In vivo critical fibrous cap thickness for rupture-prone coronary plaques assessed by optical coherence tomography

Targeting senescent cells in atherosclerosis: Pathways to novel therapies

Targeting senescent cells has recently emerged as a promising strategy for treating age-related diseases, such as atherosclerosis, which significantly contributes to global cardiovascular morbidity and mortality. This review elucidates the role of senescent cells in the development of atherosclerosis, including persistently damaging DNA, inducing oxidative stress and secreting pro-inflammatory factors known as the senescence-associated secretory phenotype. Therapeutic approaches targeting senescent cells to mitigate atherosclerosis are summarized in this review, which include the development of senotherapeutics and immunotherapies. These therapies are designed to either remove these cells or suppress their deleterious effects. These emerging therapies hold potential to decelerate or even alleviate the progression of AS, paving the way for new avenues in cardiovascular research and treatment.

Lesion-Level Effects of LDL-C-Lowering Therapy in Patients With Acute Myocardial Infarction: A Post Hoc Analysis of the PACMAN-AMI Trial

Importance

Previous studies investigated atherosclerotic changes induced by lipid-lowering therapy in extensive coronary segments irrespective of baseline disease burden (a vessel-level approach).

Objective

To investigate the effects of lipid-lowering therapy on coronary lesions with advanced atherosclerotic plaque features and presumably higher risk for future events.

Design, Setting, and Participants

The PACMAN-AMI randomized clinical trial (enrollment: May 2017 to October 2020; final follow-up: October 2021) randomized patients with acute myocardial infarction to receive alirocumab or placebo in addition to high-intensity statin therapy. In this post hoc lesion-level analysis, nonculprit lesions were identified as segments with plaque burden 40% or greater defined by intravascular ultrasound (IVUS). IVUS, near-infrared spectroscopy, and optical coherence tomography images at baseline and the 52-week follow-up were manually matched by readers blinded to treatment allocation. Data for this study were analyzed from October 2022 to November 2023.

Interventions

Alirocumab or placebo in addition to high-intensity statin therapy.

Main Outcomes and Measures

Lesion-level imaging outcome measures, including high-risk plaque characteristics and phenotypes.

Results

Of the 245 patients in whom lesions were found, 118 were in the alirocumab group (mean [SD] age, 58.2 [10.0] years; 101 [85.6%] male and 17 [14.4%] female) and 127 in the placebo group (mean [SD] age, 57.7 [8.8] years; 104 [81.9%] male and 23 [18.1%] female). Overall, 591 lesions were included: 287 lesions (118 patients, 214 vessels) in the alirocumab group and 304 lesions (127 patients, 239 vessels) in the placebo group. Lesion-level mean change in percent atheroma volume (PAV) was -4.86% with alirocumab vs -2.78% with placebo (difference, -2.02; 95% CI, -3.00 to -1.05; P < .001). At the minimum lumen area (MLA) site, mean change in PAV was -10.14% with alirocumab vs -6.70% with placebo (difference, -3.36; 95% CI, -4.98 to -1.75; P < .001). MLA increased by 0.15 mm2 with alirocumab and decreased by 0.07 mm2 with placebo (difference, 0.21; 95% CI, 0.01 to 0.41; P = .04). Among 122 lipid-rich lesions, 34 of 55 (61.8%) in the alirocumab arm and 27 of 67 (41.8%) in the placebo arm showed a less lipid-rich plaque phenotype at follow-up (P = .03). Among 63 lesions with thin-cap fibroatheroma at baseline, 8 of 26 (30.8%) in the alirocumab arm and 3 of 37 (8.1%) in the placebo arm showed a fibrous/fibrocalcific plaque phenotype at follow-up (P = .02).

Conclusions and Relevance

At the lesion level, very intensive lipid-lowering therapy induced substantially greater PAV regression than described in previous vessel-level analyses. Compared with statin therapy alone, alirocumab treatment was associated with greater enlargement of the lesion MLA and more frequent transition of presumably high-risk plaque phenotypes into more stable, less lipid-rich plaque phenotypes.

Trial Registration

ClinicalTrials.gov Identifier: NCT03067844.

The mechanisms underlying acute myocardial infarction in chronic kidney disease patients undergoing hemodialysis

Cardiovascular disease (CVD) is a leading cause of death in chronic kidney disease (CKD). Hemodialysis is one of the main treatments for patients with end-stage kidney disease. Epidemiological data has shown that acute myocardial infarction (AMI) accounts for the main reason for death in patients with CKD under hemodialysis therapy. Immune dysfunction and changes in metabolism (including a high level of inflammatory cytokines, a disorder of lipid and mineral ion homeostasis, accumulation of uremic toxins et al.) during CKD can deteriorate stability of atherosclerotic plaque and promote vascular calcification, which are exactly the pathophysiological mechanisms underlying the occurrence of AMI. Meanwhile, the hemodialysis itself also has adverse effects on lipoprotein, the immune system and hemodynamics, which contribute to the high incidence of AMI in these patients. This review aims to summarize the mechanisms and further promising methods of prevention and treatment of AMI in CKD patients undergoing hemodialysis, which can provide an excellent paradigm for exploring the crosstalk between the kidney and cardiovascular system.

Atherosclerotic plaque stabilization and regression: a review of clinical evidence

Atherosclerotic plaque results from a complex interplay between lipid deposition, inflammatory changes, cell migration and arterial wall injury. Over the past two decades, clinical trials utilizing invasive arterial imaging modalities, such as intravascular ultrasonography, have shown that reducing levels of atherogenic lipoproteins, mainly serum LDL-cholesterol (LDL-C), to very low levels can safely reduce overall atherosclerotic plaque burden and favourably modify plaque composition. Classically, this outcome has been achieved with intensive statin therapy. Since 2016, newer and potent lipid-lowering strategies, such as proprotein convertase subtilisin-kexin type 9 inhibition, have shown incremental effects on plaque regression and risk of clinical events. Despite maximal reduction in plasma LDL-C levels, considerable residual cardiovascular risk remains in some patients. Therefore, there is a need to study therapeutic approaches that address residual risk beyond LDL-C reduction to promote plaque stabilization or regression. Contemporary imaging modalities, such as coronary computed tomography angiography, enable non-invasive assessment of the overall atherosclerotic plaque burden as well as of certain local plaque characteristics. This technology could allow further study of plaque stabilization and regression using novel therapeutic approaches. Non-invasive plaque assessment might also offer the potential to guide personalized management strategies if validated for this purpose.

Sensitivity analysis of the mechanical properties on atherosclerotic arteries rupture risk with an artificial neural network method

Considering the differences between individuals, in this paper, an uncertainty analysis model for predicting rupture risk of atherosclerotic arteries is established based on a back-propagation artificial neural network. The influence of isotropy and anisotropy on the rupture risk of atherosclerotic arteries is analyzed, and the results demonstrate the effectiveness of the artificial neural network in predicting the rupture risk. Moreover, the rupture risk of atherosclerotic arteries at different inflation sizes are simulated. This study contributes to a better understanding of the underlying mechanisms of atherosclerotic arteries rupture and promotes the advancement of artificial neural networks in atherosclerosis research.

Relationship of OCT-defined plaque characteristics with CCTA-derived coronary inflammation and CMR-derived global coronary flow reserve in patients with acute coronary syndrome

BACKGROUND

The relationship of layered plaque detected by optical coherence tomography (OCT) with coronary inflammation and coronary flow reserve (CFR) remains elusive. We aimed to investigate the association of OCT-defined layered plaque with pericoronary adipose tissue (PCAT) inflammation assessed by coronary computed tomography angiography (CCTA) and global (G)-CFR assessed by cardiac magnetic resonance imaging (CMR) in patients with acute coronary syndrome (ACS).

METHODS

We retrospectively investigated 88 patients with first ACS who underwent preprocedural CCTA, OCT imaging of the culprit lesion prior to primary/urgent percutaneous coronary intervention (PCI), and postprocedural CMR. All patients were divided into two groups according to the presence and absence of OCT-defined layered plaque at the culprit lesion. Coronary inflammation was assessed by the mean value of PCAT attenuation (-190 to -30 HU) of the three major coronary vessels. G-CFR was obtained by quantifying absolute coronary sinus flow at rest and during maximum hyperemia. CCTA and CMR findings were compared between the groups.

