Examination of the in vivo mechanisms of late drug-eluting stent thrombosis: findings from optical coherence tomography and intravascular ultrasound imaging.

OBJECTIVES: This study investigated the role of uncovered stent struts on late stent thrombosis (LST) after drug-eluting stent (DES) implantation with optical coherence tomography (OCT).
BACKGROUND: Autopsy studies have identified delayed healing and lack of endothelialization of DES struts as the hallmarks of LST. DES strut coverage has not previously been examined in vivo in patients with LST.
METHODS: We studied 54 patients, including 18 with DES LST (median 615 days after implant) undergoing emergent percutaneous coronary interventions and 36 matched DES control subjects undergoing routine repeat OCT and intravascular ultrasound (IVUS) who did not experience LST for ≥3 years. Thrombus aspiration was performed during emergent percutaneous coronary intervention before OCT and IVUS assessment.
RESULTS: By OCT, patients with LST--compared with control subjects--had a higher percentage of uncovered (median [interquartile range]) (12.27 [5.50 to 23.33] vs. 4.14 [3.00 to 6.22], p < 0.001) and malapposed (4.60 [1.85 to 7.19] vs. 1.81 [0.00 to 2.99], p < 0.001) struts. The mean neointimal thickness was similar in the 2 groups (0.23 ± 0.17 mm vs. 0.17 ± 0.09 mm, p = 0.28). By IVUS, stent expansion was comparable in the 2 groups, although positive remodeling was increased in patients with LST (mean vessel cross-section area 19.4 ± 5.8 mm(2) vs. 15.1 ± 4.6 mm(2), p = 0.003). Thrombus aspiration demonstrated neutrophils and eosinophils in most cases. By multivariable analysis, the length of segment with uncovered stent struts by OCT and the remodeling index by IVUS were independent predictors of LST.
CONCLUSIONS: In this in vivo case-controlled study, the presence of uncovered stent struts as assessed by OCT and positive vessel remodeling as imaged by IVUS were associated with LST after DES.