Bioresorbable scaffolds versus permanent sirolimus-eluting stents in patients with ST-segment elevation myocardial infarction: vascular healing outcomes from the MAGSTEMI trial

AIMS: The MAGSTEMI trial showed larger endothelium-independent vasodilatation with magnesium-based bioresorbable scaffolds (MgBRS) than with sirolimus-eluting stents (SES). However, restenosis was more frequent with MgBRS. The aims of this study were to compare the healing pattern between MgBRS and SES and to describe the main causes of restenosis, as assessed by optical coherence tomography (OCT). METHODS AND RESULTS: Ninety-five consecutive patients from the randomised MAGSTEMI trial (MgBRS=48, SES=47) underwent OCT imaging at one year. Healing and bioresorption pattern were categorised into four groups: 1) indiscernible struts were observed in 33.3% versus 0% of patients (p<0.001); 2) struts integrated into the vessel wall in 22.9% versus 63.8% (p<0.001); 3) protruding struts in 37.5% versus 31.9% (p=0.568); and 4) protruding and malapposed struts in 6.3% versus 4.3% (p=0.663), respectively. MgBRS were not suitable for strut coverage analysis; SES presented with 5.6% uncovered struts. Scaffold discontinuities were observed in 10.4% and 0%, respectively (p=0.023). MgBRS presented smaller minimal lumen area (3.92±2.02 vs 6.31±1.71 mm²; p<0.001) and larger area stenosis (52.84±18.05 vs 25.02±14.58%; p<0.001). Scaffold measurements were only feasible in 50% of MgBRS, with the expansion index being smaller than in SES (0.58±0.16 vs 0.86±0.19; p<0.001). Scaffold collapse was observed in at least 50% of cases with MgBRS restenosis. CONCLUSIONS: Both MgBRS and SES exhibited a low degree of neointima healing, but lumen dimensions were smaller with MgBRS at one year. Although the advanced bioresorption state of MgBRS hampers the assessment of scaffold collapse, this seems to be the main mechanism of restenosis. Future generations of MgBRS should increase and prolong the radial force.