Room for Improvement in Cardiac Stent Development

Cardiac stents have evolved tremendously since their birth in the late 1970s, having saved and improved the lives of countless heart attack and stroke patients. These devices also help boost kidney function, enhance lower-limb blood flow, and mitigate necessary leg amputations from gangrene.
 
Despite their many benefits, however, stents nonetheless maintain a major Achilles Heel: restenosis—i.e., recurring arterial narrowing after corrective surgery. The problem has improved significantly over the last several decades but still affects 5-7 percent of peripheral artery disease convalescents.
 
Technology is largely responsible for the drop in restenosis rates thanks to advancements in bare metal and drug-eluting stents (DES). The latter devices were developed to overcome the limitations of their metal predecessors, namely neointimal hyperplasia, repeat revascularization, and late stent thrombosis. The latest DES are designed to produce solid long-term clinical results and minimize both restenosis and stent thrombosis rates.
 
MPO’s March feature story “Free Flow” provides an in-depth look at the latest cardiac stent technologies and the future prospects for this burgeoning market. Tim Girton, vice president of Interventional Cardiology research and development at Boston Scientific Corp., was among the experts interviewed for the feature; his full input is provided in the following Q&A.

Michael Barbella: What trends are impacting the cardiac stent market? What factor(s) are driving these trends?
Tim Girton: Hospitals are increasingly focused on value-based care and quality initiatives. These pressures are passed through to stent manufacturers with expectations that our devices improve outcomes, reduce costs, and improve the patient experience. While product innovation in the past was largely focused on stent design and drug-elution technology, today’s focus is on smaller niches within the market such as reducing DAPT duration, dedicated large or small vessel solutions, and a commitment to treating more complex disease states.

Barbella: What factors are currently driving growth in the cardiac stent market? How have these growth factors evolved over the past five years?
Girton: Over the past five years, the coronary drug-eluting stent market has transitioned to a relatively mature market. Current procedural volume growth is modest and largely due to an aging population combined with improved stents and delivery systems allowing the treatment of more complex patients.

Barbella: What specific area(s) are experiencing the most growth (bare metal, drug-eluting, bioresorbable scaffolds)? Why are these area(s) flourishing as opposed to other sectors?
Girton: In the U.S. market, drug-eluting stents are experiencing the most procedural volume growth. Current generation drug-eluting stents are incredibly effective and have an excellent safety profile. Bare metal stents are seldom used, and are often saved for use only in high bleeding risk and elderly patients due to concerns of bleeding from tual anti-platelet therapy after DES implantation. However, recent clinical evidence from the newest biodegradable polymer-coated stents suggests that BMS no longer have a role even in that patient subset. Finally, bioresorbable scaffolds, while once promising, have been pulled from the market amid overwhelming concerns over early and late outcomes. The newest biodegradable polymer-coated stents offer such outstanding clinica outcomes that it is hard to ever see a fully biodegradable stent being as effective and safe. The interest in bioresorbable scaffolds remains, there will be significant innovation and investment required to overcome the challenges and develop a bioresorbable scaffold with no compromises. That investment would be better served to solve clinical needs that are more critical (cancer solutions, heart failure solutions).

Barbella: What challenges are involved in developing cardiac stents? How has Boston Scientific overcome these challenges?
Girton: I think many take for granded the level of technology and know-how required to develop a truly world-class stent. Cardiac stents are an incredible combination of advanced material science (for example, the Synergy stent uses a metal alloy developed in-house specifically for stents), novel pharmaceutical sciences (a whole new drug and polymer combination that consistently releases a known quantity of drug over an extended period of time into the vessel), and process science (each stent strut is laser cut to within amazing tolerances, and coated with unique processes that enable exact amounts of a drug to be placed on the outside surface of the stent repeatably). In addition, these stents are devices that undergo a combination of both pharmaceutical scrutiny and permanent implant scrutiny by worldwide regulatory agencies, usually resulting in almost decade-long development cycles, with hundreds of millions of dollars in development costs, an culminating in lengthy and expensive clinical studies to prove their safety and efficacy. Our history in stents and DES has allowed us to build upon each iteration of our devices, and also our commitment to the space has enabled us to maintain key and unique competencies and talent that is best in the industry. At the end of the day, it is this history and talent base that allows us to constantly improve our DES.

Barbella: What new stent technologies are up and coming/on the horizon? What new stent technologies can we expect to see in the next several years?
Girton: The future of stent design for us involves identifying and designing for situations where stenting outcomes are still less-than-optimal. In other words, which anatomical variables or situations pose the greatest challenge to efficacy and/or safety. While, on average, today’s stents perform exceptionally well, there are some challenges inherent in stenting small vessels, bifurcation lesions, calcified lesions, etc. All of today’s stents are designed as what I would call general use stents, not special-purpose stents. Better stents can be made when the engineers have a more specific problem to design for.

Barbella: Please discuss the future growth prospects of the cardiac stent market. What trends and/or challenges could potentially affect future gains?
Girton: Currently there is an overwhelming amount of positive data on DES in general such that stenting has become the standard of care for interventional cardiologists. In mature markets we do not anticipate significant growth in volume, however, in many parts of the world, there is still room for procedural growth. We are always on the lookout for potentially disruptive technologies that would dramatically alter today’s practice, but as of yet we don’t see any that can offer the safety, cost, and efficacy of a well-performed stenting procedure.