 BACKGROUND: Transcatheter aortic valve replacement TAVR has become an established therapeutic option for patients with symptomatic, severe aortic valve stenosis, who are ineligible or at high risk for conventional surgical aortic valve replacement SAVR. It was recently reported that leaflet thickening and reduced leaflet motion, verified by four-dimensional computed tomography 4DCT, was not uncommon after both TAVR and SAVR. It has been emphasized that this phenomenon should be further investigated for its effect on clinical outcomes e.g. stroke and valve durability. As this valve leaflet thickening and reduced motion could be reversed by oral anticoagulant OAC treatment and was not observed in patients on chronic OAC therapy, it has been hypothesized that this phenomenon could be related to possible leaflet thrombosis or a thrombotic film on the leaflets. 