Evaluation of intravascular ultrasound findings in 5 cases of very late stent thrombosis after sirolimus-eluting stent implantation

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Objective: We examined intravascular ultrasound (IVUS) findings in patients who had very late stent thrombosis (VLST) after sirolimus-eluting stent implantation. Methods: The study population consisted of 5 patients diagnosed with acute myocardial infarction and identified as VLST by emergent coronary angiography. All of them underwent both of the thrombus aspiration and IVUS investigation before the balloon angioplasty. IVUS images just after the index SES implantation were available in 3 patients. The delta external elastic membrane-cross sectional area (ΔEEM-CSA) was defined as the increase of maximal EEM-CSA from the SES deployment to the onset of VLST. Results: The median duration from the index procedure to VLST was 53 months (interquartile range 18 to 63). Late incomplete stent apposition and vessel remodeling was found in all cases. The mean maximal EEM-CSA was significantly larger than the reference EEM-CSA (20.9±7.2 mm2 versus 12.1±4.3 mm2; p=0.028), and the mean remodeling index was 1.78±0.47. Moreover, the maximal EEM-CSA and ΔEEM-CSA positively correlated with the duration from the baseline to VLST (R2=0.95; p=0.003 and R2=0.99; p=0.03). Conclusions: SES-related VLST is strongly associated with positive remodeling and the extent positively correlates the interval from the index procedure to the events. Serial IVUS study might be useful to stratify the risk of SES-related VLST.