Percutaneous coronary intervention (PCI) for in-stent restenosis (ISR) accounts for 5-10% of PCI. ISR may be linked to mechanical complications mainly under-expansion (UE), neointimal hyperplasia and/or neoatherosclerosis. International guidelines recommends non-compliant and very-high-pressure balloons, which lead to sub-optimal angiographic and clinical results. Recently, observational studies have suggested the feasibility and safety of intravascular lithotripsy (IVL) in UE treatment. There are no prospective randomised controlled studies comparing intravascular lithotripsy with balloons in ISR with UE.

In-stent restenosis (ISR) angioplasties account for between 5 and 10% of Percutaneous coronary intervention (PCI). Several mechanisms are causing RIS, including neointimal hyperplasia, neoatherosclerosis, and/or mechanical complications, mainly stent under-expansion. In addition, the calcified lesions associated with stent under-expansion are under-diagnosed in angiography as shown by intra-coronary imaging studies. The stent under-expansion is defined as a ratio between the minimum intrastent surface area and the average vessel lumen of <80%. Currently, the management of these lesions is not codified and consists empirically of the use of non-compliant balloons, cutting balloons, and/or very high-pressure balloons. These treatments result in suboptimal angiographic results, with clinical consequences in terms of revascularization recurrence (angina, unstable angina, and in 25% of cases, acute coronary syndrome).

A growing interest in intravascular lithotripsy (IVL) use to treat these calcified lesions with stent underexpansion appears as an appealing option for a safe procedure but without robust data on efficacy. Furthermore, guidelines published in 2020 by the expert consensus of the EAPCI (European Association of Percutaneous Coronary Interventions) classified IVL among the therapeutic strategy indicated in stent under-expansion with calcified lesions. The OSCAR study is a randomized, controlled, multicenter trial investigating the use of IVL compared to other standard strategies in the treatment of in-stent restenosis with under-expansion.

Inclusion criteria :

• Patient who have undergone coronary angiography with ISR, defined as ≥50% reduction of the diameter of the intrastent lumen occurring ≥ 6 months after stent implantation
• And with a suspicion of stent under-expansion on angiography, possibly assisted by a stent enhancement technique
• The reference diameter of the target vessel must be ≥2.5 mm and ≤5.0 mm.
• Coronary flow must be TIMI 3
• Ability to cross the lesion with the OCT catheter (possibly after predilatation with a balloon up to 2 mm)
• Patient affiliated to the French National Health Insurance

Exclusion criteria :

• Heart failure with NYHA III or IV (or cardiogenic shock)
• LVEF <20%
• Chronic renal failure with clearance <30mL/mn according to CKD
• Pregnant or breast-feeding women
• Patient with a condition/comorbidity that could reduce compliance with the protocol, including pre-specified study follow-up
• Patient participating in another ongoing medical study evaluating a pharmacological or biological agent or medical device, unless authorized by the concomitant protocol.
• Patient unable to tolerate double antiaggregation (i.e., aspirin and clopidogrel or prasugrel or ticagrelor) for at least 6 months.
• Possible or defined thrombus (by angiography or endovascular imaging) in the target vessel.