New Stent Designed to Combat Stent Thrombosis

June 19, 2007
Wayne Kuznar

Internal Medicine World Report, June 2007, Volume 0, Issue 0

NEW ORLEANS—The first data on bioabsorbable stent in humans have shown no stents thrombosis and a low rate of major adverse cardiac events at 6 months, reported Patrick Serruys, MD, at the American College of Cardiology annual meeting.

Late stent thrombosis has plagued drug-eluting stents (DESs), tempering the enthusiasm with which they were initially greeted. A lack of reendothelialization, impairing healing of the artery, is the assumed culprit for the risk of thrombosis. To overcome this problem, a fully absorbable stent that contains the investigational antiproliferative drug everolimus (Abbott Vascular) has been designed. The stent material is slowly metabolized by the artery, leaving a healed, natural coronary artery behind.

Results from the first 30 patients with the bioabsorbable coronary stent implanted were presented by Dr Serruys, professor of interventional cardiology, Interuniversity Cardiological Institute of the Netherlands and Erasmus University.

The stent is coated with a polymer made of polylactic acid (which is commonly used in dissolvable sutures) that controls the release of everolimus. In animal studies, the stents have dissolved in 12 to 18 months. "We can't compare the dissolution of the stent in humans with animals," said Dr Serruys. "The vessel wall of a patient with atherosclerosis is more complex."

The bioabsorbable stent was successfully placed at the site of the lesion in 93.5% of cases.

The first series of patients to receive the bioabsorbable stent had single de novo stenoses. At 6 months of follow-up, a loss of 0.44 mm was evident in the lumen area in which the stent was deployed. This late loss compares favorably with that of bare-metal stents (BMSs) and other DESs, he said. The restenosis rate at 6 months was 11.5%, and only 1 patient had a cardiac event, a non-Q-wave myocardial infarction (MI).

The stent "retracted" by approximately 15%, "but inhibition of tissue within the stent was equal to or better than that with metal stents," Dr Serruys said. It is not yet clear whether this reduction in stent area is related to stent absorption or to the structural design of the stent. An updated design that offers a more homogeneous distribution of the stent's struts may offer better resistance to compression, he said.

Another potential stent design created to tackle the shortcomings of DESs binds circulating endothelial progenitor cells, which differentiate into a functional endothelial layer. The first real-world experience with such a stent was presented by Marcel A. M. Bejik, MD, of the department of cardiology at the University of Amsterdam, the Netherlands.

The hope is that the accelerated healing produced with such a stent would reduce in-stent thrombosis and prevent late stent thrombosis.

The stent was placed in 152 patients with 197 stenoses. Three of the patients had a periprocedural MI; 2 had bifurcated lesions, and 1 had a complex lesion in the right coronary artery. At 6 months of follow-up, 3.7% of patients required another revascularization procedure, there was 1 cardiac death, and there were only 6 major adverse coronary events (4%).

Stent Registry Finds Little Difference Between DESs and BMSs

In a registry comparing DESs with BMSs in 12,395 stent recipients in Denmark, rates of stent thrombosis were similarly low with both types of stents at 15 months (2.2% with BMSs vs 1.9% with DESs), reported Michael Maeng, MD, of Aarhus University Hospital, Skejby, Denmark.

The rates of MI were also similar between the 2 groups-3.0% with BMSs versus 3.2% with DESs.

All patients were treated with aspirin and clopidogrel (Plavix) for 12 months after stent implantation. However, Dr Maeng said there was a small but significant increase in the risk of stent thrombosis and MI between 12 and 15 months in the DES group. This increase in clinical events with DESs was probably unrelated to stopping clopidogrel at 12 months, he said.

—W.K.

Patients in this registry will be followed for 2 years.