FreshPatents.com Logo
stats FreshPatents Stats
1 views for this patent on FreshPatents.com
2014: 1 views
Updated: April 14 2014
newTOP 200 Companies filing patents this week


    Free Services  

  • MONITOR KEYWORDS
  • Enter keywords & we'll notify you when a new patent matches your request (weekly update).

  • ORGANIZER
  • Save & organize patents so you can view them later.

  • RSS rss
  • Create custom RSS feeds. Track keywords without receiving email.

  • ARCHIVE
  • View the last few months of your Keyword emails.

  • COMPANY DIRECTORY
  • Patents sorted by company.

AdPromo(14K)

Follow us on Twitter
twitter icon@FreshPatents

Method of increasing stent retention of bioabsorbable scaffolding with a sheath

last patentdownload pdfdownload imgimage previewnext patent


20120290063 patent thumbnailZoom

Method of increasing stent retention of bioabsorbable scaffolding with a sheath


A medical device includes a polymer stent crimped to a catheter having an expansion balloon. The stent is crimped to the balloon by a process that includes heating the stent to a temperature below the polymer's glass transition temperature to improve stent retention without adversely affecting the mechanical characteristics of the stent when later deployed to support a body lumen. A variable diameter sheath with a central portion that prevents expansion of the stent when the balloon is pressurized and larger diameter ends is disposed over the crimped stent-balloon assembly. The balloon is pressurized and the larger diameter ends of the sheath allow the balloon beyond the ends of the stent to expand. The balloon is then depressurized.
Related Terms: Scaffolding

Browse recent Abbott Cardiovascular Systems Inc. patents - Santa Clara, CA, US
Inventors: Yunbing Wang, Xiao Ma, Rommel C. Lumauig
USPTO Applicaton #: #20120290063 - Class: 623 111 (USPTO) - 11/15/12 - Class 623 
Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor > Arterial Prosthesis (i.e., Blood Vessel) >Stent Combined With Surgical Delivery System (e.g., Surgical Tools, Delivery Sheath, Etc.)

view organizer monitor keywords


The Patent Description & Claims data below is from USPTO Patent Application 20120290063, Method of increasing stent retention of bioabsorbable scaffolding with a sheath.

last patentpdficondownload pdfimage previewnext patent

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to medical devices; more particularly, this invention relates to methods of making polymeric stent delivery systems.

2. Background of the Invention

The art recognizes a variety of factors that affect a polymeric stent\'s ability to retain its structural integrity when subjected to external loadings, such as crimping and balloon expansion forces. These interactions are complex and the mechanisms of action not fully understood. According to the art, characteristics differentiating a polymeric, bio-absorbable stent scaffolding of the type expanded to a deployed state by plastic deformation from a similarly functioning metal stent are many and significant. Indeed, several of the accepted analytic or empirical methods/models used to predict the behavior of metallic stents tend to be unreliable, if not inappropriate, as methods/models for reliably and consistently predicting the highly non-linear behavior of a polymeric load-bearing, or scaffolding portion of a balloon-expandable stent. The models are not generally capable of providing an acceptable degree of certainty required for purposes of implanting the stent within a body, or predicting/anticipating the empirical data.

Moreover, it is recognized that the state of the art in medical device-related balloon fabrication, e.g., non-compliant balloons for stent deployment and/or angioplasty, provide only limited information about how a polymeric material might behave when used to support a lumen within a living being via plastic deformation of a network of rings interconnected by struts. In short, methods devised to improve mechanical features of an inflated, thin-walled balloon structure, most analogous to mechanical properties of a pre-loaded membrane when the balloon is inflated and supporting a lumen, simply provides little, if any insight into the behavior of a deployed polymeric stent scaffolding. One difference, for example, is the propensity for fracture or cracks to develop in a stent scaffolding. The art recognizes the mechanical problem as too different to provide helpful insights, therefore, despite a shared similarity in class of material. At best, the balloon fabrication art provides only general guidance for one seeking to improve characteristics of a balloon-expanded, bio-absorbable polymeric stent.

