Systems, devices and methods described herein relate to endovascular devices for delivering sutures for securing grafts or other objects to patient vessels. In some embodiments, a suture includes a set of two legs having proximal ends joined to each other and elongate bodies that extend parallel to one another such that the set of two legs form a U-shaped structure. A suture delivery system can include a housing configured to contain a suture in a flattened configuration, and a deployment element having a ribbon-shaped distal portion disposed in the housing and including a set of formations, where the housing and the set of formations of the deployment element are configured to collectively constrain the suture in the flattened configuration until the suture is released through the opening of the housing.