Usefulness of optical coherence tomography with angiographic coregistration in the guidance of coronary stent implantation

Mobilization of endothelial progenitor cells after implantation of CD34 antibody-covered sirolimus-eluting COMBO® stent: assessment with EPC colony-forming assay

The COMBO® stent is a unique stent on which the CD34 antibody is mounted to capture CD34 + endothelial progenitor cells (EPCs) and from which sirolimus is eluted to suppress neointimal hyperplasia. The COMBO® stent aims to induce early re-endothelialization and vascular healing and to prevent restenosis. In the clinical setting, however, the effects of the COMBO® stent have not been validated in terms of EPC biology. In this study, we assessed the kinetics of circulating EPCs, not only quantitatively by flow cytometric analysis but also qualitatively by an EPC colony-forming assay, in 25 patients undergoing COMBO® stent implantation. Among all patients, flow cytometric analysis indicated that the number of circulating CD34 + /KDR + EPCs did not change after COMBO® stent implantation compared with baseline (before stent implantation). The EPC colony-forming assay demonstrated that the number of small-type EPC colonies increased on day 2 (3 [2, 9] to 6 [4, 9]/dish, P = 0.026) and that of large-type EPC colonies more prominently increased on day 2 (1 [0, 4] to 5 [1, 10]/dish, P < 0.001) and day 7 (to 2 [1, 7], P = 0.006) after COMBO® stent implantation. Based on the results of optical coherence tomography at 3 months after stent implantation, the patients were divided into two groups: well (uncovered strut ratio < 10%, n = 14) and poor (uncovered strut ratio ≥ 10%, n = 10) stent coverage. Compared with baseline values, the number of large-type EPC colonies increased on day 2 (2.9 ± 0.8 to 7.3 ± 2.0, P = 0.026) and tended to increase on day 7 (6.8 ± 2.0/dish, P = 0.062) after COMBO® stent implantation in the well coverage group, while it did not change in the poor coverage group. Thus, the COMBO® stent might induce mature EPCs in the circulation, which might be associated with subsequent healing processes in vessel sites with stent-induced injury.

Recent advances and clinical implications of intravascular imaging

Coronary artery disease (CAD) remains a major contributor to the global mortality rate. Accurate and detailed evaluation of atherosclerotic plaque characteristics is essential for effective risk assessment and treatment planning. Although conventional coronary angiography excels at quantifying luminal stenosis, information on plaque composition and structure remains limited. Recent advances in intravascular imaging (IVI) have bridged this gap by enabling high-resolution visualization of the vessel wall and plaque morphology, thereby enhancing treatment strategies and facilitating comprehensive risk stratification. Among the principal IVI modalities, intravascular ultrasound (IVUS), optical coherence tomography (OCT), and near-infrared spectroscopy (NIRS) provide distinct benefits. IVUS accurately measures vessel diameter and plaque burden, offering critical guidance for managing complex lesions and left main artery disease. The extremely high spatial resolution of OCT allows precise identification of high-risk plaque features, such as thin fibrous caps. NIRS complements these techniques by quantitatively assessing lipid components within plaques, making it particularly useful in predicting future cardiovascular events. In this review, we summarize the latest evidence on applying IVI modalities to the evaluation and treatment of CAD. We focus on the assessment of plaque morphology, identification of high-risk lesions, and the role of IVI-guided percutaneous coronary intervention (PCI). The continued development of hybrid imaging systems and artificial intelligence-based image analysis may produce more precise and safer PCI approaches. Consequently, IVI is poised to become indispensable in managing CAD, paving the way for more personalized treatment strategies tailored to the specific lesion characteristics of each patient.

Effectiveness of the repeated 3-time-balloon-inflation method in reducing coronary stent edge dissection

The optimal procedural protocol for coronary stent deployment remains undetermined. Post-dilation with a high-pressure balloon is often performed to optimize the stent expansion. However, high-pressure dilation also carries the potential risk of coronary artery injury. A previous in vitro study reported that multiple-times balloon inflation at the same pressure resulted in better stent expansion compared to one-time balloon inflation. In our facility, we frequently perform the repeated 3-time-balloon-inflation method, wherein the stent delivery balloon was inflated 3 times at nominal pressure to deploy the stent, to improve stent expansion without high-pressure balloon inflation. Although this method seems effective in avoiding excessive high-pressure dilation, its clinical data are insufficient. In this study, we investigated the clinical outcomes of the repeated 3-time-balloon-inflation method. This retrospective study included 370 patients with 467 stented coronary lesions. These subjects were divided into two groups: one with standard balloon inflation and the other with repeated 3-time balloon inflation, and treatment outcomes were compared. The repeated 3-time-balloon-inflation group had 254 lesions, and the standard-balloon-inflation group had 213 lesions. Stent edge dissection occurred in 6 lesions (2.8%) in the standard-balloon-inflation group, whereas did not occur in the repeated 3-time-balloon-inflation group. A statistically significant difference remained even after propensity score matching (p = 0.040). The final minimum stent area and long-term clinical outcomes were not significantly different between the two groups. The repeated 3-time-balloon-inflation method may reduce stent edge dissection while demonstrating comparable minimal stent area and long-term outcomes to the standard-balloon-inflation method.

