Expert review document on methodology, terminology, and clinical applications of optical coherence tomography: physical principles, methodology of image acquisition, and clinical application for assessment of coronary arteries and atherosclerosis

Optical Coherence Tomography based treatment approach for patients with Acute Coronary Syndrome

INTRODUCTION

Areas covered:In this review, we outline the underlying causes of acute coronary syndrome (ACS) as evaluated by optical coherence tomography (OCT). We report both the definitions of each mechanism and its frequency as reported in the literature to date. Finally, we present an algorithm based on the findings in the review that gives an outlined approach to perform intervention on ACS patients.Expert opinion:Although the most common and most accepted intervention in ACS cases is stent implantation, data suggest a stentless approach in cases of plaque erosion, which generally occurs in younger patients presenting with an acute coronary syndrome that have TIMI flow of 2/3 and either a small or large burden of thrombus and underlying stenosis of less than 50%.

Vascular imaging of atherosclerosis: Strengths and weaknesses

Atherosclerosis is an inflammatory disease that can lead to several complications such as ischemic heart disease, stroke, and peripheral vascular disease. Therefore, researchers and clinicians rely heavily on the use of imaging modalities to identify, and more recently, quantify the burden of atherosclerosis in the aorta, carotid arteries, coronary arteries, and peripheral vasculature. These imaging techniques vary in invasiveness, cost, resolution, radiation exposure, and presence of artifacts. Consequently, a detailed understanding of the risks and benefits of each technique is crucial prior to their introduction into routine cardiovascular screening. Additionally, recent research in the field of microvascular imaging has proven to be important in the field of atherosclerosis. Using techniques such as contrast-enhanced ultrasound and superb microvascular imaging, researchers have been able to detect blood vessels within a plaque lesion that may contribute to vulnerability and rupture. This paper will review the strengths and weaknesses of the various imaging techniques used to measure atherosclerotic burden. Furthermore, it will discuss the future of advanced imaging modalities as potential biomarkers for atherosclerosis.

Association of plasma trimethylamine N-Oxide level with healed culprit plaques examined by optical coherence tomography in patients with ST-Segment elevation myocardial infarction

BACKGROUND AND AIMS

Healed plaque is a hallmark of previous regional plaque rupture or erosion. We hypothesized that the plasma level of trimethylamine N-oxide (TMAO) is related to healed culprit plaque in ST-segment elevation myocardial infarction (STEMI) patients.

METHODS AND RESULTS

A prospective cohort of 206 patients with STEMI, who were examined by optical coherence tomography (OCT) was enrolled in our study. After exclusion, 156 patients were categorized into healed plaque (n = 54) and nonhealed plaque (n = 102) groups. Plasma TMAO levels were detected by stable isotope dilution liquid chromatography tandem mass spectrometry in these two groups. Increased age and low BMI were more common in patients with healed plaques than in those without healed plaques. Through OCT observation, plaque rupture (81.5% vs. 45.1%, p < 0.001), thin cap fibroatheroma (TCFA) and macrophages (42.6% vs. 20.6%, p = 0.004, 70.4% vs. 26.5%, p < 0.001, respectively) were more frequently seen in patients with healed plaques than in those without healed plaques. The TMAO level in patients with healed plaques was significantly higher than that in patients with nonhealed plaques (3.9 μM [2.6-5.1] vs. 1.8 μM [1.0-2.7], p < 0.001). Furthermore, the receiver operating characteristic curve showed that TMAO can be used as a potential biomarker to predict healed plaque presence with a cutoff value of 2.9 μM (AUC = 0.810, sensitivity: 72.2%, specificity: 81.4%).

CONCLUSIONS

Healed plaque in STEMI patients is associated with a high level of plaque vulnerability and inflammation. A high level of plasma TMAO can be a useful biomarker to differentiate STEMI patients with healed culprit plaques.

Optical Coherence Tomography Predictors for a Favorable Vascular Response to Statin Therapy

Background

Specific plaque phenotypes that predict a favorable response to statin therapy have not been systematically studied. This study aimed to identify optical coherence tomography predictors for a favorable vascular response to statin therapy.

Methods and Results

Patients who had serial optical coherence tomography imaging at baseline and at 6 months were included. Thin‐cap area (defined as an area with fibrous cap thickness <200 μm) was measured using a 3‐dimensional computer‐aided algorithm, and changes in the thin‐cap area at 6 months were calculated. A favorable vascular response was defined as the highest tertile in the degree of reduction of the thin‐cap area. Macrophage index was defined as the product of the average macrophage arc and length of the lesion with macrophage infiltration. Layered plaque was defined as a plaque with 1 or more layers of different optical density. In 84 patients, 140 nonculprit lipid plaques were identified. In multivariable analysis, baseline thin‐cap area (odds ratio [OR] 1.442; 95% CI, 1.024–2.031, P=0.036), macrophage index (OR, 1.031; 95% CI, 1.002–1.061, P=0.036), and layered plaque (OR, 2.767; 95% CI, 1.024–7.479, P=0.045) were identified as the significant predictors for a favorable vascular response. Favorable vascular response was associated with a decrease in the macrophage index.

Conclusions

Three optical coherence tomography predictors for a favorable vascular response to statin therapy have been identified: large thin‐cap area, high macrophage index, and layered plaque. Favorable vascular response to statin was correlated with signs of decreased inflammation.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT01110538.

Pre-Emptive OCT-Guided Angioplasty of Vulnerable Intermediate Coronary Lesions: Results from the Prematurely Halted PECTUS-Trial

Objectives

To assess the safety and efficacy of pre-emptive treatment of optical coherence tomography- (OCT-) derived vulnerable, non-flow-limiting, non-culprit lesions in patients with myocardial infarction (MI).

Background

Intracoronary imaging with OCT can aid in the decision to treat non-flow-limiting lesions by identifying vulnerable plaques. Pre-emptive treatment of these lesions might improve patient outcome by “sealing” these plaques. Bioresorbable vascular scaffolds (BVS) have theoretical benefit for this treatment because they dissolve completely over time.

Methods

In patients presenting with MI, non-culprit lesions with a fractional flow reserve ≥0.8 were imaged with OCT. Vulnerable plaques were randomised to either percutaneous coronary intervention (PCI) with bioresorbable vascular scaffold (BVS) placement or optimal medicinal therapy (OMT). The primary outcome was a composite of all-cause mortality, non-fatal MI, and unplanned revascularisation at 1-year follow-up.

Results

The trial was stopped prematurely after retraction from the market of the Absorb BVS. At that time, a total of 34 patients were randomised. At two years, the composite endpoint occurred 3 times (18.8%) in the BVS group and 1 time (6.3%) in the OMT group. Apart from one elective PCI for stable angina in the OMT group, no target lesions in any group were revascularised.

Conclusions

Pre-emptive stenting of vulnerable plaques had no evident benefit compared to conservative treatment. However, due to the low number of included patients, no definite conclusions could be drawn. Identifying and potentially treating vulnerable plaques remains an important target for future research. This trial is registered under https://www.trialregister.nl/trial/NL4177 on 08-12-2015.

High Plasma Myeloperoxidase Is Associated with Plaque Erosion in Patients with ST-Segment Elevation Myocardial Infarction

We aimed to investigate the association between plasma myeloperoxidase (MPO) and plaque erosion in patients presenting with ST-segment elevation myocardial infarction (STEMI). Two hundred and fifty-two patients with STEMI who underwent optical coherence tomography (OCT) evaluation of culprit lesion were prospectively enrolled. Of them, 92 and 80 patients were identified with plaque rupture and plaque erosion, respectively. Plasma MPO levels, measured using enzyme-linked immunoassay, were significantly higher in patients with plaque erosion versus plaque rupture (median (interquartile range), 96.3 ng/mL [44.2-173.3] vs. 41.7 ng/mL (29.2-66.3); p < 0.001). Multivariable logistic regression analysis indicated that plasma MPO was independently associated with plaque erosion (odds ratio, 3.25; 95% confidence interval, 1.37-7.76; p = 0.008). The area under the receiver-operating characteristic curve was 0.75 for MPO to discriminate between plaque erosion and plaque rupture. Plasma MPO level significantly correlated with plaque erosion in patients with STEMI.

Optical Coherence Tomography: Current Applications for the Assessment of Coronary Artery Disease and Guidance of Percutaneous Coronary Interventions

INTRODUCTION

Coronary angiography (CAG) is the standard modality for assessment of coronary stenoses and intraprocedural guidance of percutaneous coronary interventions (PCI). However, the limitations of CAG are well recognized. Intracoronary imaging (ICI) can potentially overcome these limitations. Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) are the main ICI techniques utilized in clinical practice.

