INTRACORONARY RADIATION DECREASES THE 2ND-PHASE OF INTIMAL HYPERPLASIA IN A REPEAT BALLOON ANGIOPLASTY MODEL OF RESTENOSIS

Purpose: Repeat balloon angioplasty Is likely to induce intimal prolif eration, which is associated with a higher restenosis rate, This study examined the effect of intracoronary ionizing radiation on restenotic lesions using repeat balloon injury in a normolipemic swine. Methods and Materials: Eight domestic normolipemic pigs underwent overstretch balloon angioplasty with a 3.5 mm balloon in the LAD and LCX, followed by repeat balloon injury at the same sites 4 weeks after the initial injury. At that time a high activity (192)Iridium source was introduce d immediately after the angioplasty by random assignment to deliver 14 Gy at 2 mm in eight of the injured coronary arteries (LAD and LCX). O ne month later the animals were killed and the coronary arteries press ure perfusion fixed. Serial sections were stained with H&E and VVG, th en evaluated by histopathologic and morphometric techniques. Maximal i ntimal thickness (MIT), intimal area (IA), and intimal area corrected for the extent of injury (IA/FL) were measured in the irradiated and c ontrol arteries and were compared to control arteries with single inju ries from previous studies. Results: Repeat balloon injury induced sig nificant additional medial damage, which was associated with marked in timal hyperplasia in a concentric pattern, Intracoronary irradiation s ignificantly decreased the total of neointima area formation (IA 93 0.35 mm(2) compared to control 1.38 + 0.33 mm(2) p < 0.01) and the MIT was also significantly reduced in the irradiated vessels (0.57 + 0.18 mm vs. 0.71 + 0.08 mm, p = 0.05). Conclusions: Intracoronary irradiat ion immediately after the second balloon dilatation inhibits the intim al hyperplasia due to that injury, However, there was no effect on the existing neointima from the initial injury. (C) 1997 Elsevier Science Inc.