RESULTS

In a total of 88 patients, layered plaque was detected in 51 patients (58.0%). The patients with layered plaque had higher three-vessel-PCAT attenuation value (-68.58 ± 6.41 vs. -71.60 ± 5.21 HU, P = 0.021) and culprit vessel-PCAT attenuation value (-67.69 ± 7.76 vs. -72.07 ± 6.57 HU, P = 0.007) than those with non-layered plaque. The patients with layered plaque had lower G-CFR value (median, 2.26 [interquartile range, 1.78, 2.89] vs. 3.06 [2.41, 3.90], P = 0.003) than those with non-layered plaque.

CONCLUSIONS

The presence of OCT-defined layered plaque at the culprit lesion was associated with high PCAT attenuation and low G-CFR after primary/urgent PCI in patients with ACS. OCT assessment of culprit plaque morphology and detection of layered plaque may help identify increased pericoronary inflammation and impaired CFR, potentially providing the risk stratification in patients with ACS and residual microvascular dysfunction after PCI.

Identification of Optical Coherence Tomography-Defined Coronary Plaque Erosion by Preprocedural Computed Tomography Angiography

Background A previous coronary computed tomography (CT) angiographic study failed to discriminate optical coherence tomography-defined intact fibrous cap culprit lesions (IFC group) from those with ruptured fibrous caps (RFC group) in patients with coronary artery disease. This study aimed to evaluate the diagnostic efficacy of preprocedural coronary CT imaging in identifying subsequently performed optical coherence tomography-defined plaque rupture or erosion at culprit lesions in patients with non-ST-segment-elevation acute myocardial infarction. Methods and Results This study used data from 2 recently published studies that tested the hypothesis that coronary CT angiography (CCTA) before percutaneous coronary intervention may provide diagnostic information on the high-risk atherosclerotic burden in patients with non-ST-segment-elevation acute myocardial infarction. In the analysis of 186 patients, optical coherence tomography identified 106 RFC plaques and 80 IFC plaques as the culprit lesions. On CT, the prevalence of low-attenuation plaque, positive remodeling, napkin-ring sign, and spotty calcification were all significantly lower in the IFC group. The culprit vessel pericoronary adipose tissue inflammation and coronary artery calcium scores were significantly lower in the IFC group than in the RFC group. The absence of low-attenuation plaque, napkin-ring sign, zero coronary artery calcium, and low pericoronary adipose tissue inflammation were independent predictors of IFC. When stratified into 5 subgroups according to the number of these 4 CT factors, the prevalence of IFC was 8.3%, 20.8%, 44.6%, 75.6%, and 100% (P<0.001), respectively. Conclusions Preprocedural comprehensive coronary CT imaging, including coronary artery calcium and pericoronary adipose tissue inflammation assessment, can accurately and noninvasively identify optical coherence tomography-defined IFC or RFC culprit lesions.

Role of plaque imaging for identification of vulnerable patients beyond the stage of myocardial ischemia

Chronic coronary syndrome (CCS) is a progressive disease, which often first manifests as acute coronary syndrome (ACS). Imaging modalities are clinically useful in making decisions about the management of patients with CCS. Accumulating evidence has demonstrated that myocardial ischemia is a surrogate marker for CCS management; however, its ability to predict cardiovascular death or nonfatal myocardial infarction is limited. Herein, we present a review that highlights the latest knowledge available on coronary syndromes and discuss the role and limitations of imaging modalities in the diagnosis and management of patients with coronary artery disease. This review covers the essential aspects of the role of imaging in assessing myocardial ischemia and coronary plaque burden and composition. Furthermore, recent clinical trials on lipid-lowering and anti-inflammatory therapies have been discussed. Additionally, it provides a comprehensive overview of intracoronary and noninvasive cardiovascular imaging modalities and an understanding of ACS and CCS, with a focus on histopathology and pathophysiology.

Identification of High-Risk Coronary Lesions by 3-Vessel Optical Coherence Tomography

BACKGROUND

Optical coherence tomography (OCT) may provide a method for detecting histologically defined high-risk plaques in vivo.

OBJECTIVES

The authors aimed to investigate the prognostic value of OCT for identifying patients and lesions that are at risk for adverse cardiac events.

METHODS

Between January 2017 and May 2019, OCT of all the 3 main epicardial arteries was performed in 883 patients with acute myocardial infarction (MI) who were referred for primary percutaneous coronary intervention. The primary endpoint was the composite of cardiac death, nonculprit lesion-related nonfatal MI, and unplanned coronary revascularization. Patients were followed for up to 4 years (median 3.3 years).

RESULTS

The 4-year cumulative rate of the primary endpoint was 7.2%. In patient-level analysis, thin-cap fibroatheroma (TCFA) (adjusted HR: 3.05; 95% CI: 1.67-5.57) and minimal lumen area (MLA) <3.5 mm² (adjusted HR: 3.71; 95% CI: 1.22-11.34) were independent predictors of the primary endpoint. In lesion-level analysis, nonculprit lesions responsible for subsequent events were not angiographically severe at baseline (mean diameter stenosis 43.8% ± 13.4%). TCFA (adjusted HR: 8.15; 95% CI: 3.67-18.07) and MLA <3.5 mm² (adjusted HR: 4.33; 95% CI: 1.81-10.38) were predictive of events arising from each specific lesion. TCFAs with an MLA <3.5 mm² carried a higher risk and were sufficient for identifying patients at risk for the composite of cardiac death and nonculprit lesion-related nonfatal MI.

CONCLUSIONS

OCT imaging of angiographically nonobstructive territories in patients with acute MI can aid in identifying patients and lesions at increased risk for adverse cardiac events.

Optical coherence tomography and coronary revascularization: from indication to procedural optimization

Angiography alone is the most commonly used imaging modality for guidance of percutaneous coronary interventions. Angiography is limited, however, by several factors, including that it only portrays a low resolution, two-dimensional outline of the lumen and does not inform on plaque composition and functional stenosis severity. Optical coherence tomography (OCT) is an intracoronary imaging technique that has superior spatial resolution compared to all other imaging modalities. High-resolution imaging of the vascular wall enables precise measurement of vessel wall and luminal dimensions, more accurately informing about the anatomic severity of epicardial stenoses, and also provides input for computational models to assess functional severity. The very high-resolution images also permit plaque characterization that may be informative for prognostication. Moreover, periprocedural imaging provides valuable information to guide lesion preparation, stent implantation and to evaluate acute stent complications for which iterative treatment might reduce the occurrence of major adverse stent events. As such, OCT represent a potential future all-in-one tool that provides the data necessary to establish the indications, procedural planning and optimization, and final evaluation of percutaneous coronary revascularization.

Prior Myocardial Infarction and Treatment Effect of Ticagrelor Versus Prasugrel in Patients With Acute Coronary Syndromes - A Post-hoc Analysis of the ISAR-REACT 5 Trial

Background The efficacy and safety of ticagrelor versus prasugrel in patients with acute coronary syndrome and prior myocardial infarction (MI) remain unstudied. We aimed to assess the treatment effect of ticagrelor versus prasugrel according to prior MI status in patients with ACS. Methods and Results Patients with acute coronary syndrome planned for an invasive strategy and randomized to ticagrelor or prasugrel in the ISAR-REACT (Intracoronary Stenting and Antithrombotic Regimen: Rapid Early Action for Coronary Treatment) 5 trial were included. The primary end point was the composite of 1-year all-cause death, MI, or stroke; the secondary safety end point was the composite of 1-year Bleeding Academic Research Consortium type 3 to 5 bleeding. The study included 4015 patients (prior MI=631 patients; no prior MI=3384 patients). As compared with patients without prior MI, the primary end point occurred more frequently in patients with prior MI (12.6% versus 7.2%; hazard ratio [HR], 1.78 [95% CI, 1.38-2.29]); the secondary safety end point appears to differ little between patients with and without prior MI (5.8% versus 5.7%, respectively; HR, 1.02 [95% CI, 0.71-1.45]). With regard to the primary end point, ticagrelor versus prasugrel was associated with an HR of 1.62 (95% CI, 1.03-2.55) in patients with prior MI and an HR of 1.28 (95% CI, 0.99-1.65) in patients without prior MI (P_int=0.37). With regard to the secondary safety end point, ticagrelor versus prasugrel was associated with an HR of 1.28 (95% CI, 0.56-2.91) in patients with prior MI and an HR of 1.13 (95% CI, 0.82-1.55) in patients without prior MI (P_int=0.79). Conclusions Patients with acute coronary syndrome and prior MI are at higher risk for recurrent ischemic but not bleeding events. Prasugrel is superior to ticagrelor in reducing the risk of ischemic events without a tradeoff in bleeding regardless of prior MI status. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT01944800.

