Experimentelle Untersuchungen am porzinen „over-sized coronary stent“-

Experimental investigations at the porcine over-sized coronary
stent-model for in-stent-restenosis rate after implantation of
uncoated niob-zirkonium stents and niob-zirkonium stents coated
with iridiumoxide. Background: The treatment of atherosclerotic
stenosis in coronary artery disease with balloon expandable
coronary stents has been successfully practised in minimal invasive
cardiology in the last two decades. Today almost all commercially
coronary stents are made of stainless steel (316L) and there is a
great variety in design and coatings available. Until now no
interventional procedure has been successful to stop the vicious
circle of arterial stenosis, intervention and restenosis. Methods:
In 23 pigs (German land breed) Inflow Dynamics Starflex Design
Stents were implanted into the LAD and LCX by random for 28 days.
In the porcine over-sized coronary stent model three groups were
compared: uncoated niob-zirkonium stents, niob-zirkonium stents
coated with iridiumoxide and stainless steel stents (control
group). The implantation procedure and angiography were documented
and histological and histomorphometric studies were performed to
interpret the in-stent-restenosis rate. The statistical evaluation
of the differences between the test groups was done by the analysis
of variance (One Way ANOVA-Test) and specified (Post Hoc-Test).
Results: Three animals died postoperatively. 38 stents were
evaluated. The implantation procedure in the experimental groups
was complicated due to the elastic and plastic properties of the
niob-zirkonium stents. The injury score (IS) and the measured
neointimal area (NF) were significantly higher in the group of
niob-zirkonium stents coated with iridiumoxide. The
histomorphometric and angiographic parameters of restenosis did not
point out any significant difference between the test groups. The
histological response of the arterial wall after stent implanation
provided a homogenous appearance of tissue shaped by the score of
vascular irritation. Conclusion: A direct comparison in the stents
of uncoated niob-zirkonium and niob-zirkonium stents coated with
iridiumoxide with stainless steel stents was not possible. No new
findings for the in-stent-restenosis rate were provided by the
results of the control stents. The prototypes of the uncoated
niob-zirkonium stents and the niob-zirkonium stents coated with
iridiumoxide have to be optimized in their metallurgical
characteristics to guarantee an implantation procedure without
complications. The alloy niob-zirkonium and the
iridiumoxide-coating are excellently biocompatible. Even SUMMARY
117 after a high vascular irritation the stents are embeded into a
neointima with only a minimum of cellular response.