An implantable medical therapy delivery device includes a non-conductive filament extending along a length of an outer surface of an insulative body of the device, wherein the filament includes a plurality of fixation projections and is secured to the outer surface of the insulative body such that the projections protrude outward from the outer surface and are spaced apart from one another along the length of the outer surface. The filament may be wound about the length with an open pitch. In some cases, the insulative body includes an open-work member forming at least a portion of the outer surface thereof, and the filament may be interlaced with the open-work member. In these cases, the filament may be bioabsorbable, for example, to provide only acute fixation via the projections thereof, while the open-work member provides a structure for tissue ingrowth and, thus, more permanent or chronic fixation.