New insights into fibrous cap thickness of vulnerable plaques assessed by optical coherence tomography

Objective

Vulnerable plaques with fibrous cap thickness (FCT) of ≤65 μm are prone to rupture and/or thrombosis. However, plaques with FCT > 65 μm cause acute myocardial infarction and even sudden death. We aimed to investigate the relationship between 65 < FCT ≤ 80 μm and plaque rupture and/or thrombosis using optical coherence tomography (OCT).

Methods

OCT was performed on culprit lesions in 502 consecutively enrolled patients to identify FCT. Patients were classified into three groups according to FCT: Group A (FCT ≤ 65 μm, n = 147), Group B (65 < FCT ≤ 80 μm, n = 84) and Group C (FCT > 80 μm, n = 271). Clinical and laboratory data was collected from the inpatient medical record system.

Results

Plaques with thinner FCT, especially < 65 μm, were more susceptible to rupture and/or thrombosis (P < 0.001). Plaques with FCT between 65 and 80 μm had a higher probability of rupture and/or thrombosis than those with FCT > 80 μm (P < 0.001). In multivariable analysis, FCT ≤ 65 μm and 65 < FCT ≤ 80 μm were independent predictors for plaque rupture ([FCT ≤ 65 μm vs. FCT > 80 μm]: OR = 8.082, 95% CI = 4.861 to 13.435, P < 0.001; [65 < FCT ≤ 80 μm vs. FCT > 80 μm]: OR = 2.463, 95% CI = 1.370 to 4.430, P = 0.003), thrombosis ([FCT ≤ 65 μm vs. FCT > 80 μm]: OR = 25.224, 95% CI = 13.768 to 46.212, P < 0.001; [65 < FCT ≤ 80 μm vs. FCT > 80 μm]: OR = 3.675, 95% CI = 2.065 to 6.542, P < 0.001) and plaque rupture with thrombosis ([FCT ≤ 65 μm vs. FCT > 80 μm]: OR = 22.593, 95% CI = 11.426 to 44.674, P < 0.001; [65 < FCT ≤ 80 μm vs. FCT > 80 μm]: OR = 4.143, 95% CI = 1.869 to 9.184, P < 0.001).

Conclusions

OCT-assessed 65 < FCT ≤ 80 μm was independently associated with increased risk of plaque rupture and/or thrombosis compared with FCT > 80 μm.

The Role of Inflammation in Cardiovascular Disease

Atherosclerosis is a chronic inflammatory disease, in which the immune system has a prominent role in its development and progression. Inflammation-induced endothelial dysfunction results in an increased permeability to lipoproteins and their subendothelial accumulation, leukocyte recruitment, and platelets activation. Recruited monocytes differentiate into macrophages which develop pro- or anti-inflammatory properties according to their microenvironment. Atheroma progression or healing is determined by the balance between these functional phenotypes. Macrophages and smooth muscle cells secrete inflammatory cytokines including interleukins IL-1β, IL-12, and IL-6. Within the arterial wall, low-density lipoprotein cholesterol undergoes an oxidation. Additionally, triglyceride-rich lipoproteins and remnant lipoproteins exert pro-inflammatory effects. Macrophages catabolize the oxidized lipoproteins and coalesce into a lipid-rich necrotic core, encapsulated by a collagen fibrous cap, leading to the formation of fibro-atheroma. In the conditions of chronic inflammation, macrophages exert a catabolic effect on the fibrous cap, resulting in a thin-cap fibro-atheroma which makes the plaque vulnerable. However, their morphology may change over time, shifting from high-risk lesions to more stable calcified plaques. In addition to conventional cardiovascular risk factors, an exposure to acute and chronic psychological stress may increase the risk of cardiovascular disease through inflammation mediated by an increased sympathetic output which results in the release of inflammatory cytokines. Inflammation is also the link between ageing and cardiovascular disease through increased clones of leukocytes in peripheral blood. Anti-inflammatory interventions specifically blocking the cytokine pathways reduce the risk of myocardial infarction and stroke, although they increase the risk of infections.

Immersive educational curriculum on intracoronary optical coherence tomography image analysis among naïve readers

BACKGROUND

Optical coherence tomography (OCT) is an intravascular imaging modality for analysing coronary vessels. Image interpretation remains an obstacle for novice readers due to technical artefacts and uncertainty in tissue characterization. Despite an expanding clinical and research role for OCT, few training efforts exist, and there is an absence of a national standardized educational curriculum. We sought to determine whether an interactive, feedback-based OCT curriculum improved image interpretation among naive readers.

METHODS

Naive OCT readers completed both a Standard curriculum, comprised of self-directed didactics and consensus statements, and an Augmented curriculum, which provided real-time digital feedback of feature identification and measurements. Modules were separated by a minimum one-week washout period. After each module, and blinded to the exam answers, subjects completed an identical expert-designed 413-item exam to assess technical knowledge and ability to identify and measure vessel features. Performances were compared using Exact Wilcoxon signed-rank tests.

RESULTS

Among the 7 included subjects were 3 medical students, 3 internal medicine residents, and 1 cardiovascular medicine fellow with no prior OCT experience. The technical knowledge score (maximum 13) was significantly higher with the Augmented compared with the Standard curriculum (median 11 vs. 7, p = 0.03). After undergoing the Augmented curriculum, all 7 subjects were able to identify features of plaque rupture (Standard curriculum: 5/7 subjects, p = 0.5) and macrophages (Standard curriculum: 6/7 subjects, p = 0.99), differentiate the components between red and white thrombus (Standard curriculum: 6/7 subjects, p = 0.99), and characterize lipid plaque by attenuation, signal, homogeneity, and borders (Standard curriculum: 5/7 subjects, p = 0.5). Performances on the remaining exam portions did not differ between curricula.

CONCLUSIONS

The need for standardized, effective training in OCT image interpretation is increasingly essential as the intravascular imaging modality becomes widely utilized among interventional cardiologists and trainees. A novel interactive OCT curriculum enhanced naive readers' technical knowledge and may supplement traditional self-learning in refining analytic skills.

Optical coherence tomography in coronary atherosclerosis assessment and intervention

Since optical coherence tomography (OCT) was first performed in humans two decades ago, this imaging modality has been widely adopted in research on coronary atherosclerosis and adopted clinically for the optimization of percutaneous coronary intervention. In the past 10 years, substantial advances have been made in the understanding of in vivo vascular biology using OCT. Identification by OCT of culprit plaque pathology could potentially lead to a major shift in the management of patients with acute coronary syndromes. Detection by OCT of healed coronary plaque has been important in our understanding of the mechanisms involved in plaque destabilization and healing with the rapid progression of atherosclerosis. Accurate detection by OCT of sequelae from percutaneous coronary interventions that might be missed by angiography could improve clinical outcomes. In addition, OCT has become an essential diagnostic modality for myocardial infarction with non-obstructive coronary arteries. Insight into neoatherosclerosis from OCT could improve our understanding of the mechanisms of very late stent thrombosis. The appropriate use of OCT depends on accurate interpretation and understanding of the clinical significance of OCT findings. In this Review, we summarize the state of the art in cardiac OCT and facilitate the uniform use of this modality in coronary atherosclerosis. Contributions have been made by clinicians and investigators worldwide with extensive experience in OCT, with the aim that this document will serve as a standard reference for future research and clinical application.

Fibrous Cap Thickness Predicts Stable Coronary Plaque Progression: Early Clinical Validation of a Semiautomated OCT Technology

BACKGROUND

Imaging-based characteristics associated with the progression of stable coronary atherosclerotic lesions are poorly defined. Utilizing a combination of optical coherence tomography (OCT) and intravascular ultrasound (IVUS) imaging, we aimed to characterize the lesions prone to progression through clinical validation of a semiautomated OCT computational program.

METHODS

Patients with stable coronary artery disease underwent nonculprit vessel imaging with IVUS and OCT at baseline and IVUS at the 12-month follow-up. After coregistration of baseline and follow-up IVUS images, paired 5-mm segments from each patient were identified, demonstrating the greatest plaque progression and regression as measured by the change in plaque burden. Experienced readers identified plaque features on corresponding baseline OCT segments, and predictors of plaque progression were assessed by multivariable analysis. Each segment then underwent volumetric assessment of the fibrous cap (FC) using proprietary software.