AIM

This narrative literature review addresses the current clinical applications of OCT in relation to IVUS and CAG in patients with coronary artery disease (CAD). Items reviewed are: technical implications of OCT and IVUS, lesion characterization and decision-making, stent optimization criteria, post-stenting results, safety in terms of procedural complications, clinical outcomes, and indications.

MAIN FINDINGS

OCT is able to reveal more detail than IVUS due to its higher resolution. However, this higher resolution comes at the cost of a lower penetration depth. Pre-stenting OCT results in procedural change in more than 50% of the cases in terms of stent length and diameter. Post-stenting OCT resulting in stent optimization is reported in at least 27% of the cases. Malapposition and under-expansion are treated with post-dilatations, while edge dissections are treated with additional stent placement. Stent expansion, stent apposition, distal stent edge dissections, and reference lumen areas seem to be the most important stent optimization criteria for both decision-making and for reducing the risk of adverse events during follow-up. Both OCT and IVUS are superior in terms of post-stenting results compared with CAG alone. However, there is no consensus about whether OCT guidance results in better stent expansion than IVUS guidance. OCT, IVUS, and CAG are safe procedures with few reported procedural complications. In general, OCT guidance seems to contribute to favorable clinical outcomes compared with CAG guidance only. However, OCT guidance results in similar clinical outcomes as with IVUS guidance. OCT could be considered for lumen assessment and stent-related morphology in more complex cases in which CAG interpretation remains uncertain. Since OCT and IVUS have distinct characteristics, these techniques are complementary and should be considered carefully for each patient case based on the benefits and limitations of both techniques.

RNA-seq identifies circulating miRNAs as potential biomarkers for plaque rupture in patients with ST-segment elevation myocardial infarction

BACKGROUND

Plaque rupture (PR) and plaque erosion (PE) are the two major pathological phenotypes in acute coronary syndrome. Since microRNAs have been found to be involved in the mechanisms of PR and PE, we investigated the diagnostic utility of microRNAs in differentiating between patients with PR and patients with PE.

METHODS

MicroRNA sequencing was performed on plasma from 21 patients with PR, 20 patients with PE and 17 healthy control subjects (HCs). 24 miRNAs were selected for validation in 20 PR patients and 20 PE patients and 8 miRNAs were further validated in an independent replication cohort (82 patients with PR, 84 patients with PE and 59 HCs) by applying quantitative real-time polymerase chain reaction. Then we analyzed pathways associated with significant miRNAs in PR.

RESULTS

MiR-744-3p, miR-324-3p and miR-330-3p were significantly upregulated in the PR group compared with the PE group (Log₁₀miR-744-3p: 0.26[--0.28-1.57] versus -0.41[-0.83--0.03], p_adj < 0.001; Log₁₀miR-324-3p: 0.40[-0.09-0.84] versus -0.12[-0.53-0.29], p_adj < 0.001; Log₁₀miR-330-3p: 0.34[0.08-0.93] versus -0.07[-0.65-0.22], p_adj < 0.001), The area under the receiver operating characteristic curve for the combination of these three miRNAs in distinguishing between PR from PE in training and test set was 0.764 (0.679-0.850, sensitivity = 86.2%, specificity = 54.4%, P < 0.001) and 0.768 (0.637-0.898, sensitivity,65.4%, specificity:80.0%, P = 0.001), respectively.

CONCLUSION

A set of circulating microRNAs (miR-744-3p, miR-330-3p, and miR-324-3p) is associated with PR and has clinical utility as a diagnostic marker for distinguishing the plaque phenotype in STEMI patients.

Analysis of sweating by optical coherence tomography in patients with palmoplantar hyperhidrosis

Optical coherence tomography (OCT) is a high-resolution tomographic imaging technique that uses optical interference. OCT has enabled the non-invasive three-dimensional analysis of individual acrosyringia in the stratum corneum in human skin. However, no report on the measurement of sweating by OCT using clinical data from humans has been published to date. Twenty patients with hyperhidrosis and twenty healthy subjects were included in this study. Imaging of acrosyringia in the stratum corneum using OCT and measurement of the sweat rate using the ventilated capsule method were performed simultaneously. The hand grip exercise of the right hand was used as a load to induce sweating, and the left fingertip was measured before and after the exercise load. Five acrosyringia were extracted from each OCT image, and their volumes were calculated. The mean volume of each acrosyringium was divided by the thickness of the stratum corneum to calculate the mean cross-sectional area of the acrosyringium. Furthermore, the number of sweat droplets on the skin surface was measured. The mean cross-sectional area of acrosyringia after the load increased both in patients with hyperhidrosis and in healthy subjects (P < 0.001). The mean cross-sectional area of acrosyringia of patients with hyperhidrosis was larger than that of healthy subjects (P < 0.001). The mean cross-sectional area of acrosyringia and the sweat rate showed a positive correlation before and after the load (r = 0.88 to 0.91). The number of droplets also increased after the load (P < 0.001), and the number of droplets in patients with hyperhidrosis was higher than in healthy subjects (P < 0.001). Our study has shown that acrosyringia in the stratum corneum increase in proportion to the sweat rate. OCT is a rigorous and valuable method that can measure and quantify sweating in the body without being an invasive procedure.

Acute Myocardial Infarction in an Adolescent Receiving Anagrelide for Essential Thrombocythemia with Underlying Persistent Coronary Endothelial Dysfunction

Essential thrombocythemia (ET) is a Philadelphia chromosome-negative myeloproliferative disorder that is characterized by the overproduction of platelets and a marked increase in the numbers of mature megakaryocytes present in the bone marrow. Thrombohemorrhagic disorders are major morbidities of ET, especially those with mutations in the gene encoding Janus kinase 2 (JAK2). In this study, we report the case of an 18-year-old patient with ET carrying JAK2 mutation who developed acute ST-elevation myocardial infarction (STEMI) 5 months after a commencement of anagrelide. Coronary endothelial dysfunction confirmed by positive acetylcholine provocation test lasted a year after the occurrence of STEMI. Furthermore, intracoronary imaging using optical coherence tomography demonstrated non-atheromatous intimal fibrosis possibly due to chronic endothelial damage. The coronary pathologies reflected chronic change potentially associated with properties of ET and JAK2 mutation in addition to hyperviscosity. These observations suggest that the side effect of anagrelide in our patient was considered causative, while underlying chronic endothelial dysfunction and adverse endothelial remodeling may be predisposing factors to his fatal cardiovascular events.

Advances in Optical Detection of Human-Associated Pathogenic Bacteria

Bacterial infection is a global burden that results in numerous hospital visits and deaths annually. The rise of multi-drug resistant bacteria has dramatically increased this burden. Therefore, there is a clinical need to detect and identify bacteria rapidly and accurately in their native state or a culture-free environment. Current diagnostic techniques lack speed and effectiveness in detecting bacteria that are culture-negative, as well as options for in vivo detection. The optical detection of bacteria offers the potential to overcome these obstacles by providing various platforms that can detect bacteria rapidly, with minimum sample preparation, and, in some cases, culture-free directly from patient fluids or even in vivo. These modalities include infrared, Raman, and fluorescence spectroscopy, along with optical coherence tomography, interference, polarization, and laser speckle. However, these techniques are not without their own set of limitations. This review summarizes the strengths and weaknesses of utilizing each of these optical tools for rapid bacteria detection and identification.

Current status of hybrid intravascular ultrasound and optical coherence tomography catheter for coronary imaging and percutaneous coronary intervention

Both intravascular ultrasound (IVUS) and optical coherence tomography (OCT) play a crucial role in elucidating the pathophysiology of coronary artery disease (CAD) with the goal to improve patient outcomes of medical and/or interventional CAD management. However, no single intravascular imaging technique has been proven to provide complete and detailed evaluation of all CAD lesions due to some limitations. Although sequential use of multiple modalities may sometimes be performed, there may be issues related to risk, time, and cost. To overcome these problems, several hybrids involving dual-probe combined IVUS-OCT catheters have been developed. The aim of this review article is to demonstrate some limitations of stand-alone imaging devices for evaluation of CAD, summarize the advances in hybrid IVUS-OCT imaging devices, discuss the technical challenges, and present the potential value in the clinical setting, especially in patients receiving medical or interventional CAD management.

Influence of Ezetimibe on Plaque Morphology in Patients with ST Elevation Myocardial Infarction Assessed by Optical Coherence Tomography: An OCTIVUS Sub-Study

AIMS

The aim of the trial was to examine the influence of ezetimibe on plaque morphology in patients with ST-segment Elevation Myocardial Infarction (STEMI) with respect to fibrous cap thickness (FCT) and arcs of lipid plaque, calcific plaque, and macrophages using Optical Coherence Tomography (OCT).

