Temporary scaffolding of coronary arteries with bioabsorbable magnesium stents: a prospective, non-randomised multicentre trial

Summary

Background

Coronary stents improve immediate and late results of balloon angioplasty by tacking up dissections and preventing wall recoil. These goals are achieved within weeks after angioplasty, but with current technology stents permanently remain in the artery, with many limitations including the need for long-term antiplatelet treatment to avoid thrombosis. We report a prospective multicentre clinical trial of coronary implantations of absorbable magnesium stents.

Methods

We enrolled 63 patients (44 men; mean age 61·3 [SD 9·5 years]) in eight centres with single de novo lesions in a native coronary artery in a multicentre, non-randomised prospective study. Follow-up included coronary angiography and intravascular ultrasound at 4 months and clinical assessment at 6 months and 12 months. The primary endpoint was cardiac death, non-fatal myocardial infarction, or clinically driven target lesion revascularisation at 4 months

Findings

71 stents, 10–15 mm in length and 3·0–3·5 mm in diameter, were successfully implanted after pre-dilatation in 63 patients. Diameter stenosis was reduced from 61·5 (SD 13·1%) to 12·6 (5·6%) with an acute gain of 1·41 mm (0·46 mm) and in-stent late loss of 1·08 mm (0·49 mm). The ischaemia-driven target lesion revascularisation rate was 23·8% after 4 months, and the overall target lesion revascularisation rate was 45% after 1 year. No myocardial infarction, subacute or late thrombosis, or death occurred. Angiography at 4 months showed an increased diameter stenosis of 48·4 (17·0%). After serial intravascular ultrasound examinations, only small remnants of the original struts were visible, well embedded into the intima. Neointimal growth and negative remodelling were the main operating mechanisms of restenosis.

Interpretation

This study shows that biodegradable magnesium stents can achieve an immediate angiographic result similar to the result of other metal stents and can be safely degraded after 4 months. Modifications of stent characteristics with prolonged degradation and drug elution are currently in development.

Introduction

Coronary stent implantation, first reported in 1986,1, 2 has gained widespread acceptance, and stent thrombosis has been reduced by the use of thienopyridines and high pressure stent implantation.3, 4 Randomised clinical trials have shown that coronary stenting can reduce the rate of acute vessel occlusion,⁵ restenosis after treatment of de novo lesions,6, 7 recurrent restenosis after treatment of restenotic lesions after percutaneous transluminal coronary angioplasty,⁸ and stenosis of saphenous bypass grafts.⁹

Drug-eluting stents can achieve a further decrease in angiographic restenosis and target lesion revascularisation rate,10, 11, 12 but have generated concerns about late malapposition, hypersensitivity reaction, long-term impairment of endothelial response, and late stent thrombosis.13, 14, 15, 16 Additionally, permanent stents eliminate vasomotion within the stented segment and impair endothelial response in adjacent vessel segments.¹⁶

To overcome these limitations, an absorbable magnesium alloy was used to construct an absorbable stent.¹⁷ Studies in animals have shown complete and rapid endothelialisation, low neointima proliferation, minimum inflammatory changes, and complete absorption within 2 months.17, 18, 19 Follow-up 2 years after implantation of this absorbable metal stent showed promising results for vascular interventions below the knee, the first in human application.²⁰ The aim of our study was to establish that temporary coronary scaffolding can be safely achieved with an absorbable magnesium stent.