Bioabsorbable Stents : The PROGRESS-1 Study

The idea of having an absorbable stent is very attractive, more so whenevr we have to put multiple stents over the same site for in-stent restenosis. There is only so much space in the artery lumen and one always wonder what happens inside the lumen when you have three layers of stainless steel, overlapping each other in a "stent-wich". The other obvious advantage is that it is MRI angiogram friendly. The theoretical advantage is that we could load the AMS (absorbable metal stent) with drugs and allow it to elute with no metal left behind. However, it must first give us acceptable restenosis rates.

At the just concluded ACC'06, there was a parallel i2summit, for the interventional cardiologist. Dr Raimund Ebel, a well known interventional cardiologist from Essen, Germany presented his experience with the Biotonik magnesium alloy bioabsorbable stent. The study is called PROGRESS-1, the acronym for "Clinical performance and angiographic results of the coronary stenting and absorbable metal stent". The PROGRESS study is a prospective, multicenter, consecutive, non-randomised trial, to study the Biotronik magnesium alloy bioabsorbable stent in the treatment of single, de novo lesion in native coronary artery disease. All in all, 63 pts were treated and followed up with angiographic and IVUS followup at 4 months. Although the stent was safe with no problems with acute or subacute stent thrombosis, the ischemic events driven TLR was 23.8% and all TLR is 38.1%. This is rather disappointing as these lesions treated were essentially type A lesions, where the TLR rates should be low. The late lumen loss is 1.09mm at 4 months. as expected with bare metal stent. The mean diameter stenosis at 4 months was 48%, a little too high. Obviously, absorbable metal stents of magnesium alloy does not help restenosis. However, what PROGRESS tells us is that AMS (absorbable metal stent) are safe, but surely more work needs to be done.