Author + information
- Jinyong Ha, PhD,
- Byeong-Keuk Kim, MD,
- Jung-Sun Kim, MD,
- Dong-Ho Shin, MD,
- Young-Guk Ko, MD,
- Donghoon Choi, MD,
- Yangsoo Jang, MD and
- Myeong-Ki Hong, MD⁎ ()
- ↵⁎Division of Cardiology, Severance Cardiovascular Hospital, and Severance Biomedical Science Institute, Yonsei University College of Medicine, 250 Seongsanno, Seodaemun-gu, Seoul 120-752, Korea
Simple quantitative optical coherence tomography (OCT) measurements, such as the ratio of uncovered to total stent struts, provide only limited information regarding neointimal hyperplasia (NIH) coverage. To date, minimal methods have been proposed using OCT analysis to systematically evaluate neointimal coverage along an entire drug-eluting stent (DES). Therefore, we propose a novel method for assessing in vivo volumetric neointimal formation after DES implantation using 3-dimensional (3D) OCT. With this approach, a 2-dimensional (2D) contour plot allows the intuitive visualization of the unfolded stent structure in the coronary artery and identification of the geographic distribution of uncovered or malapposed stent struts.
To evaluate the potential of this new method, 5 patients who were treated by a sirolimus-eluting stent (Cordis Corp, Miami Lakes, Florida) and who underwent follow-up OCT examination after stent implantation were selected from the OCT registry database of our institute. OCT procedure was performed using a frequency-domain OCT system (C7-XR OCT imaging system, St. Jude Medical, St. Paul, Minnesota). All OCT images were generated at 100 frames/s while a catheter was pulled back at 20 mm/s.
To perform 3D OCT evaluation, a contour plot of in-stent neointimal coverage in circumferential and longitudinal directions was created according to the following steps. First, the lumen and stent contours of each cross-sectional image were delineated with the use of semi-automated contour-detection software (QIvus, Medis Medical Imaging Systems Inc., Leiden, the Netherlands) with manual adjustments. Second, the circumferential arc length to each stent strut and individual stent lengths were obtained when the distance (NIH thickness) between the center of each strut and the luminal border was measured for every frame at 0.2-mm intervals. Next, individual stent struts were classified into the following 4 categories: 1) covered-apposed; 2) uncovered-apposed; 3) uncovered-malapposed; and 4) side-branch. Covered struts had a positive NIH thickness, and uncovered-malapposed struts had a negative thickness value. A 2D contour plot of neointimal coverage as a function of circumferential arc length and longitudinal stent length was then created offline using Origin software (Origin 8.5.1, OriginLab Corporation, Northampton, Massachusetts). Individual strut locations were delineated by their pixel coordinates in (x, y) format.
A contour plot of representative case and its analysis are detailed in Figure 1. To validate the contour plot for volumetric OCT analysis, the corresponding OCT longitudinal cutaway view at the location of the red arrowhead (Fig. 1A) was generated by a 3D, volume-rendering program (OsiriX 3.9.4, The OsiriX Foundation, Geneva, Switzerland). The corresponding OCT cross-sections (green, purple, and black arrowheads) were compared in Figures 1B to 1D, respectively. The contour plots of 4 additional stents were also generated (Fig. 2).
A recent OCT study reported a method of evaluating spatial distribution of uncovered struts along the DES called the “spread-out-vessel graphics,” which involves a 2D plot with x- and y-axes (1). The x-axis represents the distance from the distal edge of the stent to the strut, and the y-axis represents the angle where the strut is located in the circular cross section with respect to the center of gravity of the vessel. However, these presentations did not provide comprehensive mapping or geometry of the remaining struts and their inter-relationship to differential NIH growth along the whole stent, but only showed the spatial distribution of uncovered struts alone in a single image. Compared with previously employed methods (1), our new method clearly demonstrated the various spatial distribution patterns of the uncovered DES struts, along with the stent structure and geometry, different degrees of NIH, and anatomical landmarks (i.e., side-branch vessels) within the whole stent. However, further studies with larger numbers of patients will be required for the clinical relevance of this method.
In conclusion, our novel method for assessing neointimal coverage using 3D OCT analysis can provide a more detailed understanding of the spatial distribution of uncovered and malapposed struts and of specific patterns of neointimal growth than currently employed methods can.
Please note: This study was supported by a grant from the Cardiovascular Research Center, Seoul, Korea. The first two authors contributed equally to this paper
- American College of Cardiology Foundation
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