Polymer material considered for use as a polymeric stent scaffolding, e.g. PLLA or PLGA, may be described, through comparison with a metallic material used to form a stent scaffolding, in some of the following ways. A suitable polymer has a low strength to weight ratio, which means more material is needed to provide an equivalent mechanical property to that of a metal. Therefore, struts must be made thicker and wider to have the strength needed to support a lumen, for example. The scaffolding also tends to be brittle or have limited fracture toughness. The anisotropic and rate-dependant inelastic properties (i.e., strength/stiffness of the material varies depending upon the rate at which the material is deformed) inherent in the material only compound this complexity in working with a polymer, particularly, bio-absorbable polymer such as PLLA or PLGA.

Processing steps performed on, design changes made to a metal stent that have not typically raised concerns for, or require careful attention to unanticipated changes in the average mechanical properties of the material, therefore, may not also apply to a polymer stent due to the non-linear and sometimes unpredictable nature of the mechanical properties of the polymer under a similar loading condition. It is sometimes the case that one needs to undertake extensive validation before it even becomes possible to predict more generally whether a particular condition is due to one factor or another—e.g., was a defect the result of one or more steps of a fabrication process, or one or more steps in a process that takes place after stent fabrication, e.g., crimping. As a consequence, a change to a fabrication process, post-fabrication process, diameter of the stent, length of the stent, or even relatively minor changes to a stent pattern design must, generally speaking, be investigated more thoroughly than if a metallic material were used instead of the polymer. It follows, therefore, that when choosing among different polymeric stent designs for improvement thereof, there are far less inferences, theories, or systematic methods of discovery available, as a tool for steering one clear of unproductive paths, and towards more productive paths for improvement, than when making changes in a metal stent.

It is recognized, therefore, that, whereas inferences previously accepted in the art for stent validation or feasibility when an isotropic and ductile metallic material was used, such inferences would be inappropriate for a polymeric stent. A change in a polymeric stent pattern may affect not only the stiffness or lumen coverage of the stent in its deployed state supporting a lumen, but also the propensity for fractures to develop when the stent is crimped or being deployed. This means that, in comparison to a metallic stent, there is generally no assumption that can be made as to whether a changed stent pattern may not produce an adverse outcome, or require a significant change in a processing step (e.g., tube forming, laser cutting, crimping, etc.). Simply put, the highly favorable, inherent properties of a metal (generally invariant stress/strain properties with respect to the rate of deformation or the direction of loading, and the material\'s ductile nature), which simplify the stent fabrication process, allow for inferences to be more easily drawn between a changed stent pattern and/or a processing step and the ability for the stent to be reliably manufactured with the new pattern and without defects when implanted within a living being.

A change in the geometry of the stent such as length, diameter, strut thickness, and pattern of the struts and rings of a polymeric stent scaffolding that is plastically deformed, both when crimped to, and when later deployed by a balloon, unfortunately, is not as easy to predict as a metal stent. Indeed, it is recognized that unexpected problems may arise in polymer stent fabrication steps as a result of a changed pattern that would not have necessitated any changes if the pattern was instead formed from a metal tube. In contrast to changes in a metallic stent pattern, a change in polymer stent pattern may necessitate other modifications in fabrication steps or post-fabrication processing, such as crimping and sterilization.

One problem frequently encountered with a stent for delivery to a site in a body using a balloon is reliably retaining the stent on the balloon as it passes through tortuous anatomy. If the stent is not held on the balloon with sufficient force, it can slip off of the balloon during transit to the target site. For a metallic stent, there are several approaches proposed for increasing the retention of a stent to a balloon during transit to the target site. However, methods proposed thus far for retaining the polymer stent on a balloon are in need of improvement.

In light of the foregoing problems, there is a need for improving the retention of a polymer stent on a balloon while avoiding adverse effects on the mechanical characteristics of the load bearing, polymer scaffolding when the scaffolding is fully deployed to support a lumen.

