|MThe Stent Coating Machine
TRANSLUMINA COATING TECHNIQUE AND POLYMER ISSUES
Several publications report about the possibility of using
a polymer as a good solution to store the drug and to define
a release mechanism. On the other hand, there are many publications
that rise concerns about the usage of polymers as biocompatible
implant materials. Polymers can create severe inflammatory
reactions, sometimes immediately after implantation, sometimes
after several months or years, due to the oxidative decomposition
of the polymer matrices by human macrophages or active enzymatic
(see literature Van der Giesson et al, Circulation 1996,
94, 1690-1697 and A.Curcio et al., Am.J.Physiol. Heart Circ.
Physiol. (2003), in press, online available.)
The most important factor for the efficiency of the drug
is the effect of the drug itself and the possibility of
transporting the drug to the vessel wall without any disturbances.
With a polymer there are several essential disadvantages:
- Decreased biocompatibility at least over a long time
- Decreased release due to the bonding effects between
the substance and the polymer, especially when using an
additional top or covering layer. (see Presentation TCT2003
by M. E. Russel, MD Natick MS "The BSC Drug- Eluting Stent
System: Polymer Characteristics and Drug Delivery")
- Decreased efficiency of the substance due to long storage
periods, especially for sensitive substances.
- Thick coating layers with the risk of loosing coating
layer plaques and the risk of embolism due to a high polymer/substance
ratio (e.g. 70 % for current competitors stents).
- The properties of the coating layer can change after
the crimping process. Additionally, very sensitive handling
is requested due to the risk that the thick coating layer
can be damaged during the intervention or during the postdilatation
with another balloon with larger diameter.
- Regarding the sensitiveness of the polymer and the type
of the lesion, it is noticed that in the clinical routine,
physicians sometimes have to perform pre- dilatation to
avoid damaging of the polymer coating by calcificated
lesions. This is not necessary for implantation of YUKONŽDES
Coronary Stent System - PEARL surface.
- Due to mechanical characteristics of YUKONŽDES Coronary
Stent System - PEARL surface, the flexibility of the stent
remains unchanged, compared to lower flexibility of polymer