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Coronary vascular brachytherapy reduces recurrent restenosis and is a valuable adjunct to percutaneous coronary intervention (PCI) in the treatment of in-stent restenosis (level of evidence A). Although both late (6 month) coronary restenosis and the occurrence of adverse cardiovascular events are decreased by vascular brachytherapy, late (> 30 days) thrombotic occlusion is observed more frequently in irradiation (versus placebo) treated patients (Figure 1). Dr. Teirstein, a pioneer in this field, contributes an article in this issue of the Journal that draws attention to this potentially lethal problem but falls short in making concrete recommendations for prevention. Vascular brachytherapy is associated with a dose-dependent increase in luminal thrombus that may persist for months following treatment. In addition, brachytherapy retards re-endothelialization and vascular healing. Contrary to original dogma derived by extrapolation from painfully limited animal data, stent re-endothelialization is often not completed by 30 days but may instead require 90 days in normal individuals. The deployment of another coronary stent for the treatment of in-stent restenosis may further exacerbate the delay in healing and re-endothelization secondary to brachytherapy. Clinical factors central to the pathogenesis of late thrombosis include recurrent stenting and the discontinuation of thienopyridine therapy. Although the strategy of restenting is enticing by nature of its expedient, predictable effect on post-procedural lumen diameter, its avoidance is appropriately recommended by Teirstein. In those patients in whom further stenting is not required, six months of thienopyridine therapy would appear adequate and advisable. However, in patients in whom restenting is performed, the recommendation for thienopyridine to be continued for "up to one year" may be inadequate. Although evidence-based support for sound recommendations in this population is lacking, anecdotal case-based experience may yield important insights that temper our long-term approach.
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Clinical outcomes to 270 days in the Gamma I and II trials. Although both MACE and TLR were significantly reduced by gamma irradiation, stent closure was increased in irradiated patients (versus placebo). MACE = major adverse cardiovascular events (death, myocardial infarction, urgent coronary revascularization); TLR = target lesion revascularization; Irradiation (Ir192) = gamma irradiation source.
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