Plaque quantification by coronary CT and intravascular ultrasound identifies a low CT density core as a marker of plaque instability in acute coronary syndromes

Noninvasive Atherosclerotic Phenotyping: The Next Frontier into Understanding the Pathobiology of Coronary Artery Disease

PURPOSE OF REVIEW

Despite recent advances, coronary artery disease remains one of the leading causes of mortality worldwide. Noninvasive imaging allows atherosclerotic phenotyping by measurement of plaque burden, morphology, activity and inflammation, which has the potential to refine patient risk stratification and guide personalized therapy. This review describes the current and emerging roles of advanced noninvasive cardiovascular imaging methods for the assessment of coronary artery disease.

RECENT FINDINGS

Cardiac computed tomography enables comprehensive, noninvasive imaging of the coronary vasculature, and is used to assess luminal stenoses, coronary calcifications, and distinct adverse plaque characteristics, helping to identify patients prone to future events. Novel software tools, implementing artificial intelligence solutions, can automatically quantify and characterize atherosclerotic plaque from standard computed tomography datasets. These quantitative imaging biomarkers have been shown to improve patient risk stratification beyond clinical risk scores and current clinical interpretation of cardiac computed tomography. In addition, noninvasive molecular imaging in higher risk patients can be used to assess plaque activity and plaque thrombosis. Noninvasive imaging allows unique insight into the burden, morphology and activity of atherosclerotic coronary plaques. Such phenotyping of atherosclerosis can potentially improve individual patient risk prediction, and in the near future has the potential for clinical implementation.

Myocardial Flow Reserve in Coronary Artery Disease with Low Attenuation Plaque: Coronary CTA and 13N-ammonia PET Assessments

RATIONALE AND OBJECTIVES

Physiological measurements from coronary angiography show that coronary stenosis with necrotic core plaque reduces coronary flow reserve (CFR). Myocardial flow reserve (MFR) estimated by ¹³N-ammonia PET (NH₃-PET) is a different index from CFR. Low attenuation plaque (LAP) on coronary CTA (CCTA) contains necrotic core, but the link between LAP and MFR has not been elucidated. We aimed to investigate the influence of LAP on MFR in coronary artery disease (CAD).

MATERIALS AND METHODS

The study included 105 consecutive patients who underwent NH₃-PET and CCTA within 3 months. Nonevaluable coronary arteries due to severe calcification and stent implants were excluded. Finally, 290 major vessels were retrospectively analyzed. Coronary arteries were divided into mild (1%-49%), moderate (50%-69% stenosis), and severe (≥70% stenosis) groups. Coronary plaques were classified either LAP (including soft tissue CT value <30 HU) or completely classified plaques. MFR for the major vessels were calculated and MFR <2.0 was considered a significant decrease. Comparison of MFR between territories with and without LAP, and the effect of plaque characteristics on MFR was analyzed.

RESULTS

MFR was significantly lower for territories with LAP than with calcified plaques or no plaque (2.1 ± 0.7, 2.4 ± 0.7, and 2.3 ± 0.7; p < 0.05). There was no difference between calcified plaque and no plaque territories (p = 0.79). Multivariate logistic analysis for plaque characteristics and stenosis severity revealed that LAP and severe stenosis were independent predictors for territories with MFR <2.0 with odds ratios of 3.1 (95% confidence interval, 1.2-8.1) and 3.0 (95% confidence interval, 1.7-5.3).

CONCLUSION

LAP reduced MFR compared with calcified plaque or no plaque in CAD. LAP is an independent predictor of the territory with MFR <2.0.

Site-specific Phenotype of Atherosclerotic Lesions According to Their Location Within the Coronary Tree – a CCTA-based Study of Vulnerable Plaques

