Mixed Results for Magnesium-Based Bioresorbable Scaffold vs SES in STEMI

Magnesium-based bioresorbable scaffolds (MgBRS) demonstrated increased vasomotor response compared with sirolimus-eluting stents (SES) but were associated with lower angiographic efficacy and a higher rate of target lesion revascularization in patients with ST-segment elevation myocardial infarction (STEMI), according to a study published in Circulation.

This investigator-driven, multicenter, single-blind, randomized controlled trial (ClinicalTrials.gov identifier: NCT03234348) conducted in Spain enrolled patients with STEMI who were undergoing primary percutaneous coronary intervention and had 1 target lesion considered suitable for either MgBRS or SES implantation. Between June 2017 and June 2018, 150 patients were randomly assigned to receive either MgBRS (n=74) or SES (n=76) after successful lesion preparation by either manual thrombectomy or predilatation. Patients were blinded to the study-group assignments.

The primary study end point was in-stent/in-scaffold vasodilatory response ≥3% (change in mean lumen diameter) after intracoronary nitroglycerin injection at 12-month angiographic follow-up with superiority of MgBRS over SES. The 3% threshold was used to define a significant vasomotion response. Secondary end points were device success, procedure success, device-oriented and patient-oriented composite end points and their individual components, and stent/scaffold thrombosis.

The primary end point was significantly higher in the MgBRS group at 1 year (56.5% in the MgBRS group vs 33.8% in the SES group; P =.010). The in-device change in mean luminal diameter after nitroglycerin injection was significantly higher in the MgBRS group (5.39±6.52% vs 2.16±2.66%; P <.001).

In-stent acute gain was significantly lower in the MgBRS group during the index procedure; the mean minimal luminal diameter was smaller and the mean percentage diameter stenosis was significantly higher in the MgBRS group.

Acetylcholine infusion induced a vasoconstrictive response in-scaffold and in proximal and distal coronary segments remote from target, in the MgBRS group, whereas in-stent endothelium-dependent vasomotion was significantly less reactive in the SES group.

Study limitations included its single-blind design; because of the differential features between MgBRS and SES, the participating physicians were aware of the device implanted. The sample size did not allow researchers to draw conclusions regarding clinical events. Mandatory angiographic follow-up for the primary end point does not reflect current clinical practice and may have induced an excess of target lesion revascularization events.

According to the researchers, “In the context of STEMI, MgBRS exhibited a higher rate of in-device endothelium-independent and -dependent vasomotor response than the SES implant. Current MgBRS generation was associated with decreased angiographic efficacy (ie, higher late lumen loss), higher rate of target lesion revascularization, without thrombotic safety concerns in this thrombogenic setting. Further iteration of the device with longer scaffolding time and higher radial force may help to resolve this drawback.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Sabate M, Alfonso F, Cequier A, et al. Magnesium-based resorbable scaffold vs permanent metallic sirolimus-eluting stent in patients with ST-segment elevation myocardial infarction: the MAGSTEMI randomized clinical trial [published online September 25, 2019]. Circulation. doi:10.1161/CIRCULATIONAHA.119.043467