Biomedical Engineering Reference
In-Depth Information
revascularisation (TVR) is an enormous clinical problem affecting some
250 000 patients worldwide (Schiele
et al.
, 2004). Infl ammation, thrombus
formation and compression of various components of the arterial wall have
all been advocated as factors inducing in-stent hyperplasia, but the exact
mechanism is still unknown (Lui
et al.
, 1999). It has also been questioned
whether the more aggressive techniques implemented to reduce thrombotic
complications (i.e. balloon over-dilation) actually lead to more extended
vessel damage, which may again be a contributing or initiating factor of
ISR. It is argued that the greater the damage induced by the stent deploy-
ment procedure the more pronounced the infl ammatory response and, in
general, the wound healing process (Santin
et al.
, 2004, 2005; Guildford
et al.
, 2009; Stewart
et al.
, 2009). Despite many attempts, no controlled trial
has proven successful in establishing pre-procedural markers or an effective
technical pharmacological solution to the problem (Santin
et al.
, 2005). It
is therefore not possible to predict with a high degree of certainty which
patients, vessels, or lesions will undergo ISR.
ISR after coronary intervention is generally thought to result from the
mechanism of remodelling of the vessel, as well as from a proliferative
response to injury (Santin
et al.
, 2005). However, the process of ISR also
consists of a complex interaction of cellular (platelet, infl ammatory cells,
endothelial cells and smooth muscle cells) and acellular (proteoglycans,
collagen and fi brin - see Fig. 7.4) components under the effect of cytokines
and growth factors (Virmani
,
2004; Santin
et al.
, 2004; Guildford
et al.
, 2009;
7
.
4
Typical histological analysis of a retrieved stent. Safranin-Orange
staining shows the proteoglycan-rich composition of the neointimal
tissue. Specimen kindly provided by Dr G. Bruschi, Niguarda Hospital,
Milan, Italy. Histological analysis by A. Guildford. Details of this study
have been published by Guildford
et al.
(2009).
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