Potential of an Approach Based on the Identification and Treatment of Vulnerable Coronary Plaques

In this viewpoint paper, the authors are tackling criticism to the limits of invasive imaging modalities for identification and treatment of vulnerable plaques. They believe in the clinical usefulness of invasive imaging modalities for identification of vulnerable plaques, and are suggesting an explanation for the suboptimal results of past studies, that failed to demonstrate a correlation between interventional treatment of vulnerable plaques, and reduction of hard clinical endpoints. Vulnerability studies have been based, so far, on the detection and measurement of plaques lipid content, because of its ease. However, the search for lipid “lakes” as a single common causal feature of acute coronary syndromes does not seem sufficient to identify patients at risk of adverse events. New imaging studies provided the rationale for improving clinical outcomes, adopting a more comprehensive assessment of target plaque morphology. There is little rationale in pursuing a functional assessment of coronary lesions to predict myocardial infarction. Recent studies are further confirming this hypothesis, suggesting that the clinical benefit of the fractional flow reserve-guided strategy is simply due to a significant reduction in the rate of repeated revascularizations, with no significant differences in the incidence of hard endpoints. There is a need to develop new randomized studies, requiring a feasible number of patients, to test the superiority of an approach based on vulnerable plaque sealing and treatment.     

Healed Culprit Plaques in Patients With Acute Coronary Syndromes

BackgroundHealed plaques, morphologically characterized by a layered phenotype, are frequently found in subjects with sudden cardiac death. However, in vivo data are lacking.ObjectivesThe purpose of this study was to determine the prevalence, morphological characteristics, and clinical significance of healed culprit plaques in patients with acute coronary syndromes (ACS) using optical coherence tomography (OCT).MethodsA total of 376 ACS patients (252 ST-segment elevation myocardial infarction [MI] and 124 non–ST-segment elevation acute coronary syndrome) who had undergone pre-intervention OCT imaging of the culprit lesion were enrolled. Patients were stratified according to the presence of layered phenotype, defined as layers of different optical density at OCT. Clinical and laboratory data, OCT characteristics, and 1-year outcome were compared between the 2 groups.ResultsAmong 376 patients, 108 (28.7%) healed plaques were identified. Hyperlipidemia, diabetes, and history of MI were more frequent in patients with healed plaques (44.4% vs. 33.2%; p = 0.041; 35.2% vs. 23.5%; p = 0.021; and 15.7% vs. 6.3%; p = 0.009, respectively). High-sensitivity C-reactive protein was significantly higher in patients with healed plaques (median 4.98 mg/l [interquartile range: 1.00 to 11.32 mg/l] vs. 3.00 mg/l [interquartile range: 0.30 to 10.15 mg/l]; p = 0.029). Plaque rupture (64.8% vs. 53.0%; p = 0.039), thin cap fibroatheroma (56.5% vs. 42.5%; p = 0.016), and macrophage accumulation (81.1% vs. 63.4%; p = 0.001) were common in the layered group. OCT also revealed greater area stenosis in plaques with layered phenotype (79.2 ± 9.5% vs. 74.3 ± 14.3%; p = 0.001). The incidence of major adverse cardiovascular events was similar between the 2 groups, except that the all-cause rehospitalization rate was higher among healed plaques (32.7% vs. 16.5%; p = 0.013).ConclusionsHealed plaques, a signature of prior plaque destabilization, were found at the culprit site in more than one-quarter of ACS patients. Such patients more frequently were diabetic, were hyperlipidemic, or had a history of MI. Healed plaques frequently showed OCT features of vulnerability with evidence of local and systemic inflammation. The combination of plaque vulnerability, local inflammation, and greater plaque burden in addition to systemic inflammation may outweigh the protective mechanism of plaque healing and predispose those plaques to develop occlusive thrombus.     

