First bioabsorbable stent performs well with 6-month follow-up

Reportedly the "first human" study of a new bioabsorbable stent reveals no stent thrombosis at 6 months of follow-up and a low rate of major adverse cardiac events (MACE), reported Patrick Serruys, MD, PhD, pictured right, at the 2007 American College of Cardiology annual scientific session.

Late stent thrombosis has been the Achilles’ heel of drug-eluting stents (DES), and has tempered the initial enthusiasm that greeted them. A lack of re-endothelialization, impairing healing of the artery, has been blamed for the enhanced stent thrombosis risk with DES. A fully absorbable stent has been designed that is slowly metabolized by the artery, leaving a healed natural coronary artery behind.

Dr. Serruys presented results from the first 30 patients to receive the bioabsorbable stent. The stent is coated with a polymer made of polylactic acid that controls release of the antiproliferative drug it contains (everolimus). In animal studies, dissolution time has been 12 to 18 months. "We can’t compare the dissolution of the stent in humans with animals," said Dr. Serruys, professor of interventional cardiology, Interuniversity Cardiological Institute of The Netherlands and the Erasmus University. "The vessel wall of a patient with atherosclerosis is more complex."

The first 30 patients in whom the bioabsorbable stent was deployed had single de novo stenoses averaging 8.66 mm in length. At 30 days, procedural success was 100%, without stent thrombosis and a 0% incidence of MACE.

Six-month angiographic follow-up showed that the stent "retracted" by approximately 15% "but inhibition of tissue within the stent was equal to or better than that with metal stents," he said. It is not yet clear whether this reduction in stent area is related to stent absorption or the structural design of the stent. An updated design that offers a more homogenous distribution of the stent’s struts may offer better resistance to compression, he said.

At 6 months, there was a loss of 0.44 mm in the lumen area where the stent was deployed. This late loss compares favorably with that of bare metal stents (BMS) and other DES, he said. Restenosis at 6 months was 11.5% and only one patient had a cardiac event (a non-Q-wave myocardial infarction [MI]).

In a separate registry comparing DES with BMS in 12,395 stent recipients in Denmark, rates of stent thrombosis were similarly low between the two types of stents at 15 months (2.2% with BMS vs. 1.9% with DES), reported Michael Maeng, MD, right, from Aarhus University Hospital, Skejby, Denmark. The rates of MI were also similar between the two groups at 15 months-3.0% with BMS vs. 3.2% with DES.

All patients were treated with aspirin and clopidogrel for 12 months after stent implantation. Dr. Maeng noted that there was a small but statistically significant increase in the risk of stent thrombosis and MI between 12 and 15 months in the DES group, and that this increase in events with DES was probably unrelated to stopping clopidogrel at 12 months.

Patients in this registry will be followed for 2 years, and the results of this follow-up will be available later this year, Dr. Maeng said.