Local Determinants of Thrombus Formation Following Sirolimus-Eluting Stent Implantation Assessed by Optical Coherence Tomography

Objectives We conducted this study to assess the prevalence and determinants of subclinical thrombus after sirolimus-eluting stent (SES) implantation. Background Angioscopic analyses have demonstrated the presence of thrombus is more common than the clinical incidence of SES thrombosis. Methods Fifty-three patients (53 lesions) underwent 6-month follow-up optical coherence tomography. A stent eccentricity index ([SEI] minimum/maximum stent diameter) was determined in each cross section. To evaluate unevenness of neointimal thickness, a neointimal unevenness score ([NUS] maximum neointimal thickness in the cross section/average neointimal thickness of the same cross section) was calculated for each cross section. Average SEI and NUS were calculated for each stent. Major adverse cardiac events were defined as a composite of death, myocardial infarction, and target vessel revascularization. Results Fourteen cases of thrombus (26%) were detected by optical coherence tomography (thrombus: n = 14 vs. nonthrombus: n = 39). The percentage of thrombus was associated with longer stents (36.4 ± 20.2 mm vs. 25.1 ± 9.8 mm; p = 0.008), a larger number of uncovered struts (17 ± 16 vs. 8 ± 11; p = 0.03), smaller average SEI (0.89 ± 0.04 vs. 0.92 ± 0.03; p = 0.001), and greater average NUS (2.22 ± 0.24 vs. 2.00 ± 0.33; p = 0.03). A significant relationship existed between average SEI and average NUS (p < 0.0001, R = 0.68), and between average SEI and the number of uncovered struts (p < 0.0006, R = 0.46). There was no significant difference in major adverse cardiac events during follow-up (median: 485 days, 7.1% vs. 12.8%; p > 0.99). Conclusions Longer stents and greater asymmetric stent expansion may be important determinants of thrombus formation after SES implantation. In this small cohort, the presence of thrombus did not increase the risk of major adverse cardiac events.