Aortic　valve　diseases　caused　by　the　support　from　left　ventricular　assist　devices　(LVADs)　have　attracted　increasing　attention　due　to　the　wide　application　of　the　LVADs.　However,　the　biomechanical　effects　of　the　working　modes　of　LVADs　on　the　aortic　valve　are　still　poorly　understood.　Hence,　in　this　study,　these　biomechanical　effects　are　investigated　using　a　novel　fluid-structure　interaction　method,　which　combines　the　lattice　Boltzmann　and　the　finite　element　methods.　On　the　basis　of　the　clinical　practice,　three　working　modes　of　LVADs,　namely,　the　constant　flow,　co-pulse,　and　counter　pulse　modes,　are　chosen.　Results　demonstrate　that　the　working　mode　of　LVADs　is　an　important　factor　as　it　can　change　the　biomechanical　states　of　the　aortic　valve　and　the　hemodynamic　environment　in　the　aortic　root　directly.　Compared　with　the　constant　flow　mode,　the　two　other　working　modes　can　provide　better　biomechanical　effects　on　the　aortic　valve.　However,　the　advantages　of　the　co-pulse　and　the　counter　pulse　modes　on　the　aortic　valve　are　not　the　same.　The　LVADs　in　the　co-pulse　mode　can　remarkable　reduce　the　pressure　load　of　the　leaflets　during　the　diastolic　phase　(maximum　stress:　co-pulse　mode,　0.85　MPa;　constant　flow　mode,　1.23　MPa;　counter　pulse　mode,　1.50　MPa).　By　contrast,　the　LVADs　in　the　counter　pulse　mode　can　achieve　the　highest　effective　orifice　area　of　the　aortic　valve　(co-pulse　mode:　0.12　cm(2),　constant　flow　mode:　0.17　cm(2),　counter　pulse　mode:　0.25　cm(2)).　In　sum,　the　co-pulse　mode　is　suitable　for　patients　with　certain　cardiac　function,　because　this　mode　keeps　the　valve　open　intermittently　and　reduces　the　pressure　load　on　the　aortic　leaflets　during　the　diastolic　phase　to　prevent　valve　remodeling.　By　contrast,　the　counter　pulse　mode　is　suitable　for　patients　with　severely　impaired　cardiac　function,　because　this　mode　keeps　the　valve　open　as　much　as　possible　and　provides　high　blood　perfusion.　(C)　2020　Elsevier　B.V.　All　rights　reserved.