Optical coherence tomography endpoints in stent clinical investigations: strut coverage

Abstract

Late stent thrombosis (LST) and very LST (VLST) are infrequent complications after drug-eluting stent (DES) implantation, but they carry a significant risk for patients. Delayed healing, which may be represented by incomplete stent coverage, has been observed in necropsy vessel specimens treated with DES. As a result, in vivo assessment of stent coverage, as well as stent apposition using optical coherence tomography (OCT), have been recently used as surrogate safety endpoints in clinical trials testing DES platforms. By adopting strut coverage assessed by OCT, one can assess the safety profile of the new generation of DES in preregistration studies. This article focuses on stent strut coverage as a central predictor of late DES thrombosis from the histopathological point of view, discusses the limitations of the current imaging modalities and presents the technical characteristics of OCT for the detection of neointimal coverage after stent implantation. We also review the preclinical and clinical investigations using this novel imaging modality.

Quantitative Optical Frequency Domain Imaging Assessment of In-Stent Structures in PatientsWith ST-Segment Elevation Myocardial Infarction

“…10- 14 Interestingly, a previous study demonstrated that lumen and stent areas showed low variability (<10%) within the various sampling distances ranging from 0.3 to 2.4 mm. 15 The variability in detecting uncovered stent struts, however, increased across the sampling distances, and the relative difference reached more than 50% at 0.90-mm analysis compared to 0.06-mm analysis as a reference. This suggests that quantification of lumen and stent areas is stable over a wide range of SR but that heterogeneously distributed structures such as uncovered struts are influenced by SR.…”

Evaluation of Zotarolimus-Eluting Metal Stent in Animal Ureters

“…Nearinfrared light is used because it is less absorbed and scattered than visible light; it results in improved image quality and renders OCT superior for visualization of microscopic structures such as vessels and ureters with stents. 12,13 The optical beam scans radially the lumen of the ureter in a sequential manner similar to radar, and optical reflections from the vessel wall are measured. Information during the movement of the optic fiber from the reflective boundaries and the intensity of backscattering light are collected (time domain OCT).…”

“…13 The above high resolution properties result in images reaching histology-level capacity for detection and quantification of even small layers of newly formed tissue over ZES struts. The layers of the ureter were evaluated by the OCT according to the description used by Mueller-Lisse and associates 14 that was successfully correlated to histologic results.…”

Are the findings of optical coherence tomography sufficient for the evaluation of the safety and efficacy of the next generation of drug eluting stents?

“…These studies are obviously prone to selection bias with Type I error. Additionally incomplete stent coverage without apposition has been associated with subclinical thrombus formation at followup [13][14][15][16][17]. The number of uncovered struts may be important in determining thrombus formation following sirolimus stent implantation.…”