Time Course of Stent Endothelialization After Intravascular Radiation Therapy in Rabbit Iliac Arteries

Background— Late total occlusion after vascular brachytherapy (VBT) continues to be a serious complication. Delayed reendothelialization was suggested as a pivotal cause, but the time course for complete healing is unknown. Methods and Results— Seventy-two rabbit iliac arteries underwent stent implantation and were treated with γ-radiation using 192Ir. The prescribed doses were 0 Gy (controls, n=24 arteries), 15 Gy (n=24), or 30 Gy (n=24) at 2 mm. Animals were killed at 1 month (n=24), 3 months (n=24), or 6 months (n=24) and were analyzed for histomorphometry or scanning electron microscopy. Intimal area was reduced after VBT at 3 months with 15 and 30 Gy (0.66±0.07 and 0.66±0.04 mm2, respectively) compared with controls (1.01±0.11 mm2, P<0.05) and at 6 months with 30 Gy (0.75±0.09 versus 1.28±0.26 mm2 in controls, P<0.01). Intimal area was similar at 6 months between 15 Gy and controls. At 1 month, 92±4% of the control stented segment was covered with endothelial cells, whereas only 37±4% and 37±8% was c...