Clinical use of intracoronary imaging. Part 2: acute coronary syndromes, ambiguous coronary angiography findings, and guiding interventional decision-making: an expert consensus document of the European Association of Percutaneous Cardiovascular Interventions

Recent developments in diagnosis and risk stratification of non-ST-elevation acute coronary syndrome

In the past year, a number of important papers have been published on non-ST-elevation acute coronary syndrome, highlighting progress in clinical care. The current review focuses on early diagnosis and risk stratification using biomarkers and advances in intracoronary imaging.

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.

A Challenging and Unexpected Case of MINOCA Using Multimodality Imaging

We describe a challenging case of a patient with MINOCA due to isolated right ventricular myocardial infarction with microvascular obstruction identified on cardiac magnetic resonance imaging. This case highlights that even a comprehensive, guideline-based assessment of these patients can initially fail to detect the underlying pathology. (Level of Difficulty: Beginner.).

Calcified Lesion Assessment and Intervention in Complex Percutaneous Coronary Intervention: Overview of Angioplasty, Atherectomy, and Lithotripsy

Calcific coronary artery disease intervention is associated with uniformly worse short-term procedural and long-term clinical results compared with treatment of non-calcified lesions. Multiple intravascular imaging tools currently exist to aid the identification and detailed characterization of intracoronary calcium, and guide appropriate follow-on management strategies. Several unique device therapies, to include angioplasty, atherectomy, and lithotripsy may be employed to enhance lesion preparation, stent implantation and optimization, and improve patient outcomes. Current low use of both imaging and ablative technologies in the US offers significant future opportunities for improving the comprehensive evaluation and management of these complex lesion subsets and patients.

Flexible endoscopic micro-optical coherence tomography for three-dimensional imaging of the arterial microstructure

Micro-optical coherence tomography (µOCT) is a novel imaging approach enabling visualization of the microstructures of biological tissues at a cellular or sub-cellular level. However, it has been challenging to develop a miniaturized flexible endoscopic µOCT probe allowing helical luminal scanning. In this study, we built a flexible endoscopic µOCT probe with an outer diameter of 1.2 mm, which acquires three-dimensional images of the arterial microstructures via helical scanning with an axial and lateral resolutions of 1.83 µm and 3.38 µm in air, respectively. Furthermore, the depth of focus of the µOCT imaging probe was extended two-fold using a binary phase spatial filter. We demonstrated that the present endoscopic µOCT could image cellular level features of a rabbit artery with high-risk atheroma and a bioresorbable scaffold-implanted swine coronary artery. This highly-translatable endoscopic µOCT will be a useful tool for investigating coronary artery disease and stent biology.

OCT-NIRS Imaging for Detection of Coronary Plaque Structure and Vulnerability

A combination optical coherence tomography and near-infrared spectroscopy (OCT-NIRS) coronary imaging system is being developed to improve the care of coronary patients. While stenting has improved, complications continue to occur at the stented site and new events are caused by unrecognized vulnerable plaques. An OCT-NIRS device has potential to improve secondary prevention by optimizing stenting and by identifying vulnerable patients and vulnerable plaques. OCT is already in widespread use world-wide to optimize coronary artery stenting. It provides automated lumen detection and can identify features of coronary plaques not accurately identified by angiography or intravascular ultrasound. The ILUMIEN IV study, to be completed in 2022, will determine if OCT-guided stenting will yield better clinical outcomes than angiographic guidance alone. While the superb spatial resolution of OCT enables the identification of many plaque structural features, the detection by OCT of lipids, an important component of vulnerable plaques, is limited by suboptimal specificity and interobserver agreement. In contrast, NIRS has been extensively validated for lipid-rich plaque detection against the gold-standard of histology and is the only FDA-approved method to identify coronary lipids. Studies in patients have demonstrated that NIRS detects lipid in culprit lesions causing coronary events. In 2019, the positive results of the prospective Lipid-Rich Plaque Study led to FDA approval of NIRS for detection of high-risk plaques and patients. The complementarity of OCT for plaque structure and NIRS for plaque composition led to the sequential performance of NIRS and OCT imaging in patients. NIRS identified lipid while OCT determined the thickness of the cap over the lipid pool. The positive results obtained with OCT and NIRS imaging led to development of a prototype combined OCT-NIRS catheter that can provide co-registered OCT and NIRS data in a single pullback. The data will provide structural and chemical information likely to improve stenting and deliver more accurate identification of vulnerable plaques and vulnerable patients. More precise diagnosis will then lead to OCT-NIRS guided treatment trials to improve secondary prevention. Success in secondary prevention will then facilitate development of improved primary prevention with invasive imaging and effective treatment of patients identified by non-invasive methods.