RESULTS

Among 23 patients (70% men; median age, 67 years), experienced-reader analysis demonstrated that for every 100 μm increase in mean FC thickness, plaques were 87% less likely to progress (P = .01), which persisted on multivariable analysis controlling for baseline plaque burden (P = .05). Automated FC analysis (n = 17 paired segments) confirmed this finding (P = .01) and found thinner minimal FC thickness (P = .01) and larger FC surface area of <65 μm (P = .02) and <100 μm (P = .04) in progressing segments than in regressing segments. No additional imaging features predicted plaque progression.

CONCLUSIONS

A semiautomated FC analysis tool confirmed the significant association between thinner FC and stable coronary plaque progression along entire vessel segments, illustrating the diffuse nature of FC thinning and suggesting a future clinical role in predicting the progression of stable coronary artery disease.

High-Risk Coronary Plaque Features: A Narrative Review

Advances in coronary plaque imaging over the last few decades have led to an increased interest in the identification of novel high-risk plaque features that are associated with cardiovascular events. Existing practices focus on risk stratification and lipid monitoring for primary and secondary prevention of cardiac events, which is limited by a lack of assessment and treatment of vulnerable plaque. In this review, we summarize the multitude of studies that have identified plaque, haemodynamic and patient factors associated with risk of acute coronary syndrome. Future progress in multi-modal imaging strategies and in our understanding of high-risk plaque features could expand treatment options for coronary disease and improve patient outcomes.

Comparison of Point-of-Care and Highly Sensitive Laboratory Troponin Testing in Patients Suspicious of Acute Myocardial Infarction and Its Efficacy in Clinical Outcome

Background

The use of high-sensitivity troponin (hs-cTnI) assays is recommended in current guidelines for managing patients with acute coronary syndrome (ACS) symptoms. However, point-of-care (POC) assays are frequently used in emergency departments (EDs) to reduce turnaround time and length of stay. This study aimed to compare the results of POC-cTnI testing with those of the gold standard, automated central laboratory testing of troponin (i.e., hs-cTnI). The primary and secondary outcomes were the diagnostic performance of POC-cTnI in diagnosing acute myocardial infarction (AMI) and major adverse cardiovascular events (MACE) during 30 days, respectively.

Materials and Methods

In this diagnostic accuracy study, 136 patients with suspected ACS who were referred or admitted to the Al Zahra Hospital, Shiraz, Iran, were included between March (2020) and July (2020). For the diagnosis of AMI, central laboratory cTnI levels were assessed at the time of presentation (0 hour) and reassessed at least 3 hours later. The POC-cTnI was measured at 0 hour in all patients and at 3 hours if a patient was diagnosed with AMI but had a 0-hour negative result for the POC-cTnI assay. Additionally, the 30-day follow-up period for these participants began on the day of the initial presentation to assess MACE.

Results

Out of 180 patients, 136 patients (median age of 59.5 years; 57.5% male) were left for the qualitative POC-cTnI and hs-cTnI assays. In 86 (63.24%) subjects, hs-cTnI was positive (either initial or serial); however, AMI was diagnosed in 85 patients according to positivity of troponin by hs-cTnI and clinical signs and symptoms, which were diagnosed by a cardiologist. The sensitivity, specificity, and negative predictive value of 0-hour POC-cTnI were observed to be 91.76% (95% CI: 83.77–96.62%), 98.04% (95% CI: 89.55–99.95%), and 87.72% (95% CI: 77.82–93.56%), respectively. Moreover, considering both the 0-hour and 3-hour POC-cTnI, all AMI cases were correctly identified, yielding a perfect test performance result. None of the 50 patients with negative cTnI results (by 0-hour and 3-hour POC-cTnI and hs-cTnI) experienced at least one MACE.

Conclusion

In this small sample-size study, a new qualitative POC-cTnI assay was statistically equal to a hs-cTnI assay in terms of diagnostic accuracy for AMI or MACE in patients with suspected myocardial infarction. The POC-cTnI was observed to be acceptable for the identification of AMI and prediction of MACE in the ED environment.

Ticagrelor Monotherapy After PCI in High-Risk Patients With Prior MI: A Prespecified TWILIGHT Substudy

OBJECTIVES

The aim of this study was to evaluate if patients with prior myocardial infarction (MI) could benefit from ticagrelor monotherapy in terms of bleeding reduction without any compromise in ischemic event prevention.

BACKGROUND

Patients with history of MI who undergo percutaneous coronary intervention (PCI) remain at risk for recurrent ischemic events. The optimal antithrombotic strategy for this cohort remains debated.

METHODS

In this prespecified analysis of the randomized TWILIGHT (Ticagrelor With Aspirin or Alone in High-Risk Patients after Coronary Intervention) trial, the authors evaluated the impact of history of MI on treatment effect of ticagrelor monotherapy versus ticagrelor plus aspirin in patients undergoing PCI with drug-eluting stent with at least 1 clinical and 1 angiographic high-risk feature and free from adverse events at 3 months after index PCI. The primary endpoint was Bleeding Academic Research Consortium type 2, 3, or 5 bleeding, and the key secondary endpoint was the composite of all-cause death, MI, or stroke, both at 12 months after randomization.

RESULTS

A total of 1,937 patients (29.7%) with and 4,595 patients (70.3%) without prior MI were randomized to ticagrelor and placebo or ticagrelor and aspirin. At 1 year after randomization, patients with prior MI experienced higher rates of death, MI, or stroke (5.7% vs 3.2%; P < 0.001) but similar BARC types 2 to 5 bleeding (5.0% vs 5.5%; P = 0.677) compared with patients without prior MI. Ticagrelor monotherapy consistently reduced the risk for the primary bleeding outcome in patients with (3.4% vs 6.7%; HR: 0.50; 95% CI: 0.33-0.76) and without (4.2% vs 7.0%; HR: 0.58; 95% CI: 0.45-0.76; P_interaction = 0.54) prior MI. Rates of the key secondary ischemic outcome were not significantly different between treatment groups irrespective of history of MI (prior MI, 6.0% vs 5.5% [HR: 1.09; 95% CI: 0.75-1.58]; no prior MI, 3.1% vs 3.3% [HR: 0.92; 95% CI: 0.67-1.28]; P_interaction = 0.52).

CONCLUSIONS

Ticagrelor monotherapy is associated with significantly lower risk for bleeding events compared with ticagrelor plus aspirin, without any compromise in ischemic prevention, among high-risk patients with history of MI undergoing PCI. (Ticagrelor With Aspirin or Alone in High-Risk Patients After Coronary Intervention [TWILIGHT]; NCT02270242).

Gender-based in vivo comparison of culprit plaque characteristics and plaque microstructures using optical coherence tomography in acute coronary syndrome

Introduction: Women perform worse after acute coronary syndrome (ACS) than men. The reason for these differences is unclear. The aim was to ascertain gender differences in the culprit plaque characteristics in ACS.

Methods: Patients with ACS undergoing percutaneous coronary intervention for the culprit vessel underwent optical coherence tomography (OCT) imaging. Culprit plaque was identified as lipid rich,fibrous, and calcific plaque. Mechanisms underlying ACS are classified as plaque rupture, erosion,or calcified nodule. A lipid rich plaque along with thin-cap fibroatheroma (TCFA) was a vulnerable plaque. Plaque microstructures including cholesterol crystals, macrophages, and microvessels were noted.

Results: A total of 52 patients were enrolled (men=29 and women=23). Baseline demographic features were similar in both the groups except men largely were current smokers (P <0.001). Plaque morphology,men vs. women: lipid rich 88.0% vs. 90.5%; fibrous 4% vs 0%; calcific 8.0% vs. 9.5% (P = 0.64). Of the ACS mechanisms in males versus females; plaque rupture (76.9 % vs. 50 %), plaque erosion (15.4 % vs.40 %) and calcified nodule (7.7 % vs. 10 %) was noted (P = 0.139). Fibrous cap thickness was (50.19 ±11.17 vs. 49.00 ± 10.71 mm, P = 0.71) and thin-cap fibroatheroma (96.2% vs. 95.0%, P = 1.0) in men and women respectively. Likewise no significant difference in presence of macrophages (42.3 % vs. 30%, P = 0.76), microvessels (73.1% vs. 60 %, P = 0.52) and cholesterol crystals (92.3% vs. 80%, P = 0.38).

Conclusion: No significant gender-based in-vivo differences could be discerned in ACS patients’ culprit plaques morphology, characteristics, and underlying mechanisms.

In vivo relationship between near-infrared spectroscopy-detected lipid-rich plaques and morphological plaque characteristics by optical coherence tomography and intravascular ultrasound: a multimodality intravascular imaging study

AIMS

We assessed morphological features of near-infrared spectroscopy (NIRS)-detected lipid-rich plaques (LRPs) by using optical coherence tomography (OCT) and intravascular ultrasound (IVUS).

