This includes ensuring compli- ance with DAPT and adequate stent sizing and expansion.836 6.3. Restenosis: Recommendations Class I 1. Patients who develop clinical restenosis after balloon angioplasty should be treated with BMS or DES if anatomic factors are appropriate and if the patient is able to comply with and tolerate DAPT.837 (Level of Evidence: B) 2. Patients who develop clinical restenosis after BMS should be treated with DES if anatomic factors are appropriate and the patient is able to comply with and tolerate DAPT.838 840 (Level of Evidence: A) Class IIa 1. IVUS is reasonable to determine the mechanism of stent restenosis.495 (Level of Evidence: C) Class IIb 1. Patients who develop clinical restenosis after DES may be considered for repeat PCI with balloon angioplasty, BMS, or DES containing the same drug or an alternative antiproliferative drug if anatomic factors are appropriate and the patient is able to comply with and tolerate DAPT.495 (Level of Evi- dence: C) 6.3.1. Background and Incidence After balloon angioplasty, mechanisms contributing to reste- nosis include smooth muscle cell migration and proliferation, platelet deposition, thrombus formation, elastic recoil, and negative arterial remodeling. Stents block elastic recoil and negative remodeling, and the predominant mechanism for restenosis after stent implantation is neointimal hyperplasia. Restenosis rates vary, depending on whether angiographic restenosis (defined as 50% diameter stenosis at follow-up angiography) or clinical restenosis (symptomatic and requir- ing target-lesion revascularization or target-vessel revascular- ization) is measured, as well as on patient characteristics, coronary anatomy considerations, and device type (balloon angioplasty, BMS, or DES). 