Apparatus (10) is provided that includes an extra-vascular ring (12) and an endo vascular stent-graft (14). The ring (12) comprises a structural member (30), which is configured to assume an elongate hollow shape (32), which has first and second longitudinal ends (40, 42), and is suitable for placement at least partially around an aorta (20) so as to provide a generally cylindrical landing zone. The endovascular stent-graft (14) is suitable for endovascular placement inside the aorta (20) such that a portion of the stent-graft (14) is positioned against an internal wall of the aorta (20) at the landing zone provided by the structural member (30). If the structural member (30) is unrolled to a planar shape (82), one side (90) of the planar shape (82) is defined by the first longitudinal end (40), and at least the first longitudinal end (40) has a profile that defines a series of curved portions and has no singularities or discontinuities, which profile extends along at least 50% of the first longitudinal end (40).
