A tubular valve body has an upstream end and a downstream end, and has a central longitudinal axis, and defines a lumen along the axis. Prosthetic leaflets are disposed within the lumen, and are configured to facilitate one-way movement of fluid through the lumen in an upstream-to-downstream direction. The valve body has a cellular structure defined by a plurality of joists connected at nodes, the joists and nodes delimiting cells of the cellular structure. The nodes include minor nodes at which 2-4 joists are connected, and major nodes at which 6-8 joists are connected. The cells of the cellular structure comprise a first circumferential row of first-row cells. Each of the first-row cells is connected to each of its circumferentially-adjacent first-row cells at a respective one of the major nodes, and is longitudinally delimited by two of the minor nodes. Other embodiments are described.