The Effects of Clopidogrel Duration On Carotid Artery In-stent Restenosis

Objective There is limited data supporting a specific duration for dual antiplatelet therapy in carotid artery stenting (CAS), and most clinical evidence is derived from studies involving coronary interventions. As a result, the appropriate duration of dual antiplatelet therapy after CAS has yet to be determined. We aimed to elucidate whether the duration of dual antiplatelet therapy played a role in the rate of carotid in-stent restenosis. Methods A retrospective analysis of all patients who underwent CAS at our institution over a 20-year period (1996-2016) was performed (n=279). Patients who did not complete their follow-up duplex studies or were not discharged on clopidogrel were excluded from the study. Patients were separated into short-term (<6 weeks, n=159) and long-term (>6 weeks, n=112) clopidogrel users based on duration of therapy. We defined clinically significant in-stent restenosis as >50% restenosis (PSV = 224 cm/s) in symptomatic patients and >80% restenosis (PSV = 325 cm/s) in asymptomatic patients status-post prior CAS based on published velocity criteria. Rates of in-stent restenosis at 1-year, 2-year, and 5-year intervals were analyzed between the two groups using chi-squared analysis. Results Demographic information was largely similar between the two groups; however, short-term clopidogrel users were more likely to have a history of atrial fibrillation (9.43% vs. 1.68%, p=0.008) and were less likely to have a history of CABG (16.35% vs. 29.41%, p=0.009), diabetes (33.34% vs. 49.58%, p=0.006) and CAD (50.31% vs. 63.03%, p=0.035). All patients were on long-term aspirin therapy. There was no significant difference between overall rates of in-stent restenosis between the short-term and long-term clopidogrel users (5.03% vs. 9.24%, p=0.168) within 5 years of the index procedure. Similar results were observed when these groups were evaluated at 1-year (5.61 % vs. 3%, p=0.321), 2-year (2.02% vs. 6.59%, p=0.072), and 5-year (2.24% vs. 3.57%, p=0.635) follow-up. Conclusion No statistically significant difference was observed in the rate of in-stent restenosis after CAS between short-term and long-term clopidogrel therapy. Patients in whom there is no other indication for longer duration clopidogrel therapy may be considered for shorter duration course of dual antiplatelet therapy following CAS.