 For those randomized to group A LAAO group, an interventional LAA occlusion will be performed. The type of LAA occlusion system will be left on the discretion of the implant center; however, only Amulet device St. Jude Medical and the Watchman device Boston Scientific are available for use in this study. The goal will be to achieve approximately half of patients implanted with the Watchman system Boston Scientific and the other half implanted with the Amulet system St. Jude Medical. The protocol and LAA imaging for the procedure will use the current praxis of the surgeon: the procedure can be done under TEE, ICE, or angiographic visualization and control, depending on the experience and preference of the particular center and surgeon. 