Background: The evaluation of site-specific phenotype according to the topographic location of atherosclerotic lesions within the coronary tree has not been studied so far. The present study is based on the premise that the location of coronary plaques can influence their composition and degree of vulnerability. Aim: To evaluate different phenotypes of vulnerable coronary plaques across the three major coronary arteries in terms of composition, morphology, and degree of vulnerability, in patients with chest pain and low-to-intermediate probability of coronary artery disease, using coronary computed tomography angiography (CCTA) and a complex plaque analysis. Material and methods: This was a cross-sectional study on 75 subjects undergoing CCTA for chest pain, who presented at least one vulnerable coronary plaque (VP), defined as the presence of ≥1 CT vulnerability marker (low attenuation plaque, napkin-ring sign, spotty calcifications, positive remodeling). The study included per plaque analysis of 90 vulnerable coronary lesions identified in various locations within the coronary tree as follows: n = 30 VPs in the left anterior descending artery (LAD), n = 30 VPs in the circumflex artery (CXA), and n = 30 VPs in the right coronary artery (RCA). Results: The RCA exhibited significantly longer VPs (p = 0.001), with the largest volume (p = 0.0007) compared to those arising from the LAD and CXA. Vulnerable plaques located in the LAD exhibited a significantly more calcified phenotype (calcified volume: LAD – 44.07 ± 63.90 mm3 vs. CXA – 12.40 ± 19.65 mm3 vs. RCA – 33.69 ± 34.38 mm3, p = 0.002). Plaques from the RCA presented a more non-calcified phenotype, with the largest non-calcified (p = 0.002), lipid rich (p = 0.0005), and fibrotic volumes (p = 0.003). Low-attenuation plaques were most frequent in the RCA (p = 0.0009), while the highest vulnerability degree was present in lesions located in the LAD, which presented the highest number of vulnerability markers per plaque (p = 0.01). Conclusions: Vulnerable plaques arising from the right coronary artery are longer, more vo-luminous and with larger lipid and non-calcified content, whereas those located in the left anterior descending artery present a higher volume of calcium, but also a higher degree of vulnerability. The least vulnerable lesions were present in the circumflex artery.

Risk stratification in coronary artery disease using NH3-PET myocardial flow reserve and CAD-RADS on coronary CT angiography

Myocardial flow reserve (MFR) derived from ¹³N-ammonia positron emission tomography (NH₃-PET) can predict the prognosis of patients with various heart diseases. Coronary computed tomography angiography (CCTA) is a non-invasive investigation for ischemic heart disease. The coronary artery disease reporting and data system (CAD-RADS) was established to standardize and facilitate the reporting of CCTA data regarding CAD. This study aimed to investigate the prognostic value of CAD-RADS and MFR. A total of 133 patients who underwent NH₃-PET and CCTA within 3 months were enrolled. Patients were divided into groups with CAD-RADS 0-2 and ≥ 3 and into groups with MFR ≥ 2.0 and < 2.0. The endpoint was major adverse cardiac events (MACE) comprising all-cause death, acute coronary syndrome, hospitalization due to heart failure, and cerebrovascular disease. The ability of CAD-RADS and MFR to predict MACE was analyzed using Kaplan-Meier analysis. There was no significant difference in MFR between patients with CAD-RADS 0-2 and ≥ 3 (2.3 ± 0.9 vs. 2.2 ± 0.7, p = 0.50). The MACE rate for patients with CAD-RADS 0-2 and ≥ 3 was equivalent (log-rank test, p = 0.64). Patients with MFR < 2.0 had a significantly higher MACE rate than those with MFR ≥ 2.0 (p = 0.017). In patients with CAD-RADS ≥ 3, patients with MFR < 2.0 had a significantly higher MACE rate than those with MFR ≥ 2.0 (p = 0.034). CAD-RADS did not contribute to MACE prediction. Conversely, MFR was useful in predicting MACE, allowing for further risk stratification in addition to CAD-RADS.

[Computed Tomography Coronary Angiography Possibilities in "High Risk" Plaque Identification in Patients with non-ST-Elevation Acute Coronary Syndrome: Comparison with Intravascular Ultrasound]

