Patients who received Abbott Laboratories' novel dissolving vascular stent had a significantly higher rate of serious adverse heart events than those treated with the company's widely used Xience drug-coated metal stent two years after implantation, according to data presented on Saturday.
New guidelines for blood vessel size and proper implantation techniques put in place for the new Absorb stent since the study began, however, should lead to better results, researchers said.
They reported that 19 percent of those who received Absorb in the 2,008-patient trial had it implanted in blood vessels now deemed too small for the device, hurting overall results.
"The difference between Absorb and Xience when they're both implanted in properly-sized vessels with good procedural technique is likely to be quite modest and possibly not clinically important," said Dr. Stephen Ellis, director of interventional cardiology at Cleveland Clinic, who presented the data at the American College of Cardiology scientific meeting in Washington.
Stents are tiny tubes used to prop open diseased arteries cleared of blockages. The two stents demonstrated similar safety between one and two years, but a difference turned up by the end of year two.
Absorb, which is larger than traditional metal stents, is made of a plastic designed to fully dissolve over the course of about three years, leaving a naturally flexible blood vessel.
After two years, 10.9 percent of Absorb patients had experienced target lesion failure, versus 7.9 percent for Xience, a statistically significant difference.
TLF combines heart-related death, heart attack related to the treated vessel and need for repeat procedure due to reclogging of the treated part of the artery. The TLF finding was driven by a higher rate of heart attacks - 7.3 percent for Absorb versus 4.9 percent for Xience.
The difference between the two stents declined and was no longer statistically significant when the smaller-vessel patients were excluded, researchers reported.
The U.S. Food and Drug Administration said it was informing healthcare providers of the increased rate of major adverse cardiac events observed in patients receiving Absorb in the study. The agency said it will continue to monitor Absorb's performance in clinical studies and reports submitted to it.
Absorb won U.S. approval last July, but longer-term data is needed to assess its true value.
All of the benefit of using the larger, more-difficult-to- place stent, "if there is going to be a benefit, will come after it has been fully absorbed," said Ellis.
"We await long-term outcomes," he added. "If this device doesn't produce better long-term outcomes, there's no point in using it."