Apparatus and methods are described including an implantable device having first and second longitudinal ends, the device having a length of less than 80 mm when the device is unconstrained. The device includes struts arranged such that, when the device is unconstrained, along a continuous portion of the device having a length that is at least 5 mm, a maximum inter-strut distance defined by any set of two adjacent struts is more than 1.5 times as great as a maximum inter-strut distance defined by any set of two adjacent struts within longitudinal portions of the device within 3 mm of the longitudinal ends of the device. Other applications are also described.
