['Recently, various modifications have been made to aortic root replacement procedures to include the pseudosinus in the synthetic graft, but its effect on valve function still remains to be elucidated. The purpose of this study was to compare the flow dynamics and its influence on the stress/strain in the valve leaflet in two types of aortic root, either with or without the pseudosinus, with a simulation model.', 'The proximal portions of the ascending aorta and aortic valves were modeled with blood flowing inside. Blood flow and the motion of aortic valve leaflets were studied while applying a physiologic pressure waveform using fluid-structure interaction finite element analysis. Waveforms were varied to simulate the change in cardiac contractility.', 'In the aorta without the sinus, the time during which the valve was open was longer and the rapid valve closing velocity was faster under all conditions studied. In the pseudosinus model, we could clearly observe vortex formation from the early phase of ejection, which seemed to facilitate the gradual but smooth closure of the valve. Valve leaflets without the sinus were subject to greater stress and underwent bending deformation in the longitudinal direction.'] Does the sinus of Valsalva relieve abnormal stress on aortic valve leaflets by facilitating smooth closure?