Treating in-stent restenosis (ISR) by percutaneous coronary intervention (PCI) is still a challenging approach for there is a substantial (up to 20%) risk of procedural complications and recurrent restenosis (target lesion failure, or TLF) after PCI. In particular, one of the primary causes of ISR has been found to be stent underexpansion. One of the best indicators of results following PCI of ISR in this situation is luminal gain. But underlying calcifications frequently impede luminal gain and ideal stent expansion.

The study device, OPN™ balloon (SIS Medical, Fauenfeld, Switzerland) is a twin layer and highly non-compliant balloon (NCB), which can be used at very high-pressures (burst pressure rate up to 35 atm). Several reports have described its benefits in “undilatable” and highly calcified native coronary lesions. In cases with ISR, correction of stent under-expansion and neointimal compression by using the OPN™ NCB could lead to increased luminal gain and thus improved clinical outcomes. However, physicians are often afraid of aggressive dilatation applying high-pressures (e.g. > 25 atm) for treatment of heavily calcified lesions since they fear periprocedural complications, especially vessel dissections and perforations. We have previously describe the use of the OPN™ NCB in a small population of patients with ISR treated with a bioresorbable scaffold. But the safety and utility of this balloon device has not been systematically evaluated in a large all-comer ISR population yet.