Tracheal Self-Expandable Metallic Stents: A Comparative Study of Three Different Stents in a Rabbit Model. 
The objective of this study was to assess tracheal reactivity after the deployment of different self-expandable metal stents (SEMS).  Forty female New Zealand rabbits were divided into four groups.  Three groups received three different SEMS: steel (ST), nitinol (NiTi), or nitinol drug-eluting stent (DES); the fourth group was the control group (no stent).  Stents were deployed percutaneously under fluoroscopic guidance.  Animals were assessed by multi-slice, computed tomography (CT) scans, and tracheas were collected for anatomical pathology (AP) study.  Data from CT and AP were statistically analyzed and correlated.  The DES group had the longest stenosis (20.51±14.08mm vs. 5.84±12.43 and 6.57±6.54mm in NiTi and ST, respectively, day 30; P<.05), and higher granuloma formation on CT (50% of cases).  The NiTi group showed the lowest grade of stenosis (2.86±6.91% vs. 11.28±13.98 and 15.54±25.95% in DES and ST, respectively; P<.05).  The AP study revealed that the ST group developed intense proliferative reactivity compared to the other groups.  In the DES group, a destructive response was observed in 70% of the animals, while the NiTi was the least reactive stent.  CT was more effective in detecting wall thickening (positive correlation of 68.9%; P<.001) than granuloma (not significant).  The ST group developed granulomas and significant stenosis.  NiTi was the least reactive stent, while DES caused significant lesions that may be related to drug dosage.  This type of DES stent is therefore not recommended for the treatment of tracheobronchial stenosis.