Boston Scientific's "blockbuster" Synergy stent for opening blocked arteries on the heart commands a higher price than its competitors, but so far the jury is out on whether it can prevent long-term problems seen in lower-priced models.

Company executives are confident that their Minnesota-designed Synergy drug-eluting stent, which is coated on the outside with a one-of-a-kind biodegradable polymer, will eventually show its value as the years progress for thousands of patients in an ongoing clinical trial. The material is absorbed by the body, theoretically cutting health problems linked to coatings that linger for years on stents like Medtronic's Resolute Integrity.

But when the one-year data from the ongoing trial were unveiled this week, it was Medtronic that touted the results.

"At one year, patients with coronary artery disease who were treated with a biodegradable polymer stent showed no clinical benefits over patients treated with Resolute Integrity," Medtronic said in the release, calling the results of the ongoing Bio-Resort trial "highly anticipated."

Coronary stents are metal mesh tubes inserted in arteries to improve blood flow and prevent chest pain and heart attacks. Modern stents are coated with special drugs to promote vessel healing, but studies have suggested the long-lasting polymer coatings that slowly release the drugs may actually inflame the tissues in the long term and delay arterial healing. Degradable and absorbable polymers are supposed to eliminate those long-term problems.

Bio-Resort is following about 3,500 patients in the Netherlands who were randomized in equal proportions to either Boston Scientific's Synergy stent, Medtronic's Resolute Integrity or Biotronik's Orsiro stent. The Boston Scientific absorbable-coating device received Food and Drug Administration approval in 2015, while Medtronic's durable-coating stent received approval in 2013. Biotronik's biodegradable polymer device is expected to receive U.S. sales approval in 2018.

The "head-to-head" trial design is somewhat uncommon for medical device companies, in that different manufacturers are paying independent researchers to randomize patients to one of three drug-eluting stents and then gathering data on them for years. For medical devices, it's more common to see clinical trials comparing new devices against drugs, surgery, or a company's own offerings.

The study that led to earlier-than-expected U.S. approval for Boston Scientific's Synergy stent compared patients who received the Synergy to those randomized to the company's older device, the Promus Element Plus. That study found that Synergy was "non-inferior" to the older stent in a medically complex population of patients.

Weeks after Synergy's approval, Boston Scientific CEO Mike Mahoney told investors in an earnings call that the company intended to seek an increase over traditional stent prices, based on Synergy's performance, including what he called "best-in-class" low rates of the artery becoming re-blocked after implant. He declined to comment on an analyst's suggestion that the market could absorb a 10 percent price increase premium.

"I think it is important to note that this is a premium product, but ... this is a product that we will need to go through a contracting process with hospitals, given our pricing strategy," Mahoney said.

Last month, Mahoney called Synergy a "blockbuster device" in the company's interventional cardiology division, which had revenue of $568 million in the three months ended Sept. 30, representing 13 percent growth. Sales of drug-eluting stents like Synergy grew 14 percent during the quarter, and Synergy is expected to comprise at least half the company's drug-eluting stent revenue by 2016's end.

One key reason to run a head-to-head clinical trial is to prove an increase in price is justified. As Medtronic pointed out this week, the statistically significant evidence so far only shows that Synergy is no worse than a stent coated with a durable polymer.

Mark Johnson, the U.S. program director for vascular interventions at Biotronik, said one-year results may not allow enough time to see the differences, because Biotronik's polymer degrades over 18 months.

"Biotronik would expect an improvement in our product over Medtronic, or any of the other permanent polymer stents, but not until the polymer is degraded," Johnson said. "So a non-inferiority result at 12 months is what the study designers sought to accomplish, and they did. And Biotronik is very pleased with those results."

The polymer on Boston Scientific's device is designed to disappear from the device within roughly three months. Still, Boston Scientific stands behind its stent, and it will closely watch the long-term comparison to Medtronic's durable-polymer stent.

"We believe the outstanding safety and healing of the Synergy bioabsorbable polymer stent in numerous trials demonstrates an advancement in stent technology and we look forward to the longer-term data which continue to show the impact of the long-term polymer exposure," Dr. Craig Thompson, chief medical office of Boston Scientific's interventional cardiology division, said in an e-mail.

Joe Carlson • 612-673-4779