METHODS AND RESULTS

In 87 statin naïve patients with STEMI treated with primary percutaneous intervention, a non-culprit study plaque in a non-infarct related coronary artery was assessed with OCT at baseline and after 12 months. Patients were treated with atorvastatin 80 mg and randomized (1:1) to ezetimibe 10 mg (n = 43) or placebo (n = 44). An increase in median FCT (ezetimibe 200 (140-260) μm to 240 (190-305) μm (p = 0.002) vs. placebo 205 (135-260) μm to 230 (180-270) μm (p < 0.001), between groups p = ns), a reduction in lipid arc (ezetimibe 1728.5 (1022.5-3904.7)° to 1164.5 (736.6-2580.1)° (p = 0.001) vs. placebo 1671.6 (978.3-2868.7)° to 1373.7 (791.2-2267.3)° (p = 0.019), between groups p = ns), and macrophage arc (ezetimibe 1730.3 (965.7-2984.4)° to 1324.8 (819.0-2819.7)° (p < 0.05) vs. placebo 1570.5 (794.7-3016.8)° to 1418.9 (584.1-2501.1)° (p < 0.01), between groups p = ns) were observed.

CONCLUSION

Aggressive LDL-lowering resulted in changes in OCT assessed plaque composition by increased FCT thickness and a reduction in lipid content and macrophage infiltration. Addition of ezetimibe 10 mg to atorvastatin 80 mg resulted in further LDL reduction, but no additional change in plaque composition was found.

Low Plasma Adiponectin Levels Are Associated With Vulnerable Plaque Features in Patients With Acute Coronary Syndrome: An Optical Coherence Tomography Study

BACKGROUND

Vulnerable plaques are the primary cause of acute coronary syndrome (ACS). The association between in-vivo plaque vulnerability and adiponectin levels in ACS still remains to be determined.

OBJECTIVE

The purpose of this study was to investigate the correlation between adiponectin levels and vulnerable plaque features in ACS patients.

METHODS

We enrolled 107 ACS patients admitted to our institution; 83 with Non-ST elevation ACS (NSTE-ACS) and 24 with ST-elevation myocardial infarction (STEMI). Adiponectin levels were measured in these patients. Coronary angiography and subsequent optical coherence tomography (OCT) analysis of culprit lesions were performed.

RESULTS

Adiponectin level was lower in patients with complex angiographic lesions, compared to those with non-complex lesions (7.13 ± 3.04 vs. 8.94 ± 2.84 μg/ml, P = 0.002). Adiponectin level was lower in patients with plaque rupture (PR), micro-thrombi, and thin cap fibroatheroma (TCFA), compared to those with non-vulnerable features (7.19 ± 2.95 vs 8.79 ± 3.02 μg/ml, P = 0.007 & 7.29 ± 2.97 vs 8.44 ± 3.09 μg/ml, P = 0.04 and 4.76 ± 0.65 vs 9.74 ± 2.35 μg/ml, P < 0.001 μg/ml respectively). There was a significant negative correlation between adiponectin levels and lipid rich plaque extent and maximum lipid arc (r = -0.05, P < 0.001 & r = -0.03, P = 0.03, respectively). However, a significant positive correlation was observed between adiponectin levels and fibrous cap thickness (r = 0.95, P < 0.001).

CONCLUSION

Low adiponectin levels were associated with complex angiographic lesions and vulnerable plaque features in ACS patients, where there was a significant correlation between it and PR, TCFA, and lipid rich plaque.

Recent Advances in Vascular Imaging

Recent advances in vascular imaging have enabled us to uncover the underlying mechanisms of vascular diseases both ex vivo and in vivo. In the past decade, efforts have been made to establish various methodologies for evaluation of atherosclerotic plaque progression and vascular inflammatory changes in addition to biomarkers and clinical manifestations. Several recent publications in Arteriosclerosis, Thrombosis, and Vascular Biology highlighted the essential roles of in vivo and ex vivo vascular imaging, including magnetic resonance image, computed tomography, positron emission tomography/scintigraphy, ultrasonography, intravascular ultrasound, and most recently, optical coherence tomography, all of which can be used in bench and clinical studies at relative ease. With new methods proposed in several landmark studies, these clinically available imaging modalities will be used in the near future. Moreover, future development of intravascular imaging modalities, such as optical coherence tomography-intravascular ultrasound, optical coherence tomography-near-infrared autofluorescence, polarized-sensitive optical coherence tomography, and micro-optical coherence tomography, are anticipated for better management of patients with cardiovascular disease. In this review article, we will overview recent advances in vascular imaging and ongoing works for future developments.

The association of diabetes mellitus with neointimal formation following deployment of second-generation drug-eluting stents: an optical coherence tomographic study

OBJECTIVES

The purpose of this study was to evaluate the association of diabetes mellitus (DM) with neointimal formation after implantation of second-generation drug-eluting stent (DES) visualized by optical coherence tomography (OCT).

METHODS

Patients with single de novo coronary artery disease treated with second-generation DES between June 2014 and June 2017 in our department underwent OCT examination at 1-year follow-up and were enrolled in this retrospective study. The primary end point was in-stent mean neointimal thickness (MNT), and secondary end points included uncovered stent strut, minimal lumen area (MLA), neointimal burden, neointimal hyperplasia (NIH) patterns and stent thrombosis (ST) after 1 year of OCT follow-up.

RESULTS

A total of 68 patents with DM (DM group) and 216 patients without DM (non-DM group) were enrolled. At 1-year follow-up, the DM group compared with the non-DM group, showed: MNT [160 (85-245) μm vs. 120 (60-220) μm, P = 0.038] and neointimal burden [21.4 (8.3-30.1)% vs. 14.0 (5.7-26.1)%, P = 0.023] to be significantly increased. Concurrently, MLA [4.60 (3.53-6.06) mm vs. 5.76 (4.28-7.20) mm2, P = 0. 0.002] was significantly reduced. Interestingly, the degree of uncovered struts (7.3 ± 7.1% vs. 7.7 ± 6.7%, P = 0.704), NIH patterns (P = 0.984), and ST (7.9% vs. 7.4%, P = 0.88) were comparable between the two groups. After propensity score matching, the MNT [160 (90-240) μm vs. 110 (60-220) μm, P = 0.048] and neointimal burden [21.4 (8.3-30.1)% vs. 15.4 (5.6-26.3)%, P = 0.044] remained significantly different in the DM compared to the non-DM group.

CONCLUSION

DM leads to significant increase in MNT and neointimal burden even with second-generation DES, nevertheless stent strut coverage, ST and NIH characteristics remained comparable among the cohorts at 1-year.

Human monocyte-derived macrophages: Pathogenetic role in plaque rupture associated to systemic inflammation

BACKGROUND

Macrophages play a key role in coronary plaque destabilization. In-vitro human monocyte-derived macrophages (MDMs) are used to study macrophages infiltrating tissue. Optical coherence tomography (OCT) provides an in-vivo insight of the coronary arteries. We compared the MDMs morpho-phenotype and culprit plaque features at OCT in acute coronary syndrome (ACS) patients according to the underlying plaque pathobiology.

METHODS

Sixty-six patients undergoing coronary angiography and pre-angioplasty OCT of the culprit vessel were allocated to three groups according to mechanism of ACS at OCT and C-reactive protein levels (cut-off: 2 mg/Ll): 1) plaque rupture with systemic inflammation; 2) plaque rupture without systemic inflammation, 3) plaque with intact fibrous cap. A blood sample was collected to obtain MDMs, categorized as having "round" or "spindle" morphology.

RESULTS

Thirty-two patients (48.5%) were assigned to Group 1, 10 (15.2%) to Group 2 and 24 (36.4%) to Group 3. The "round" MDMs were significantly more frequent in Group 1 (39.25 ± 4.98%) than in Group 2 (23.89 ± 3.10%) and Group 3 (23.02 ± 7.89%), p = 0.008. MDMs in Group 1 as compared to Groups 2 and 3 showed lower efferocytosis (8.74 ± 1.38 vs 9.74 ± 2.15 vs 11.41 ± 2.41; p = 0.012), higher tissue factor levels (369.84 ± 101.13 vs 301.89 ± 59.78 vs 231.74 ± 111.47; p = 0.001) and higher heme oxygenase-1 expression (678.78 ± 145.43 vs 419.12 ± 74.44 vs 409.78 ± 64.33; p = 0.008).

CONCLUSIONS

MDMs of ACS patients show morpho-phenotypic heterogeneity with prevalence of pro-thrombotic and pro-oxidative properties in case of plaque rupture and systemic inflammation. Such MDMs subpopulation may take part to the cellular pathways leading to fibrous cap rupture with the subsequent thrombus formation.

