Abstract 4478: Local Determinants and Clinical Significance of Thrombus Formation Following Sirolimus-Eluting Stent Implantation: Insights from Optical Coherence Tomography Analysis

Angioscopic analyses have shown the presence of subclinical thrombus in sirolimus-eluting stents (SES) is more common than the clinical incidence of stent thrombosis. However, the determinants and long term significance of subclinical thrombus remain unknown. Thirty five patients (44 stents) who received SES underwent 6 months follow-up optical coherence tomography (OCT). Patients were divided into 2 groups according to the presence of thrombus by OCT. Cross-sectional images were analyzed every 1mm. Stent eccentricity index (SEI; minimum stent diameter divided by maximum stent diameter) was determined in each cross section (CS). To assess the unevenness of neointimal thickness (NIT), a neointimal unevenness score (NUS) was calculated for each CS as maximum NIT in the CS divided by the average NIT of the same CS. Average SEI and NUS were also calculated for each stent. Major adverse cardiac event (MACE) was defined as a composite of death, myocardial infarction, and target vessel revascularization. Eight cases of thrombus were detected by OCT (18%). The thrombus cases were associated with longer stent length, larger numbers of uncovered struts, smaller average SEI, and greater average NUS (Table ). A significant relationship existed between the average SEI and average NUS ( P <0.0001, R=0.66), as well as between average SEI and the number of uncovered struts ( P =0.005, R=0.47). There was no significant difference in MACE during follow-up (median: 655days) (Thrombus: 0%, Non-thrombus: 7.4%, P=0.43). Based on OCT, longer stents, a larger number of uncovered stent struts, asymmetric stent expansion, and unevenness of NIT may be important determinants of thrombus formation in patients treated with SES. Asymmetric stent expansion may interfere with even neointimal coverage after SES deployment, perhaps a key mechanism for thrombus formation. In this small cohort, the presence of thrombus did not seem to increase the risk of MACE.