Iliac anastomotic stenting with a sirolimus-eluting biodegradable poly-L-lactide stent: a preliminary study after 6 weeks.
OBJECTIVE
To assess technical feasibility and biocompatibility of a new biodegradable sirolimus-eluting poly-L-lactide (PLLA) vascular anastomotic stent.


METHODS
A polytetrafluoroethylene bifurcated graft was implanted in 9 pigs through a midline abdominal incision. After transverse graft limb incision, 6 unloaded PLLAs, 6 sirolimus-loaded PLLAs, and 6 unloaded stainless steel (316L) stents were randomly implanted at both iliac anastomotic sites. Stents were deployed with a 6-mm balloon under direct vision without the use of angiography. Prior to sacrifice after 6 weeks, contrast-enhanced computed tomography (CT) was performed to determine patency of the target vessels. Stented segments were surgically explanted and processed for histology to measure the mean luminal diameter and intimal thickness and to assign vascular injury and inflammation scores.


RESULTS
No animals were lost during the study period. All stented graft limbs were patent on CT and histology. At the anastomotic sites and iliac arteries, the mean luminal diameter of SIR-PLLA stents (4.11+/-0.15 and 4.08+/-0.13 mm, respectively) were comparable to metal stents (4.23+/-0.35 and 4.21+/-0.26 mm, respectively), but significantly higher compared to unloaded PLLA stents [3.32+/-0.56 mm (p<0.001) and 3.29+/-0.39 mm (p=0.013), respectively]. At the iliac arteries, the mean intimal thickness was significantly lower with SIR-PLLA stents (0.09+/-0.02 mm) compared to unloaded PLLA stents (0.31+/-0.15 mm, p<0.001) and metal stents (0.19+/-0.04 mm, p=0.004). Vascular injury scores demonstrated only mild vascular trauma for all stents (SIR-PLLA: 0.42+/-0.63, PLLA: 0.51+/-0.62, metal: 0.50+/-0.62). Only mild inflammatory reaction was noted around SIR-PLLA stent struts (1.14+/-0.46), which was comparable to metal stents (1.27+/-0.45) but significantly lower than PLLA stents (1.79+/-0.56, p<0.001).


CONCLUSIONS
SIR-PLLA stents showed comparable luminal diameter compared to metal stents, so incorporating sirolimus could reduce the inflammatory and neointimal response to PLLA stents. These findings need to be assessed with longer follow-up to confirm maintenance of efficacy.
Bünger
Carsten Michael
CM
Department of Surgery, University of Rostock, Germany. carsten.buenger@medizin.uni-rostock.de
Grabow
Niels
N
Kröger
Christina
C
Lorenzen
Björn
B
Hauenstein
Karlheinz
K
Goosmann
Martin
M
Schmitz
Klaus-Peter
KP
Kreutzer
Hans Jürgen
HJ
Lootz
Daniel
D
Ince
Hüseyin
H
Nienaber
Christoph A
CA
Klar
Ernst
E
Schareck
Wolfgang
W
Sternberg
Katrin
K
D020341:Absorbable Implants; D000714:Anastomosis, Surgical; D000818:Animals; D019917:Blood Vessel Prosthesis Implantation; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D004195:Disease Models, Animal; D005121:Extremities / Q000098:blood supply; D005240:Feasibility Studies; D005260:Female; D006083:Graft Occlusion, Vascular / Q000209:etiology / Q000503:physiopathology; D007083:Iliac Artery / Q000187:drug effects* / Q000503:physiopathology / Q000601:surgery*; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D015601:Injury Severity Score; D008422:Materials Testing; D011091:Polyesters / Q000494:pharmacology*; D011474:Prosthesis Design / Q000295:instrumentation; D011897:Random Allocation; D012107:Research Design; D020123:Sirolimus / Q000494:pharmacology*; D015607:Stents; D013552:Swine; D017539:Tunica Intima / Q000293:injuries / Q000503:physiopathology; D014654:Vascular Patency / Q000187:drug effects
D020099:Coated Materials, Biocompatible; D007166:Immunosuppressive Agents; D011091:Polyesters; C033616:poly(lactide); D020123:Sirolimus