the movement of the respective blade device 22 along the predetermined first path and the predetermined second path between the crimp position and the retracted position are both substantially linear and coincident, more sophisticated non-linear paths may be implemented, especially with respect to the respective predetermined first paths (e.g., P1. in
Referring now to
To facilitate the formation of a substantially circular transverse cross-sectional dimension of the substantially cylindrical crimped stent 21 about the delivery device 31, the transverse cross-sectional dimension of the edge wall 26 is curvilinear, and preferably a circular sector. The arc length (radians) of the circular sector, of course, depends primarily upon the number of blade devices radially positioned about the common longitudinal axis 27 of the crimp aperture 28 defined. For example, at least two, and preferably at least four, main blade assemblies 35, 35′, 35″, 35′″ are employed. In this specific embodiment, hence, each edge wall 26 defines about a quarter circular sector each. When the four opposed blade devices 22, 22′, 22″, 22′″ are assembled in the crimp position (
More than four blade assemblies may of course be implemented, increasing the crimping continuity and uniformity between the adjacent edges walls. It will be appreciated, however, that while the adjacent edge walls 26, 26′, 26″, 26′″ defining the crimp aperture, are preferably substantially continuous perimetrically, in the crimp position, small longitudinally extending gaps between the adjacent blade devices are permitted without departing from the true spirit and nature of the present invention. It will further be appreciated that the edge walls need not be conical frustum-shaped sectors. In fact, the transverse cross-sectional dimension of the edge walls could be relatively straight, as compared to curvilinear, in the transverse cross-sectional dimension, albeit tapering inwardly from the proximal portion to the distal portion. This would be especially true when a greater number blade devices are employed.
Each blade device may be constructed of a material or a combination of materials such as nylon, delrin, steel, aluminum, titanium, TEFLON®, plastics, composite materials, and other suitable materials. Such material selections depend in part upon the material properties, such as the thermo insulation, the thermo conductivity, and whether friction therebetween is low or high, etc. It is further contemplated that the blade device 22 may be constructed as a unitary member, or may be constructed of multiple pieces that may be assembled to form a unitary member. For example, the contacting edge walls employed to collectively crimp the stent may be provided by replaceable blade inserts or the like (not shown).
It is further contemplated that blade device 22 may include a coating disposed thereon. For example, blade device 22 may be coated with a material that reduces friction, increases hardness, or alters other mechanical properties of the device according to the present invention. To reduce friction between adjacent blades or to reduce friction between the edge walls and the stent to be crimped, by way of example, it is contemplated that the blade devices may be polished to a high degree in addition to or instead of coating the blade. For example, if it is desirable to form a blade of stainless steel, the blade may be constructed having a highly polished surface finish to reduce friction and to further reduce the possibility of scratching or otherwise damaging a stent to be crimped.
The translational movement of the blade devices 22, 22′, 22″, 22′″, as will be discussed, may be performed by a control unit (not shown). The control unit, for instance, may be provided by a computer or the like, wherein the computer includes a program designed to control the sequential and simultaneous movement of the plurality of blade devices along the predetermined first path P1, from the crimp position to the retracted position, and along the predetermined second path P2, simultaneously from the retracted position back to the crimp position.
Referring now to the sequence of
Initially, when the crimping assembly 20 is placed in the crimp position (
On an opposite proximal end of the aligned blade devices 22, 22′, 22″, 22′″ is an entrance port 57 into the crimp aperture 28 that enables sliding entrance of the uncrimped stent 21 therein for initial loading thereof (
As mentioned, the distal end uncrimped stent 21, in the first diameter about the delivery device 31, is initially positioned or slid through the entrance port 57 of the crimp aperture at a proximal end of the placed. Preferably, the width of the inwardly tapered crimp aperture 28, at the proximal portion thereof, is sufficiently sized to receive a significant length, if not all, the stent therein for stability of the stent and delivery device, during the crimping process. According, the stent 21/delivery device 31 combinations should be manually inserted into the crimp aperture 28, via the entrance port 57 until a small degree of resistance is felt. Too much resistance may indicate crimping damage to the stent at the distal end thereof, via longitudinal sliding contact with the edge walls. Such shear stress along the outer surface of some stents may be problematic; such as for example drug coated stents.
Once the stent/delivery device combination is initially place in the crimp aperture through the entrance port 57, the crimping cycle can commence. Referring now to
The first path P1 the second path P2 are also substantially contained within the respective plane that longitudinally bisects the respective blade device, and that extends through the common longitudinal axis 27 (
Moreover, at a minimum, the slope of movement of the blade device, relative to the common longitudinal axis 27, along the first path P1 from the point PT at the crimp position (PTC) to and the retracted position (PTR), is at least substantially equal to the slope of the taper of the respective edge wall 26. Any such slope less than that of the edge wall my induce too much shear stress on the outer surface of the stent as the edge wall 26 slides thereagainst during movement from the respective crimp position and the respective retracted position along the substantially linear first path P1.
In fact, in accordance with one specific embodiment of the present invention, the slope of this linear first path P1, relative to the common longitudinal axis 27, is actually greater than that of the taper of the respective edge wall 26. Hence, as represented in
Briefly, it will further be appreciated that the length of the first path P1, as well as that of the second path P2, shown in the drawings, are exaggerated for the reason of illustration. While the actual length of the first path P1 may vary, such length may generally be in the range mm.
