Failure of a novel balloon-expandable γ-emitting (103Pd) stent to prevent edge effects

Background-Balloon-expandable beta -particle-emitting (P-32) stents inhibit within-stent neointimal hyperplasia but induce lumen narrowing beyond the stent margins, ie, the so-called "edge effects." Methods and Results-We prospectively investigated the performance of novel stents impregnated with the gamma -emitting isotope Pd-103, designed to reduce edge effects, in 24 rabbits. The stents had a length of 18 min and were mounted on 20-mm-long delivery balloons for deployment. Angiograms were obtained immediately and I month after direct implantation of control and 1-, 2-, and 4-mCi Pd-103 stents into the iliac arteries without predilatation or postdilatation. Late lumen loss was measured with quantitative angiography. Neointimal hyperplasia and vascular remodeling were evaluated by histomorphometry. Late lumen loss was inhibited within Pd-103 stents (control 0.18 mm, 1 mCi 0.08 mm, 2 mCi 0.05 mm, and 4 mCi -0.03 mm, P <0.05 all activities versus control). Conversely, late lumen loss occurred at the edges of Pd-103 stents, correlating with areas of high balloon/artery ratios and vessel overstretch injury. Edge effects were primarily due to neointimal hyperplasia but were also caused by negative vessel remodeling at high stent activities. Conclusions-Edge effects after implantation of radioisotope stents can occur independently of the isotope chosen for stent impregnation.