Interactions Between Morphological Plaque Characteristics and Coronary Physiology: From Pathophysiological Basis to Clinical Implications

High-risk coronary plaque refers to a distinct set of plaque characteristics prone to future coronary events. Coronary physiology represents a group of indexes reflective of the local physiological environment and hemodynamic changes in the macrovascular and microvascular system. Although a large body of evidence has supported the clinical relevance of these 2 factors, currently, identifying plaque morphology cannot reliably capture the lesion subset that causes hard events. Also, the guideline-directed approach based on physiological indexes cannot fully predict and prevent clinical events. In parallel, there is accumulating evidence that these 2 aspects of coronary artery disease influence each other with significant clinical implications, despite traditionally being considered to have separate effects on significances, treatments, and outcomes. In this state-of-the-art review, the authors explore the clinical evidence of pathophysiological interplay of physiological indexes related to local hemodynamics, epicardial stenosis, and microvascular dysfunction with plaque morphological characteristics that provide a better understanding of the nature of coronary events. Furthermore, the authors examine the emerging data on the complementary role between plaque morphology and coronary physiology in prognostication and how to apply this concept to overcome the limitations of individual assessment alone. Finally, they propose the potential benefit of integrative assessment of coronary anatomy, plaque quantity and quality, and physiological aspects of a target lesion and vessels for personalized risk profiling and optimized treatment strategy.     

Intravascular Polarimetry in Patients With Coronary Artery Disease

ObjectivesThe 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.BackgroundPolarization-sensitive OFDI measures birefringence and depolarization of tissue together with conventional cross-sectional optical frequency domain images of subsurface microstructure.MethodsThirty 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.ResultsThe 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.ConclusionsIntravascular polarimetry provides quantitative metrics that help characterize coronary arterial tissues and may offer refined insight into coronary arterial atherosclerotic lesions in patients.     

Clinical Utility of Intravascular Imaging: Past,Present, and Future

Although it is the tool used by most interventional cardiologists to assess the severity of coronary artery disease and guide treatment, coronary angiography has many limitations because it is a shadowgraph, depicting planar projections of the contrast-filled lumen that are often foreshortened rather than imaging the diseased vessel itself. Currently available intravascular imaging technologies include grayscale intravascular ultrasound (IVUS), optical coherence tomography (OCT) (the light analogue of IVUS), and near-infrared spectroscopy that detects lipid within the vessel wall and that has been combined with grayscale IVUS in a single catheter as the first combined imaging device. They provide tomographic or cross-sectional images of the coronary arteries that include the lumen, vessel wall, plaque burden, plaque composition and distribution, and even peri-vascular structures—information promised, but rarely provided angiographically. Extensive literature shows that these tools can be used to answer questions that occur during daily practice as well as improving patient outcomes. Is this stenosis significant? Where is the culprit lesion? What is the anatomy of an unusual or ambiguous angiographic lesion? What is the right stent size and length? What is the likelihood of distal embolization or periprocedural myocardial infarction during stent implantation? Has the intervention been optimized? Why did this stent thrombose or restenose? This review summarizes these uses of intravascular imaging as well as the outcomes data supporting their incorporation into routine clinical practice.     

Principles of Intravascular Lithotripsy for Calcific Plaque Modification

A significant proportion of lesions treated with transcatheter interventions in the coronary and peripheral vascular beds exhibit moderate to severe calcific plaques known to portend lower procedural success rates, increased peri-procedural adverse events, and unfavorable clinical outcomes compared with noncalcific plaques. Adapted from lithotripsy technology used for treatment of ureterorenal calculi, intravascular lithotripsy (IVL) is a novel technique for the treatment of severely calcific plaque lesions that uses acoustic shockwaves in a balloon-based delivery system. Shockwaves induce calcium fractures, which facilitate stent expansion and luminal gain. In this review, the authors summarize the physics, preclinical and clinical data on IVL use in the coronary and peripheral vasculature, and future directions of IVL in transcatheter cardiovascular therapies.     