Predictive value of the QFR in detecting vulnerable plaques in non-flow limiting lesions: a combined analysis of the PROSPECT and IBIS-4 study

Studies have shown that the quantitative flow ratio (QFR), recently introduced to assess lesion severity from coronary angiography, provides useful prognostic information; however the additive value of this technique over intravascular imaging in detecting lesions that are likely to cause events is yet unclear. We analysed data acquired in the PROSPECT and IBIS-4 studies, in particular the baseline virtual histology-intravascular ultrasound (VH-IVUS) and angiographic data from 17 non-culprit lesions with a presumable vulnerable phenotype (i.e., thin or thick cap fibroatheroma) that caused major adverse cardiac events or required revascularization (MACE) at 5-year follow-up and from a group of 78 vulnerable plaques that remained quiescent. The segments studied by VH-IVUS were identified in coronary angiography and the QFR was estimated. The additive value of 3-dimensional quantitative coronary angiography (3D-QCA) and of the QFR in predicting MACE at 5 year follow-up beyond plaque characteristics was examined. It was found that MACE lesions had a greater plaque burden (PB) and smaller minimum lumen area (MLA) on VH-IVUS, a longer length and a smaller minimum lumen diameter (MLD) on 3D-QCA and a lower QFR compared with lesions that remained quiescent. By univariate analysis MLA, PB, MLD, lesion length on 3D-QCA and QFR were predictors of MACE. In multivariate analysis a low but normal QFR (> 0.80 to < 0.97) was the only independent prediction of MACE (HR 3.53, 95% CI 1.16-10.75; P = 0.027). In non-flow limiting lesions with a vulnerable phenotype, QFR may provide additional prognostic information beyond plaque morphology for predicting MACE throughout 5 years.

Intravascular Imaging to Guide Lithotripsy in Concentric and Eccentric Calcific Coronary Lesions

BACKGROUND

Calcified coronary lesions still represent a challenge for coronary angioplasty, with sub-optimal acute PCI results causing more frequent late stent failure.

PURPOSE

The study aimed at the evaluation of the immediate procedural outcome in a real-world consecutive population of a selective use of lithotripsy based on the intravascular imaging assessment with IVUS or OCT.

METHODS AND RESULTS

Thirty-one calcified stenoses (28 patients) out of a total of 455 lesions (370 patients) treated between November 2018 and May 2019 received IVL under intravascular imaging guidance. The majority of the IVL lesions had angiographically severe calcifications and were selected after intravascular imaging. A smaller group was identified by poor expansion after high-pressure balloon dilatation, in one case despite preliminary small burr Rotablation. After IVL, when OCT was performed calcium fractures were observed in 71% of cases. After OCT/IVUS guided stent optimization a satisfactory lumen enlargement (minimal stent area 7.09 ± 2.77 mm²) was observed with good stent expansion (residual area stenosis<20% in 29 lesions, 93.5%) Peri-procedural complications were limited to one dissection at the distal edge requiring an additional stent and 3 peri-procedural myocardial infarctions. There were no periprocedural coronary perforations or pericardial effusions, and no in-hospital or 30 days stent thrombosis. When patients were divided into two subgroups according to a calcium arc ≤180° (Group A: 10 lesions, calcium arc 140 ± 24°; Group B: 21 lesions, calcium arc 289 ± 53°), at OCT Group B presented also a higher number of calcium fractures post IVL than group A (group A: 38% vs group B: 92%, p = 0.03). The in-stent minimum lumen diameter (MSD), the in stent minimal lumen area (MSA) and the acute gain, however, were similar between the two groups (acute gain group A: 1.22 ± 0.29 mm; group B: 1.31 ± 0.52 mm, p = 0.63).

