Bioabsorbable coronary stent shows promise in two-year study
21 March 2009
A study published online in The Lancet from the ABSORB
clinical trial demonstrates that Abbott's bioabsorbable drug eluting
stent, currently in development, successfully treated coronary artery
disease and was absorbed into the walls of treated arteries within two
years. The two-year data also demonstrated that after the bioabsorbable
device was absorbed, the treated blood vessels appeared to move and
function similar to unstented arteries.
"Abbott's bioabsorbable drug eluting stent leaves behind a vessel
that expands and contracts in a manner similar to a vessel that has
never been stented, which could be an advantage over permanent
metal-based stent implants," said Patrick W. Serruys, MD, PhD, professor
of interventional cardiology at the Thoraxcentre, Erasmus University
Hospital, Rotterdam, the Netherlands; lead author of The Lancet
publication; and co-principal investigator of the first phase of the
"This bioabsorbable device has the potential to provide optimal
vessel scaffolding and drug delivery capability over the crucial first
several months after a stenting procedure while avoiding the long-term
restrictions of metallic stents," he added.
"Abbott's bioabsorbable stent may be a major breakthrough in the
treatment of narrowed coronary arteries. The two-year ABSORB trial
results show that the bioabsorbable device did its job of relieving
coronary obstructions and preventing re-narrowing, and that it did this
safely," said John Ormiston, MD, medical director at Mercy Hospital in
Auckland, New Zealand and principal investigator in the first phase of
the ABSORB trial.
"With no rigid stent remaining, vasomotion — the natural movement of
the artery — was restored, and the artery appeared to behave like a
normal artery. Who would want a permanent device if a temporary one may
do the job and then disappear?"
Interventional cardiology specialist, Professor Franz Eberli from the
University Hospital Zurich (Switzerland) and official spokesperson for
the European Society of Cardiology, said: “In addition to the ABSORB
study presenting the longest ever follow-up data for a bioabsorbable
stent, the investigators used multiple imaging systems, including
optical coherence tomography.
"This technical advance has allowed them to get really detailed
images of the intra coronary structures for the first time. What really
impressed me was the smoothness of the vessel wall at two years, and
images showing the stents had disappeared to a great extent, which was a
very promising finding.
"The study showed an overall 19% loss in luminal diameter at 18
months and an angiographic in-stent late loss of 0.48mm at two years.
These results fall intermediate between those commonly seen for bare
metal stents (which typically have an in stent late loss of 1.0 mm), and
drug eluting stents (which typically have an in-stent late loss of 0.15
to 0.3 mm). But the upside of this bioabsorbable stent data is that
patients don't appear to be getting any in-stent thrombosis here.
"Since in-stent late loss increased by only 0.05 mm between 6 months
and two years, the most probable explanation for the in-stent late loss
is early recoil after stent implantation. This indicates that this
bioabsorbable stent initially is not exerting enough radial force to
keep the vessels perfectly open.
"The challenge facing stent designers is to achieve a balance between
sufficient radial strength, and a structure that can be reabsorbed in a
reasonable time period. Industry is already acting on this data and
looking to produce stronger second generation bioabsorbable stents by
developing novel stent designs that retain integrity and radial strength
for a longer time period.
"The fact that vasomotion (the ability to undergo vasodilation and
vasoconstriction) was restored in response to vasoactive agents in the
stented vessel segment was a really good sign. It shows that after two
years the physiological function of the stented part of the vessel has
been almost completely restored, and that patients will not get any
symptoms of angina or limitations in physical activity.
"In contrast, for first generation drug eluting stents, studies have
shown “paradoxical vasoconstriction” in the area of the stent, where the
vessel constricts instead of opening during exercise.
"This is a proof of principle study that teaches us a lot about the
way bioabsorbable stents work and affect remodelling of the stented
vessel segment. But with only 30 patients included in the study, numbers
are too small to show us if the technology is safe.
"Furthermore the study was only performed in patients with single
de novo coronary lesions, who are considered by far the most
straight forward cases. The study doesn't show us if the new stent will
work in real world situations of patients with long lesions,
calcification or bifurcations.”
Bookmark this page