A robotically controlled guide instrument system, comprising an elongate flexible guide instrument; a drive assembly coupled to a proximal portion of the guide instrument and configured to maneuver a distal portion of the guide instrument; a master controller including a user interface that may be manipulated to actuate the drive assembly and thereby maneuver the distal portion the guide instrument; and a closure device detachably coupled to a delivery member carried by the guide instrument, the guide instrument maneuverable to position the closure device proximate an opening of a left atrial appendage of a person's heart such that the prosthesis may be detached from the delivery member and implanted to substantially close off the left atrial appendage.