Intracoronary irradiation (2,000 cGy) delivered to a target porcine coronary segment before balloon overdilation markedly reduces neointima formation at 30 days and thus significantly impairs the restenosis process.

Intracoronary irradiation (2,000 cGy) produces persistent impairment of neointimal proliferation 6 months after balloon injury, with no evidence of late radiation sequelae.

No abstract

Most patients with syndrome X have abnormal coronary arteries by intravascular ultrasound. Intravascular ultrasound identifies three distinct morphologic groups: normal coronary arteries, atheromatous plaque and intimal thickening. Exercise-vasomotion is normal in patients with syndrome X who have normal coronary arteries by ultrasound; patients with abnormal arteries (plaque or intimal thickening) have an abnormal (constrictive) response to exercise. Propranolol loading attenuates vasoreactivity in all subgroups, suggesting divergent therapeutic utility.

A significant component of restenosis after coronary angioplasty is due to medial proliferation. Targeted ablation of the proliferating cells by ionizing radiation may prevent restenosis. We delivered high-dose intracoronary gamma-irradiation in porcine coronary arteries and assessed vasomotor function acutely and at 32 days, with pathological analysis at 32 days. Changes in luminal area were assessed by intravascular ultrasound. Irradiated segments acutely displayed vasoconstriction to acetylcholine, with loss of smooth muscle response to nitroglycerin. Restudy revealed restoration of normal vasodilatory response to acetylcholine but persistent loss of response to nitroglycerin. Histopathology at 32 days revealed minor neointima formation without luminal compromise and diffuse fibrosis of the smooth muscle layer. The surrounding myocardium was normal. Focal medial fibrosis without significant endothelial or myocardial damage can be achieved via this technique; intracoronary irradiation, therefore, may be an effective way of impairing the restenosis process.