Terminology
When the first-in-human implantation of a bioresorbable device into the coronary artery was reported in 2007, the term ‘fully bioabsorbable stent’ was used.1 Later, in 2011, Onuma and colleagues explained that the term ‘bioresorbable’ provides a more precise description of the complete cleavage of macromolecules to small molecules with total elimination and the term ‘scaffold’ was introduced.2 However, the structure looks and behaves exactly like a stent, which is a commonly used term, understood by both medical professionals and patients. Thus, to prevent possible confusion we believe that the term ‘bioresorbable stent’ would be most fitting.
Technology
In 2014, there are many bioresorbable stents in different stages of development of which three are described in more detail below. The most clinical literature currently available is with two generations of the balloon expandable Absorb® device (Abbott Vascular, Santa Clara, California, US). This is formed by a poly-l-lactic-acid polymer backbone (processed for an increased radial strength in the 1.1 version) and a thin amorphous everolimus/poly-lactic-acid matrix coating for controlled drug release. The implant is radiolucent but two platinum markers at each end allow easy visualization with angiography. The single strut thickness is 156 microns. According to preclinical studies the polymer backbone is fully resorbed in 2–3 years; the polymer coating is absorbed more quickly.3 The Absorb stent is commercially available in Europe. The Dreams® device (Biotronic, Bulach, Switzerland) is a balloon expandable, paclitaxel-eluting magnesium alloy-based bioresorbable coronary stent.4 The implant is radiolucent with no markers and has a single strut thickness of 125 microns. The absorption process takes 9–12 months. Mechanical properties are similar to the current generation of metallic stents including safe overdilatation. The Dreams stent has not yet received a CE mark.
The DESolve® stent (Elixir Medical, Sunnyvale, California, US) is also a balloon expandable scaffold made of a poly-l-lactic-acid-based polymer with a strut thickness of 150 microns. It provides sufficient radial strength for over 3 months and is fully bioresorbed in 1–2 years. Interestingly, self-apposing properties have been described and the stent can also be overexpanded by at least 1 mm without evidence of strut fracture in laboratory conditions. The DESolve stent received a CE mark in May 2013.