Shelley Wood

May 21, 2013

PARIS, France — A new sirolimus-eluting stent boasting a biodegradable polymer and a thin-strut design that is 25% thinner than the market-leading, permanent-polymer stent has shown promising results at nine months, investigators reported here today.

The Orsiro stent (Biotronik) uses a cobalt-chromium platform coated with bioerodable poly-L-lactide acid (PLLA) embedded with sirolimus; the strut thickness is 60 µm, as compared with 81 µm for the permanent-polymer, everolimus-eluting Xience Prime stent (Abbott Laboratories), which served as the comparator in this study.

Presenting the BIOFLOW II results here at EuroPCR 2013 , Dr Stephan Windecker (Swiss Cardiovascular Center, Bern, Switzerland) stressed that the study was designed with an angiographic primary end point and that larger randomized controlled trials are needed to address clinical end points. Nevertheless, the clinical event rate was low and "comparable" between the new stent and the Xience Prime at nine months.

The trial enrolled 452 patients 2:1 to Orsiro or Xience Prime. At nine months, in-stent late lumen loss was nearly identical between stents: 0.10 mm for Orsiro and 0.11 mm for Xience Prime. Other angiographic end points were also very similar. Target lesion revascularization was just 2.1% and 2.7% for Orsiro and Xience Prime, respectively, while target lesion failure was 4.8% and 5.3%, with no statistical difference between the two.

Speaking with the media, Windecker pointed out that newer imaging modalities like optical coherence tomography (OCT) was still in its infancy when the first drug-eluting-stent (DES) trials were performed. Today, OCT, along with intravascular ultrasound (IVUS), offer an intriguing glimpse at the healing pattern and progression of strut coverage with next-generation stents like Orsiro. In BIOFLOW II, mean neointimal area was significantly lower with the newer stent at nine months, while the percentage of covered struts was 98.3% for Orsiro and 97.5% for Xience Prime (p=0.042). No stent thrombosis occurred in either stent group.

While only "hypothesis-generating," Windecker stressed, "one thing you could speculate on is that neointimal hyperplasia may be somewhat less with the Orsiro as compared with the Xience Prime," yet this does not translate into suboptimal strut coverage. The suggestion is that the thinner stent may foster a very thin but uniform stent coverage.

"Whether this difference does translate into any clinical difference is premature to say," he said. "What I can say is that a large-scale clinical trial of more than 2000 patients has just completed enrollment, and after two, three, or four years we will gain more insights."

Asked whether cardiologists have the appetite to read news stories about incremental advances in DES technology, Windecker acknowledged that the progress being made today is of a different order than the strides made when studies were comparing the first DES with bare metal stents 10 years ago.

But it is still important to continue to improve on outcomes with the stents available today, he stressed. "Although event rates are very low, we still have reocclusions and, particularly during longer-term follow-up, you still have repeat revascularizations."

There is also the diabetic population to consider, in whom restenosis remains a bigger problem. Finally, he pointed out, "PCI remains inferior to coronary bypass in complex patients, so without further improvement, even if there is newer technology, we wouldn't be able to address these more complex lesions [percutaneously]."

Asked during the afternoon hotline session what particular aspect of the stent was the likely driver of the promising OCT/IVUS findings, Windecker said that while the stent coating and thin strut design were both important, he believes the bioabsorbable polymer is likely the key.

Commenting on the trial results, Dr Ashok Seth (Fortis Escorts Heart Institute, Delhi, India) stressed the need for all-comers trials, of longer duration, before the new devices can be accepted as alternatives to approved DES. The problem, he added, will be actually showing a clinical advantage, given the excellent outcomes with modern-day stents.

Biotronik sponsored the study. Windecker disclosed receiving institutional grants/research support from Abbott, Biosensors, Biotronik, Boston Scientific, Cordis, Edwards Lifesciences, Medtronic, and St Jude. Seth has previously disclosed having no relevant conflicts.

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