Negative vascular remodelling after implantation of bioabsorbable magnesium alloy stents in porcine coronary arteries: a randomised comparison with bare-metal and sirolimus-eluting stents

Objective: We sought to assess vascular remodelling and neointima formation after implantation of bioabsorbable magnesium alloy stents (AMS). Design: Randomised experimental study. Interventions: AMS (n = 11), sirolimus-eluting stents (Cypher; n = 11) and bare-metal stents (BMS; n = 9) were randomly implanted in 31 porcine coronary arteries (n = 11 pigs). Main outcome measures: Neointima formation was measured by histomorphometry at 90 days. Vascular remodelling defined as change in external elastic membrane area from index intervention to follow-up was assessed by serial intravascular ultrasound (IVUS). Results: By histomorphometry, lumen (median (quartiles); AMS: 1.75 mm(2) (1.07-3.26), Cypher 2.52 mm(2) (2.22-5.01), BMS 4.55 mm(2) (3.2-7.44); p = 0.013) and external elastic membrane area (AMS: 5.56 mm(2) (4.09-6.95), Cypher 7.95 mm(2) (6.45-10.92), BMS 9.08 mm(2) (7.85-11.63); p = 0.014) were smallest after AMS implantation. By IVUS, external elastic membrane area at follow-up was smallest (AMS: 7.5 (2.8) mm(2), Cypher 9.1 (2.7) mm(2), BMS 9.9 (3.1) mm(2); p = 0.33) and change in external elastic membrane area from index intervention to follow-up (remodelling; AMS: 21.0 (3.1) mm(2), Cypher 1.0 (0.8) mm(2), BMS 0.9 (1.2) mm(2); p = 0.30) was greatest in the AMS group. In a dichotomised IVUS assessment of vascular remodelling, six AMS stents were remodelled (negative remodelling: n = 5; positive remodelling: n = 1) at 90-day follow-up (AMS versus Cypher + BMS: p = 0.001). Neointima formation was smallest in the AMS group (p < 0.05 for both histomorphometry and IVUS). Conclusion: Coronary implantation of absorbable magnesium stents, compared to two non-absorbable stents, was associated with the smallest lumen area at three-month follow-up because of negative vascular remodelling.