Radiomics-Based Precision Phenotyping Identifies Unstable Coronary Plaques From Computed Tomography Angiography

ObjectivesThe aim of this study was to precisely phenotype culprit and nonculprit lesions in myocardial infarction (MI) and lesions in stable coronary artery disease (CAD) using coronary computed tomography angiography (CTA)-based radiomic analysis.BackgroundIt remains debated whether any single coronary atherosclerotic plaque within the vulnerable patient exhibits unique morphology conferring an increased risk of clinical events.MethodsA total of 60 patients with acute MI prospectively underwent coronary CTA before invasive angiography and were matched to 60 patients with stable CAD. For all coronary lesions, high-risk plaque (HRP) characteristics were qualitatively assessed, followed by semiautomated plaque quantification and extraction of 1,103 radiomic features. Machine learning models were built to examine the additive value of radiomic features for discriminating culprit lesions over and above HRP and plaque volumes.ResultsCulprit lesions had higher mean volumes of noncalcified plaque (NCP) and low-density noncalcified plaque (LDNCP) compared with the highest-grade stenosis nonculprits and highest-grade stenosis stable CAD lesions (NCP: 138.1 mm³ vs 110.7 mm³ vs 102.7 mm³; LDNCP: 14.2 mm³ vs 9.8 mm³ vs 8.4 mm³; both P_trend < 0.01). In multivariable linear regression adjusted for NCP and LDNCP volumes, 14.9% (164 of 1,103) of radiomic features were associated with culprits and 9.7% (107 of 1,103) were associated with the highest-grade stenosis nonculprits (critical P < 0.0007) when compared with highest-grade stenosis stable CAD lesions as reference. Hierarchical clustering of significant radiomic features identified 9 unique data clusters (latent phenotypes): 5 contained radiomic features specific to culprits, 1 contained features specific to highest-grade stenosis nonculprits, and 3 contained features associated with either lesion type. Radiomic features provided incremental value for discriminating culprit lesions when added to a machine learning model containing HRP and plaque volumes (area under the receiver-operating characteristic curve 0.86 vs 0.76; P = 0.004).ConclusionsCulprit lesions and highest-grade stenosis nonculprit lesions in MI have distinct radiomic signatures compared with lesions in stable CAD. Within the vulnerable patient may exist individual vulnerable plaques identifiable by coronary CTA-based precision phenotyping.     

Nonculprit Lesion Myocardial Infarction Following Percutaneous Coronary Intervention in Patients With Acute Coronary Syndrome

BackgroundRecent emphasis on reduced duration and/or intensity of antiplatelet therapy following percutaneous coronary intervention (PCI) irrespective of indication for PCI may fail to account for the substantial risk of subsequent nontarget lesion events in acute coronary syndrome (ACS) patients.ObjectivesThe authors sought to examine the effect of more potent antiplatelet therapy on the basis of the timing and etiology of recurrent myocardial infarction (MI) or cardiovascular death following PCI for ACS.MethodsIn the TRITON-TIMI 38 study (Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition With Prasugrel–Thrombolysis In Myocardial Infarction 38), which randomized patients to prasugrel or clopidogrel, 12,844 patients with ACS received at least 1 stent. MI and cardiovascular death were categorized as: 1) procedural (related to revascularization); 2) definite or probable stent thrombosis (ST); or 3) spontaneous (non-ST or non–procedure-related). Median follow-up was 14.5 months.ResultsAmong the first events occurring within 30 days, 584 (69.0%) were procedural, 126 (14.9%) ST-related, and 136 (16.1%) spontaneous. After 30 days, 22 (4.7%) were procedural, 63 (13.5%) were ST-related, and 383 (81.8%) spontaneous. Prasugrel significantly reduced the incidence of MI or cardiovascular death for ST-related (1.0% vs. 2.1%; p < 0.001) and spontaneous events (3.9% vs. 4.8%; p = 0.012), with a directionally consistent numerical reduction for procedural events (4.4% vs. 5.1%; p = 0.078). Prasugrel increased spontaneous, but not procedural, major bleeding.ConclusionsLong-term potent antithrombotic therapy reduces de novo (spontaneous) atherothrombotic events in addition to preventing complications associated with stenting of the culprit lesion following ACS. In patients undergoing PCI for ACS, spontaneous events predominate after 30 days, with the later-phase cardiovascular benefit of potent dual antiplatelet therapy driven largely by reducing de novo atherothrombotic ischemic events. (Comparison of Prasugrel [CS-747] and Clopidogrel in Acute Coronary Syndrome Subjects Who Are to Undergo Percutaneous Coronary Intervention; NCT00097591)     

Air Pollution and Coronary Plaque Vulnerability and Instability: An Optical Coherence Tomography Study