Influence of Plaque Characteristics on Early Vascular Healing in Patients With ST-Elevation Myocardial Infarction

OBJECTIVES

To compare the early vascular healing of ruptured plaques (RP) and non-ruptured plaques (NRP) one month after primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI), using optical coherence tomography (OCT).

BACKGROUND

Vascular healing and strut coverage are important factors in reducing the risk of stent thrombosis after PCI. Influence of underlying lesion characteristics and differences in healing response between RP and NRP are unknown.

METHODS

Twenty-six STEMI-patients underwent PCI and implantation of a polymer-free drug-coated Biofreedom stent (BF-BES). OCT was performed pre-PCI, post-PCI and at 1-month follow-up. The patients were divided into two groups: RP = 15 and NRP = 11. OCT analyses of culprit lesion, post stent implantation at baseline and follow-up were performed to determine the difference in vascular healing based on presence of uncovered and/or malapposed stent struts and intraluminal filling defects.

RESULTS

The stent coverage did not differ significantly between the two groups at 1-month follow-up with percentage of uncovered struts: RP 26.5% [IQR 15.0-49.0] and NRP 28.1% [IQR 15.5-38.8] for NRP (p = 0.78). At 1-month, RP showed an increased percentage of late acquired malapposed struts (1.4% [IQR 0.8-2.4] vs. 0.0% [IQR 0.0-1.4], p = 0.03) and a larger total malapposition area (1.3 mm² [IQR 0.4-2.5] vs. 0.0 mm² [IQR 0.0-0.9], p = 0.01), compared to NRP.

CONCLUSION

Three out of four struts were covered within one month after stenting. The vascular healing was comparable in RP and NRP on stent coverage. However, RP had more and larger late acquired malapposition areas.

Systemic and local factors associated with reduced thrombolysis in myocardial infarction flow in ST-segment elevation myocardial infarction patients with plaque erosion detected by intravascular optical coherence tomography

Local factors of plaque rupture (e.g. lipid burden) are related to preprocedural thrombolysis in myocardial infarction (TIMI) flow grade during primary percutaneous coronary intervention (PCI). However, the pathological mechanism differs between plaque erosion and rupture. We aimed to identify the factors associated with reduced TIMI flow in plaque erosion. A total of 329 ST-segment elevation myocardial infarction (STEMI) patients with optical coherence tomography (OCT) identified plaque erosion were divided into 2 groups by preprocedural TIMI flow grade [TIMI 0-1 group (n = 219) and TIMI 2-3 group (n = 110)]. Patients in TIMI 0-1 group were older (age > 50 years, 68.5% vs. 51.8%, P = 0.003), and had more diabetes mellitus (18.3% vs. 8.2%, P = 0.015). Plaque erosion with TIMI flow 0-1 was less frequently located in the left anterior descending artery (LAD, 58.4% vs. 72.7%, P = 0.011), but more frequently located in the right coronary artery (RCA, 34.2% vs. 7.3%, P = 0.001) than those with TIMI flow 2-3. TIMI 0-1 group had more lipid plaques (53.9% vs. 41.8%, P = 0.039), macrophage accumulation (59.8% vs. 41.8%, P = 0.002), and calcification (34.2% vs. 21.8%, P = 0.020). In the multivariable analysis, age > 50 years, diabetes mellitus, RCA location, and macrophage accumulation were the independent predictors of reduced TIMI flow grade in STEMI patients with plaque erosion. Systemic factors (older age and diabetes mellitus) and local factors (RCA location and macrophage accumulation) were independently associated with reduced coronary flow in STEMI patients with plaque erosion. CLINICAL TRIAL REGISTRATION : ClinicalTrials.gov NCT03084991 May 17, 2017 (retrospectively registered).

The relationship between coronary artery calcium density and optical coherence tomography-derived plaque characteristics

BACKGROUND AND AIMS

Although coronary artery calcium (CAC) density has been associated with plaque stability, pathological evidence is lacking. We investigated the relationship between coronary computed tomography (CCT)-derived CAC density and multiple calcified and high-risk plaque (HRP) characteristics using optical coherence tomography (OCT).

METHODS

We analyzed 83 plaques from 33 stable angina patients who underwent both CCT and OCT. CAC density was measured at calcium plaques with ≥90 Hounsfield units (HU) and ≥130 HU using custom CT software. The correlation between median CAC density and OCT-derived calcium size (thickness and area) was assessed. To investigate whether median CAC densities measured at the 90 HU threshold were associated with plaque vulnerability, OCT-derived plaque characteristics and HRP characteristics were compared between the low (90-129 HU), intermediate (130-199 HU) and high (≥200 HU) CAC HU groups.

RESULTS

Median CAC densities at 130 HU were moderately associated with calcium thickness (R = 0.573, p < 0.001) and area (R = 0.560, p < 0.001). Similar results were observed at 90 HU (thickness, R = 0.615, p < 0.001; area, R = 0.612, p < 0.001). Among groups with low, intermediate and high HU levels, calcium thickness (0.42 ± 0.14 mm, 0.60 ± 0.17 mm and 0.77 ± 0.19 mm, respectively; p < 0.001) and area (0.55 ± 0.29 mm², 1.20 ± 0.58 mm² and 1.78 ± 0.87 mm², respectively; p < 0.001) were significantly greater in the high HU group. HRP characteristics, however, did not differ among the three groups.

CONCLUSIONS

OCT-derived calcium size, but not HRP characteristics, were associated with CAC density, suggesting that CAC density is driven mainly by calcified plaque size but not local plaque vulnerability.

Culprit lesion morphology in patients with ST-segment elevation myocardial infarction assessed by optical coherence tomography

AIMS

This study sought to evaluate the incidence of ruptured plaques and nonruptured plaques (NRP) and to compare patient characteristics and detailed plaque morphology features between the two culprit types in ST-segment elevation myocardial infarction (STEMI) patients, using optical coherence tomography (OCT).

METHODS AND RESULTS

Using OCT, the culprit lesions in patients with STEMI were assessed prior to stent implantation. The culprit lesion was categorized as ruptured plaques or NRP, and the plaque components were evaluated. Fifty-two patients (69.3%) presented with ruptured plaques and 23 (30.7%) with NRP. Patients with NRP were younger (58.0 ± 10.4 vs 64.7 ± 9.9 years, P = 0.01) and more often smokers (72.7% vs 37.1%, P = 0.001), compared to ruptured plaques. NRP contained significantly more fibrotic plaque (20.0% [interquartile range (IQR) 13.7-29.8] vs 11.3% [IQR 6.9-18.1], P = 0.005), but less lipidic plaque (44.0% ± 13.7 vs 59.3% ± 13.6, P < 0.001), less superficial [5.0% (IQR 2.8-7.5) vs 8.1% (IQR 5.7-11.0), P = 0.005] and profound macrophages [0.9% (IQR 0.0-1.7) vs 2.2% (IQR 0.9-4.7), P = 0.003]. The prevalence, numbers and lengths of thin-cap fibroatheroma (TCFA) were significantly lower in NRP, compared to ruptured plaques [47.8% vs 88.5%, 0 (IQR 0-1) vs 1 (IQR 1-2) and 0 mm (IQR 0-2.7) vs 4.5 mm (IQR 2.3-7.7), P < 0.001].

CONCLUSIONS

One-third of STEMI patients had culprit lesions without an OCT-detectable ruptured plaque. Culprit lesions with NRP contained less vulnerable plaque components, such as lipid plaque, TCFAs and macrophages compared to ruptured plaques.

Study of saline optical coherence tomography-guided percutaneous coronary intervention (SOCT-PCI Study)

AIM

The aim of this study was to evaluate the feasibility of heparinised saline as flushing media for frequency-domain optical coherence tomography (FD-OCT) image acquisition during percutaneous coronary intervention (PCI) optimisation.

METHODS AND RESULTS

Twenty-seven patients undergoing FD-OCT-guided PCI were enrolled. Heparinised saline was injected into the coronary during FD-OCT image acquisition. A total of 118 runs were analysed for image quality and diagnostic value. FD-OCT runs were categorised as follows: good runs (GRs), clinically usable runs (CURs) and clinically not usable runs (NURs); GRs and CURs were combined as clinically effective runs (ERs). Saline FD-OCT enabled visualisation of all possible coronary lesions. Of the 118 runs analysed, 61%, 27.1%, 11.9% and 88.1% were GRs, CURs, NURs and ERs, respectively. Sixty-one percent of total runs were left coronary system (LCS) and 39% were right coronary system (RCS) runs. Among LCS runs, 55.6%, 30.6%, 13.8% and 86.2% were GRs, CURs, NURs and ERs, respectively. Among RCS runs, 69.6%, 21.7%, 8.7% and 91.3% were GRs, CURs, NURs and ERs, respectively.

CONCLUSION

This is the first study to demonstrate the technical feasibility of isolated saline FD-OCT for PCI optimisation.

