Effect of antiplatelet therapy on restenosis after experimental angioplasty

Restenosis is recognized as a common complication of PTCA and can limit the long-term benefit of this procedure. To study the effect of antiplatelet agents in preventing restenosis, 25 New Zealand rabbits had bilateral iliac stenoses created by balloon deendothelialization and a 2% cholesterol diet for 6 weeks. After angiographic delineation of the iliac atherosclerosis, successful angioplasty was performed in all rabbits, with an average increase in luminal diameter of 0.9 mm (81%). Seven rabbits received aspirin (32 mg/day) plus dipyridamole (25 mg/day) and 9 received sulfinpyrazone (100 mg/day); 9 were given no antiplatelet drugs and served as controls. After 4 weeks of drug therapy and a continued atherogenic diet, angiography was repeated and the rabbits were killed for histologic examination. The angiographic luminal diameter was similar for these groups both before and immediately after angioplasty. However, the luminal diameter 4 weeks later was significantly larger in both the aspirin plus dipyridamole and the sulfinpyrazone groups compared with the control rabbits (1.3 +/- 0.6 and 1.8 +/- 0.5 mm vs 0.7 +/- 0.6 mm, respectively, p less than 0.05). Histologic examination revealed intraluminal clot in 4 of 9 control rabbits and in none of the drug-treated rabbits. Also, less intimal thickening was evident. In conclusion, aspirin plus dipyridamole and sulfinpyrazone inhibited angiographic restenosis after transluminal angioplasty in this experimental model. These findings support the use of antiplatelet agents in clinical angioplasty and suggest that platelet aggregation at the angioplasty site may promote restenosis.