Optimal interventional strategy for the treatment of coronary in-stent restenosis

In-stent restenosis (ISR) has been an important issue in the era of percutaneous coronary intervention (PCI) since the first bare metal stent (BMS) was applied to clinical settings. BMS substantially reduces acute vessel closure and restenosis after PCI by attenuating early arterial recoil and contraction, two major limitations of plain old balloon angioplasty (POBA). Thereby, it has been considered as a major advancement over POBA. However, ISR caused by neointimal hyperplasia after stent implantation hampers the benefit of BMS by increasing the rate of target lesion revascularization (TLR) or target vessel revascularization (TVR). With the innovation of stent technology, drug-eluting stents (DES) designed to inhibit excessive neointimal growth was produced and anticipated to reduce the incidence of ISR. Indeed, the RAVEL trial (1), a double-blind randomized study comparing sirolimus-eluting stent with its non-coated counterpart, reported no restenosis in the sirolimus stent group, and 23.4% of the patient in the BMS group developed binary restenosis (P<0.001) at 6-month follow-up. Despite of these promising results, there’s still a certain proportion of ISR occurring after DES implantation due to the expansion of indications for PCI to complex coronary lesions in high-risk patients. Meanwhile, the advent of DES brought new challenges for the interventional cardiologists, such as the higher rate of late stent thrombosis and more bleeding events due to prolonged duration of dual anti-platelet therapy (DAPT). According to the type of stents previously implanted, ISR is classified as BMS ISR and DES ISR. As the literature (2,3) mentioned, 20% to 53% BMS ISR present as unstable angina and 3.5% to 20% as myocardial infarction (MI); The proportion of DES ISR manifesting as unstable angina and MI is 16% to 66% and 1% to 20% respectively. Given the clinical and prognostic importance of ISR, the debate on the optimal strategy to prevent and treat ISR is far from over.