Prevalence and quantitative assessment of macrophages in coronary plaques

Although optical coherence tomography (OCT) proved to be able to identify macrophage clusters, there are no available data on the possibility to obtain reproducible measurements of their circumferential extension and location. The purpose of the present post-hoc analysis of the CLIMA study was to revise the clinical and demographic variables of patients having coronary plaques with macrophages and to investigate the reproducibility of their quantitative assessment. A total of 577 patients out of 1003 undergoing OCT showed macrophage accumulation. Three groups were identified; group 1 (426 patients) without macrophages, group 2 (296) patients with low macrophage content (less than median value [67°] of circumferential arc) and group 3 (281) with high macrophage content arc [> 67°]. Patients with macrophages (groups 2 and 3) showed a higher prevalence of family history for coronary artery disease and hypercholesterolemia and had a significantly larger body mass index. Furthermore, group 3 had more commonly triple vessel disease and higher value of LDL cholesterol levels compared to the two other groups. The inter-observer agreement for macrophage interpretation was good: R values were 0.97 for the circumferential arc extension, 0.95 for the minimum distance and 0.98 for the mean distance. A non-significant correlation between circumferential extension of macrophages and hsCRP values was found (R = 0.013). Quantitative assessment of macrophage accumulations can be obtained with high reproducibility by OCT. The presence and amount of macrophages are poorly correlated with hsCRP and identify patients with more advanced atherosclerosis and higher LDL cholesterol levels.

Methylene blue-filled biodegradable polymer particles as a contrast agent for optical coherence tomography

Optical coherence tomography (OCT) images largely lack molecular information or molecular contrast. We address that issue here, reporting on the development of biodegradable micro and nano-spheres loaded with methylene blue (MB) as molecular contrast agents for OCT. MB is a constituent of FDA approved therapies and widely used as a dye in off-label clinical applications. The sequestration of MB within the polymer reduced toxicity and improved signal strength by drastically reducing the production of singlet oxygen and leuco-MB. The former leads to tissue damage and the latter to reduced image contrast. The spheres are also strongly scattering which improves molecular contrast signal localization and enhances signal strength. We demonstrate that these contrast agents may be imaged using both pump-probe OCT and photothermal OCT, using a 830 nm frequency domain OCT system and a 1.3 µm swept source OCT system. We also show that these contrast agents may be functionalized and targeted to specific receptors, e.g. the VCAM receptor known to be overexpressed in inflammation.

Association of ABO blood groups and non-culprit plaque characteristics in acute coronary syndrome: an optical coherence tomography study

Background

Cardiovascular disease (CVD) poses a serious threat to human health. Research shows that ABO blood groups, especially non-O blood types, are closely related to the incidence of cardiovascular diseases (CVDs). This study aimed to determine the associations of blood types with non-culprit coronary plaque characteristics using optical coherence tomography (OCT).

Methods

A total of 257 acute coronary syndrome (ACS) patients (average age, 59.39±10.08 years, 80% male) who underwent OCT of 3 vessels were identified. Subjects were divided into 2 groups: the O blood group (71 patients with 121 plaques) and the non-O group (186 patients with 329 plaques). The non-culprit coronary plaque features of the two groups were compared using OCT.

Results

The non-type O group had larger lipid arcs, thinner fibrous caps, and a greater number of thin-cap fibro atheromas (TCFAs). The type A, B, and AB blood groups had larger lipid arcs than the type O blood group, as well as thinner fibrous caps and more TCFAs. The type A blood group had thinner fibrous caps and a greater number of TCFAs than the type B and AB blood groups.

Conclusions

ACS patients with type non-O blood had more non-culprit plaques. Patients with type A blood, in particular, had more vulnerable characteristics than those with type O blood.

The association between glucose-related variables and plaque morphology in patients with ST-segment elevated myocardial infarction

Background

Plaque rupture (PR) and plaque erosion (PE) are main causes of acute myocardial infarction with different demographic and histology characteristics and need different treatment strategy. PR and PE can be identified with optical coherence tomography (OCT) accurately, but convenient and effective noninvasive markers for them are rarely found. History of diabetes mellitus (DM) was reported to be a potential predictor of PR in ST-segment elevated myocardial infarction (STEMI) patients, but the predictive value of other glucose-related variables for it is still uncertain. Present study aimed to clear the relationship between some glucose-related variables and plaque morphology in patients with STEMI.

Methods

We consecutively enrolled 872 STEMI patients and divided them into PR group (n = 616) and PE group (n = 256) based on OCT diagnostic criteria. The relationship of glucose-related variables, including random plasma glucose on admission (ARPG), glycosylated hemoglobin (HbA1c), post-PCI fasting plasma glucose (PFPG), DM history, glucose variable tendency (GVT) and the acute-to-chronic glycemic ratio (A/C), to the PR risk of STEMI patients was analyzed. The correlation between the glucose-related variables and plaque morphology was analyzed meanwhile.

Results

Among the glucose-related variables, ARPG and GVT were confirmed to be independent predictors for PR after adjusting for other traditional risk factors in nondiabetic patients. The higher the ARPG level, the more PR risk the STEMI patients had. And high HbA1c and APPG were demonstrated to have a weak and positive correlation with lipid constituents and stenosis degree of culprit vessel.

Conclusions

Compared to HbA1c, DM history, and some other glucose-related variables, ARPG and GVT were risk factors for PR in STEMI patients, especially those without DM. And high HbA1c and ARPG were positively correlated with the development of vulnerable plaque in culprit vessels.

Trial registration Present study is a retrospective one and the population came from the EROSION study of our center previously. It was approved by the Ethics Committee of the Second Affiliated Hospital of Harbin Medical University (Approval reference number, KY2017-249), and all patients provided written informed consent prior to the inclusion in the study and the investigation conformed to the principles outlined in the Declaration of Helsinki.

Seasonal Variations in the Pathogenesis of Acute Coronary Syndromes

Background Seasonal variations in acute coronary syndromes (ACS) have been reported, with incidence and mortality peaking in the winter. However, the underlying pathophysiology for these variations remain speculative. Methods and Results Patients with ACS who underwent optical coherence tomography were recruited from 6 countries. The prevalence of the 3 most common pathologies (plaque rupture, plaque erosion, and calcified plaque) were compared between the 4 seasons. In 1113 patients with ACS (885 male; mean age, 65.8±11.6 years), the rates of plaque rupture, plaque erosion, and calcified plaque were 50%, 39%, and 11% in spring; 44%, 43%, and 13% in summer; 49%, 39%, and 12% in autumn; and 57%, 30%, and 13% in winter (P=0.039). After adjusting for age, sex, and other coronary risk factors, winter was significantly associated with increased risk of plaque rupture (odds ratio [OR], 1.652; 95% CI, 1.157-2.359; P=0.006) and decreased risk of plaque erosion (OR, 0.623; 95% CI, 0.429-0.905; P=0.013), compared with summer as a reference. Among patients with rupture, the prevalence of hypertension was significantly higher in winter (P=0.010), whereas no significant difference was observed in the other 2 groups. Conclusions Seasonal variations in the incidence of ACS reflect differences in the underlying pathobiology. The proportion of plaque rupture is highest in winter, whereas that of plaque erosion is highest in summer. A different approach may be needed for the prevention and treatment of ACS depending on the season of its occurrence. Registration URL: https://www.clini​caltr​ials.gov. Unique identifier: NCT03479723.

Evaluation of Left Main Coronary Artery Using Optical Frequency Domain Imaging and Its Pitfalls

Objectives

We aimed to assess the quality of optical frequency domain imaging (OFDI) of the left main (LM) arterial wall and describe and analyse potential artefacts in this setting.

Background

OFDI is increasingly used to assess ambiguous lesions and optimize LM percutaneous coronary intervention. However, its ability to provide artefact-free high-quality images of coronary ostia and large segments such as the LM remains uncertain.

Methods

We included 42 consecutive patients who underwent OFDI, including LM imaging. Each OFDI frame was subdivided into four quadrants and analysed. The number of quadrants with artifacts was calculated within the proximal, mid, and distal LM and the first 5 mm of the left anterior descending artery (LAD) and/or left circumflex artery (LCX).

Results

The quadrants analysis showed an overall artifact rate of 8.9%, mostly out-of-field (45.1%) or residual blood (44.7%) artefacts. Most artifacts were located in the proximal LM (18.6%) with a stepwise reduction of artifact rates towards distal segments (mid LM 5.8%; distal LM 3.6%, ostial LAD 2.6%, and ostial LCX 0%; p < 0.001). While 20 (48.8%) patients had angiographically visible plaques, OFDI showed plaques in 32 patients (76.2%; p=0.007).