Aim      To evaluate structural characteristics of atherosclerotic plaques (ASP) by coronary computed tomography arteriography (CCTA) and intravascular ultrasound (IVUS).Material and methods  This study included 37 patients with acute coronary syndrome (ACS). 64-detector-row CCTA, coronarography, and grayscale IVUS were performed prior to coronary stenting. The ASP length and burden, remodeling index (RI), and known CT signs of unstable ASP (presence of dot calcification, positive remodeling of the artery in the ASP area, irregular plaque contour, presence of a peripheral high-density ring and a low-density patch in the ASP). The ASP type and signs of rupture or thrombosis were determined by IVUS.Results The IVUS study revealed 45 unstable ASP (UASP), including 25 UASP with rupture and 20 thin-cap fibroatheromas (TCFA), and 13 stable ASP (SASP). No significant differences were found between distribution of TCFA and ASP with rupture among symptom-associated plaques (SAP, n=28) and non-symptom-associated plaques (NSAP, n=30). They were found in 82.1 and 73.3 % of cases, respectively (p&gt;0.05), which indicated generalization of the ASP destabilization process in the coronary circulation. However, the incidence of mural thrombus was higher for SAP (53.5 and 16.6 % of ASP, respectively; p&lt;0.001). There was no difference between UASP and SASP in the incidence of qualitative ASP characteristics or in values of quantitative ASP characteristics, including known signs of instability, except for the irregular contour, which was observed in 92.9 % of UASP and 46.1 % of SASP (p=0.0007), and patches with X-ray density ≤46 HU, which were detected in 83.3 % of UASP and 46.1 % of SASP (р=0.01). The presence of these CT criteria 11- and 7-fold increased the likelihood of unstable ASP (odd ratio (OR), 11.1 at 95 % confidence interval (CI), from 2.24 to 55.33 and OR, 7.0 at 95 % CI, from 5.63 to 8.37 for the former and the latter criterion, respectively).Conclusion      According to IVUS data, two X-ray signs are most characteristic for UASP, the irregular contour and a patch with X-ray density ≤46 HU. The presence of these signs 11- and 7-fold, respectively, increases the likelihood of unstable ASP.

Effect of Evolocumab on Vulnerable Coronary Plaques: A Serial Coronary Computed Tomography Angiography Study

This study investigated the effects of evolocumab on vulnerable coronary plaques and factors associated with the change in stability and size of plaques in patients taking statins. Vulnerable coronary plaques were defined using coronary computed tomography (CT) angiography as having a density of <50 HU within the region of interest and a remodeling index ≥1.1. The changes in minimum CT density, remodeling index, and percent stenosis of vulnerable coronary plaques after six months of evolocumab administration were retrospectively analyzed in 136 vulnerable coronary plaques from 98 patients (68 men and 30 women; mean age: 72.9 ± 8.7 years) treated with a statin. The administration of evolocumab significantly increased the minimum CT density (39.1 ± 8.1 HU to 84.9 ± 31.4 HU, p < 0.001), reduced the remodeling index (1.29 ± 0.11 to 1.19 ± 0.10, p < 0.001), and decreased the percent stenosis (27.0 ± 10.4% to 21.2 ± 9.8%, p < 0.001). Multiple linear regression analysis revealed that baseline percent stenosis (standard coefficient (β) = -0.391, p = 0.002) independently correlated with the change in minimum CT density, whereas the baseline remodeling index (β = -0.368, p < 0.001) independently correlated with a change in the remodeling index. Evolocumab stabilized vulnerable coronary plaques and reduced their size. These results suggest that evolocumab protects against coronary artery disease progression in patients taking statins.

Vulnerable Plaques Producing an Acute Coronary Syndrome Exhibit a Different CT Phenotype than Those That Remain Silent

Background: All plaques that trigger acute coronary syndromes (ACS) present various characteristics of vulnerability. However, not all vulnerable plaques (VP) lead to an ACS. This raises the question as to which of the established CT vulnerability features hold the highest probability of developing ACS.

Aim: To identify the distinct phenotype of VP that exposes the unstable atheromatous plaque to a higher risk of rupture.

Material and Methods: In total, 20 patients in whom cardiac computed tomographic angiography (CCTA) identified the presence of a vulnerable plaque and who developed an ACS within 6 months after CCTA examination were enrolled in the study, and compared to 20 age- and gender-matched subjects with VPs who did not develop an ACS. All included patients presented VPs at baseline, defined as the presence of minimum 50% degree of stenosis and at least one CT marker of vulnerability (low attenuation plaques [LAP], napkin-ring sign [NRS], positive remodeling [PR], spotty calcifications [SCs]).

Results: The two groups were not different in regards to age, gender, cardiovascular risk factors, and comorbidities. Patients who developed an ACS at six months presented higher volumes of lipid-rich (p = 0.01) and calcified plaques (p = 0.01), while subjects in the control group presented plaques with a larger fibrotic content (p = 0.0005). The most frequent vulnerability markers within VPs that had triggered ACS were LAPs (p <0.0001) and PR (p <0.0001). Multivariate analysis identified LAP as the strongest independent predictor of ACS at 6 months in our study population (OR 8.18 [1.23-95.08], p = 0.04).