METHODS AND RESULTS

IVUS-NIRS and OCT were performed in the two non-infarct-related arteries (non-IRAs) in patients undergoing percutaneous coronary intervention for treatment of an acute coronary syndrome. A lesion was defined as the 4 mm segment with the maximum amount of lipid core burden index (maxLCBI4mm) of each LRP detected by NIRS. We divided the lesions into three groups based on the maxLCBI4mm value: <250, 250-399, and ≥400. OCT analysis and IVUS analysis were performed blinded for NIRS. We measured fibrous cap thickness (FCT) by using a semi-automated method. A total of 104 patients underwent multimodality imaging of 209 non-IRAs. NIRS detected 299 LRPs. Of those, 41% showed a maxLCBI4mm <250, 39% a maxLCBI4mm 251-399, and 19% a maxLCBI4mm ≥400. LRPs with a maxLCBI4mm ≥400, as compared with LRPs with a maxLCBI4mm 250-399 and <250, were more frequently thin-cap fibroatheroma (TCFA) (42.1% vs. 5.1% and 0.8%; P < 0.001) with a smaller minimum FCT (80 μm vs. 110 μm and 120 μm; P < 0.001); a higher IVUS-derived percent atheroma volume (53% vs. 53% and 44%; P < 0.001) and a higher remodelling index (1.08 vs. 1.02 and 1.01; P < 0.001). MaxLCBI4mm correlated with OCT-derived FCT (r = 0.404; P < 0.001) and was the best predictor for TCFA with an optimal cut-off value of 401 (area under the curve = 0.882; P < 0.001).

CONCLUSION

LRPs with increasing maxLCBI4mm exhibit OCT and IVUS features of presumed plaque vulnerability including TCFA morphology, increased plaque burden, and positive remodelling.

Lesion Geometry as Assessed by Optical Coherence Tomography Is Related to Myocardial Ischemia as Determined by Cardiac Magnetic Resonance Imaging

INTRODUCTION

Although the relationship between the geometry of coronary stenosis and the presence of myocardial ischemia is well known, the association between stenosis geometry and severity and/or extent of ischemia is still unexplored. Thus, we investigated this relationship using optical coherence tomography (OCT) to assess stenosis parameters and cardiac magnetic resonance imaging (CMR) to determine both extent and severity of ischemia.

METHODS

We analyzed 55 lesions from 51 patients with stable angina. Pre-interventionally, all patients underwent OCT-analysis of stenosis morphology as well as CMR to determine both the extent and severity of myocardial ischemia.

RESULTS

Percent area stenosis (%AS) was significantly associated with ischemic burden (r = 0.416, p = 0.003). Similar results could be obtained for other stenosis parameters as well as for several other parameters assessing the extent of ischemia. Furthermore, OCT-derived stenosis parameters were associated with the product of ischemic burden and severity of ischemia (%AS: r = 0.435, p = 0.002; similar results for other parameters). A Poiseuille's-law-modelled combination of stenosis length and minimal lumen diameter yielded a good diagnostic efficiency (AUC 0.787) in predicting an ischemic burden >10%.

CONCLUSIONS

Our data highlight the key role of the geometry of coronary lesions in determining myocardial ischemia.

The Napkin-Ring Sign – the Story Behind Invasive Coronary Angiography

Coronary artery disease (CAD) represents one of the leading causes of morbidity and mortality across Europe. Most of the patients do not experience any warning sign before the coronary event develops, therefore screening this group of patients is essential to prevent major cardiac events. Coronary computed tomography angiography (CCTA) offers a noninvasive approach of the coronary arteries, providing information not only on the presence and severity of the coronary stenosis, but is also able to characterize the structure of the coronary wall. CCTA allows complex evaluation of the extension of CAD, and by assessing the structure of the atherosclerotic plaque, it can identify its degree of vulnerability. The napkin-ring sign (NRS) represents a ring-like attenuation of the non-calcified portion of the coronary lesion and has a high specificity (96–100%) for the identification of thin cap fibroatheroma (TCFA) or culprit lesion in acute coronary syndromes (ACS). It is also an independent predictor for ACS events and the strongest predictor for future ACS. Modern CCTA can provide submillimeter isotropic spatial resolution. Thus, CT attenuation-based tissue interpretation enables the assessment of total coronary plaque burden and individual plaque components, with a similar accuracy as intravascular ultrasoud-based investigations. This review aims to present the important role of CCTA as a potent screening tool for patients with CAD, and the current evidences in the detection and quantification of vulnerable plaques.

Multi-modality intravascular imaging for guiding coronary intervention and assessing coronary atheroma: the Novasight Hybrid IVUS-OCT system

Intravascular imaging has evolved alongside interventional cardiology as an adjunctive tool for assessing plaque pathology and for guiding and optimising percutaneous coronary intervention (PCI) in challenging lesions. The two modalities which have dominated the field are intravascular ultrasound (IVUS), which relies on sound waves and optical coherence tomography (OCT), relying on light waves. These approaches however have limited efficacy in assessing plaque morphology and vulnerability that are essential for guiding PCI in complex lesions and identifying patient at risk that will benefit from emerging therapies targeting plaque evolution. These limitations are complementary and, in this context, it has been recognised and demonstrated in multi-modality studies that the concurrent use of IVUS and OCT can help overcome these deficits enabling a more complete and accurate plaque assessment. The Conavi Novasight Hybrid IVUS-OCT catheter is the first commercially available device that is capable of invasive clinical coronary assessment with simultaneously acquired and co-registered IVUS and OCT imaging. It represents a significant evolution in the field and is expected to have broad application in clinical practice and research. In this review article we present the limitations of standalone intravascular imaging techniques, summarise the data supporting the value of multimodality imaging in clinical practice and research, describe the Novasight Hybrid IVUS-OCT system and highlight the potential utility of this technology in coronary intervention and in the study of atherosclerosis.

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.

Reviewing imaging modalities for the assessment of plaque erosion

Plaque rupture followed by intracoronary thrombus formation is recognized as the most common pathophysiological mechanism in acute coronary syndromes (ACS). The second most common underlying substrate for ACS is plaque erosion whose hallmark is thrombus formation without cap disruption. Invasive and non-invasive methods have emerged as a promising tool for evaluation of plaque features that either predict or detect plaque erosion. Optical coherence tomography (OCT), high-definition intravascular ultrasound (IVUS), near-infrared spectroscopy (NIRS), and near-infrared autofluorescence (NIRF) have been used to study plaque erosion. The detection of plaque erosion in the clinical setting, mainly facilitated by OCT, has shed light upon the complex pathophysiology underlying ACS not related to plaque rupture. Coronary computed tomography angiography (CCTA), which is to date the most commonly used non-invasive technique for coronary plaque evaluation, may also have a role in the evaluation of patients predisposed to erosion. Also, computational models enabling quantification of endothelial shear stress may pave the way to new research in coronary plaque pathophysiology. This review focuses on the recent imaging techniques for the evaluation of plaque erosion including invasive and non-invasive assessment.

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.

Advances in IVUS/OCT and Future Clinical Perspective of Novel Hybrid Catheter System in Coronary Imaging

Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) have been developed and improved as both diagnostic and guidance tools for interventional procedures over the past three decades. IVUS has a resolution of 100 μm with a high tissue penetration and capability of assessing the entire structure of a coronary artery including the external elastic membrane, whereas OCT has a higher resolution of 10–20 μm to assess endoluminal structures with a limited tissue penetration compared to IVUS. Recently, two companies, CONAVI and TERUMO, integrated IVUS and OCT into a single catheter system. With their inherent strength and limitations, the combined IVUS and OCT probes are complementary and work synergistically to enable a comprehensive depiction of coronary artery. In this review, we summarize the performance of the two intracoronary imaging modalities—IVUS and OCT—and discuss the expected potential of the novel hybrid IVUS–OCT catheter system in the clinical field.

Optical coherence tomography versus intravascular ultrasound for culprit lesion assessment in patients with acute myocardial infarction

Introduction

In patients with acute myocardial infarction (AMI) undergoing primary percutaneous coronary intervention (PCI) the implanted stent may not fully cover the whole intravascular ultrasound (IVUS)-derived thin-cap fibroatheroma (TCFA) related to the culprit lesion (CL).

Aim

Whether this phenomenon is more pronounced when optical coherence tomography (OCT) assessment of the CL is performed is not known.

