Biodegradable Stents – A New Era?

Abstract

Percutaneous coronary intervention (PCI) deploying metallic stentsis now a standard and routine procedure for the treatment of flow-limitingcoronary stenosis in patients with ischaemic heart disease and isan alternative to surgery. Stents were invented to overcome limitationsof balloon angioplasty coronary dissections, acute and subacute elasticrecoil, intimal hyperplasia and negative vessel remodelling. However,the long-term results of baremetal stents are affected by in-stentrestenosis, which can occur in up to 30% of cases, and stent thrombosis,which can be life-threatening. Although neointimal hyperplasia hascertainly been delayed with antiproliferative drug-eluting stents(DES), healthy endothelium eventually grows to cover the struts,resulting in stent thrombosis in 0.5-1.5% cases, despite dual antiplateletagents. The need for permanent coronary scaffolding and a drug-elutingimplant is not justified beyond the first six to 12 months when theprocess of intimal hyperplasia and acute on chronic recoil is completed.Other drawbacks of the persistence of metallic stents include interferencewith the ability of non-invasive techniques such as multislice computedtomography or magnetic resonance imaging (MRI) to assess the in-stentpatency, occlusion or impaired access to ostia of side branches,impairment of physiological vessel tone reactivity and inabilityto use the stented segment to anastomose grafts during bypass surgery.To circumvent these issues, biodegradable or absorbable stents havebeen devised. With time, these are intended to degrade within thecoronary artery, akin to dissolving sutures, while providing thevessel with temporary scaffolding until endothelialisation has established.We review these innovative devices and their impact on the futureof coronary intervention.