An expandable blood flow shunt formed of an elastic material and configured to be inserted into a puncture wound in a tissue wall between two anatomical chambers and expand from a collapsed state to an expanded state to maintain a blood flow opening therebetween, the tissue wall defining a reference plane generally perpendicular to the opening, the shunt comprising, in an expanded state: a central flow tube defined by an opposed pair of lateral side walls (170a, 170b) formed by struts extending between an opposed pair of end walls (172a, 172b) formed by struts, the central flow tube defining a central axis therethrough angled from a reference axis extending perpendicular through the reference plane, each side wall (170a, 170b) including an upper row of cells and a lower row of cells defined by the corresponding struts and stacked along the central axis; two distal flanges (152a, 152b) formed by struts each attached to a first axial end of the central flow tube, the distal flanges (152a, 152b) extending away from one another in opposite longitudinal directions generally parallel to the reference plane; and two proximal flanges (154a, 154b) formed by struts each attached to a second axial end of the central flow tube opposite the first axial end, the proximal flanges (154a, 154b) extend away from one another in opposite longitudinal directions generally parallel to the reference plane, the proximal flanges (154a, 154b) extend in the same directions as the distal flanges (152a, 152b) such that each proximal flange (154a, 154b) parallels one of the distal flanges (152a, 152b) to form a clamping pair of flanges with a gap therebetween sized to clamp onto the tissue wall, characterised in that the two rows of cells (184a, 184b) in each side wall (170a, 170b) stop short of the opposed end walls (172a, 172b) of the central flow tube to define spaces (186a, 186b) therebetween such that the upper row of cells connects to a first end wall only and the lower row of cells connects to a second end wall only. a central flow tube defined by an opposed pair of lateral side walls (170a, 170b) formed by struts extending between an opposed pair of end walls (172a, 172b) formed by struts, the central flow tube defining a central axis therethrough angled from a reference axis extending perpendicular through the reference plane, each side wall (170a, 170b) including an upper row of cells and a lower row of cells defined by the corresponding struts and stacked along the central axis; two distal flanges (152a, 152b) formed by struts each attached to a first axial end of the central flow tube, the distal flanges (152a, 152b) extending away from one another in opposite longitudinal directions generally parallel to the reference plane; and two proximal flanges (154a, 154b) formed by struts each attached to a second axial end of the central flow tube opposite the first axial end, the proximal flanges (154a, 154b) extend away from one another in opposite longitudinal directions generally parallel to the reference plane, the proximal flanges (154a, 154b) extend in the same directions as the distal flanges (152a, 152b) such that each proximal flange (154a, 154b) parallels one of the distal flanges (152a, 152b) to form a clamping pair of flanges with a gap therebetween sized to clamp onto the tissue wall, characterised in that the two rows of cells (184a, 184b) in each side wall (170a, 170b) stop short of the opposed end walls (172a, 172b) of the central flow tube to define spaces (186a, 186b) therebetween such that the upper row of cells connects to a first end wall only and the lower row of cells connects to a second end wall only.