Dr Raimund Erbel

Speaking with heartwire, lead investigator Dr Raimund Erbel (University Clinic, Essen, Germany) said that after four months, despite the complete disappearance of the stent, "the vessel lumen is nicely opened and we have not seen elastic recoil as a problem."

The results of the study, known as the Clinical Performance and Angiographic Results of the Coronary Stenting and Absorbable Metal Stents trial, known as PROGRESS-AMS, were presented during an i2 Summit late-breaking clinical-trials session here at the American College of Cardiology 2006 Scientific Sessions. The PROGRESS study was a prospective, multicenter, consecutive, nonrandomized trial evaluating the clinical feasibility of the stent, made by Biotronik in Berlin, Germany, in the treatment of a single de novo lesion in a native coronary artery.

During a morning press briefing, Erbel said pediatric cardiologists initially pushed for absorbable stents in young people, where the vessels are still growing, as well as for children with congenital birth defects who might require frequent reintervention. Also, for older patients being revascularized at an earlier age, an absorbable stent would be gone by the time the patient needed to return for a reintervention, meaning multiple interventions might be carried out in the same lesion without stent-in-stent problems.

Dr John Hodgson (St Joseph's Hospital and Medical Center, Phoenix, AZ), who moderated the press conference, told heartwire that the growing number of patients receiving more and more stents makes an absorbable stent a promising option.

"Some people are getting four and five stents in a row," he said. "They have 90 mm of stents, which is like a lead pipe in there. It's not meant to be that way. The artery is meant to flex and move."

Some people are getting four and five stents in a row. They have 90 mm of stents, which is like a lead pipe in there. It's not meant to be that way.

Investigators presented data on the first 63 patients treated with the novel absorbable stent. The reference diameter of the treated vessels ranged from 3.0 to 3.5 mm, and all were less than 15 mm in length. The target vessel was roughly split among the right coronary artery (36.5%), left anterior descending (34.9%), and left circumflex artery (28.6%). All patients were pretreated with aspirin and clopidogrel 300 mg, with clopidogrel treatment (75 mg) continuing for at least six months after the procedure.

Investigators report that the study met its primary end point, which was a four-month MACE rate of less than 30% (MACE was defined as cardiac death, nonfatal MI, and ischemia-driven target lesion revascularization [TLR]). At four months, the MACE rate was 23.8% and was driven entirely by TLR. Investigators reported no myocardial infarction and no cardiac death. In addition, there were no reported cases of in-stent thrombosis.

"We have a safe new technique, which is giving us temporary stenting," said Erbel. "There are no side effects, particularly subacute thrombosis, so the safety appears to be present."

One of the advantages of the absorbable stent, Erbel pointed out, is that the new stents are compatible with magnetic resonance (MR) and computed tomography (CT) imaging, which will, it is hoped, allow revascularized patients to undergo noninvasive imaging over time to determine the health of the vessel. Using MR in one patient during the four-month follow-up, investigators saw only an open vessel and no stent. An IVUS study also revealed complete stent degradation, reported Erbel, which typically takes between two and three months to break down.

The next step, currently under way, said Erbel, is to coat the stent with a drug that will help prevent restenosis. The high rate of target lesion revascularization in PROGRESS is higher than what is seen in drug-eluting stents, Erbel said, but such comparisons are difficult. Investigators say the findings are in line with other bare-metal-stent results.

We're going to be leaving lots and lots of metal in people, so if we can open the vessel effectively and prevent restenosis, that's a winner.

Hodgson said that with the dramatic advances in keeping CAD patients alive, leaving them full of stents might not necessarily be the best idea. If a stent can provide the acute opening needed and if it can be combined with a drug that prevents the restenosis process in the first nine months, that is all that is needed, he said.

"After that, you don't need that stent any more and for that area of the vessel to be permanently encased in metal for the next 50 years makes no sense," said Hodgson. "We're treating 30- and 40-year-olds, and it's only getting worse as the obese and diabetic population continues to grow up. We're going to be leaving lots and lots of metal in people, so if we can open the vessel effectively and prevent restenosis [with an absorbable stent], that's a winner. The patient can come back next year with a new lesion, or in two or three years, and get a new stent."