Optical coherence tomography to guide percutaneous coronary intervention

Percutaneous coronary intervention (PCI) has been most commonly guided by coronary angiography. However, to overcome the inherent limitations of conventional coronary angiography, there has been an increasing interest in the adjunctive tools of intracoronary imaging for PCI guidance. Recently, optical coherence tomography (OCT) has garnered substantial attention as a valid intravascular imaging modality for guiding PCI. However, despite the unparalleled high-resolution imaging capability of OCT, which offers detailed anatomical information on coronary lesion morphology and PCI optimisation, its broad application in routine PCI practice remains limited. Several factors may have curtailed the widespread adoption of OCT-guided PCI in daily practice, including the transitional challenge from intravascular ultrasound (IVUS), the experienced skill required for image acquisition and interpretation, the lack of a uniform algorithm for OCT-guided PCI optimisation, and the limited clinical evidence. Herein, we provide an in-depth review of OCT-guided PCI, involving the technical aspects, optimal strategies for OCT-guided PCI, and the wide application of OCT-guided PCI in various anatomical subsets. Special attention is given to the latest clinical evidence from recent randomised clinical trials with respect to OCT-guided PCI.

Prevalence of low-attenuation plaques and statin therapy in plaque rupture type of acute coronary syndrome

BACKGROUND

We sought to investigate the differences in coronary plaque morphology on coronary computed tomography angiography (CCTA) and medical therapy between acute coronary syndrome (ACS) and stable ischemic heart disease (SIHD). We also explored the relationship between plaque morphology on CCTA at the initial phase and lesion morphology in the acute phase of ACS.

METHODS

In 5967 patients who underwent invasive coronary angiography, 58 ACS and 91 SIHD patients who had prior CCTA imaging of the culprit lesion and denied ischemic heart disease at CCTA scanning were enrolled.

RESULTS

Although the prevalence of positive remodeling was not different (P = 0.27), low-attenuation plaques (LAP) on prior CCTA were significantly higher in ACS than in SIHD (52% vs. 24%, P < 0.01). The frequency of coronary stenosis grading did not differ between the two groups (P = 0.14). In ACS patients, the frequencies of plaque rupture and lipid-rich plaque assessed by optical coherence tomography (OCT) were significantly higher in LAP than in non-LAP (73% vs. 23%, P < 0.01; 82% and 23%, P < 0.01). Multivariate regression analysis revealed that statin use and LAP on prior CCTA were predictors of future ACS events (P < 0.01, and P < 0.05, respectively).

CONCLUSIONS

LAP on CCTA, not positive arterial remodeling, and lack of statin therapy were associated with ACS development. In addition, LAP more frequently led to the development of the plaque rupture type of ACS compared with non-LAP. Lipid-lowering therapy with statins might be useful to prevent plaque rupture in patients with LAP regardless of coronary stenosis.

Detection of myocardial bridge by optical coherence tomography

Myocardial bridge (MB) is less commonly documented by angiography than autopsy. Optical coherence tomography (OCT) may be useful to detect angiographically undetectable MB. To investigate OCT characteristics of MB, 86 LAD vessels were imaged by OCT. MB was defined as presence of intermediate optical intensity, "fine" layer surrounding coronary artery by OCT. Frequency and characteristics of the angio-detectable and angio-undetectable but OCT-detectable MB were investigated. In a subset of patients with angio-detectable MB, cyclic changes in coronary arterial dimensions were analyzed. OCT detected MB in 44 of 86 (51%). Arc of the MB was significantly larger (334.8 ± 58.5° vs. 268.4 ± 92.1°, P = 0.008) and length was significantly longer (22.6 ± 11.7 mm vs. 14.5 ± 8.1 mm, P = 0.014) in angio-detectable MB than OCT-detectable but angio-undetectable MB. Both vessel (6.8 ± 1.5 to 5.3 ± 1.0 mm2, P = 0.035) and lumen area (4.4 ± 1.5 to 3.1 ± 0.7 mm2, P = 0.040) decreased significantly from diastole to systole. Adventitial (0.08 ± 0.03 to 0.08 ± 0.02 mm, P = 0.828) and intima + plaque thickness (0.12 ± 0.05 to 0.10 ± 0.03 mm, P = 0.398) did not change significantly during cardiac cycle. On the other hand, medial thickness increased significantly from diastole to systole (0.08 ± 0.03 to 0.12 ± 0.03 mm, P = 0.022). In conclusion, MB is frequently detected as intermediate intensity, fine layer by OCT. During systole, vessel and lumen size decrease with increased medial thickness. Therefore, we should be careful for OCT interpretation of the coronary arteries with MB.