Sirolimus-eluting stents to abolish intimal hyperplasia and improve flow in porcine arteriovenous grafts - A 4-week follow-up study

Background - The patency of arteriovenous ( AV) expanded polytetrafluoroethylene (ePTFE) hemodialysis grafts is severely compromised by intimal hyperplasia (IH) at the venous anastomosis and in the venous outflow tract. We addressed the potential of primary placement of a sirolimus-eluting stent (SES) in a validated porcine model. Methods and Results - In 25 pigs, ePTFE AV grafts were created bilaterally between the carotid artery and the jugular vein, whereupon a self-expandable nitinol stent ( 14 SESs and 11 bare-metal stents) was implanted over the venous anastomosis in 1 of the 2 grafts. After exclusion of technical failures and 1 unilateral occlusion, 16 pigs ( 9 SESs and 7 bare-metal stents) were included for further analysis. After 28 days, we measured graft flow and performed quantitative angiography. The pigs were then euthanized, and grafts with adjacent vessels were excised for histological analysis. Minimal luminal diameter was substantially larger in the SES group compared with unstented controls ( 5.9 +/- 0.2 versus 3.8 +/- 0.4 mm, respectively, P = 0.01), which was accompanied by more prominent graft flow ( SES, 1360 +/- 89 mL/min versus unstented, 861 +/- 83 mL/min, P = 0.05). IH at the venous anastomosis was 77% less in the SES group compared with unstented controls (0.44 +/- 0.05 versus 1.92 +/- 0.5 mm(2), respectively, P = 0.01), whereas IH increased markedly when bare-metal stents were used (5.7 +/- 1.4 mm(2), P = 0.05). Conclusions - SESs in the venous outflow of AV grafts significantly reduce IH and increase vessel diameter and graft flow compared with unstented grafts. These findings suggest that SESs have the potential to improve primary patency of AV grafts in hemodialysis patients.