New research published in the Journal of the American College of Cardiology: Cardiovascular Interventions provides insight into the modern world of bioresorbable stents, while trying to explain why they’ve failed more often than traditional drug-eluting counterparts.

Bioresorbable coronary scaffolds have been on the market for more than a year now, offering the option of non-permanent, non-metallic heart stents to patients suffering from cardiovascular disease. But, in comparison to those traditional metal stents, bioresorbable scaffolds (BRS) have seen a higher rate of target lesion failure in patients, resulting in clinical restenosis and further intervention.

Tommaso Gori, MD, PhD, and a team of researchers conducted a recent study in an attempt to identify incidence, characteristics and predictors of restenosis in heart patients fitted with BRS. While in-scaffold thrombosis has been heavily researched in the past, Gori and co-authors wrote in their study, scaffold restenosis hasn’t seen the same attention.

Researchers studied a total of 657 patients who’d been implanted with 883 BRS between May 2012 and January 2015. All patients were being treated for coronary artery stenosis, and 67 percent were identified as having acute coronary syndrome. The majority of patients were men. Around 20 percent were diabetics.

The subjects who were fitted with a BRS used a bioresorbable stent manufactured by Abbott Vascular. The Absorb BVS, which was pulled from the sales market by Abbott in mid-September, was the first dissolving stent of its kind available in the U.S., and it was approved by the FDA in July of 2016 to treat patients with coronary artery disease. The company announced Sept. 8 that distribution of the bioresorbable scaffold would halt due to low commercial sales.

Gori and his team followed up with their study subjects for an average of 1,076 days and found that 41 individuals experienced 49 cases of scaffold restenosis. In 73 percent of those cases, restenosis was presented as stable angina or incident finding, and more than half of the cases displayed complex angiographic patterns. Independent predictors of the restenosis included prior revascularization, diabetes, lesions and, most prominently, implantation technique. Both oversizing and undersizing of scaffolds, as well as residual stenosis, were linked to an increased risk of restenosis.

While the study’s authors found the three-year incidence of scaffold restenosis in BRS was similar to the same statistic in newer, metallic, drug-eluting stents, benign presentation and complex angiographic patterns seemed to be unique to BRS. Predictors of restenosis aligned between the two types of stents, as well.

The BRS was associated with more successful implantation technique, according to the research, which in turn resulted in less scaffold restenosis. Because BRS have a larger strut and larger abluminal surface area, the scaffolds exert lower pressure at the time of implantation, leading to less stress on blood vessels.

“Despite significant progress with drug-eluting technologies, in-stent restenosis remains one of the limiting factors for the success of coronary stent implantation, and an important challenge for new technologies,” the authors wrote. “The pathophysiology of this phenomenon is multifactorial and comprises patient-related factors (e.g., diabetes and a history of restenosis), procedure-related factors (number and size of stents used, stent overlap, percent residual stenosis), and lesion-related factors.”