CONCLUSIONS

A standardized algorithm applying intravascular imaging guidance of IVL facilitated second generation DES expansion delivers excellent immediate lumen expansion and patient outcome, both in concentric and eccentric calcifications.

The Role of Imaging for MINOCA (Myocardial Infarction with No Obstructive Coronary Artery Disease): a Review of Literature and Current Perspectives

Purpose of Review

The objective of this review is to summarize scientific statements on the diagnosis and management of myocardial infarction with no obstructive coronary artery disease (MINOCA); define the diagnostic role of optical coherence tomography (OCT), intravascular ultrasound (IVUS), and cardiac magnetic resonance imaging (CMR); and provide representative case examples.

Recent Findings

The majority of patients with MINOCA are evaluated by conventional coronary angiography. However, intracoronary imaging using OCT or IVUS permits more accurate understanding of the underlying pathology. These and other imaging modalities provide significant diagnostic and prognostic value.

Summary

Although nonobstructive disease is the hallmark of the disease, MINOCA is associated with significant morbidity and mortality. Every effort to define the underlying pathology is necessary and requires more standardized use of imaging in clinical practice.

Left Main Coronary Interventions: A Practical Guide

Coronary artery bypass surgery has been the accepted treatment for left main coronary artery disease for over 50 years. Balloon angioplasty was later used then abandoned because of deaths likely due to restenosis or thrombotic occlusion. However, rapid innovations in drug-eluting stent designs leading to more biocompatible thin strut platforms with optimal drug elution profiles and further advances in modern pharmacotherapy involving potent P2Y₁₂ inhibitors combined with utilization of intracoronary imaging and physiologic assessment for procedural planning and optimization have transformed percutaneous interventions into successful alternatives to coronary artery bypass graft surgery (CABG) in selected LM anatomic territories. Herein, we provide an evidence-based practical guide on how to approach and perform LM percutaneous interventions (PCI).

Intravascular Ultrasound-guided Versus Angiography-guided Percutaneous Coronary Intervention: Evidence from Observational Studies and Randomized Controlled Trials

Coronary angiography has been considered the gold standard for the diagnosis of coronary artery disease and guidance of percutaneous coronary intervention (PCI). However, 2D-projection angiography cannot completely reflect the 3D coronary lumen. Intravascular ultrasound (IVUS) can overcome a number of limitations of coronary angiography by providing more information about the dimensions of the vessel lumen, plaque characteristics, stent deployment, and the mechanisms of device failure. Growing data from observational studies and randomized controlled trials have confirmed the clinical benefit of IVUS guidance during PCI. This article summarizes the evidence regarding IVUS guidance to highlight its advantages and to support the use of IVUS during PCI.

Guidelines for the management of myocardial infarction/injury with non-obstructive coronary arteries (MINOCA): a position paper from the Dutch ACS working group

Patients with myocardial infarction and non-obstructive coronary arteries (MINOCA), defined as angiographic stenosis <50%, represent a conundrum given the many potential underlying aetiologies. Possible causes of MINOCA can be subdivided into coronary, myocardial and non-cardiac disorders. MINOCA is found in up to 14% of patients presenting with an acute coronary syndrome. Clinical outcomes including mortality, and functional and psychosocial status, are comparable to those of patients with myocardial infarction and obstructive coronary arteries. However, many uncertainties remain regarding the definition, clinical features and management of these patients. This position paper of the Dutch ACS working group of the Netherlands Society of Cardiology aims to stress the importance of considering MINOCA as a dynamic working diagnosis and to guide the clinician in the management of patients with MINOCA by proposing a clinical diagnostic algorithm.

