Debaters Question Need for Further Stent Innovation

A timely debate at TCT 2015 revolved around the notion of whether interventional cardiology has reached a point where the resources needed to further improve stents and develop durable polymers could be better spent elsewhere. Most panelists, who cited a number of unresolved issues, favored continued efforts at innovation.

Room for improvement

Issues with current stents underscore the need for further advances, according to Elazer R. Edelman, MD, PhD, of Brigham and Women’s Hospital, Boston, Mass. Since the development of the first BMS, evolution of design and materials has continued, resulting in reductions in intimal hyperplasia, flow disturbances and stent thrombosis, he said. However, there is more than can be done to improve outcomes, he argued. “We still don’t know what the [best] physical properties are, and we still have a problem with devices that fracture, are thrombogenic and generate particulate material.”

One area where improvement is particularly necessary is drug delivery, Edelman noted. In current DES design, the drug pools around the struts when it is released; efforts should be made to enhance drug distribution, he argued. Other unresolved problems involve coating integrity, vascular compatibility, and the way in which drug release and coating resorption mesh. “We’re now at a point where there is a good reason to innovate — we can innovate, we can show improvement and we can show benefit,” Edelman observed.

Plateau has been reached

Alternatively Lisette Okkels Jensen, MD, DMSci, PhD, of Odense University Hospital in Denmark, argued that the results of current stents are so good that a therapeutic plateau has been reached. In both the BIOSCIENCE and CENTURY II trials, for example, stents with biodegradable polymer provided results similar to those with stents with durable polymer, she said.

Furthermore, the series of trials included in the Danish SORT OUT program, which compared several second- and third-generation DES in all-comers populations, showed low event rates across stent types over the short and long term, with follow-up lasting up to 5 years.

Thus, Jensen concluded, current metallic platforms, delivery systems and durable polymers cannot be meaningfully improved. “However, it is important [to note] that the traditional 1-year primary endpoint may not predict the 5-year clinical outcome in patients treated with a DES,” she added. “Long-term follow-up is also needed to assess whether a third-generation DES with bioabsorbable polymer will perform better than second-generation DES and whether the bioabsorbable polymer is a class effect or if differences between the third-generation DES also exist.”

Support for further Innovation

During a panel discussion following the debate, Rafael Beyar, MD, DSc, of Rambam Medical Center, Haifa, Israel, said there is no question that stent design has a large impact on results. He argued that even though the field is 80% to 90% of the way toward an ideal device, further innovation should still be sought.

Panelist Lorenz Räber, MD, PhD, of University Hospital Bern in Switzerland, pointed out several clinical situations that have not been addressed by existing trials. For example, no studies have demonstrated that new-generation DES are superior to earlier-generation DES in diabetic patients. Additionally, in the setting of acute STEMI, thrombosis rates reaching 2% to 3% remain a major unresolved issue, he said. “There are many windows of opportunity where we can improve stent technology,” Räber concluded.

Disclosures:

• Edelman reports receiving grant/research support from Boston Scientific Corporation and Medtronic and consultant/honoraria fees from Atrium/Maquet and Micell.
• Jensen reports receiving honoraria from Abbott Vascular, AstraZeneca, Biotronik and St. Jude Medical and grant/research support from Biosensors International, Biotronik, St. Jude Medical and Terumo Corporation.
• Räber reports no relevant conflicts of interest.
• Beyar reports holding equity in Corindus.