ObjectivesWe assessed the relationship between exposure to air pollutants and mechanisms of coronary instability evaluated by optical coherence tomography (OCT) in patients with acute coronary syndrome (ACS).BackgroundAir pollution is an emerging key player in determining the residual risk of coronary events. However, pathophysiological mechanisms linking air pollution and coronary events have been not adequately investigated.MethodsPatients with ACS undergoing OCT imaging were retrospectively selected. Mechanism of culprit lesion instability was classified as plaque rupture (PR) or intact fibrous cap (IFC) by OCT, and the presence of macrophage infiltrates (MØI) and thin-cap fibroatheroma (TCFA) at the culprit site was also assessed. Based on each case’s home address, exposure to several pollutants was evaluated, including particulate matter 2.5 (PM2.5), PM10, and carbon monoxide (CO). Only patients with >2 years of available data on air pollution exposure prior to ACS were enrolled.ResultsWe included 126 patients (median age: 67.0 years of age; IQR: 55.5-76.0; 97 male patients [77.0%]). Sixty-six patients (52.4%) had PR as the mechanism of plaque instability. Patients with PR were exposed to significantly higher PM2.5 levels than to IFC, and PM2.5 was independently associated with PR (odds ratio: 1.194; 95% CI: 1.036 to 1.377; P = 0.015). Moreover, exposure to higher levels of PM2.5 was independently associated with the presence of TCFA and of MØI at the culprit site. Interestingly, PM2.5, PM10, and Co levels were positively and significantly correlated with serum levels of C-reactive protein.ConclusionsWe provide novel insights into the missing link between air pollution and increased risk of coronary events. In particular, exposure to higher concentrations of air pollutants is associated with the presence of vulnerable plaque features and with plaque rupture as a mechanism of coronary instability. An enhanced systemic and plaque inflammatory activation may explain these findings.     

Predictors of Rapid Plaque Progression: An Optical Coherence Tomography Study

ObjectivesThis study sought to identify morphological predictors of rapid plaque progression.BackgroundTwo patterns of plaque progression have been described: slow linear progression and rapid step-wise progression. The former pattern will cause stable angina when the narrowing reaches a critical threshold, whereas the latter pattern may lead to acute coronary syndromes or sudden cardiac death.MethodsPatients who underwent optical coherence tomography (OCT) imaging during the index procedure and follow-up angiography with a minimum interval of 6 months were selected. Nonculprit lesions with a diameter stenosis of ≥30% on index angiography were assessed. Lesion progression was defined as a decrease of angiographic minimum lumen diameter ≥0.4 mm at follow-up (mean, 7.1 months). Baseline morphological characteristics of plaques with rapid progression were evaluated by OCT. In a subgroup with follow-up OCT imaging for plaques with rapid progression, morphological changes from baseline to follow-up were assessed.ResultsAmong 517 lesions in 248 patients, 50 lesions showed rapid progression. These lesions had a significantly higher prevalence of lipid-rich plaque (76.0% vs. 50.5%, respectively), thin-cap fibroatheroma (TCFA) (20.0% vs. 5.8%, respectively), layered plaque (60.0% vs. 34.0%, respectively), macrophage accumulation (62.0% vs. 42.4%, respectively), microvessel (46.0% vs. 29.1%, respectively), plaque rupture (12.0% vs. 4.7%, respectively), and thrombus (6.0% vs. 1.1%, respectively) at baseline compared with those without rapid progression. Multivariate analysis identified lipid-rich plaque (odds ratio [OR]: 2.17; 95% confidence interval [CI]: 1.02 to 4.62; p = 0.045]), TCFA (OR: 5.85; 95% CI: 2.01 to 17.03; p = 0.001), and layered plaque (OR: 2.19; 95% CI: 1.03 to 4.17; p = 0.040) as predictors of subsequent rapid lesion progression. In a subgroup analysis for plaques with rapid progression, a new layer was detected in 25 of 41 plaques (61.0%) at follow-up.ConclusionsLipid-rich plaques, TCFA, and layered plaques were predictors of subsequent rapid plaque progression. A new layer, a signature of previous plaque disruption and healing, was detected in more than half of the lesions with rapid progression at follow-up. (Massachusetts General Hospital Optical Coherence Tomography Registry; NCT01110538)     

