INTRACORONARY IRRADIATION MARKEDLY REDUCES NEOINTIMAL PROLIFERATION AFTER BALLOON ANGIOPLASTY IN SWINE - PERSISTENT BENEFIT AT 6-MONTH FOLLOW-UP

Objectives. This study examined the long-term efficacy of intracoronar y irradiation for limiting neointimal proliferation after overstretch balloon angioplasty in a porcine model of restenosis. In addition, thi s study sought to identify any adverse late sequelae of this novel the rapy for restenosis. Background. Restenosis after coronary angioplasty represents in part a proliferative response of vascular smooth muscle at the site of injury. We have shown previously that high dose intrac oronary radiation induces focal medial fibrosis and markedly reduces n eointimal proliferation early after balloon angioplasty in swine. Meth ods. Twenty-two juvenile swine underwent intervention at a target segm ent of the left coronary artery. In 11 swine, a 2-cm ribbon of iridium -192 was positioned at the target segment and 2,000 cGy was delivered to the vessel wall. Subsequently, overdilation balloon angioplasty was performed at the irradiated segment. In 11 control swine, overdilatio n balloon angioplasty was performed without previous irradiation. Twen ty animals survived and underwent histopathologic analysis at 180 +/- 8 days. Results. Mean (+/-SD) neointimal area was 1.59 +/- 0.78 and 0. 46 +/- 0.35 mm(2) (p < 0.001) in control and irradiated animals, respe ctively. Mean percent area stenosis was 37.9 +/- 12.4% and 14.2 +/- 9. 0% (p < 0.001) in the control and irradiated animals, respectively. Th us, by 6 month follow-up, intracoronary irradiation before balloon ang ioplasty had reduced the bulk of the neointimal lesion by 71.1% and re duced percent area stenosis by 62.5% compared with that in control ani mals. There was no evidence of radiation vasculopathy or myocardial da mage at 6 months. Conclusions. Intracoronary irradiation (2,000 cGy) p roduces persistent impairment of neointimal proliferation 6 months aft er balloon injury, with no evidence of late radiation sequelae.