The invention relates generally to expandable medical implants for maintaining support of a body lumen and, in particular, to an axially nested, diametrically expandable, slide and lock vascular device for enlarging an occluded portion of a vessel. The axially nested vascular device desirably achieves both competitive crossing profiles while maintaining other key features, such as, for example, radial strength and luminal patency. The collapsed profile can also be made very thin without compromising radial strength. Thus, the vascular device can advantageously be deployed in small and difficult to reach areas or vessels. The axial nesting substantially eliminates radial overlap between mating structural elements thereby desirably allowing for a low, uniform profile.