Sex-Specific Computed Tomography Coronary Plaque Characterization and Risk of Myocardial Infarction

ObjectivesThis study was designed to investigate whether coronary computed tomography angiography assessments of coronary plaque might explain differences in the prognosis of men and women presenting with chest pain.BackgroundImportant sex differences exist in coronary artery disease. Women presenting with chest pain have different risk factors, symptoms, prevalence of coronary artery disease and prognosis compared to men.MethodsWithin a multicenter randomized controlled trial, we explored sex differences in stenosis, adverse plaque characteristics (positive remodeling, low-attenuation plaque, spotty calcification, or napkin ring sign) and quantitative assessment of total, calcified, noncalcified and low-attenuation plaque burden.ResultsOf the 1,769 participants who underwent coronary computed tomography angiography, 772 (43%) were female. Women were more likely to have normal coronary arteries and less likely to have adverse plaque characteristics (p < 0.001 for all). They had lower total, calcified, noncalcified, and low-attenuation plaque burdens (p < 0.001 for all) and were less likely to have a low-attenuation plaque burden >4% (41% vs. 59%; p < 0.001). Over a median follow-up of 4.7 years, myocardial infarction (MI) occurred in 11 women (1.4%) and 30 men (3%). In those who had MI, women had similar total, noncalcified, and low-attenuation plaque burdens as men, but men had higher calcified plaque burden. Low-attenuation plaque burden predicted MI (hazard ratio: 1.60; 95% confidence interval: 1.10 to 2.34; p = 0.015), independent of calcium score, obstructive disease, cardiovascular risk score, and sex.ConclusionsWomen presenting with stable chest pain have less atherosclerotic plaque of all subtypes compared to men and a lower risk of subsequent MI. However, quantitative low-attenuation plaque is as strong a predictor of subsequent MI in women as in men. (Scottish Computed Tomography of the HEART Trial [SCOT-HEART]; NCT01149590)     

Biomechanical Stress Profiling of Coronary Atherosclerosis: Identifying a Multifactorial Metric to Evaluate Plaque Rupture Risk

ObjectivesThe purpose of this study was to derive a biomechanical stress metric that was based on the multifactorial assessment of coronary plaque morphology, likely related to the propensity of plaque rupture in patients.BackgroundPlaque rupture, the most frequent cause of coronary thrombosis, occurs at locations of elevated tensile stress in necrotic core fibroatheromas (NCFAs). Finite element modeling (FEM), typically used to calculate tensile stress, is computationally intensive and impractical as a clinical tool for locating rupture-prone plaques. This study derived a multifactorial stress equation (MSE) that accurately computes peak stress in NCFAs by combining the influence of several morphological parameters.MethodsIntravascular ultrasound and optical frequency domain imaging were conducted in 30 patients, and plaque morphological parameters were defined in 61 NCFAs. Multivariate regression analysis was applied to derive the MSE and compute a peak stress metric (PSM) that was based on the analysis of plaque morphological parameters. The accuracy of the MSE was determined by comparing PSM with FEM-derived peak stress values. The ability of the PSM in locating plaque rupture sites was tested in 3 additional patients.ResultsThe following parameters were found to be independently associated with peak stress: fibrous cap thickness (p < 0.0001), necrotic core angle (p = 0.024), necrotic core thickness (p < 0.0001), lumen area (p < 0.0001), necrotic core including calcium areas (p = 0.017), and plaque area (p = 0.003). The PSM showed excellent correlation (R = 0.85; p < 0.0001) with FEM-derived peak stress, thus confirming the accuracy of the MSE. In only 56% (n = 34) of plaques, the thinnest fibrous cap thickness was a determining parameter in identifying the cross section with highest PSM. In coronary segments with plaque ruptures, the MSE precisely located the rupture site.ConclusionsThe MSE shows potential to calculate the PSM in coronary lesions rapidly. However, further studies are warranted to investigate the use of biomechanical stress profiling for the prognostic evaluation of patients with atherosclerosis.     

