The efficacy of drug-eluting stents (DES) over bare metal stents (BMS) has been demonstrated in large randomised clinical trials leading to their widespread use in clinical practice. However, major concerns regarding the long-term safety of the first-generation DES include the increased risk of late stent thrombosis (LST), very late stent thrombosis (VLST), and the need for prolonged dual antiplatelet therapy (DAPT) with its inherent risk of bleeding. Although the cause of LST/VLST is probably multifactorial, the durable polymer surface coating of DES may play a role. The durable polymer carrier can cause persistent inflammatory response which leads to poor healing due to delayed re-endothelialisation, positive remodelling with late acquired malapposition and the risk of LST/VLST.
Other concerns with durable polymer are the ongoing inflammatory response which may induce the “late catch-up” phenomenon and an acceleration of neoatherosclerosis which may also trigger a subsequent risk of late device failure (stenosis and thrombosis).
Second-generation DES are designed to improve the safety and efficacy profile of earlier-generation stents. One of these innovations has been the development of biodegradable polymer which is often abluminally coated. This ensures the polymer is applied in the minimum amount necessary for its function and is then removed over time, theoretically limiting the delay in arterial healing.