Intracoronary Radiation Before Stent Implantation Inhibits Neointima Formation in Stented Porcine Coronary Arteries

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Abstract
Background Stent implantation has been shown to reduce restenosis by establishing a larger lumen but not by reducing neointima formation. We have previously shown that ionizing radiation reduced neointima formation after balloon injury in a swine model of restenosis. The purpose of this study was to determine whether endovascular irradiation of the coronary artery before stent implantation would affect neointima formation. Methods and Results Nine normolipemic pigs underwent coronary angiography, and segments of the left anterior descending and left circumflex arteries were chosen as targets for stenting. A high-activity 192 Ir source was used to deliver 14 Gy by random assignment to one of the vessels. After this, 3.5-mm tantalum stents were implanted in both arteries. Three additional pigs were treated with a 90 Sr/Y source (a pure β-emitter) delivering 14 Gy to five segments of coronary vessels that were stented immediately after irradiation. Stent-to-artery ratio was similar in the radiated and the control arteries. Animals received aspirin 325 mg daily and were killed at 28 days. The intimal area was significantly reduced in the irradiated stented arteries compared with control arteries treated with stent only (1.98 mm 2 with 192 Ir and 2.53 mm 2 with 90 Sr/Y versus 3.82 mm 2 in the control stented arteries, P <.005). Conclusions Endovascular radiation before coronary stenting reduces neointima formation and may further reduce the restenosis rate after stent implantation.

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