Bioresorbable scaffolds (BRS) might be working their back into the hands of cardiologists with the latest positive signals from a first-in-human study of a new sirolimus-eluting BRS.

The poly-l-lactic acid (PLLA) device has a strut thickness of 115 μm – smaller than the 150 μm of the ABSORB BRS which was used and then recalled in Australia – and a similar degradation time of about two years.

The prospective non-randomised RENASCENT II study of the APTITUDE device in 60 patients in Italy and Colombia showed clinical device success in all but one patient (98.3%).

There were no major cardiovascular events in hospital or up to 30 days post-op.

At nine months, target vessel failure was 3.4% and there was no target lesion revascularisation (TLR). Additionally, no ischaemia-related TLR or scaffold thrombosis was reported in up to two years of follow-up.

There were two cases of asymptomatic binary stenosis at the two-year follow-up but no intervention was required.

Less than half (43.6%) of patients remained on dual antiplatelet therapy at two years.

The investigators said the device showed a good safety performance with the low angiographic in-scaffold late lumen loss (0.35 mm at 9 months and 0.37 mm at 24 months).

“Furthermore, OCT [optical coherence tomography] analysis showed high strut apposition and coverage rates at nine months.”

“The 24-month clinical experience with the PLLA APTITUDE BRS has demonstrated that the polymer is safe and effective in improving coronary luminal diameter in patients undergoing elective PCI.”

An accompanying editorial in the journal Eurointervention highlighted the 0% rate of target lesion revascularisation, TVF and scaffold thrombosis at two years.

“When compared to two-year ABSORB II data, the RENASCENT II data demonstrate numerically superior rates of TVF and scaffold thrombosis. This is despite both scaffolds showing similar resorption periods, with greater than 85% scaffold degradation at 18 months and complete resorption at 24 months.”

The editorial also said optimal implant strategy has emerged.

“The 60 patients enrolled in the RENASCENT II study underwent a rigorous implantation technique with proper image-guided vessel sizing, mandatory lesion preparation, post-deployment imaging, and high post-dilatation rates.”

“These steps, absent in early ABSORB trials because of concerns about scaffold fracture, demonstrated improved outcomes up to three years and have become the standard technique for BRS technologies.”

It suggested the study was helping with the “road back to trust in BRS technology” although well-powered RCTs were required.

An Australian perspective

Interventional cardiologist Dr Nigel Jepson told the limbic it was an exciting study and the signal for the technology was good.

“Up until about 2018 there was something like 10 to 20 devices that were either in pre-clinical or clinical, and about three or four had a CE mark in Europe.”

“So the interventional world was very excited about it … and then reality struck that in routine clinical use the results were becoming clearer that they weren’t as good as metallic stents at one year, certainly at two years and three years. So the world lost confidence in the technology … I thought it was a massive shame,” he said.

He agreed with the editorial that patient and lesion selection were critical when using BRS.

“It comes back to who your patient is. Obviously a younger patient is going to be able to benefit after complete degradation of the scaffolding, having no permanent metal in their artery for the future.”

“The metallic stent failure rate is 0.4-0.6% per year. If you’re 80, so what? If you’re 40, that’s a lot of years for that risk of stent thrombosis to accumulate – over decades.”

Dr Jepson said he was optimistic that BRS will make a reappearance.

“I think a lot of people see it as the future. We think the devices should replace metallic stents but we can’t use them unless we have new iterations, thinner struts, and an evidence base.”

“One of the issues going forward is ultra high molecular weight polylactic acid gives it more radial strength and with a thinner stent strut but they seem to still be talking about degradation times of 24 months.”

“We know the ABSORB device still had some fragments there at three years so that is one of the big challenges to absorbable technology – to have degradation earlier because theoretically while the device hasn’t completely gone, you probably do need dual antiplatelet therapy.”