Intracoronary β-Radiation Exacerbates Long-Term Neointima Formation in Balloon-Injured Pig Coronary Arteries

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Abstract
Background Long-term biological effects of ionizing radiation on coronary arteries remain poorly defined. We examined late arterial responses 6 months after balloon angioplasty and β-radiation in normal pig coronary arteries. Methods and Results Coronary arteries of 25 adult pigs were randomized to receive 20 Gy (n=8) or 30 Gy (n=9) of 186 Re β-radiation or sham radiation (n=8) immediately after balloon angioplasty. Aspirin was given daily during follow-up. The study vessels were analyzed histopathologically at 6 months. β-Radiation decreased lumen area (20 Gy, 1.55±0.99 mm 2 ; 30 Gy, 1.03±0.82 mm 2 ; and 0 Gy, 2.05±0.80 mm 2 ; P 2 ; 30 Gy, 1.51±0.97 mm 2 ; and 0 Gy, 0.89±0.31 mm 2 ; 0 Gy versus 20 Gy, P 2 ; 20 Gy, 0.98±1.57 mm2; and 0 Gy, 0.00±0.01 mm 2 ; P 2 ; 30 Gy, 2.38±0.98 mm 2 ; and 0 Gy, 1.23±0.29 mm 2 ; 0 Gy versus 20 or 30 Gy, P Conclusions Intracoronary β-radiation did not inhibit neointima formation in balloon-injured normal pig coronary arteries 6 months after the interventional procedure. Unresorbed thrombus contributed to, but was not the sole component of, augmented neointima formation. Irradiated vessels demonstrated more adventitial thickening and fibrosis. These observations may have relevance for long-term clinical outcomes after intracoronary β-radiation.

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