Conclusions: VPs producing an ACS exhibit a different phenotype compared to VPs that remain silent. The CCTA profile of VPs producing an ACS includes the presence of low attenuation, positive remodeling, and lipid-rich atheroma. The presence of these features in VPs identifies very high-risk patients, who can benefit from adapted therapeutic strategies in order to prevent an ACS.

From CT to artificial intelligence for complex assessment of plaque-associated risk

The recent technological developments in the field of cardiac imaging have established coronary computed tomography angiography (CCTA) as a first-line diagnostic tool in patients with suspected coronary artery disease (CAD). CCTA offers robust information on the overall coronary circulation and luminal stenosis, also providing the ability to assess the composition, morphology, and vulnerability of atherosclerotic plaques. In addition, the perivascular adipose tissue (PVAT) has recently emerged as a marker of increased cardiovascular risk. The addition of PVAT quantification to standard CCTA imaging may provide the ability to extract information on local inflammation, for an individualized approach in coronary risk stratification. The development of image post-processing tools over the past several years allowed CCTA to provide a significant amount of data that can be incorporated into machine learning (ML) applications. ML algorithms that use radiomic features extracted from CCTA are still at an early stage. However, the recent development of artificial intelligence will probably bring major changes in the way we integrate clinical, biological, and imaging information, for a complex risk stratification and individualized therapeutic decision making in patients with CAD. This review aims to present the current evidence on the complex role of CCTA in the detection and quantification of vulnerable plaques and the associated coronary inflammation, also describing the most recent developments in the radiomics-based machine learning approach for complex assessment of plaque-associated risk.

Intracoronary Imaging for Assessment of Vascular Healing and Stent Follow-up in Bioresorbable Vascular Scaffolds

Bioresorbable Vascular Scaffolds (BVS) are polymer-based materials implanted in the coronary arteries in order to treat atherosclerotic lesions, based on the concept that once the lesion has been treated, the material of the implanted stent will undergo a process of gradual resorption that will leave, in several years, the vessel wall smooth, free of any foreign material and with its vasomotion restored. However, after the first enthusiastic reports on the efficacy of BVSs, the recently published trials demonstrated disappointing results regarding long-term patency following BVS implantation, which were mainly attributed to technical deficiencies during the stenting procedure. Intracoronary imaging could play a crucial role for helping the operator to correctly implant a BVS into the coronary artery, as well as providing relevant information in the follow-up period. This review aims to summarize the role of intracoronary imaging in the follow-up of coronary stents, with a particular emphasis on the role of intravascular ultrasound and optical coherence tomography for procedural guidance during stent implantation and also for follow-up of bioabsorbable scaffolds.

Computed Tomographic Angiography for Risk Stratification in Patients with Acute Chest Pain - The Triple Rule-out Concept in the Emergency Department

BACKGROUND

Acute chest pain is one of the most common reasons for Emergency Department (ED) visits and hospital admissions. As this could represent the first symptom of a lifethreatening condition, urgent identification of the etiology of chest pain is of utmost importance in emergency settings. Such high-risk conditions that can present with acute chest pain in the ED include Acute Coronary Syndromes (ACS), Pulmonary Embolisms (PE) and Acute Aortic Syndromes (AAS).

DISCUSSION

The concept of Triple Rule-out Computed Tomographic Angiography (TRO-CTA) for patients presenting with acute chest pain in the ED is based on the use of coronary computed tomographic angiography as a single imaging technique, able to diagnose or exclude three lifethreatening conditions in one single step: ACS, AAS and PE. TRO-CTA protocols have been proved to be efficient in the ED for diagnosis or exclusion of life-threatening conditions and for differentiation between various etiologies of chest pain, and application of the TRO-CTA protocol in the ED for acute chest pain of uncertain etiology has been shown to improve the further clinical evaluation and outcomes of these patients.

CONCLUSION

This review aims to summarize the main indications and techniques used in TRO protocols in EDs, and the role of TRO-CTA protocols in risk stratification of patients with acute chest pain.

CTA Assessment of Coronary Atherosclerotic Plaque Evolution after BVS Implantation – a Follow-up Study

Background: Computed tomography angiography (CTA) occupies an important place in the evaluation of coronary atherosclerotic lesions, both before and after the implantation of bioresorbable stents (BVS), providing an accurate assessment of the treated lesions.

Aim of the study: This study aims the prospective follow-up of atherosclerotic plaques electively treated with BVS implantation via CTA evaluation in terms of morphological and virtual histology aspects.