Conclusion

OFDI can accurately evaluate the LM and detect and assess angiographically unvisualized atherosclerotic plaques providing accurate assessment of >90% of the quadrants of the LM and the ostia of its bifurcation branches. However, artifacts mainly located in the proximal LM and decreasing distally in a stepwise fashion should be considered in the interpretation of OFDI in this setting.

Penetration capability of near infrared Laguerre-Gaussian beams through highly scattering media

The higher capability of optical vortex beams of penetrating turbid media (e.g., biological fluids) with respect to the conventional Gaussian beams is, for the first time to our knowledge, demonstrated in the 1.3 µm wavelength range which is conventionally used for optical coherence tomography procedures in endoscopic intravascular scenarios. The effect has been demonstrated by performing transmittance measurements through suspensions of polystyrene microspheres in water with various particulate concentrations and, in reflection, by using samples of human blood with different thicknesses. The reduced backscattering/increased transmittance into such highly scattering media of Laguerre-Gaussian beams with respect to Gaussian ones, in the near infrared wavelength region, could be potentially exploited in clinical applications, leading to novel biomedical diagnoses and/or procedures.

Degree of luminal narrowing and composition of thrombus in plaque erosion

As the degree of luminal narrowing increases, shear stress increases, and high shear stress is known to activate platelets. However, the relationship between the degree of luminal narrowing and the composition of thrombus in patients with plaque erosion has not been studied. A total of 148 patients with plaque erosion and thrombus detected by optical coherence tomography were divided into tertiles based on the minimum lumen area (MLA) at the culprit lesion. Thrombus was categorized as platelet-rich or fibrin-rich. Among 148 patients, 50 (34%) were in the mild stenosis group, 49 (33%) were in the moderate stenosis group, and 49 (33%) were in the severe stenosis group. The composition of thrombus was significantly different among the 3 groups (prevalence of platelet-rich thrombus was 60% in the mild stenosis group; 78% in the moderate stenosis group; and 84% in the severe stenosis group; P = 0.021). The pattern of fibrin-rich thrombus showed the opposite: 40%, 22%, and 16%, respectively. In the multivariate analysis, current smoking was independently associated with fibrin-rich thrombus (odds ratio [OR] 2.364 [95% CI 1.004-5.567], P = 0.049). This study demonstrated that platelet-rich thrombus was the predominant type of thrombus in plaque erosion. The prevalence of fibrin-rich thrombus was highest in the mild stenosis group.

Proteomics Profiling Reveals Insulin-Like Growth Factor 1, Collagen Type VI α-2 Chain, and Fermitin Family Homolog 3 as Potential Biomarkers of Plaque Erosion in ST-Segment Elevated Myocardial Infarction

BACKGROUND

Plaque erosion (PE) has been considered a secondary pathogenesis of ST-segment elevated myocardial infarction (STEMI) following plaque rupture (PR). Previous studies demonstrated that they had different demographic and histology characteristics and need different treatment strategy. But there are few non-invasive plasma biomarkers for distinguishing them. The present study aimed to identify non-invasive predictive biomarkers for PE and PR in patients with STEMI.

METHODS AND RESULTS

A total 108 patients were recruited and grouped into a PE group (n=36), a PR group (n=36), and an unstable angina pectoris (UAP) (n=36) group for analysis. A 9-plex tandem mass tag (TMT)-based proteomics was used to compare plasma protein profiles of PE, PR, and UAP. In total, 36 significant differential proteins (DPs) were identified among groups, 10 of which were screened out using bio-information analysis and validated with enzyme-linked immunosorbent assay (ELISA). The relationship of angiography and optical coherence tomography (OCT) imaging data and the 10 target DPs was analyzed statistically. Logistic regression showed elevated collagen type VI α-2 chain (COL6A2) and insulin-like growth factor 1 (IGF1), and decreased fermitin family homolog 3 (FERMT3), were positively associated with PE. Multivariate analysis indicated IGF1, FERMT3, and COL6A2 had independent predictive ability for PE. IGF1 was inversely correlated with lumen stenosis and the lipid arc of the plaque.

CONCLUSIONS

IGF1, COL6A2, and FERMT3 are potential predictive biomarkers of PE in STEMI patients. And IGF1 was negatively correlated with the developing of culprit plaque.

Use of Optical Coherence Tomography in Coronary Artery Disease: Review Article

Optical coherence tomography is a catheter-based imaging modality in heart catheterizations, which provides a significantly higher resolution of intravascular pathology by means of using light as opposed to ultrasound. The applications of this modality may include a detailed assessment of atherosclerotic plaques, stent evaluation including coverage and restenosis and percutaneous coronary intervention optimization. In this article, we provide a review of current literature highlighting the advantages and disadvantages of the use of optical coherence tomography in the catheterization lab.

Clinical considerations and recommendations for OCT-guided carotid artery stenting

Introduction: Optical Coherence Tomography (OCT) is an intravascular imaging providing high-resolution images of morphological features of arterial wall. Nowadays, OCT is an accepted intravascular modality to study coronary arteries, stent implantation, and vessel injury. In the last decade, an increasing interest have been focused on the application of OCT in carotid arteries.Areas covered: Literature evidence in the application of OCT in carotid arteries still remains debated. So far, OCT has been used as a research tool, aiming to evaluate atherosclerotic plaques' features and stents' behavior after implantation. This paper is intended to summarize clinical evidences and practices in the use of OCT in carotid arteries district and during CAS procedures. Literature review was completed via Pubmed search using Keywords.Expert opinion: CAS is a safe and effective procedure when performed by trained physicians with a tailored approach. In this scenario, ambiguous pictures at ultrasound, angiography, and IVUS might be clarified using OCT.By providing unprecedented microstructural information on atherosclerotic plaques, OCT may identify the features of vulnerable carotid plaque and, by identifying possible defects after stent implantation as malapposition and plaque prolapse, it may help the tailoring approach to CAS.

Current Advances in the Diagnostic Imaging of Atherosclerosis: Insights into the Pathophysiology of Vulnerable Plaque

Atherosclerosis is a lipoprotein-driven inflammatory disorder leading to a plaque formation at specific sites of the arterial tree. After decades of slow progression, atherosclerotic plaque rupture and formation of thrombi are the major factors responsible for the development of acute coronary syndromes (ACSs). In this regard, the detection of high-risk (vulnerable) plaques is an ultimate goal in the management of atherosclerosis and cardiovascular diseases (CVDs). Vulnerable plaques have specific morphological features that make their detection possible, hence allowing for identification of high-risk patients and the tailoring of therapy. Plaque ruptures predominantly occur amongst lesions characterized as thin-cap fibroatheromas (TCFA). Plaques without a rupture, such as plaque erosions, are also thrombi-forming lesions on the most frequent pathological intimal thickening or fibroatheromas. Many attempts to comprehensively identify vulnerable plaque constituents with different invasive and non-invasive imaging technologies have been made. In this review, advantages and limitations of invasive and non-invasive imaging modalities currently available for the identification of plaque components and morphologic features associated with plaque vulnerability, as well as their clinical diagnostic and prognostic value, were discussed.

Macrophage-Enriched lncRNA RAPIA: A Novel Therapeutic Target for Atherosclerosis

OBJECTIVE

Despite the current antiatherosclerotic and antithrombotic therapies, the incidence of advanced atherosclerosis-associated clinical events remains high. Whether long noncoding RNAs (lncRNAs) affect the progression of atherosclerosis and whether they are potential targets for the treatment of advanced atherosclerosis are poorly understood. Approach and Results: The progression of atherosclerotic lesions was accompanied by dynamic alterations in lncRNA expression, as revealed by RNA sequencing and quantitative polymerase chain reaction. Among the dynamically changing lncRNAs, we identified a novel lncRNA, lncRNA Associated with the Progression and Intervention of Atherosclerosis (RAPIA), that was highly expressed in advanced atherosclerotic lesions and in macrophages. Inhibition of RAPIA in vivo not only repressed the progression of atherosclerosis but also exerted atheroprotective effects similar to those of atorvastatin on advanced atherosclerotic plaques that had already formed. In vitro assays demonstrated that RAPIA promoted proliferation and reduced apoptosis of macrophages. A molecular sponge interaction between RAPIA and microRNA-183-5p was demonstrated by dual-luciferase reporter and RNA immunoprecipitation assays. Rescue assays indicated that RAPIA functioned at least in part by targeting the microRNA-183-5p/ITGB1 (integrin β1) pathway in macrophages. In addition, the transcription factor FoxO1 (forkhead box O1) could bind to the RAPIA promoter region and facilitate the expression of RAPIA.

CONCLUSIONS

The progression of atherosclerotic lesions was accompanied by dynamic changes in the expression of lncRNAs. Inhibition of the pivotal lncRNA RAPIA may be a novel preventive and therapeutic strategy for advanced atherosclerosis, especially in patients resistant or intolerant to statins.

