Abstract: A dual-lumen cannula for cavopulmonary assistance includes a body defining an infusing lumen and a draining lumen and a deployable barrier disposed on an exterior surface of the body. Deploying the barrier within a vascular lumen substantially occludes fluid flow therethrough other than in an intravascular zone defined by the deployed barrier. The deployable barrier includes a first deployable wall spaced apart from a second deployable wall. The infusing lumen includes outlets disposed such that on initiation of fluid flow through the infusing lumen, that fluid flow promotes deployment of the first and second deployable walls, which in embodiments are foldable membrane umbrellas or cones having at least one end thereof attached to the cannula body. Percutaneous dual-lumen cannula based cavopulmonary assist devices incorporating the dual lumen cannula and methods for using to support or remedy failing Fontan circulation are described.