Material and methods: This is a prospective observational study which enrolled 30 patients electively treated with BVS implantation, in whom CTA was performed after PTCA in order to assess the morphological and virtual histology aspects of coronary plaques. In order to evaluate the impact determined by pre- and post-implantation procedures, statistical analysis was performed among 6 subgroups.

Results: After BVS implantation, a significant reduction was observed in terms of stenosis % (61.63 ± 12.63% in subgroup 1A vs. 24.41 ± 12.48% in subgroup 1B, p <0.0001) and eccentricity index (0.46 ± 0.24 in subgroup 1A vs. 0.43 ± 0.24 in subgroup 1B, p <0.0001). In terms of plaque components, there were significant differences with regard to lipid volume and lipid % (20.07 ± 15.67 mm3 in subgroup 1A vs. 11.05 ± 10.83 mm3 in subgroup 1B, p = 0.01), which presented a significant reduction after BVS implantation. The calcium score evaluated locally (82.97 ± 107.5 in subgroup 1A vs. 96.54 ± 85.73 in subgroup 1B, p = 0.25) and on the target coronary artery (148.2 ± 222.3 in subgroup 1A vs. 206.6 ± 224.0 in subgroup 1B, p = 0.10), as well as the total calcium score (377.6 ± 459.5 in subgroup 1A vs. 529.5 ± 512.9 in subgroup 1B, p = 0.32), presented no significant differences when compared with and without post-dilatation lesions. As far as CT vulnerability markers are concerned, the study groups presented significant differences only in terms of spotty calcifications (66.66% in subgroup 1A vs. 79.16% in subgroup 1B, p = 0.05) and low attenuation (37.5% in subgroup 1A vs. 20.83% in subgroup 1B, p = 0.01).

Conclusions: Following the analysis of coronary artery plaques after the implantation of BVS, significant changes were noted both in the morphology of the atherosclerotic plaques treated with these devices and in the lumen and coronary wall.

CTA Evaluation of Bioresorbable Scaffolds versus Metallic Coronary Stents – a Feasibility Study

Background: Computed tomography angiography (CTA) presents important limits in in-stent restenosis (ISR) evaluation in case of metallic coronary stents, due to the artifacts determined by stent struts, which alter in-stent plaque analysis. In case of bioresorbable scaffolds, stent strut resorption allows accurate evaluation of the vessel wall. Aim of the study: This study aims to compare the feasibility of CTA as a follow-up imaging method for ISR diagnosis following elective PTCA procedures, between bioresorbable scaffolds and metallic coronary stents.

Material and methods: We conducted a prospective, observational study on 73 patients with elective PTCA procedures in their medical history, in whom 113 stents were assessed via CTA in order to diagnose ISR. Based on stent type, the patients were divided into two groups: Group 1 – patients with bioresorbable vascular scaffolds (BVS) (n = 30); and Group 2 – patients with bare metal stents (BMS) (n = 43). Plaque analysis was possible only in the BVS group with a post-processing research-dedicated software, Syngo.via Frontier, which identified plaque morphology and virtual histology composition.

Results: After CTA evaluation, the BVS group presented a significantly higher incidence of severe coronary artery disease (CAD) (Group 1 – 73% vs. Group 2 – 30%, p <0.0001). The proximal part of the right coronary artery (RCA) presented a significantly higher percentage of metallic stents (14% BMS vs. 2% BVS, p = 0.0029). The comparative analysis of CTA sensibility for the visual evaluation of ISR identified a significantly higher percentage of diagnostic CT evaluations in the BVS group (Group 1 – 94% vs. Group 2 – 76.19%, p = 0.0006). CTA evaluation provided the most accurate results for the 3.0 and 3.5 mm devices. Regarding CTA sensibility for ISR diagnosis, the BVS group presented the smallest incidence of non-diagnostic CT evaluations.

Conclusions: CTA evaluation of bioresorbable scaffolds is superior to metallic stent assessment, the latter being influenced by numerous sources of error dependent mainly on the presence of the metal structure.

Impact of coronary plaque geometry on plaque vulnerability and its association with the risk of future cardiovascular events in patients with chest pain undergoing coronary computed tomographic angiography-the GEOMETRY study: Protocol for a prospective clinical trial

INTRODUCTION

Coronary computed tomography angiography (CCTA) has emerged as a valuable noninvasive imaging tool for assessing atheromatous plaque morphology and composition, and several CCTA features have been validated as reliable indicators of the plaque-associated risk. However, the role of lesion geometry as a CCTA feature of plaque vulnerability has not been investigated so far.

