An endovascular stent-graft (5) is configured to initially be positioned in a 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) includes a structural member (10), including 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. The stent-graft (5) further includes a fluid flow guide (16), including at least one biologically-compatible substantially fluid-impervious flexible sheet, and 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, and 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). Other embodiments are also described.