Intravascular Imaging During Percutaneous Coronary Intervention: JACC State-of-the-Art Review

Coronary angiography has historically served as the gold standard for diagnosis of coronary artery disease and guidance of percutaneous coronary intervention (PCI). Adjunctive use of contemporary intravascular imaging (IVI) technologies has emerged as a complement to conventional angiography—to further characterize plaque morphology and optimize the performance of PCI. IVI has utility for preintervention lesion and vessel assessment, periprocedural guidance of lesion preparation and stent deployment, and postintervention assessment of optimal endpoints and exclusion of complications. The role of IVI in reducing major adverse cardiac events in complex lesion subsets is emerging, and further studies evaluating broader use are underway or in development. This paper provides an overview of currently available IVI technologies, reviews data supporting their utilization for PCI guidance and optimization across a variety of lesion subsets, proposes best practices, and advocates for broader use of these technologies as a part of contemporary practice.     

Increased Vulnerability and Distinct Layered Phenotype at Culprit and Nonculprit Lesions in STEMI Versus NSTEMI

ObjectivesThis study aimed to investigate the pancoronary plaque vulnerability (including culprit and nonculprit lesions) and layered phenotype in patients with ST-segment elevation myocardial infarction (STEMI) vs non-STEMI (NSTEMI).BackgroundPancoronary vulnerability should account for distinct clinical manifestations of acute myocardial infarction (AMI). Layered plaque is indicative of previous coronary destabilization and thrombosis.MethodsA total of 464 patients with AMI who underwent 3-vessel optical coherence tomography imaging were consecutively studied and divided into a STEMI group (318 patients; 318 culprit and 1,187 nonculprit plaques) and a NSTEMI group (146 patients; 146 culprit and 560 nonculprit plaques). Patients were followed up for a median period of 2 years.ResultsCompared with NSTEMI, culprit lesions in STEMI had more plaque rupture, thrombus, thin-cap fibroatheroma (TCFA), calcification, macrophage accumulation, and microvessels. The prevalence of plaque rupture (8.2% vs 4.8%; P = 0.018), microvessels (57.5% vs 45.2%; P < 0.001), and calcification (40.7% vs 30.2%; P = 0.003) at nonculprit lesions was higher in STEMI than NSTEMI. The layer area and thickness at the culprit and nonculprit lesions were significantly larger in STEMI than in NSTEMI. Multivariate analyses showed that culprit layer area (odds ratio: 1.443; 95% CI: 1.138-1.830; P = 0.002) was predictive of STEMI (vs NSTEMI), in addition to culprit TCFA, culprit thrombus, and non–left circumflex artery location of the culprit lesion. Although the type of AMI was not related to clinical outcomes, high-sensitivity C-reactive protein, culprit calcified nodule, and nonculprit TCFA predicted the 2-year major adverse cardiovascular events in patients with AMI.ConclusionsPatients with STEMI had increased plaque vulnerability (ie, more plaque rupture and microvessels) and distinct layered phenotype at the culprit and nonculprit lesions compared with patients with NSTEMI. Culprit lesion features of large layer area, TCFA, thrombus, and non–left circumflex artery location predicted the clinical presentation of STEMI.     

Label-Free Visualization and Quantification of Biochemical Markers of Atherosclerotic Plaque Progression Using Intravascular Fluorescence Lifetime

ObjectivesThis study aimed to systematically investigate whether plaque autofluorescence properties assessed with intravascular fluorescence lifetime imaging (FLIm) can provide qualitative and quantitative information about intimal composition and improve the characterization of atherosclerosis lesions.BackgroundDespite advances in cardiovascular diagnostics, the analytic tools and imaging technologies currently available have limited capabilities for evaluating in situ biochemical changes associated with luminal surface features. Earlier studies of small number of samples have shown differences among the autofluorescence lifetime signature of well-defined lesions, but a systematic pixel-level evaluation of fluorescence signatures associated with various histological features is lacking and needed to better understand the origins of fluorescence contrast.MethodsHuman coronary artery segments (n = 32) were analyzed with a bimodal catheter system combining multispectral FLIm with intravascular ultrasonography compatible with in vivo coronary imaging. Various histological components present along the luminal surface (200-μm depth) were systematically tabulated (12 sectors) from each serial histological section (n = 204). Morphological information provided by ultrasonography allowed for the accurate registration of imaging data with histology data. The relationships between histological findings and FLIm parameters obtained from 3 spectral channels at each measurement location (n = 33,980) were characterized.ResultsOur findings indicate that fluorescence lifetime from different spectral bands can be used to quantitatively predict the superficial presence of macrophage foam cells (mFCs) (area under the receiver-operator characteristic curve: 0.94) and extracellular lipid content in advanced lesions (lifetime increase in 540-nm band), detect superficial calcium (lifetime decrease in 450-nm band area under the receiver-operator characteristic curve: 0.90), and possibly detect lesions consistent with active plaque formation such as pathological intimal thickening and healed thrombus regions (lifetime increase in 390-nm band).ConclusionsOur findings indicate that autofluorescence lifetime provides valuable information for characterizing atherosclerotic lesions in coronary arteries. Specifically, FLIm can be used to identify key phenomena linked with plaque progression (e.g., peroxidized-lipid–rich mFC accumulation and recent plaque formation).     

