Inclusion Criteria:  Low-flow (SVi<35 ml/m2) low-gradient (mean gradient <40 mmHg) AS with estimated AVA<1.0 cm2 referred to the Department of Cardiology, Odense University Hospital. Age > 18 years. Signed informed consent.  Exclusion Criteria:  Other moderate-severe valvular heart disease. Unwilling to participate in the study. Poor echocardiographic window. Inability to follow-up due to temporary citizenship Registration Number (CPR-Number) or emigration within the study period. Pregnant women. Patients with severe chronic renal failure (eGFR<40 ml/min) will not undergo cardiac MRi or CT angiography. Known contrast allergy.