Background: Although aspirin (ASA) is usually selected after dual-antiplatelet therapy (DAPT) duration in patients with drug eluting stent (DES) implantated, there is less information of the efficacy of clopidogrel (CLP) monotherapy. We aimed to investigate the difference of the intra-coronary reaction between single antiplatelet monotherapies such as ASA and CLP, using serial optical coherence tomography (OCT).
Methods and Results: We prospectively studied 50 patients treated with second generation DES (68 DESs). From an open-labeled study, all patients were randomized into 2 groups; ASA and CLP groups (37 in ASA, 31 in CLP), and DAPT duration was 12 months after implantation. All patients underwent serial OCT at 8-12 and 18-24 months after DES implantation. Although there were not significant differences in baseline OCT parameters between two groups, the change of maximum length of segments with stent malapposition (malapposed length) significantly decreased in CLP group than in ASA group (-0.88±1.29 mm vs -0.16±0.61 mm, p=0.002), and the strut-vessel distance also decreased in CLP group than in ASA group (-108±159 μm vs -52±106 μm, p-0.045). Intra-stent thrombus > 250 μm newly appeared in 4 DESs (1(3.2%) in CLP group and 3(8.1%) in ASA group), and disappeared in 5 DESs (3(9.7%) in CLP group and 2(5.4%) in ASA group), at 2nd OCT assessment. The change of malapposed length was significantly greater in patients with than without newly appeared intra-stent thrombus (1.03±0.80 mm vs -0.58±0.98 mm, p=0.002), while the change of strut-vessel distance was significantly shorter in patients with than without disappeared thrombus group (-238±248 μm vs -65±116 μm, p=0.002).
Conclusion: The present serial OCT study revealed that CLP monotherapy is safe and might be more effective than ASA from the aspect of vascular response.