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.

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.

Intravascular Lithotripsy for Stent Underexpansion Despite Utilization of Rotational Atherectomy for Plaque Modification

Percutaneous coronary intervention (PCI) in the context of heavily calcified coronary arteries can be challenging. Intravascular lithotripsy (IVL) has been suggested as an alternative to rotational atherectomy (RA). We report a case of stent under expansion, despite plaque modification using rotational atherectomy that was successfully managed with intravascular lithotripsy.

Intravascular Polarimetry for Tissue Characterization of Coronary Atherosclerosis

The microscopic tissue structure and organization influence the polarization of light. Intravascular polarimetry leverages this compelling intrinsic contrast mechanism by using polarization-sensitive optical frequency domain imaging to measure the polarization properties of the coronary arterial wall. Tissues rich in collagen and smooth muscle cells appear birefringent, while the presence of lipid causes depolarization, offering quantitative metrics related to the presence of important components of coronary atherosclerosis. Here, we review the basic principle, the interpretation of polarization signatures, and first clinical investigations of intravascular polarimetry and discuss how this extension of contemporary intravascular imaging may advance our knowledge and improve clinical practice in the future.

A novel machine learning-derived radiotranscriptomic signature of perivascular fat improves cardiac risk prediction using coronary CT angiography

BACKGROUND

Coronary inflammation induces dynamic changes in the balance between water and lipid content in perivascular adipose tissue (PVAT), as captured by perivascular Fat Attenuation Index (FAI) in standard coronary CT angiography (CCTA). However, inflammation is not the only process involved in atherogenesis and we hypothesized that additional radiomic signatures of adverse fibrotic and microvascular PVAT remodelling, may further improve cardiac risk prediction.

METHODS AND RESULTS

We present a new artificial intelligence-powered method to predict cardiac risk by analysing the radiomic profile of coronary PVAT, developed and validated in patient cohorts acquired in three different studies. In Study 1, adipose tissue biopsies were obtained from 167 patients undergoing cardiac surgery, and the expression of genes representing inflammation, fibrosis and vascularity was linked with the radiomic features extracted from tissue CT images. Adipose tissue wavelet-transformed mean attenuation (captured by FAI) was the most sensitive radiomic feature in describing tissue inflammation (TNFA expression), while features of radiomic texture were related to adipose tissue fibrosis (COL1A1 expression) and vascularity (CD31 expression). In Study 2, we analysed 1391 coronary PVAT radiomic features in 101 patients who experienced major adverse cardiac events (MACE) within 5 years of having a CCTA and 101 matched controls, training and validating a machine learning (random forest) algorithm (fat radiomic profile, FRP) to discriminate cases from controls (C-statistic 0.77 [95%CI: 0.62-0.93] in the external validation set). The coronary FRP signature was then tested in 1575 consecutive eligible participants in the SCOT-HEART trial, where it significantly improved MACE prediction beyond traditional risk stratification that included risk factors, coronary calcium score, coronary stenosis, and high-risk plaque features on CCTA (Δ[C-statistic] = 0.126, P < 0.001). In Study 3, FRP was significantly higher in 44 patients presenting with acute myocardial infarction compared with 44 matched controls, but unlike FAI, remained unchanged 6 months after the index event, confirming that FRP detects persistent PVAT changes not captured by FAI.

CONCLUSION

The CCTA-based radiomic profiling of coronary artery PVAT detects perivascular structural remodelling associated with coronary artery disease, beyond inflammation. A new artificial intelligence (AI)-powered imaging biomarker (FRP) leads to a striking improvement of cardiac risk prediction over and above the current state-of-the-art.

Clinical expert consensus document on standards for measurements and assessment of intravascular ultrasound from the Japanese Association of Cardiovascular Intervention and Therapeutics

Intravascular ultrasound (IVUS) provides precise anatomic information in coronary arteries including quantitative measurements and morphological assessment. To standardize the IVUS analysis in the current era, this expert consensus document summarizes the methods of measurements and assessment of IVUS images.