Second generation Absorbable Metal Stents (AMS)

The concept of absorbable metal stents aims to maintain the benefits of bare metal stents while reducing the risks which arise from the permanent presence of "foreign" material in the human body.

This concept reflects the current thinking that mechanical scaffolding is needed for a period of only a few months until complete remodelling and healing processes have taken place.

The benefits associated with absorbable stents include: the advantage of enabling non-invasive imaging of the stented vessel, easier endovascular re-intervention, and the potential use in paediatric cases.

After absorption they do not impair local vasomotion and potentially minimise the risks of late stent thrombosis and prolonged anticoagulant therapy.

Several companies are developing absorbable stents based on biodegradable polymers while BIOTRONIK has decided to pursue an AMS technology.

The second generation AMS, which will serve as a stent platform for the drug-eluting version (DREAMS), has now been developed.

Initial clinical trials with the first generation (AMS-1) demonstrated product feasibility and safety in over 150 human cases but failed to show sufficient device efficacy. Subsequently, development activities focused on prolonging degradation and scaffolding time as well as reducing strut thickness.

As a result, the second generation AMS feature a reduced strut thickness of 125 µm and provide a significant increase in scaffolding time compared to AMS-1.

These improvements were possible due to further optimisation of the magnesium alloy and a design change to a modern 6- crown design. Despite these changes, the stent platform retains the same favourable mechanical properties as its predecessor, resulting in excellent deliverability.

In parallel, BIOTRONIK is progressing with the drug elution concept. Prototypes of the DREAMS stent have shown the first positive results in animal studies.