Comparison of a microporous thermoplastic polyurethane-covered stent with a self-expanding bare nitinol stent in a porcine iliac artery model.
OBJECTIVE
To compare outcomes with a thermoplastic polyurethane (TPU)-covered self-expanding nitinol stent-graft (TPU graft) with those of a bare self-expanding nitinol stent in a porcine model.


METHODS
Fourteen TPU grafts and 14 commercially available bare nitinol stents were implanted, one each, in the iliac arteries of 14 minipigs. Follow-up was performed at 1 week (six animals), 4 weeks (four animals), and 12 weeks (four animals). The primary study endpoint was in-stent stenosis assessed with quantitative angiography and microscopy. Secondary endpoints were injury, inflammation, and endothelialization.


RESULTS
After 1 week, the maximum percentage luminal loss was significantly greater in TPU grafts (average, 16.2%; range, 0.0%-35.8%) than in bare nitinol stents (8.2%; 0.0%-17.3%) (P = .04). Three of the four TPU grafts were occluded after 4 weeks, and all four TPU grafts were occluded after 12 weeks. Binary stenosis was seen in three of four bare nitinol stents after both 4 and 12 weeks. At 4-week follow-up, the average percentage luminal loss was significantly greater in TPU grafts (85.2%; 40.8%-100%) than in bare nitinol stents (49.5%; 37.9%-62.4%) (P = .003). The difference in neointimal height and percentage average stenosis between TPU grafts (1,028.7 microm and 68.4%) and bare nitinol stents (1,033.6 microm [918.0-1,118.40 microm] and 68.1% [60.44%-71.99%]) was not statistically significant. After 12 weeks, the average percentage luminal loss was 100% in TPU grafts due to occlusion of all stent-grafts and 24.9% (8.0%-63.9%) in bare nitinol stents (P = .011).


CONCLUSIONS
TPU grafts failed to provide improved patency compared with the bare nitinol stents because of excessive neointimal growth and subsequent occlusion. In addition, the bare nitinol stents showed considerable in-stent stenosis at angiography and microscopy.
Radeleff
Boris
B
Department of Diagnostic Radiology, University of Heidelberg, Im Neuenheimer Feld 110, 69120 Heidelberg, Germany. Boris_radeleff@med.uni-heidelberg.de
Grenacher
Lars
L
Christoph
Patricia
P
Sommer
Christof M
CM
Stampfl
Ulrike
U
Ramsauer
Stefanie
S
Henn
Tina
T
Kurz
Patrick
P
Lopez-Benitez
Ruben
R
Berger
Irina
I
Richter
Goetz M
GM
D000497:Alloys / Q000009:adverse effects / Q000737:chemistry; D000818:Animals; D001807:Blood Vessel Prosthesis / Q000009:adverse effects*; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D004195:Disease Models, Animal; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006083:Graft Occlusion, Vascular / Q000175:diagnosis / Q000209:etiology*; D006358:Hot Temperature; D006801:Humans; D007083:Iliac Artery / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D010969:Plastics / Q000009:adverse effects / Q000737:chemistry; D011140:Polyurethanes / Q000009:adverse effects* / Q000737:chemistry; D016062:Porosity; D011859:Radiography; D015607:Stents / Q000009:adverse effects*; D013552:Swine
D000497:Alloys; D020099:Coated Materials, Biocompatible; D010969:Plastics; D011140:Polyurethanes; C013616:nitinol