Patients with severe aortic stenosis accepted for transcatheter intervention or open surgery are included before the intervention, and then followed up with clinical visits during the first year after intervention. Imaging with echocardiography and computed tomography (CT) are performed together with additional imaging with magnetic resonance imaging (MRI) and Positron emissions tomography (PET)-CT in a subgroup of the study population. Blood samples, physical performance and questionnaires with focus on frailty and heart failure are also collected at each visit. A follow up with information of the outcomes after 2-5 years will be performed through national registries.