Local catheter-based intracoronary radiation therapy for restenosis.

Intracoronary radiation therapy was shown to be effective in limiting "restenosis-like" phenomena by inhibiting neointima formation after balloon angioplasty in porcine coronary arteries. Using the same treatment doses, both gamma and beta emitters demonstrated similar results, despite differences in isotope characteristics (e.g., penetration, activity, dose rate, and treatment time). In addition, intracoronary radiation delivered via a catheter-based system prior to coronary stenting reduced neointimal hyperplasia in the porcine model and may further reduce restenosis when coupled with stent implantation. Radioactive stents are of value, especially in large vessels, because of their low activity and proximity to the vessel wall. Adventitial labeling and immunostaining have suggested that the mechanisms by which radiation reduces restenosis are (1) inhibition of smooth muscle cell proliferation in the adventitia and (2) favorable effects on vessel remodeling. Technical radiation considerations are also discussed, including isotope selection, treatment dose, homogeneous dosimetry, treatment time, and total body dose to the patient and healthcare personnel. New catheter-based delivery systems for intracoronary use are currently being developed and are described. Preliminary clinical and angiographic studies using endovascular radiation after balloon angioplasty in both stented and nonstented peripheral and coronary arteries indicate favorable long-term results. In response to the growing enthusiasm for this approach, larger populations must be studied to determine whether this new therapy will influence the restenosis rate and clinical events after angioplasty and, in a broader sense, the field of interventional cardiology.