Kalman-Based Real-Time Functional Decomposition for the Spectral Calibration in Swept Source Optical Coherence Tomography

This paper presents a real-time functional decomposition adaptive algorithm for the optimal sampling of the interferometric signal in Swept-Source Optical Coherence Tomography imaging systems, which completely eliminates the input signal dependent nonlinearities that are problematic in current state-of-the-art OCT realizations that use interpolation and resampling. The proposed adaptive calibration algorithm uses the Kalman approach to estimate the wavenumber index parameter k from the Mach-Zender Interferometer signal which is then applied to an adaptive level crossing sampler to generate a sampling clock that k-linearizes the data on real-time during the sampling process. Such a system implements an artifact-free realization of the technology removing the need for classical interpolation and resampling. The new real-time linearization scheme has the additional capability of increasing the imaging acquisition speed by 10X while providing robustness to noise, properties that are demonstrated through mathematical analysis and simulation results throughout the paper.

Determining the Significance of Coronary Plaque Lesions: Physiological Stenosis Severity and Plaque Characteristics

The evaluation of coronary lesions has evolved in recent years. Physiologic-guided revascularization (particularly with pressure-derived fractional flow reserve (FFR)) has led to superior outcomes compared to traditional angiographic assessment. A greater importance, therefore, has been placed on the functional significance of an epicardial lesion. Despite the improvements in the limitations of angiography, insights into the relationship between hemodynamic significance and plaque morphology at the lesion level has shown that determining the implications of epicardial lesions is rather complex. Investigators have sought greater understanding by correlating ischemia quantified by FFR with plaque characteristics determined on invasive and non-invasive modalities. We review the background of the use of these diagnostic tools in coronary artery disease and discuss the implications of analyzing physiological stenosis severity and plaque characteristics concurrently.

An assessment of the quality of optical coherence tomography image acquisition

Optical coherence tomography (OCT) provides excellent image resolution, however OCT optimal acquisition is essential but could be challenging owing to several factors. We sought to assess the quality of OCT pullbacks and identify the causes of suboptimal image acquisition. We evaluated 784 (404 pre-PCI; 380 post-PCI) coronary pullbacks from an anonymized OCT database from our Cardiovascular Imaging Core Laboratory. Imaging of the region-of-interest (ROI-lesion or stented segment plus references) was incomplete in 16.1% pullbacks, caused by pullback starting too proximal (63.7%), inappropriate pullback length (17.1%) and pullback starting too distal (11.4%). The quality of image acquisition was excellent in 36.3% pullbacks; whereas 4% pullbacks were unanalyzable. Pullback quality was most commonly affected by poor blood displacement from inadequate contrast volume (27.4%) or flow (25.6%), followed by artifacts (24.1%). Acquisition mode was 'High-Resolution' (54 mm) in 74.4% and 'Survey' (75 mm) in 25.6% of cases. The 54 mm mode was associated with incomplete ROI imaging (p = 0.020) and inadequate contrast volume (p = 0.035). We observed a substantial frequency of suboptimal image acquisition and identified its causes, most of which can be addressed with minor modifications during the procedure, ultimately improving patient outcomes.

Plaque morphology assessed by optical coherence tomography in the culprit lesions of the first episode of acute myocardial infarction in patients with low low-density lipoprotein cholesterol level

BACKGROUND

There remains a residual risk for acute myocardial infarction (AMI) even with low low-density lipoprotein cholesterol (LDL-C) levels. This study aimed to characterize the culprit lesion morphology of AMI by optical coherence tomography (OCT) in patients with low LDL-C.

METHODS

Four-hundred and nine culprit lesions of 409 patients with their first presentation of AMI imaged by OCT were investigated. OCT analysis included the presence of plaque rupture and thin-capped fibroatheroma (TCFA). Fibrous cap thickness and lipid length were also measured. Intravascular ultrasound (IVUS) was performed in 368 (90.0%) patients. OCT and IVUS findings were compared between patients with LDL-C < 100 mg/dl (lower-LDL group) and those with LDL ≥ 100 mg/dl (higher-LDL group).

RESULTS

Lower-LDL group included 93 (22.7%) patients. Plaque rupture (54.8% vs. 68.7%, p = 0.018) and TCFA (39.8% vs. 54.6%, p = 0.013) were less frequently observed in lower-LDL than in higher-LDL. Fibrous cap was thicker [73 (59-109) µm vs. 63 (57-83) µm, p = 0.028] and lipid length was smaller [5.4 (2.3-9.9) mm vs. 7.1 (4.1-10.5) mm, p = 0.012] in lower-LDL than in higher-LDL. There were no significant differences in IVUS parameters including plaque burden or remodeling index between the two groups.

CONCLUSIONS

Patients with lower LDL-C showed more prevalent intact fibrous cap and less vulnerable features in the culprit lesions, which may suggest the need for exploring a specific strategy for the prevention of plaque erosion in low LDL-C subjects.

Coronary Atherosclerotic Phenotype and Plaque Healing in Patients With Recurrent Acute Coronary Syndromes Compared With Patients With Long-term Clinical Stability: An In Vivo Optical Coherence Tomography Study

Importance

At one end of the coronary artery disease (CAD) spectrum, there are patients with multiple recurrent acute coronary syndromes (rACS), and at the other end there are those with long-standing clinical stability. Predicting the natural history of these patients is challenging because unstable plaques often heal without resulting in ACS.

Objective

To assess in vivo the coronary atherosclerotic phenotype as well as the prevalence and characteristics of healed coronary plaques by optical coherence tomography (OCT) imaging in patients at the extremes of the CAD spectrum.

Design, Setting, and Participants

This is an observational, single-center cohort study with prospective clinical follow-up. From a total of 823 consecutive patients enrolled in OCT Registry of the Fondazione Policlinico A. Gemelli-IRCCS, Rome, Italy, from March 2009 to February 2016, 105 patients were included in the following groups: (1) patients with rACS, defined as history of at least 3 acute myocardial infarctions (AMIs) or at least 4 ACS with at least 1 AMI; (2) patients with long-standing stable angina pectoris (ls-SAP), defined as a minimum 3-year history of stable angina; and (3) patients with a single unheralded AMI followed by a minimum 3-year period of clinical stability (sAMI). Data were analyzed from January to August 2018.

Exposures

Intracoronary OCT imaging of nonculprit coronary segments.

Main Outcomes and Measures

Coronary plaque features and the prevalence of healed coronary plaques in nonculprit segments as assessed by intracoronary OCT imaging.

Results

Of 105 patients, 85 were men (81.0%); the median (interquartile range) age was 68 (63-75) years. Median (interquartile range) time of clinical stability was 9 (5.0-15.0) years in the ls-SAP group and 8 (4.5-14.5) years in the sAMI group. Patients in the rACS and sAMI groups showed similar prevalence of lipid-rich plaque and thin-cap fibroatheroma, which was significantly higher than in those with ls-SAP (lipid-rich plaque 80.0% [n = 24 of 30] vs 76.3% [n = 29 of 38] vs 37.8% [n = 14 of 37], respectively; P < .001; thin-cap fibroatheroma 40.0% [n = 12 of 30] vs 34.2% [n = 13 of 38] vs 8.1% [n = 3 of 37], respectively; P = .006). Spotty calcifications were more frequently observed in patients with rACS than in those with ls-SAP and sAMI (70.0% [n = 21 of 30] vs 40.5% [n = 15 of 37] vs 44.7% [n = 17 of 38], respectively; P = .04). Healed coronary plaques were rarely observed in patients with rACS, whereas their prevalence was significantly higher in patients with ls-SAP and sAMI (3.3% [n = 1 of 30] vs 29.7% [n = 11 of 37] vs 28.9% [n = 11 of 38], respectively; P = .01).

Conclusions and Relevance

Patients with rACS have a distinct atherosclerotic phenotype compared with those with ls-SAP, including higher prevalence of thin-cap fibroatheroma and lower prevalence of healed coronary plaques, suggesting that atherosclerotic profile and plaque healing may play a role in leading the natural history of patients with CAD.

Optical coherence tomography-defined plaque vulnerability in relation to functional stenosis severity stratified by fractional flow reserve and quantitative flow ratio

OBJECTIVES

We sought to investigate that the quantitative flow ratio (QFR) might be associated with optical coherence tomography (OCT)-defined plaque vulnerability.

BACKGROUND

Both functional stenosis severity and plaque instability are related to adverse clinical outcomes in patients with coronary artery disease. Recent studies have shown an association between physiological stenosis severity and the presence of thin-cap fibroatheroma (TCFA). Measurement of QFR is a novel method for rapid computational estimation of fractional flow reserve (FFR).