Material and methods

Thus, we aimed to assess CLs in 40 patients with AMI treated with PCI, using VH (virtual histology)-IVUS and OCT before and after intervention. The results were blinded to the operator and PCI was done under angiography guidance.

Results

Uncovered lipid-rich plaques were identified in the stent reference segments of 23 (57.5%) patients: in 13 (32.5%) of them in the distal reference segment and in 19 (47.5%) of them in the proximal reference segment. In 9 of them (22.5%) lipid plaques were found in both reference segments. In 36 (90%) patients OCT confirmed lipid plaques identified as VH-derived TCFA by VH-IVUS in the reference segments of the stented segment. However, OCT confirmed that only in 2 (5%) patients were uncovered lipid plaques true TCFA as defined by histology. Comparing IVUS and OCT qualitative characteristics of the stented segments OCT detected more thrombus protrusions and proximal and distal stent edge dissections compared to IVUS (92.5 vs. 55%, p = 0.001; 20% vs. 7.5%, p = 0.03 and 25% vs. 5%, p < 0.001, respectively).

Conclusions

Due to its superior resolution, OCT identifies TCFA more precisely. OCT more often shows remaining problems related to stent implantation than IVUS after angiographically guided PCI.

Multi-parameter characterization of atherosclerotic plaques based on optical coherence tomography, photoacoustic and viscoelasticity imaging

Detection of atherosclerotic plaque vulnerability is the critical step in prevention of acute coronary events. Fibrous cap thickness, lipid core size, and inflammation extent are three key parameters for assessing plaque vulnerability. Here, we report on multimodality imaging of mice aortic plaques using a system that integrates optical coherence tomography (OCT), photoacoustic imaging (PAI), and photoacoustic viscoelasticity imaging (PAVEI). The thickness of fibrous cap is accurately evaluated by OCT, and PAI helps to determine the distribution and size of lipid core. The mechanical properties of plaques are closely related to the plaque compositions and the content and distribution of macrophages, while PAVEI can characterize the plaque viscoelasticity through the phase delay of photoacoustic signal. Experimental results demonstrate that the OCT-PAI-PAVEI system can comprehensively characterize the three traits of atherosclerotic plaques, thereby identifying high-risk lesions.

Spatial Distribution of Vulnerable Plaques: Comprehensive In Vivo Coronary Plaque Mapping

OBJECTIVES

The authors performed a comprehensive analysis on the distribution of coronary plaques with different phenotypes from our 3-vessel optical coherence tomography (OCT) database.

BACKGROUND

Previous pathology studies demonstrated that thin-cap fibroatheroma (TCFA) is localized in specific segments of the epicardial coronary arteries. A detailed description of in vivo coronary plaques of various phenotypes has not been reported.

METHODS

OCT images of all 3 coronary arteries in 131 patients were analyzed every 1 mm to assess plaque phenotype and features of vulnerability. In addition, plaques were divided into tertiles according to percent area stenosis (%AS).

RESULTS

Among 534 plaques identified in 393 coronary arteries, 27.0% were fibrous plaques, 13.3% were fibrocalcific plaques, 40.8% were thick-cap fibroatheromas, and 18.9% were TCFAs. TCFAs showed clustering in the proximal segment, particularly in the left anterior descending artery. On the other hand, fibrous plaques were relatively evenly distributed throughout the entire length of the coronary arteries. In patients with acute coronary syndromes (ACS), TCFAs showed stronger proximal clustering in the left anterior descending, 2 clustering peaks in the right coronary artery, and 1 clustering peak in the circumflex artery. The pattern of TCFA distribution was less obvious in patients without ACS. The prevalence of TCFA was higher in the highest %AS tertile, compared with the lowest %AS tertile (30% vs. 9%; p < 0.001).

CONCLUSIONS

The present 3-vessel OCT study showed that TCFAs cluster at specific locations in the epicardial coronary arteries, especially in patients with ACS. TCFA was more prevalent in segments with tight stenosis. (The Massachusetts General Hospital Optical Coherence Tomography Registry; NCT01110538).

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.

Coronary Atherosclerosis Imaging

Identifying patients at increased risk of coronary artery disease, before the atherosclerotic complications become clinically evident, is the aim of cardiovascular prevention. Imaging techniques provide direct assessment of coronary atherosclerotic burden and pathological characteristics of atherosclerotic lesions which may predict the progression of disease. Atherosclerosis imaging has been traditionally based on the evaluation of coronary luminal narrowing and stenosis. However, the degree of arterial obstruction is a poor predictor of subsequent acute events. More recent techniques focus on the high-resolution visualization of the arterial wall and the coronary plaques. Most acute coronary events are triggered by plaque rupture or erosion. Hence, atherosclerotic plaque imaging has generally focused on the detection of vulnerable plaque prone to rupture. However, atherosclerosis is a dynamic process and the plaque morphology and composition may change over time. Most vulnerable plaques undergo progressive transformation from high-risk to more stable and heavily calcified lesions, while others undergo subclinical rupture and healing. Although extensive plaque calcification is often associated with stable atherosclerosis, the extent of coronary artery calcification strongly correlates with the degree of atherosclerosis and with the rate of future cardiac events. Inflammation has a central role in atherogenesis, from plaque formation to rupture, hence in the development of acute coronary events. Morphologic plaque assessment, both invasive and non-invasive, gives limited information as to the current activity of the atherosclerotic disease. The addition of nuclear imaging, based on radioactive tracers targeted to the inflammatory components of the plaques, provides a highly sensitive assessment of coronary disease activity, thus distinguishing those patients who have stable disease from those with active plaque inflammation.

Reliable in vivo intravascular imaging plaque characterization: A challenge unmet

Intravascular imaging has enabled in vivo assessment of coronary artery pathology and detection of plaque characteristics that are associated with increased vulnerability. Prospective invasive imaging studies of coronary atherosclerosis have demonstrated that invasive imaging modalities can detect lesions that are likely to progress and cause cardiovascular events and provided unique insights about atherosclerotic evolution. However, despite the undoubted value of the existing imaging techniques in clinical and research arenas, all the available modalities have significant limitations in assessing plaque characteristics when compared with histology. Hybrid/multimodality intravascular imaging appears able to overcome some of the limitations of standalone imaging; however, there are only few histology studies that examined their performance in evaluating plaque pathobiology. In this article, we review the evidence about the efficacy of standalone and multi-modality/hybrid intravascular imaging in assessing plaque morphology against histology, highlight the advantages and limitations of the existing imaging techniques and discuss the future potential of emerging imaging modalities in the study of atherosclerosis.

Coronary Artery Microcalcification: Imaging and Clinical Implications

Strategies to prevent acute coronary and cerebrovascular events are based on accurate identification of patients at increased cardiovascular (CV) risk who may benefit from intensive preventive measures. The majority of acute CV events are precipitated by the rupture of the thin cap overlying the necrotic core of an atherosclerotic plaque. Hence, identification of vulnerable coronary lesions is essential for CV prevention. Atherosclerosis is a highly dynamic process involving cell migration, apoptosis, inflammation, osteogenesis, and intimal calcification, progressing from early lesions to advanced plaques. Coronary artery calcification (CAC) is a marker of coronary atherosclerosis, correlates with clinically significant coronary artery disease (CAD), predicts future CV events and improves the risk prediction of conventional risk factors. The relative importance of coronary calcification, whether it has a protective effect as a stabilizing force of high-risk atherosclerotic plaque has been debated until recently. The extent of calcium in coronary arteries has different clinical implications. Extensive plaque calcification is often a feature of advanced and stable atherosclerosis, which only rarely results in rupture. These macroscopic vascular calcifications can be detected by computed tomography (CT). The resulting CAC scoring, although a good marker of overall coronary plaque burden, is not useful to identify vulnerable lesions prone to rupture. Unlike macrocalcifications, spotty microcalcifications assessed by intravascular ultrasound or optical coherence tomography strongly correlate with plaque instability. However, they are below the resolution of CT due to limited spatial resolution. Microcalcifications develop in the earliest stages of coronary intimal calcification and directly contribute to plaque rupture producing local mechanical stress on the plaque surface. They result from a healing response to intense local macrophage inflammatory activity. Most of them show a progressive calcification transforming the early stage high-risk microcalcification into the stable end-stage macroscopic calcification. In recent years, new developments in noninvasive cardiovascular imaging technology have shifted the study of vulnerable plaques from morphology to the assessment of disease activity of the atherosclerotic lesions. Increased disease activity, detected by positron emission tomography (PET) and magnetic resonance (MR), has been shown to be associated with more microcalcification, larger necrotic core and greater rates of events. In this context, the paradox of increased coronary artery calcification observed in statin trials, despite reduced CV events, can be explained by the reduction of coronary inflammation induced by statin which results in more stable macrocalcification.

