LOW-TAVR is a real-world, retrospective and prospective, multicenter Italian registry aimed at evaluating the characteristics and clinical outcomes of patients with severe low flow, low gradient aortic stenosis undergoing transcatheter aortic valve replacement (TAVR) and, in particular: * risk factors * gender differences * comorbidities * pharmacological treatment * TAVR procedural characteristics * periprocedural and in-hospital complications * clinical outcome at 30-day, 1-year, 2-year and 5-year follow-up