Cardiovascular stents - Biomaterials and Devices for the Circulatory System - page 185

performance of DLC coated stents, however, has been mixed. Airoldi and
colleagues (2004) compared DLC coated stents (Diamond Flex AS, Phytis
Medical Devices, Berlin, Germany) with uncoated stainless steel stents and
showed in a study covering 347 patients that carbon coatings did not provide
a signifi cant improvement in clinical or angiographic outcome over stainless
steel stents of the same design. A similar outcome was reported by Meireles
and colleages (2007) on comparison of the Phytis™ DLC-coated stent
(Phytis Medical Devices, Berlin, Germany) with stainless steel stents (Multi-
Link Penta™, Abbott Laboratories, Abbot Park, IL) where, again, no
signifi cant difference was seen in retenosis rates six months after implanta-
tion. However, Salahas et al. (2007), have reported the results of a non-
randomised observational study which demonstrated that DLC Phytis™
stents (Phytis Medical Devices, Berlin, Germany) are easy to use, biologi-
cally compatible, safe and clinically effective at six-month follow-up and
associated them with very low rates of ischaemia-driven target lesion revas-
cularisation (TLR) and TVR. The authors suggested that these results
support the use of DLC-coated in patients with un-complex long lesions in
at least medium-sized coronary vessels or patients that cannot tolerate the
anti-platelet therapy associated with the use of drug eluting stents. The
development of DLC coatings is ongoing, with efforts to improve their
mechanical stability, corrosion barrier properties and biocompatibility by
doping the carbon with other ions such as silicon (Maguire et al. , 2005) and
fl uorine (Hasebe et al. , 2007).
Arguably, a more successful approach to utilising carbon as a stent coating
has arisen from the development of pyrolytic carbon technology developed
initially by Sorin Biomedica (Saluggia, Italy) in the early 1960s. The result-
ing Carbostent™ was integrally coated with a permanent thin fi lm (0.3-
0.5 µm) of turbostratic carbon (Carbofi lm™) which had previously been
applied to heart valves to impart improved thromboresistance and bio-
compatibility. The fi lm, vapour deposited at room temperature under high
vacuum, provides a permanently bound, biocompatible coating with appro-
priate mechanical properties (Colombo & Takagi, 2001). However, although
some studies have suggested low rates of acute and sub-acute thrombosis
and restenosis associated with carbon-coated (Carbostent™) stents (Anto-
niucci et al. , 2000, 2001; Bartorelli et al. , 2002), no improvement in major
adverse cardiac events (myocardial infarction, reintervention and death),
angiographic results or reduction in restenosis rate was shown when com-
pared to bare stainless steel stents (Sick et al. , 2004). This has been echoed
by Haase and colleagues (2003) who demonstrated no clinically relevant
reduction of ISR or major adverse cardiac events in stents coated with
turbostratic carbon compared with uncoated stainless steel stents. More
recently, Wöhrle and colleagues reported the long-term angiographic results
of a stent with a high density, ultra-thin fi lm (0.3-0.5

￿ ￿ ￿ ￿ ￿

μ m) of turbostratic