Intravascular Polarimetry in Patients With Coronary Artery Disease

OBJECTIVES

The aims of this first-in-human pilot study of intravascular polarimetry were to investigate polarization properties of coronary plaques in patients and to examine the relationship of these features with established structural characteristics available to conventional optical frequency domain imaging (OFDI) and with clinical presentation.

BACKGROUND

Polarization-sensitive OFDI measures birefringence and depolarization of tissue together with conventional cross-sectional optical frequency domain images of subsurface microstructure.

METHODS

Thirty patients undergoing polarization-sensitive OFDI (acute coronary syndrome, n = 12; stable angina pectoris, n = 18) participated in this study. Three hundred forty-two cross-sectional images evenly distributed along all imaged coronary arteries were classified into 1 of 7 plaque categories according to conventional OFDI. Polarization features averaged over the entire intimal area of each cross section were compared among plaque types and with structural parameters. Furthermore, the polarization properties in cross sections (n = 244) of the fibrous caps of acute coronary syndrome and stable angina pectoris culprit lesions were assessed and compared with structural features using a generalized linear model.

RESULTS

The median birefringence and depolarization showed statistically significant differences among plaque types (p < 0.001 for both, one-way analysis of variance). Depolarization differed significantly among individual plaque types (p < 0.05), except between normal arteries and fibrous plaques and between fibrofatty and fibrocalcified plaques. Caps of acute coronary syndrome lesions and ruptured caps exhibited lower birefringence than caps of stable angina pectoris lesions (p < 0.01). In addition to clinical presentation, cap birefringence was also associated with macrophage accumulation as assessed using normalized SD.

CONCLUSIONS

Intravascular polarimetry provides quantitative metrics that help characterize coronary arterial tissues and may offer refined insight into coronary arterial atherosclerotic lesions in patients.

Cholesterol-crystalized coronary atheroma as a potential precursor lesion causing acute coronary syndrome: a case report

Background

Histopathological studies have reported the presence of cholesterol crystals in the culprit lesion in patients with sudden cardiac death. Given that cholesterol crystals themselves promote pro-inflammatory cascades, they may destabilize atherosclerotic plaques, leading to the occurrence of acute coronary events.

Case summary

A 60-year-old man presented with ST-segment elevation myocardial infarction. Emergent coronary angiography revealed a severely stenotic lesion (=culprit lesion) and another non-obstructive lesion in the proximal and middle segments of the left anterior descending artery (LAD), respectively. Optical coherence tomography (OCT) imaging showed that both lesions exhibited lipid-rich plaque with cholesterol crystals, and the non-obstructive lesion in the mid-LAD did not have a thin fibrous cap (its thickness = 230 μm). A drug-eluting stent was successfully implanted at the culprit lesion in the proximal LAD. On non-contrast T1-weighted magnetic resonance imaging performed 10 days after percutaneous coronary intervention (PCI), a high-intensity signal was identified at the non-obstructive mid-LAD lesion. This lesion was medically managed with aspirin, clopidogrel, and rosuvastatin due to the absence of myocardial ischaemia. However, 12 months after PCI, the patient was hospitalized again due to unstable angina pectoris. Coronary angiography revealed substantial progression of the mid-LAD lesion. Optical coherence tomography imaging prior to the second PCI showed a severely narrowed lesion containing cholesterol crystals and covered by organized thrombus. This lesion harbored an extensive amount of lipidic materials on near-infrared spectroscopy (maximum 4-mm lipid core burden index = 809).

Discussion

In our case, atherosclerotic plaques containing cholesterol crystals was associated with the occurrence of acute coronary syndrome. Our findings suggest that plaque with cholesterol crystals is a potential precursor to future acute coronary events.

Lipoprotein (a) level is associated with plaque vulnerability in patients with coronary artery disease: An optical coherence tomography study

Background

High lipoprotein (a) [Lp(a)] levels are an independent factor for worse prognosis in patients with coronary artery disease (CAD). However, the association between serum Lp(a) level and coronary plaque vulnerability remains to be determined.

Methods

A total of 255 consecutive patients with CAD who underwent optical coherence tomography imaging of culprit lesions were included. Patients were divided into 2 groups according to their Lp(a) levels (the higher Lp(a) group [≥25 mg/dL], n = 87; or the lower Lp(a) group [<25 mg/dL], n = 168).

Results

The prevalence of thin-cap fibroatheroma (TCFA) was significantly higher in the higher Lp(a) group than in the lower Lp(a) group (23% [n = 20] vs. 11% [n = 19], p = 0.014). Although the prevalence of TCFA was comparable between the 2 groups among patients with a lower LDL cholesterol (LDL-C) level (<100 mg/dL), TCFA was significantly more prevalent in the higher Lp(a) group than in the lower Lp(a) group (39% [14/36] vs. 10% [5/50], p = 0.001) among patients with a higher LDL-C level (≥100 mg/dL).

Conclusions

A higher Lp(a) level was associated with a higher frequency of TCFA, particularly in patients with a higher LDL-C level.

•

High Lp(a) (≥25 mg/dL) was observed in 34% of patients requiring PCI.

•

Higher Lp(a) was associated with the higher prevalence of thin-cap fibroatheroma.

•

High LDL-C enhanced the association between Lp(a) and thin-cap fibroatheroma.

Vulnerability analysis on the interaction between Asymmetric stent and arterial layer

The utilization of Asymmetric stent for recovering atherosclerotic diseases, particularly non-symmetric obstruction, is a quite challenging breakthrough treatment. In terms of eccentric plaque, the non-uniform stiffness of arterial layer causes the increasingly complex issues of vulnerability. This study investigated the vulnerability of the interaction between the Asymmetric stent and the surrounding arterial layer using structural transient dynamic analysis in ANSYS. Four combinations of stent deployment, i.e. the Sinusoidal stent expanded by the offset balloon, the Sinusoidal stent expanded by the ordinary cylindrical balloon, the Asymmetric stent expanded by the offset balloon, and the Asymmetric stent expanded by the ordinary cylindrical balloon, are generated for this comparative study. Multilayer material properties from recent in vitro experiments are adopted for the surrounding arterial layer, such as a fibrous cap, lipid core, diseased-healthy intima, and diseased-healthy media. In order to address plaque vulnerability, the Cauchy stresses and Hencky strains are used for stress measure because of convenience in comparison with the uniaxial/biaxial tension test data. The location-specific threshold value from the diseased human carotid artery is adopted for rupture criteria. The simulation indicated that as regards the eccentric plaque, the plaque vulnerability is caused by the plaque shape and components rather than caused by the geometrical structure of the stent or balloon expansion method. Nevertheless, the non-symmetric inflation of balloon, which leads against the plaque, contributed to an increase in the vulnerability of fibrous cap of fibroatheroma plaque.

Three-Dimensional Fibrous Cap Structure of Coronary Lipid Plaque - ST-Elevation Myocardial Infarction vs. Stable Angina

BACKGROUND

Fibrous cap thickness (FCT) is one of the key features of coronary vulnerable plaque. FCT is measured at an arbitrary point, determined on visual assessment of 2-D cross-sectional imaging. This method has poor reproducibility. The aim of this study was to compare the 3-D structure of FC in non-culprit lipid plaques between patients with ST-elevation myocardial infarction (STEMI) and with stable angina (SA) on optical coherence tomography. Methods and Results: A total of 54 non-culprit plaques from 23 STEMI and 23 SA patients were evaluated. Thin cap fibroatheroma (TCFA), defined as lipid plaque with FCT <80 µm, was identified using a novel algorithm. The number of TCFA, surface area of each TCFA, and the sum total area of TCFA in the target vessel were measured. Patients with STEMI had a greater median number of TCFA (9, IQR 1-17 vs. 2, IQR 0-5; P=0.002), the largest median single TCFA area (0.40, IQR 0.14-0.69 vs. 0.08, IQR 0.04-0.16 mm²; P<0.001) and median sum total area of TCFA (1.04, IQR 0.41-1.95 vs. 0.24, IQR 0.08-0.48 mm², P<0.004).

CONCLUSIONS

Patients with STEMI, as compared with those with SA, have greater vulnerability to non-culprit plaque.