As indicated above and as illustrated in this configuration, the respective drive devices 37, 37′, 37″, . . . 37n of the drive assembly 30 provide a substantially linear first path P1 and second path P2 similar to that shown in
By way of example, as shown in
The next component, represented by the second leg L2 of the first path P1 that extends generally parallel to the common longitudinal axis 27 in a proximal direction. As shown in
The last leg L3 of the first path P1 represents another vertical component, moving the edge wall 26 radially downward in a direction toward the common longitudinal axis and into contact with the outer surface of the stent 21, to the final retracted position of this blade device 22. Contact with the outer surface of the stent during this last leg L3 is also assured since these stents are resilient and/or self-expanding. As will be described, this contact is necessary to enable movement of the stent/delivery assembly along the second path P2.
It will be appreciated that any such radial displacement along the first path P1 (in all first path embodiments) depends upon the total number of blades applied. That is, the greater the number of blades, the smaller the radial expansion of the stent when the contained in the crimp aperture. Thus, the greater the number of blades, the smaller the radial displacement, as well as a smaller axial movement. This is beneficial when the process is near completion at the exit of the stent/delivery device from the crimp aperture. At this portion of the crimp procedure, smaller axial (and radial) increments are advantageous since the crimp of the stent is already at an advanced stage. Accordingly, it follows that near the beginning of the crimp process, the increments of the first path P1 and corresponding second path P2 can be larger than the increments near the end of the crimp process.
To execute such two dimensional movement, at least two cooperating drive devices (not shown) may be required for each main blade assembly, each enabling reciprocal movement in a substantially linear direction, albeit directed 90° apart for example. Through cooperative movement, even more complicated arc, elliptical, or circular first path P1 mappings can be generated.
In accordance with the present invention, the remaining blade devices 22′, 22″, 22′″ are sequentially operated in a similar manner with no particular order. By way of example,
Once all the blade devices 22, 22′, 22″, 22′″ are oriented in the retracted position (
As this crimping cycle is repeated over and over, the stent/delivery device combination is incrementally moved axially along the crimp aperture 28 from the proximal portion 23 to the distal portion 25. As the stent is moved axially along the crimp aperture, the edge walls incrementally crimp the stent from the first diameter to the reduced second diameter. Hence, to uniformly crimp along the entire length of the stent/delivery device, due to the tapered nature of the collective edge walls, it may be necessary to pass the stent fully through the crimp aperture 28 and out of the exit port 56. The number of crimp cycles necessary to perform this procedure will of course depend upon the length of the stent and the longitudinal length of each cycle.
In one specific embodiment, when perhaps 6 or more blades are applied, the movement of the blades needs to be independent, and not entirely sequential. For example, if the crimping assembly employed 8 blade assemblies, every other blades (e.g., 1, 3, 5 and 7) could move relatively simultaneously along the first path P1 from the respective crimp position to the respective retracted position. Subsequently, blades 2, 4, 6 and 8 could move relatively simultaneously along the first path P1. The key in this situations is that with a sufficient number of remaining blades circumferentially surrounding the loaded stent, to axially as well as radially retain is in place, the first set of blades are retracted simultaneously.
In another specific embodiment of the present invention, it is further contemplated that the crimping assembly may additionally include a chiller unit (not shown) wherein the chiller unit is configured to chill or cool the crimp aperture 28 collectively formed between the blade devices 22, 22′, 22″, . . . 22n. This is advantageous when stents that must be cooled or chilled in order to reduce their diameters. For example, Nitinol stents must be cooled in order to reduce the diameter of the stent from an expanded diameter to a delivery diameter. The chiller may be integrally formed with the crimping assembly or may be a separate component that may be designed to work in conjunction with the apparatus.
Further still, it is contemplated that the blade devices may be modified in order to function correctly with the chiller unit. The crimp aperture 28 itself, formed by edge walls 26, 26′, 26″, . . . 26n, is a highly insulated chamber, and is suitable for cryogenic or other thermotreating processing. By providing an end cap or the like, the exit port 56 of the crimp aperture 28 can be sufficiently sealed. A hub portion of the end cap may be sized for a friction fit into the exit port, and an O-ring may further be provided to form a fluid tight seal. A set of access ports may extend through the end cap that provide access to the crimp aperture 28 for selective cooling thereof.
Another embodiment includes cooling of the blade devices themselves through cooling channels or passages. In this configuration, the blade devices could include communication orifices or the like that communicate a coolant from the coolant channels with the crimp aperture for cooling thereof.
Although the present invention has been described in connection with the preferred form of practicing it and modifications thereto, those of ordinary skill in the art will understand that many other modifications can be made thereto within the scope of the claims that follow. Accordingly, it is not intended that the scope of the invention in any way be limited by the above description, but instead be determined entirely by reference to the claims that follow.
The present application claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 60/872,134, naming Arkady Kokish et al as inventors, filed Nov. 30, 2006, and entitled STENT CRIMPING ASSEMBLY AND METHOD, which is incorporated herein by reference in its entirety and for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 60872134 | Nov 2006 | US |
