Collapse of a new-generation magnesium scaffold

A71-year-old male presented with non-ST-segment elevation myocardial infarction. Coronary angiography revealed a severe lesion in the left anterior descending coronary artery (Figure 1A1). Optical coherence tomography (OCT) revealed mild diffuse atherosclerotic coronary disease, with a lipid-rich and mildly calcified plaque at the site of the severe lesion. Following vessel sizing and predilation (non-compliant balloon: 2.5 mm, 20 bar), the lesion was treated with a bioresorbable magnesium scaffold (MgS; 2.5×18 mm; Freesolve [Biotronik]). Post-dilation with a non-compliant balloon (3.0 mm, 16 bar distally and up to 24 bar proximally) achieved satisfactory angiographic and OCT results, yet distal expansion reached only 93% (Figure 1A2, Figure 1B1-Figure 1B3, Moving image 1). Six months later, the patient was readmitted with unstable angina. Coronary angiography demonstrated severe in-stent restenosis (Figure 1A3). OCT (Moving image 2) showed protruding scaffold struts with a characteristic bumpy luminal contour (Figure 1C1) without significant reduction in proximal minimal lumen area (MLA). However, mid-to-distal segments showed a reduced MLA, residual struts with acquired malapposition...