Interventional cardiology

Bioresorbable scaffolds: not quite standing up to their promise

Lessons learned from previous trials of bioresorbable vascular scaffolds (BVS) appear to have resulted in patient outcomes comparable to those in patients receiving metallic drug-eluting stents (DES).

Excessive rates of adverse events driven by scaffold thrombosis have dogged previous studies of the BVS and led to the devices being taken off the market.

However the ABSORB IV study aimed to optimise patient selection to those with recent MI and typically soft, amenable lesions as well as avoiding use of the devices in small vessels.

The study, which randomised 2,604 patients with coronary artery disease and acute coronary syndromes from 147 hospitals across five countries, also incorporated refinements in technique such as routine high-pressure post-deployment scaffold dilatation.

It found 30-day and one-year outcomes including all-cause mortality, target vessel failure and recurrent angina were similar in both groups of patients. Ischaemia-driven revascularisation was increased with BVS at 30 days but not at one year.

There was also a signal towards more device thrombosis with BVS than DES at 30 days (p=0.0553) but not at one year (p=0.1586).

The researchers acknowledged that although they showed non-inferiority of the first generation BVS compared with the everolimus-eluting stent, event rates were lower than anticipated.

They said it was possible that in a larger study statistically significant increases in target lesion failure and device thrombosis with BVS might have emerged.

“Compliance with dual antiplatelet therapy through 1 year was high, and might have contributed to the present favourable results,” they also said.

Perth cardiologist Dr Matthew Erickson, a co-investigator of the study, told the limbic it was hard for the BVS to compete when the current generation of metallic stents were so good.

“You have to be much more selective about which patients you put the BVS in. It’s less forgiving than a metallic stent.”

“Even though stent thrombosis is uncommon, it was still twice as likely to occur with this dissolvable stent and the reason is probably because the stent strut thickness is about double that of a normal stent so it probably compromises the lumen a little bit more.”

“You also have to take longer to put the stent in and be very particular about it. Once you put the stent in you’ve got to re-balloon the artery to make sure you maximize the size. So it takes longer to put in and if people are trying to do things quickly and take short cuts, there is the risk there might be more complications with it.”

However he said the promise of next generation BVS, that were thinner and more expandable, was real.

“The benefit is that in a few years there is no stent struts there at all. It is totally dissolved so you don’t have to worry when someone needs to have an operation, you could be much more confident to say stop all your blood thinners.”

He said it was also not possible to put a bypass graft in patients with extensive stenting.

“So for young patients where they have lots of disease you can actually restructure their arteries so there is no narrowing, and in the future if they need bypass surgery, you can find a spot to put a bypass graft on.”

The ongoing study will follow-up patients next at three years.

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