Apparatus for use with a delivery catheter (30), the apparatus comprising an endovascular stent-graft (5), which is configured to initially be positioned in the delivery catheter (30) in a radially-compressed state, and to assume a radially-expanded state upon being deployed from the delivery catheter (30). The stent-graft (5) comprises: a structural member (10), which comprises a plurality of structural stent elements (15), at least a portion of which structural stent elements (15) define a stent body (8) when the stent-graft (5) assumes the radially-expanded state； and a fluid flow guide (16), which comprises at least one biologically-compatible substantially fluid-impervious flexible sheet, and which is coupled to the stent body (8). When the stent-graft (5) assumes the radially-expanded state, the fluid flow guide (16) is shaped so as to define radially-diverging and radially-converging portions (13, 19), which together define a bulge (20) that extends radially outward, which bulge (20) has a greatest cross-sectional area that is equal to at least 120% of a cross-sectional area of a narrowest portion (17) of the stent-graft (5) rostral to the bulge (20). Furthermore, when the stent-graft (5) assumes the radially-expanded state: a first subset (22) of the structural stent elements (15) of the stent body (8) are configured to cause the fluid flow guide (16) to define the bulge (20)； a second subset (23) of the structural stent elements (15) of the stent body (8) are not configured to cause the fluid flow guide (16) to define the bulge (20)； and the structural stent elements (15) of the first subset (22) at least partially overlap the structural stent elements (15) of the second subset (23) lengthwise along the stent body (8).
