Resorbable Magnesium Scaffold in Coronary Bifurcations - Report of in Vitro Experiments

The aim of this work is to evaluate in an in vitro setting the behavior of resorbable magnesium scaffolds (RMS) in bifurcations.

As coronary bifurcations represent an important portion of all PCIs, it is crucial to understand whether RMS is applicable in these complex lesions.

Performance of RMS was evaluated with focus on bifurcations. In bifurcations RMS was tested for (1) main branch stenting with side branch opening and proximal optimization; for (2) main branch stenting with final kissing and proximal optimization; for (3) T-and-protrusion technique; for (4) string technique, which is a minimalistic version of conventional culotte technique. All tests were performed using 3.50 × 25 mm RMS. Results were evaluated by fluoroscopy, optical coherence tomography (OCT) and micro-computed tomography (μCT), for scaffold conformability, strut apposition, structural deformation and strut fracture.

All planned procedural steps were performed successfully with good result according to fluoroscopy. By OCT the overall malapposition rate in bifurcation cases was 4.3%, occurring predominantly in the carinal area. No malapposition was seen at the proximal main branch confirming proper conformability of RMS. μCT analysis has shown that final kissing dilation resulted in fully stretched struts in cases, where performed with 3.5 and 3.0 mm balloons. In one case a broken connector (T-and-protrusion) and in another case, a broken strut (String technique) were identified.

RMS can structurally cope with bifurcations. Still, for cases and techniques where overexpansion beyond the recommended limit is needed, RMS might not be the proper device due to risk of strut fracture.