SUMMARY

OF THE INVENTION

Various embodiments of the present invention include a method of making a stent delivery system, comprising the steps of: providing a polymeric scaffolding crimped tightly over a delivery balloon; providing a tubular sheath comprising a middle portion and two end portions, wherein the middle portion of the sheath have an inside diameter equal to or 1-2% larger than the outer diameter of the crimped scaffolding and the end portions of the sheath have a diameter 3-100% greater than the diameter of the crimped scaffolding; disposing the polymeric scaffolding and balloon within the tubular sheath, wherein the middle portion of the sheath is disposed over the scaffolding and the end portions of the sheath extend beyond the ends of the scaffolding over end portions of the balloon; pressurizing the balloon to cause the end portions of the balloon to inflate beyond the outer diameter of the crimped scaffolding; and depressurizing the balloon.

Further embodiments of the present invention include a method of making a stent delivery system, comprising the steps of: providing a polymeric scaffolding; crimping the scaffolding to a final crimped diameter over a balloon to form a crimped stent-balloon assembly, wherein the crimping includes at least one crimping step in which the scaffolding is crimped to a first diameter greater than the final diameter and holding the scaffolding at the first diameter while the balloon is inflated to a pressure against the scaffolding; providing a tubular sheath comprising a central portion; disposing the polymeric stent and balloon within the tubular sheath, wherein the central portion prevents expansion of the stent when the balloon is pressurized; pressurizing the balloon to cause end portions of the balloon proximal and distal to ends of the stent to expand; and depressurizing the balloon.

Additional embodiments of the present invention include a stent delivery system, comprising: a tubular sheath comprising a middle portion and two end portions; a polymeric scaffolding crimped tightly over a delivery balloon, wherein the polymeric scaffolding and balloon are disposed within the tubular sheath; wherein the middle portion of the sheath has an inside diameter equal to or 1-2% larger than the outer diameter of the crimped scaffolding and the end portions of the sheath have a diameter greater than the diameter of the crimped scaffolding; wherein the middle portion of the sheath is disposed over the scaffolding and the end portions of the sheath extend beyond the ends of the scaffolding over end portions of the balloon.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference, and as if each said individual publication or patent application was fully set forth, including any figures, herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a process for fabricating a scaffolding of a polymer stent and crimping the fabricated stent to a balloon according to the invention. FIG. 2 depicts an axial cross-section of a flared restraining sheath.

FIG. 3 depicts an exemplary restraining sheath with a step-change in diameter between a middle portion and end portions.

FIG. 4 illustrates a method of expanding balloon ends of a crimped stent-balloon assembly using the restraining sheath of FIG. 2.

FIG. 5 depicts an expanded view of the proximal end of a restraining sheath disposed over a stent-balloon assembly of FIG. 4.

FIG. 6 depicts the expanded view of FIG. 5 after the balloon is depressurized.

FIG. 7 depicts and exemplary stent pattern 700 from US 2008/0275537.



Download full PDF for full patent description/claims.

Advertise on FreshPatents.com - Rates & Info


You can also Monitor Keywords and Search for tracking patents relating to this Method of increasing stent retention of bioabsorbable scaffolding with a sheath patent application.
###
monitor keywords



Keyword Monitor How KEYWORD MONITOR works... a FREE service from FreshPatents
1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored.
3. Each week you receive an email with patent applications related to your keywords.  
Start now! - Receive info on patent apps like Method of increasing stent retention of bioabsorbable scaffolding with a sheath or other areas of interest.
###


Previous Patent Application:
Introducer with ratchet handle drive
Next Patent Application:
Pre-positioned anastomosis device and related methods of use
Industry Class:
Prosthesis (i.e., artificial body members), parts thereof, or aids and accessories therefor
Thank you for viewing the Method of increasing stent retention of bioabsorbable scaffolding with a sheath patent info.
- - - Apple patents, Boeing patents, Google patents, IBM patents, Jabil patents, Coca Cola patents, Motorola patents

Results in 0.62864 seconds


Other interesting Freshpatents.com categories:
Amazon , Microsoft , IBM , Boeing Facebook -g2-0.1953
     SHARE
  
           

FreshNews promo


stats Patent Info
Application #
US 20120290063 A1
Publish Date
11/15/2012
Document #
13103882
File Date
05/09/2011
USPTO Class
623/111
Other USPTO Classes
29515
International Class
/
Drawings
8


Scaffolding


Follow us on Twitter
twitter icon@FreshPatents