Methods, devices, and systems are provided for performing endovascular repair of atrioventricular and other cardiac valves in the heart. A delivery device for delivering an implantable device to a target area includes a fluid management system for directing fluid and delivery device components to the target area. The delivery device includes a grip line assembly configured to control a gripper in the implantable device for grasping tissue at the target area. The delivery device includes a lock line assembly configured to control a locking mechanism in the implantable device to lock the implantable device in a desired orientation. The delivery device includes a deployment handle configured to provide staged deployment of the implantable device. A delivery assembly includes a housing and a delivery device partially housed within the housing and being adjustable using one-handed operation.