METHODS

We investigated 327 de novo intermediate-to-severe coronary lesions in 295 stable patients who underwent OCT, FFR, and QFR computation. The lesions were divided into tertiles based on either the FFR or QFR. The OCT findings were compared among these tertiles of FFR and QFR. Each tertile was defined as follows: FFR-T1 (FFR < 0.72), FFR-T2 (0.72 ≤ FFR ≤ 0.79), and FFR-T3 (FFR > 0.79) and QFR-T1 (QFR < 0.73), QFR-T2 (0.73 ≤ QFR ≤ 0.78), and QFR-T3 (QFR > 0.78).

RESULTS

The prevalence of OCT-defined TCFA showed graded differences in proportion to the QFR tertiles (25.0% vs. 12.8% vs. 6.6%, p = .003). An overall significant difference in the prevalence of TCFA was found among FFR tertiles (p = .048), although pairwise comparison did not show statistical significance. Compared with FFR-based classifications, the model that integrated the FFR and QFR categorization improved the incremental reclassification efficacy (relative integrated discrimination improvement, 0.069; p = .002; continuous net reclassification improvement, 0.356; p = .022) for predicting the presence of TCFA.

CONCLUSIONS

OCT-defined plaque instability was associated with the QFR in angiographically intermediate-to-severe lesions. Compared with the FFR alone, the QFR can provide incremental efficacy in predicting the presence of TCFA.

Comprehensive multimodality characterization of hemodynamically significant and non-significant coronary lesions using invasive and noninvasive measures

BACKGROUND

There is limited knowledge about morphological molecular-imaging-derived parameters to further characterize hemodynamically relevant coronary lesions.

OBJECTIVE

The aim of this study was to describe and differentiate specific parameters between hemodynamically significant and non-significant coronary lesions using various invasive and non-invasive measures.

METHODS

This clinical study analyzed patients with symptoms suggestive of coronary artery disease (CAD) who underwent native T1-weighted CMR and gadofosveset-enhanced CMR as well as invasive coronary angiography. OCT of the culprit vessel to determine the plaque type was performed in a subset of patients. Functional relevance of all lesions was examined using quantitative flow reserve (QFR-angiography). Hemodynamically significant lesions were defined as lesions with a QFR <0.8. Signal intensity (contrast-to-noise ratios; CNRs) on native T1-weighted CMR and gadofosveset-enhanced CMR was defined as a measure for intraplaque hemorrhage and endothelial permeability, respectively.

RESULTS

Overall 29 coronary segments from 14 patients were examined. Segments containing lesions with a QFR <0.8 (n = 9) were associated with significantly higher signal enhancement on Gadofosveset-enhanced CMR as compared to segments containing a lesions without significant stenosis (lesion-QFR>0.8; n = 19) (5.32 (4.47-7.02) vs. 2.42 (1.04-5.11); p = 0.042). No differences in signal enhancement were seen on native T1-weighted CMR (2.2 (0.68-6.75) vs. 2.09 (0.91-6.57), p = 0.412). 66.7% (4 out of 6) of all vulnerable plaque and 33.3% (2 out of 6) of all non-vulnerable plaque (fibroatheroma) as assessed by OCT were hemodynamically significant lesions.

CONCLUSION

The findings of this pilot study suggest that signal enhancement on albumin-binding probe-enhanced CMR but not on T1-weighted CMR is associated with hemodynamically relevant coronary lesions.

Ventricular Fibrillation During Optical Coherence Tomography/Optical Frequency Domain Imaging - A Large Single-Center Experience

BACKGROUND

The risks of ventricular fibrillation (Vfib) associated with frequency-domain optical coherence tomography (OCT)/optical frequency domain imaging (OFDI) remain undetermined.

METHODS AND RESULTS

We retrospectively studied the occurrence of Vfib during OCT/OFDI for unselected indications. The frequency of Vfib and patient and procedural characteristics were investigated. A total of 4,467 OCT/OFDI pullback examinations were performed in 1,754 patients (median of 2.0 [2.0-3.0] pullbacks for 1.0 [1.0-1.3] vessels). OCT/OFDI was performed during PCI in 899 patients (51.3%). The contrast injection volume per pullback was 14.4 (11.7-17.2) mL with a flow rate of 3.4 (3.2-3.5) mL/s. Vfib occurred in 31 pullbacks (0.69%) in 30 patients (1.7%). No cases of Vfib occurred when using low-molecular-weight dextran. On multivariate analysis, contrast volume was the only independent factor for predicting Vfib (odds ratio, 1.080; 95% confidence interval, 1.008-1.158, P=0.029). The best cutoff value of contrast volume for predicting Vfib was 19.2 mL (area under the curve, 0.713, P<0.001; diagnostic accuracy, 87.1%).

CONCLUSIONS

The present large, single-center registry study indicated that Vfib during OCT/OFDI was rare for unselected indications. Contrast injection volume used to displace blood should be limited to avoid Vfib.

Plasma Trimethylamine N-Oxide as a Novel Biomarker for Plaque Rupture in Patients With ST-Segment-Elevation Myocardial Infarction

BACKGROUND

Trimethylamine N-oxide (TMAO) is reported to promote the pathogenesis of atherosclerosis and be associated with cardiovascular events risk. It is unknown whether plasma TMAO is associated with plaque morphology in patients with acute myocardial infarction. We investigated the relationship between the culprit plaque morphology and plasma TMAO concentration in patients with ST-segment-elevation myocardial infarction.

METHODS AND RESULTS

A prospective series of 211 patients with ST-segment-elevation myocardial infarction who underwent preintervention optical coherence tomography examination for the culprit lesion were enrolled; 77 and 69 patients were categorized as plaque rupture and plaque erosion, respectively. Plasma TMAO levels, detected using stable isotope dilution liquid chromatography tandem mass spectrometry, were significantly higher in patients with plaque rupture than in those with plaque erosion (3.33 μM; interquartile range: 2.48-4.57 versus 1.21 μM; interquartile range: 0.86-1.91; P<0.001). After adjustments for traditional risk factors, elevated TMAO levels remained independently correlated with plaque rupture (adjusted odds ratio: 4.06, 95% CI, 2.38-6.91; P<0.001). The area under the receiver operating characteristic curve for plaque rupture versus plaque erosion was 0.89. At a cutoff level of 1.95 μM, TMAO had a sensitivity of 88.3% and specificity of 76.8% in discriminating plaque rupture from plaque erosion.

CONCLUSIONS

High levels of plasma TMAO independently correlated with plaque rupture in patients with ST-segment-elevation myocardial infarction. Moreover, TMAO might be a useful biomarker for plaque rupture to improve risk stratification and management in patients with ST-segment-elevation myocardial infarction.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifiers: NCT03593928.

Relationship of a thinned medial layer to the attenuated contractile response in atherosclerotic coronary arteries

Coronary arteries with advanced atherosclerosis do not necessarily have greater contractile responses than those with early atherosclerosis. This study aimed to clarify the relationship between thickness of the medial layer and the contractile response to acetylcholine (ACh) in coronary artery using optical coherence tomography (OCT). The OCT and the vasomotor response to ACh in the left anterior descending coronary artery were assessed in 32 patients with previous myocardial infarction. The intimal and medial layer areas were measured by planimetric analysis of the OCT images. The coronary contractile response to ACh had a positive linear relationship with medial area (r = 0.61, P < 0.001). In contrast, the relationship between the coronary contractile response to ACh and intimal area was described by an inverted U-shaped curve that was fitted to a quadratic regression model (R² = 0.35, P = 0.002, y-axis, contraction; x-axis, intimal area). The contractile response increased as the intimal layer thickened up to the inflection point; thereafter, the contractile response declined. The relationship between medial area and intimal area was also described by an inverted U-shaped curve that was fitted to a quadratic regression model (R² = 0.41, P < 0.01, y-axis, medial area; x-axis, intimal area). The medial area increased as the intimal area thickened up to the inflection point; thereafter, the medial area thinned. In conclusion, the thinned medial layer was associated with the attenuated contractile response in a coronary artery with greater atherosclerosis.NEW & NOTEWORTHY This is the first clinical study to show the relationship between the contractile response and the thickness of medial smooth muscle layer in coronary artery of patients with previous myocardial infarction using OCT. The contractile response to acetylcholine was attenuated, and medial layer area was thinned in coronary artery with greater atherosclerosis compared with those in coronary artery with mild or moderate atherosclerosis. The coronary contractile response was positively correlated with thickness of the medial layer in coronary arteries with either mild or greater atherosclerosis. Thus, coronary arteries with advanced atherosclerosis do not necessarily have greater contractile responses than those with early atherosclerosis, which could be related to the thinned medial layer.