Bioresorbable scaffold for treatment of bifurcation lesion

Abstract

Bioresorbable scaffolds for treatment of bifurcation lesion are described herein. Generally, an expandable scaffold may be fabricated from a high molecular weight isotropic PLLA material, wherein the scaffold incorporates one or more strain relief features which are configured to allow side branch treatment.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of U.S. patent application Ser. No. 14 / 334,562 filed Jul. 17, 2014, which claims the benefit of priority to U.S. Prov. App. 61 / 866,859 filed Aug. 16, 2013, each of which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention relates generally to stent or scaffold delivery and deployment methods and apparatus. More particularly, the present invention relates to methods and apparatus for bioresorbable scaffolds which may be used for the treatment of bifurcation lesions.BACKGROUND OF THE INVENTION[0003]In treating diseased vessels, particularly blood vessels which have one or more side branches extending from a main vessel, difficulties may arise when implanting stents at these junctions to treat lesions. For instance, when implanting a stent along the main vessel, the openings to the side branches may become restricted by the stent walls. Although open cells a...

AI Technical Summary

Benefits of technology

[0011]An example of such a casting process is to utilize a dip-coating process. The utilization of dip-coating to create a polymeric substrate having such desirable characteristics results in substrates which are able to retain the inherent properties of the starting materials. This in turn results in substrates having a relatively high radial strength which is retained through any additional manufacturing processes for implantation. Additionally, dip-coating the polymeric substrate also allows for the creation of substrates having multiple layers.

[0014]Parameters such as the number of times the mandrel is immersed, the sequence and direction of dipping, the duration of time of each immersion within the solution, as well as the delay time between each immersion or the drying or curing time between dips and dipping and / or withdrawal rates of the mandrel to and / or from the solution may each be controlled to result in the desired mechanical characteristics. Formation via the dip-coating process may result in a polymeric substrate having half the wall thickness while retaining an increased level of strength in the substrate as compared to an extruded polymeric structure.

[0016]Dip-coating can be used to impart an orientation between layers (e.g., linear orientation by dipping; radial orientation by spinning the mandrel; etc.) to further enhance the mechanical properties of the formed substrate. As radial strength is a desirable attribute of stent design, post-processing of the forged substrate may be accomplished to impart such attributes. Typically, polymeric stents suffer from having relatively thick walls to compensate for the lack of radial strength, and this in turn reduces flexibility, impedes navigation, and reduces arterial luminal area immediately post implantation. Post-processing may also help to prevent material creep and recoil (creep is a time-dependent permanent deformation that occurs to a specimen under stress, typically under elevated temperatures) which are problems typically associated with polymeric stents.

[0018]Yet another method may apply the expansion force by application of a pressurized inert gas such as nitrogen within the substrate lumen. A completed substrate may be placed inside a molding tube which has an inner diameter that is larger than the cast cylinder. A distal end or distal portion of the cast cylinder may be clamped or otherwise closed and a pressure source may be coupled to a proximal end of the cast cylinder. The entire assembly may be positioned over a nozzle which applies heat to either the length of the cast cylinder or to a portion of cast cylinder. The increase in diameter of the cast cylinder may thus realign the molecular orientation of the cast cylinder to increase its radial strength. After the diameter has been increased, the cast cylinder may be cooled.

[0019]Once the processing has been completed on the polymeric substrate, the substrate may be further formed or machined to create a variety of device. One example includes stents created from the cast cylinder by cutting along a length of the cylinder to create a rolled stent for delivery and deployment within the patient vasculature. Another example includes machining a number of portions to create a lattice or scaffold structure which facilitates the compression and expansion of the stent.

Problems solved by technology

However, the stent that has been placed in the main vessel may obstruct part of the opening to the side branch and cause flow reduction or other negative effects.

However, enlarging the open cells of an already expanded stent may form or create cracks in the stent struts leading to failure for metallic stents and particularly for bioresorbable polymeric stents.

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