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WASHINGTON -- A slew of second-generation, sirolimus-eluting bioresorbable vascular scaffolds are emerging as researchers apply the lessons learned from Absorb, their first-in-human studies show.

Changes in device design were implemented in four new scaffolds, for which investigators all reported positive data at the annual meeting here. Thinner struts, shorter resorption profiles, and the avoidance of small diameter lesions appeared to be a common goal across the board.

"The race is on," said , of The Christ Hospital in Cincinnati. "It's nice to see the competition build."

FANTOM II

The Fantom bioresorbable vascular scaffold -- featuring complete visibility under X-ray, single-step continuous inflation, and no need for refrigeration or special handling -- was associated with promisingly low event rates, according to the FANTOM II trial results.

The rate of acute procedural success was 99.1% among patients implanted with the device (n=240), according to , of Institute Dante Pazzanese de Cardiologia in Sao Paulo, Brazil. The 125-µm strut Fantom was associated with 98.1% strut coverage.

By the half-year mark, late lumen loss was low, at 0.25 mm on average. By that point, major adverse cardiovascular events were found in 2.1% of patients. Abizaid reported rates of the individual components of that endpoint:

• Target vessel MI, 1.3%
• Clinically-driven target lesion revascularization, 0.8%
• Cardiac death, 0.4%

"Most everything we can learn from this study is from the angiography and optical coherence tomography [OCT] and it's quite impressive," said panelist , of Saint Luke's Mid America Heart Institute in Kansas City, Mo., during a press conference.

"I was concerned that they wouldn't get good angiographic data with such a thin strut. The late loss is ... not as low as Xience but it is in the range that should inhibit restenosis. The big question is long-term safety and whether it provides an advantage," he suggested.

MeRes-1

Another sirolimus-eluting bioresorbable vascular scaffold, the MeRes100, was also linked with good outcomes in early data from the MeRes-1 trial.

The MeRes100 features a 100 µm strut and paired platinum markers at either end of the scaffold for improved visibility.

Boasting strut coverage at 99.3%, the device was subsequently linked to no adverse events at 6 months -- although there was a non-cardiac death from anaphylactic shock induced by aminophylline (0.9%) not related to the device, reported , of Fortis Escorts Heart Institute in New Delhi, India.

Patients got the device at 16 sites in India (n=108). Late lumen loss measured an average of 0.15 mm over 6 months.

A randomized pivotal trial against a second-generation metallic everolimus-eluting stent is planned, Seth commented.

"We used to say 'bigger is better' -- well, I think thinner is better. This should bode well not only for early but late outcomes," said Kereiakes, speaking on the discussion panel at the press conference.

FORTITUDE

Meanwhile, the first-generation Amaranth bioresorbable vascular scaffold, with the same 150-µm strut thickness as Absorb, was associated with acceptable outcomes at 9 months.

Amaranth uses an ultra-high molecular weight poly-L-lactide polymer (PLLA) to elute sirolimus, as described by , of Milan's San Raffaele Scientific Institute, in the FORTITUDE study.

The 63 patients enrolled at multiple sites across Italy and Colombia got intravascular ultrasound (IVUS) imaging to guide scaffold implantation.

Colombo reported procedural success to be 96.8% and strut coverage 96%. Periprocedural target-vessel MI -- at 3.2% -- accounted for all in-hospital events observed.

By 9 months, late lumen loss reached 0.27 mm on average. In addition, there was an overall adverse event rate of 4.9%, which included:

• Death in 1.6%
• Target-vessel MI in 3.3%
• Ischemia-driven target lesion revascularization in 1.6%

"Due to the unique polymer features, these future-generation scaffolds have the potential to match the biological performance of current metallic drug-eluting stents," Colombo suggested.

But can these event rates be reduced even further?

A second-generation version of Amaranth comes in 115 µm and sub-100 µm sizes and is under investigation in the RENAISANCE II and III studies.

FUTURE-I

Developed in China, the Firesorb scaffold was another sirolimus-eluting scaffold that showed promising outcomes at 6 months, according to the FUTURE-I study.

The Firesorb features a strut thickness measuring 100 or 125 µm as well as low drug dosage and is balloon expandable.

The single-center analysis of 45 patients found 98.5% of struts covered on average. At 30 days, there were no deaths, 2.2% incidence of MI, and 2.2% incidence of repeat revascularization. There were no additional adverse events observed by 6 months, , of Fu Wai Hospital in Beijing, told the audience at TCT.

"The 6-month clinical, angiographic, IVUS, and OCT results of the FUTURE-I first-in-man study demonstrated the feasibility, preliminary safety and efficacy of the thin-strut PLLA-based sirolimus-eluting Firesorb bioresorbable scaffold in the treatment of patients with single de novo coronary lesions," Xu concluded, adding that the Firesorb will be studied in a randomized controlled trial, FUTURE-II.