Contemporary Issues in Chronic Total Occlusion Percutaneous Coronary Intervention

Remarkable progress has been achieved in chronic total occlusion (CTO) percutaneous coronary intervention (PCI) in recent years, with refinement of the indications and technical aspects of the procedure, imaging, and complication management. Randomized controlled trials and rigorous prospective registries have provided high-quality data on the benefits and risks of CTO PCI. Global collaboration has led to an agreement on nomenclature, indications, endpoint definition, and principles of clinical trial design that have been distilled in global consensus documents such as the CTO Academic Research Consortium. Increased use of preprocedural coronary computed tomography angiography and intraprocedural intravascular imaging, as well as development of novel techniques and structured CTO crossing and complication management algorithms, allow a systematic, stepwise approach to this difficult lesion subset. This state-of-the-art review provides a comprehensive discussion about the most recent developments in the indications, preprocedural planning, technical aspects, complication management, and future directions of CTO PCI.     

Coronary Plaque Features on CTA Can Identify Patients at Increased Risk of Cardiovascular Events

ObjectivesThis study sought to assess whether coronary atherosclerosis analysis by coronary computed tomography angiography (CTA) may improve prognostic stratification among patients with diffuse coronary artery disease (CAD)BackgroundCoronary CTA has recently emerged as a promising noninvasive tool for advanced analysis of coronary atherosclerosis.MethodsThe multicenter CAPIRE (Coronary Atherosclerosis in outlier subjects: Protective and novel Individual Risk factors Evaluation) study is part of the GISSI Outlier Project. A prospective cohort of subjects who underwent coronary CTA for suspected CAD was enrolled. Based on risk factor (RF) burden, patients were defined as having a low clinical risk (0 to 1 RF with the exclusion of patients with diabetes mellitus as single RF) or at high clinical risk (3 or more RFs). Patients with 2 RFs were not enrolled in the study. Coronary CTA advanced plaque assessment was performed. Outcome measures were 3 combined endpoints: acute coronary syndrome (ACS), cardiac death + ACS, and cardiac death + ACS + late revascularization.ResultsAmong the 544 patients enrolled in the CAPIRE study, in 522 patients, a mean follow-up of 37 ± 10 months was obtained (16 patients were excluded due to 1 < segment involvement score <5 at core lab coronary CTA analysis and 6 patients were lost at follow-up). Higher atherosclerotic burden was found in patients with higher clinical risk, but prevalence of elevated noncalcified plaque volume did not significantly differ between low- versus high-risk patients. Quantitative plaque parameters by coronary CTA were associated with composite endpoints at multivariable analysis when corrected for univariate predictors. Elevated noncalcified plaque volume, expressed as dichotomic variable, was associated with all combined endpoints. Even if the low absolute number of events represents a limitation to the present study, patients with low noncalcified plaque volume had similar risk of cardiac events independently from the presence of multivessel disease, while patients with high noncalcified plaque volume had higher rates of cardiac events.ConclusionsThe CAPIRE study confirmed the prognostic value of atherosclerosis assessment by coronary CTA, demonstrating high noncalcified plaque volume as the most ACS-predictive parameter in patients with extensive CAD. (GISSE Outliers CAPIRE [CAPIRE]; NCT02157662)