Comparison of Rosuvastatin Versus Atorvastatin for Coronary Plaque Stabilization

Statins are widely used to lower cholesterol and to reduce cardiovascular events. Whether all statins have similar effects on plaque stabilization is unknown. We aimed to investigate coronary plaque response to treatment with different statins that result in similar lipid reduction using serial multimodality intracoronary imaging. Patients with de novo coronary artery disease requiring intervention were randomized to rosuvastatin 10mg (R10) or atorvastatin 20mg (A20) daily. Optical coherence tomography and intravascular ultrasound were performed at baseline, 6 months, and 12 months. Untreated nonculprit plaques were analyzed by optical coherence tomography for thin-cap fibroatheroma, minimum fibrous cap thickness, lipid arc, and lipid length. Total and percent atheroma volume, respectively were analyzed by intravascular ultrasound. Forty-three patients completed the protocol (R10: 24 patients, 31 plaques; A20: 19 patients, 30 plaques). The decrease in serum lipids was similar. From baseline to 6 months to 12 months, minimum fibrous cap thickness increased in the R10 group (61.4 ± 15.9 µm to 120.9 ± 57.9 µm to 171.5 ± 67.8 µm, p <0.001) and the A20 group (60.8 ± 18.1 µm to 99.2 ± 47.7 µm to 127.0± 66.8 µm, p <0.001). Prevalence of thin-cap fibroatheroma significantly decreased in the R10 and A20 groups (-48% and -53%, respectively, p <0.001 for intragroup comparisons). Only the R10 group had a decrease in macrophage density (-23%, p = 0.04) and microvessels (-12%, p = 0.002). Total atheroma volume decreased in the R10 group (109.2 ± 62.1 mm³ to 101.8 ± 61.1 mm³ to 102.5 ± 62.2 mm³, p = 0.047) but not in the A20 group (83.3 ± 48.5mm³ to 77.6 ± 43.0 mm³ to 77.9 ± 48.6 mm³, p = 0.07). In conclusion, although both statins demonstrated similar reductions in lipid profiles, the rosuvastatin group showed more rapid and robust plaque stabilization, and regression of plaque volume compared to the atorvastatin group.

Comparison of Vascular Response to Statin Therapy in Patients With Versus Without Diabetes Mellitus

Diabetes mellitus (DM) increases cardiovascular morbidity and mortality. A statin is routinely prescribed to patients with DM. However, whether a statin therapy is equally effective in plaque stabilization in DM patients compared with non-DM patients is unknown. A total of 117 lipid-rich plaques were imaged in 90 patients (54 plaques in 41 DM patients and 63 plaques in 49 non-DM patients) with coronary artery disease, those who were treated with a statin and underwent serial optical coherence tomography imaging were included in this study (mean follow-up period, 362 ± 38 days). The changes in minimum fibrous cap thickness (FCT) and lipid index between baseline and 1-year follow-up were compared between the 2 groups. Minimum FCT increased and lipid index decreased with statin therapy in both groups. No significant differences were observed in percent changes of minimum FCT (p = 0.796) and lipid index (p = 0.336) between DM and non-DM patients. Statin therapy induced a significant increase in FCT and a significant decrease in lipid index in both groups. Vascular response to statin therapy was similar between the 2 groups irrespective of DM status.

Metabolomics in early detection and prognosis of acute coronary syndrome

Acute coronary syndrome (ACS) is one of the most dangerous types of coronary heart disease (CHD) and contributes to significant mortality and morbidity worldwide. Outcomes in these patients remain a challenge despite improvements in diagnosis and treatment. Risk stratification continues to be problematic and the identification of novel predictors is crucial for improved outcomes. As such, there is a strong need for the development of novel analytical methods as well as the characterization of better predictive and prognostic biomarkers to enable more personalized treatment. Metabolite profile analysis may greatly assist in interpreting altered pathway dynamics, especially when combined with other 'omics' technologies such as transcriptomics and proteomics. In this review, we describe ACS pathophysiology and recent advances in the role of metabolomics in the diagnosis and the molecular pathogenesis of ACS. We briefly describe key technologies used in metabolomics research and statistical approaches for data reduction and pathway analysis and discuss their application to CHD.

Imaging the event-prone coronary artery plaque

Acute coronary events, the dreaded manifestation of coronary atherosclerosis, remain one of the main contributors to mortality and disability in the developed world. The majority of those events are associated with atherosclerotic plaques-related thrombus formation following an acute disruption, that being rupture or erosion, of an event-prone lesion. These historically termed vulnerable plaques have been the target of numerous benchtop and clinical research endeavors, yet to date without solid results that would allow for early identification and potential treatment. Technological leaps in cardiovascular imaging have provided novel insights into the formation and role of the event-prone plaques. From intracoronary optical coherence tomography that has enhanced our understanding of the pathophysiological mechanisms of plaque disruption, over coronary computed tomography angiography that enables non-invasive serial plaque imaging, and positron emission tomography poised to be rapidly implemented into clinical practice to the budding field of plaque imaging with cardiac magnetic resonance, we summarize the invasive and non-invasive imaging modalities currently available in our armamentarium. Finally, the current status and potential future imaging directions are critically appraised.

Clinical significance of optical coherence tomography-guided angioplasty on treatment selection

The present study aimed to observe whether optical coherence tomography (OCT)-guided angioplasty is able to provide useful clinical information beyond that obtained by angiography as well as provide recommendations for physicians that may improve treatment selection. This prospective study included 83 patients with coronary artery disease (>18 years) undergoing coronary angiography (CAG) for ST-elevation myocardial infarction (n=13), non-ST-elevation myocardial infarction (n=19), stable angina (n=22), unstable angina (n=10), silent ischemia (n=11), or elective percutaneous coronary intervention (n=8). Following the initial CAG (CAG-pre), the patients underwent OCT before angioplasty (OCT-pre, 24 patients), after angioplasty (OCT-post, 22 patients), or both (37 patients). The thrombus burden, calcification and plaque dissection or rupture were compared between the OCT-pre and CAG-pre recordings. Following angioplasty, stent malapposition, suboptimal stent deployment, suboptimal stent lesion coverage, and edge dissection were compared between OCT-post and CAG-post alone. Among the 83 patients, 45.7% had single-vessel and 54.3% had multiple-vessel disease. OCT pre- and post-angioplasty revealed significantly more information on the procedure than CAG alone. This clinical information changed the clinical strategies in 41/83 (49.4%) patients, including 58 modifications of therapeutic strategy (69.9%, 58/83): Thrombus aspiration in 2 cases (2.4%), administration of glycoprotein IIb/IIIa inhibitors in 8 cases (9.6%), additional balloon inflation in 23 cases (27.7%), additional stent implantation in 17 cases (20.5%), avoiding stent implantation in 4 cases (4.8%), collateral intervention in 2 cases (2.4%), and guidewire reposition in 2 cases (2.4%). In conclusion, OCT-pre and OCT-post provided additional clinical information beyond that obtained by angiography alone, which resulted in modification of the treatment strategies in half of the included patients.

Repeatability Assessment of Intravascular Polarimetry in Patients

Intravascular polarimetry with polarization sensitive optical frequency domain imaging (PS-OFDI) measures polarization properties of the vessel wall and offers characterization of coronary atherosclerotic lesions beyond the cross-sectional image of arterial microstructure available to conventional OFDI. A previous study of intravascular polarimetry in cadaveric human coronary arteries found that tissue birefringence and depolarization provide valuable insight into key features of atherosclerotic plaques. In addition to various tissue components, catheter and sample motion can also influence the polarization of near infrared light as used by PS-OFDI. This paper aimed to evaluate the robustness and repeatability of imaging tissue birefringence and depolarization in a clinical setting. 30 patients scheduled for percutaneous coronary intervention at the Erasmus Medical Center underwent repeated PS-OFDI pullback imaging, using commercial imaging catheters in combination with a custom-built PS-OFDI console. We identified 274 matching cross sections among the repeat pullbacks to evaluate the reproducibility of the conventional backscatter intensity, the birefringence, and the depolarization signals at each spatial location across the vessel wall. Bland-Altman analysis revealed best agreement for the birefringence measurements, followed by backscatter intensity, and depolarization, when limiting the analysis to areas of meaningful birefringence. Pearson correlation analysis confirmed highest correlation for birefringence (0.86), preceding backscatter intensity (0.83), and depolarization (0.78). Our results demonstrate that intravascular polarimetry generates robust maps of tissue birefringence and depolarization in a clinical setting. This outcome motivates the use of intravascular polarimetry for future clinical studies that investigate polarization properties of arterial atherosclerosis.