Association between the efficacy of dual antiplatelet therapy and the development of in-stent neointimal hyperplasia in porcine coronary arteries

Objective We set out to compare the effectiveness of platelet aggregation therapy in association with the development of in-stent neointimal hyperplasia in porcine coronary arteries. Methods Thirty-two pigs underwent coronary stenting with bare-metal stents under general anaesthesia. One hundred milligrams of aspirin and loading doses of either 300 mg clopidogrel (group C, n=13) or 2 x 500 mg ticlopidine (group T, n=19) were administered before intervention. During the follow-up, the animals received a daily dose of 100 mg aspirin and 75 mg clopidogrel or 2 x 250 mg ticlopidine, respectively. After 4 weeks, the histopathological and histomorphometric parameters of the explanted stented coronaries were assessed. Levels of circulating cytokines and platelet activation factors were measured. ADP-induced and collagen-induced aggregation was measured immediately before stenting and then every 3rd day. The aggregation profiles were calculated and correlated with the histological parameters. Results The fibrin deposition scores and inflammation scores were higher in group T than in group C, with similar injury scores. Endothelialization was complete in both groups. A significantly lower neointimal area (1.08 +/- 0.36 vs. 1.58 +/- 0.5, group C vs. T, P=0.026) and percentage of area stenosis (29.8 +/- 12.1 vs. 44.3 +/- 16.3, group C vs. T, P=0.032) were observed in group C. The loading dose of clopidogrel significantly reduced the platelet activation parameters before the first angiography as compared with ticlopidone. Clopidogrel treatment resulted in a significantly better aggregation profile relative to ticlopidine (mean ADP-induced aggregation: 28.4 +/- 9.1 vs. 52.5 +/- 12.0%, P<0.001). Significant (P<0.05) positive linear correlations were observed between the ADP-induced aggregation profile and the neointimal area (r=0.584), percentage of area stenosis (r=0.666), inflammation (r=0.476) and fibrin deposition (r=0.496). Conclusion The effectiveness of dual antiplatelet therapy plays an important role in the inhibition of in-stent neointimal hyperplasia. Coron Artery Dis 19:635-643 (C) 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins.