The one-year findings are in for the magnesium alloy absorbable coronary stents. The devices continue to show safety and to restore patency to occluded coronary arteries.

The one-year findings are in for the magnesium alloy absorbable coronary stents. The devices continue to show safety and to restore patency to occluded coronary arteries. On intravascular ultrasound, they appear to be completely absorbed within four months of implantation.

Post-implantation data from PROGRESS-1, the first-in-man coronary study of Biotronik's absorbable metal stent, were presented at a late-breaking clinical trials session during the American Heart Association's Scientific Sessions 2007. The principal investigator is Dr. Ron Waksman of Washington Hospital Center and Georgetown University in Washington, DC.

Eight of 60 patients in the trial underwent intravascular ultrasound for stent evaluation. Dr. Waksman announced that "the stent struts were completely absorbed with no evidence of stent malapposition, excess of calcification or any other adverse findings."

The rate of recoil was about five per cent and foreshortening occurred in about five per cent of the absorbable stents. Ischemia-driven revascularization of the target lesion was 28 per cent at 12 months.

"There have been no deaths, MI or stent thromboses in any of the patients," the speaker reported.

From four months to late follow up, paired ultrasound analysis showed stable stent outcomes. Compared with findings with bare metal stents, "the rate of neointima formation is low," he said. Late vessel remodeling has been identified as the major contributor to late restenosis.

"We conclude that absorbable metal stents are safe and associated with a long-term clinical safety profile," Dr. Waksman said. "The late intravascular ultrasound results demonstrate complete absorption of the stent with no significant changes in stent volume and neointima and durability of the results after four months."

"We need to change the composition of the stent, by adding rare elements to the magnesium alloy to slow down the absorbability," Dr. Waksman told Reuters Health. "If we expose just magnesium to saline, it will be gone in a couple of minutes. We need to change it to reduce the late recoil and increase the radial force."

He said he expects that these stents will eventually replace bare metal stents, but not drug-eluting stents. "For example," he noted, "by changing the formulation, we will end up with a thick stent, which cannot be used in smaller vessels.

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