Frequency and characteristics of incomplete stent apposition during and after sirolimus-eluting stent implantation

OBJECTIVES: Incomplete stent apposition (ISA) is frequently observed after sirolimus-eluting stent (SES) implantation. This study investigated the incidence, morphological features, and possible mechanisms of this phenomenon. METHODS: Fifty-two lesions in 47 eligible patients were treated with SES and serial intravascular ultrasound (IVUS) assessment at the time of post-intervention and 8-month follow-up. ISA was carefully identified from the IVUS images of these lesions. Specifically, quantitative two dimensional IVUS analysis was performed if the lesions demonstrated ISA, including routine IVUS parameters as well as other measurements related to ISA. RESULTS: Overall, ISA was observed in 13 lesions (25.0%) at follow-up. Persistent ISA (n = 6, 11.5%), defined as ISA consistently observed both at post-intervention and follow-up, and late-acquired ISA (n = 7, 13.5%)were systematically compared. Eighty-three percent of cases of persistent ISA were located around the stent edges, whereas all cases of late-acquired ISA were in the stent body. In the persistent ISA group, no serial changes were observed in the lumen area or external elastic membrane area (EEMA) from post-intervention to follow-up. However, in the late-acquired ISA group, EEMA and lumen area significantly increased from post-intervention to follow-up (EEMA: 13.4 +/- 3.2 vs 17.6 +/- 3.3 mm2, respectively, p < 0.0001 ; lumen area: 6.7 +/- 1.4 vs 9.2 +/- 1.8 mm2, respectively, p = 0.004). No adverse clinical events were observed in either group. CONCLUSIONS: ISA was frequently observed during and after SES implantation in clinical practice. No clinical disadvantages were observed during 16 month clinical follow-up periods. Positive remodeling may potentially cause late-acquired ISA.