c-myc or c-myb oligonucleotides). There is a vast amount of
experimental data, with early results from gene therapy trials for
angiogenesis, but clinical trials for restenosis are awaited.
Brachytherapy
Over the last few years there has been considerable interest in
intravascular brachytherapy (radiation therapy). The ability of
ionising radiation to halt cell growth by damaging the DNA of
dividing cells, and the view that neointimal hyperplasia
represented a benign proliferative condition led to its application
in vascular disease. A variety of catheter based delivery systems
and radioactive stents are available using either beta (e.g.^32 P) or
gamma (e.g.^192 Ir) sources. A number of studies have shown
impressive results on reducing restenosis rates and many more
are underway but enthusiasm for the technique should be
tempered because there are concerns about long term safety.
Indeed there are very recent reports of unexpected late thrombotic
occlusion.
Photodynamic therapy (PTD) involves the local activation of a
systemically administered photosensitising agent by non-
ionising radiation in the form of non-thermal laser light. Many of
the sensitising agents that have been studied have been products
of porphyrin metabolism such as 5-aminolaevulinic acid. Much
of the work in this field to date has been in the treatment of cancer
but there is an accumulation of small and large animal data
showing a reduction in neointimal hyperplasia after balloon
injury. Favourable vessel wall remodelling has also been
observed in a pig model of balloon coronary and iliac angioplasty.
Reports of the clinical application of photodynamic therapy are
limited but a clinical pilot study of adjuvant PDT in superficial
femoral angioplasty showed it to be a safe and effective
technique. Further work needs to be done to establish its role in
coronary disease.
FFuurrtthheerr rreeaaddiinngg
Jenkins MP, Buonaccorsi GA et al. Reduction in the response to coronary
and iliac artery injury with photodynamic therapy using 5-amino-
laevulinic acid. Cardiovasc Res2000; 4455 : 478–85.
Kullo IJ, Simari RD, Schwartz RS. Vascular gene transfer; from bench to
bedside. Arterioscler Thromb Vasc Biol1999; 1199 : 196–207.