The cardiovascular device market is growing, with research forecasting that the cardiac implant medical device market alone will exceed $27 billion by the year 2017, according to the May 2013 Renub Research study “Global Cardiac Implant Devices Market Forecast, Clinical Trials, M&A”. There is tremendous opportunity in this industry, but with it comes intensifying pressure on device OEMs to innovate on the traditional implant model. As a result, engineers are increasingly required to explore new and different solutions to achieve in vivo drug delivery, implant success, fewer revisions, and improved patient outcomes.
Biomaterials for Cardiovascular Applications
As device OEMs look to the next phase of performance, fibers have the capability to deliver the same level of stability as traditional metals and ceramics with the more biomimetic form of natural materials. From traditional textile fibers such as nylon, polyethylene terephthalate (PET), and polyether ketone (PEEK) to breakthrough composites, biomaterials are evolving and have the potential to revolutionize medical device capabilities.
To aid in both support and repair, as well as in the regrowth of natural cells within the body for recovery from conditions affecting the heart and circulatory system, high-density, non-stretch biomaterials have become increasingly important to device design.
There are a multitude of cardiovascular applications that can be well supported by these knitted and woven fabrics, as well as by non-woven felt scaffolds. Examples of applications include: cardiovascular grafts; heart valve repair; annuloplasty rings; containment devices; tethers; pledgets (absorbent pads); hemostasis applications; vascular repair/replacement conduits; correcting and/or creating occlusions; stent support products; as well as a multitude of combination products.
Textile Engineering for Clinical Precision
Specialized textile engineering techniques enable device developers to capitalize on the unique properties of different materials. Processes such as braiding, weaving, knitting, and needle-punching non-wovens help magnify strength, texture, flexibility, and many other performance characteristics for customized device requirements. (See Figure 1) For engineers, the possibilities for improved mechanical performance, anatomic accuracy, and subsequent clinical benefit are limitless.
Braiding is one of the most commonly used processing techniques for creating fabric-based implants. Braided structures are easily customizable, which means tubes, flat braids, and other geometries with very specific dimensions are possible. The braiding process can produce structures with great strength in a small surface area. Thanks to their strength, ability to expand and compress, and the possibility to customize other performance capabilities, braided materials are ideal for many applications.
For cardiovascular applications, such as sewing threads for aortic repair grafts, strength requirements are usually more precise. Small diameter braids are particularly useful for these kinds of applications, because they can be created in a very thin form factor without sacrificing strength. A secure stitch is critical to graft success, which means braids must meet very precise specifications to deliver the necessary performance.
Using Non-Wovens in Regenerative Medicine
The potential for regenerative medicine in cardiovascular device applications has grown exponentially. Replacing cartilage with synthetic materials has been of interest—and practice—for decades, but OEMs are now recognizing the benefits of not only building artificial implants, but also using materials that enable the regrowth of damaged tissue and help the body heal itself. Absorbable fibers, such as polyglycolide (PGA), poly(L-lactic acid) (PLLA), polydioxanone (PDO), and other copolymers, help to aid in repair and regrowth of native tissue before they are absorbed by the body and completely replaced with natural cells. For absorbable applications in particular, correctly selecting the most effective polymer is critical to device performance.
Developers must be able to engineer degradation profile and total lifespan alongside characteristics like strength, abrasion resistance, elongation, and pore size to ensure the successful growth of new tissue with the correct mechanical properties.
To deliver the high degree of performance required for cardiovascular in vivo applications (as well as applications in many other areas of the body), nonwoven absorbable scaffold that combines the benefits of traditional 3D non-woven scaffold technology with advanced manufacturing techniques is an ideal choice. Composed of a variety of synthetic, absorbable polymer fibers, the 3D structure provides a fibrous platform with high surface area and superior void volume to promote natural tissue in-growth and cellular regeneration at the site of surgery or damage. These customized fabrics can be shaped in a variety of geometries, including flat felts, tubes, cuffs, cones, and more. Because they are most commonly composed of absorbable biomaterials that enable regrowth of natural cells, non-woven structures such as tubular conduits are well-suited for vascular replacement technologies and heart valve repair. (See Figure 2)
To successfully deliver a device that performs as intended in the body, consideration of lifespan is essential. Tissue regeneration of a heart valve, for example, will require support for cell regrowth for a specific duration of time in order to ensure optimal healing and the recovery of as natural a function as possible. Wound treatments, on the contrary, must disintegrate more quickly to keep from hindering the growth of new cells on a particular surface. Degradation profiles can range from days to more than a year depending on the polymer type, so engineering to deliver to device specifications is critical for performance.
Non-wovens can be precisely engineered to maintain material integrity for the required life of the device. These have seen their greatest use in tissue engineering applications as absorbable scaffolds, but these kinds of textiles are increasingly being incorporated into cardiovascular devices using fibrous components, such as suture fasteners, pledgets, and a variety of reconstruction procedures throughout the body.