Effects of overexpansion on stents' recoil, symmetry/asymmetry, and neointimal hyperplasia in aortas of hypercholesterolemic rabbits.
BACKGROUND
It is not known whether overexpansion modifies stent recoil, symmetric distribution of struts, and neointimal hyperplasia.


OBJECTIVE
The objectives were (a) to evaluate whether stent overexpansion modifies the geometric configuration of the stent in the arterial wall, (b) to determine the relationship between overexpansion and stent recoil, and (c) to evaluate the relationship between the distribution of struts and neointimal hyperplasia.


METHODS
Twenty tubular stainless steel 316L stents (3.0 and 3.5 mm in diameter) were implanted at 20 and 10 atm, respectively, in the abdominal aorta of New Zealand rabbits fed a hypercholesterolemic diet (1% cholesterol). Sham operations were also performed in seven animals. Eight weeks after implantation or sham operation, an intravascular ultrasound (IVUS) study was performed to measure stent recoil and aid in stent classification (symmetric or asymmetric) according to strut distribution. The degree of injury and neointimal hyperplasia were also evaluated in hematoxylin-eosin stained sections.


RESULTS
The symmetry/asymmetry of stents assessed by IVUS, as well as the neointimal hyperplasia, was similar in both groups. Stent recoil was significantly greater in the 3.0-mm stent (overexpanded) group (0.28+/-0.02 mm), as compared with stent recoil in the 3.5-mm stent group (0.10+/-0.01 mm, P<.05). The neointimal hyperplasia in histological slices, independent of the implant technique, was predominantly in zones with higher strut concentration as compared with zones with fewer struts.


CONCLUSIONS
Stent overexpansion enhanced stent recoil and did not modify symmetric and asymmetric strut distribution. Neointimal hyperplasia was not modified by the implant technique. Interestingly, significant hyperplasia was observed in locations with greater strut concentration, independent of overexpansion.
Berrocal
Daniel H
DH
Department of Interventional Cardiology, Hospital Italiano de Buenos Aires, and Department of Pathology, Faculty of Medicine, University of Buenos Aires, Buenos Aires, Argentina.
González
Germán E
GE
Fernández
Alejandro
A
Perez
Susana
S
Wilensky
Luciana
L
Morales
Celina
C
Grinfeld
Liliana
L
Gelpi
Ricardo J
RJ
D000818:Animals; D001012:Aorta, Abdominal / Q000473:pathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D019917:Blood Vessel Prosthesis Implantation / Q000295:instrumentation* / Q000379:methods; D006937:Hypercholesterolemia / Q000150:complications; D006965:Hyperplasia; D016491:Peripheral Vascular Diseases / Q000209:etiology / Q000601:surgery*; D011817:Rabbits; D015607:Stents; D017539:Tunica Intima / Q000473:pathology* / Q000601:surgery