MATERIAL AND METHODS

Here we present the study protocol of the GEOMETRY trial, a prospective, single center, cohort study in which we aim to investigate the relationship between plaque geometry (as expressed by cross-sectional and longitudinal plaque eccentricity) and the risk for major adverse cardiac events (MACE) during 2 years of follow-up, in order to validate plaque eccentricity as a new CCTA marker of coronary plaque vulnerability. One thousand patients with suspected coronary artery disease (CAD) and pretest probability of CAD between 15% and 85%, who undergo CCTA and in whom CCTA identifies the presence of at least 1 significant coronary plaque (producing a luminal narrowing of at least 50%) will be enrolled in the study. Based on the results of complex image post-processing and plaque analysis, patients will be divided into 2 groups: group 1-patients in whom CCTA analysis identifies only non-eccentric coronary plaque; and group 2-patients in whom CCTA analysis reveals the presence of at least 1 eccentric significant coronary plaque producing a significant luminal narrowing. Study outcomes will consist in the rate of major cardiovascular events and the rate of plaque progression during follow-up.The study is funded by the Romanian Ministry of European Funds, the Romanian Government and the European Union, as part of the research grant number 103544/2016 - PlaqueIMAGE (contract number 26/01.09.2016).

CONCLUSION

In conclusion, GEOMETRY will be the first CCTA-based study that will investigate the impact of geometric distribution of coronary atheromatous plaque on the future risk of cardiovascular events and on the rate of plaque progression, introducing and validating a new potential feature of plaque vulnerability represented by plaque geometry.

Stem cell-derived exosomes - an emerging tool for myocardial regeneration

Cardiovascular diseases (CVDs) continue to represent the number one cause of death and disability in industrialized countries. The most severe form of CVD is acute myocardial infarction (AMI), a devastating disease associated with high mortality and disability. In a substantial proportion of patients who survive AMI, loss of functional cardiomyocytes as a result of ischaemic injury leads to ventricular failure, resulting in significant alteration to quality of life and increased mortality. Therefore, many attempts have been made in recent years to identify new tools for the regeneration of functional cardiomyocytes. Regenerative therapy currently represents the ultimate goal for restoring the function of damaged myocardium by stimulating the regeneration of the infarcted tissue or by providing cells that can generate new myocardial tissue to replace the damaged tissue. Stem cells (SCs) have been proposed as a viable therapy option in these cases. However, despite the great enthusiasm at the beginning of the SC era, justified by promising initial results, this therapy has failed to demonstrate a significant benefit in large clinical trials. One interesting finding of SC studies is that exosomes released by mesenchymal SCs (MSCs) are able to enhance the viability of cardiomyocytes after ischaemia/reperfusion injury, suggesting that the beneficial effects of MSCs in the recovery of functional myocardium could be related to their capacity to secrete exosomes. Ten years ago, it was discovered that exosomes have the unique property of transferring miRNA between cells, acting as miRNA nanocarriers. Therefore, exosome-based therapy has recently been proposed as an emerging tool for cardiac regeneration as an alternative to SC therapy in the post-infarction period. This review aims to discuss the emerging role of exosomes in developing innovative therapies for cardiac regeneration as well as their potential role as candidate biomarkers or for developing new diagnostic tools.

Morphological Features and Plaque Composition in Culprit Atheromatous Plaques of Patients with Acute Coronary Syndromes

Background: The independent role of each plaque feature in relation to plaque vulnerability is still the subject of ongoing research. This study aimed to compare the morphologic characteristics of vulnerable atheromatous coronary plaques with the ones of stable, non-vulnerable plaques, and in plaques with different locations in the coronary tree, in order to identify the most relevant imaging-based biomarkers associated with coronary plaque vulnerability.

Material and methods: This was a prospective observational, non-randomized study that included 50 patients with unstable angina who underwent computed tomography angiography for assessment of the entire coronary artery tree followed by complex morphologic analysis of all lesions, divided into two groups: group 1 – 25 patients with vulnerable plaque (VP) and group 2 – 25 age- and gender-matched patients with non-vulnerable plaque (NVP).

Results: Lesions with a stenosis degree >70% were significantly longer than those with a stenosis degree <70% (8.27 ± 2.74 mm vs. 5.56 ± 4.11 mm, p = 0.04). VP presented significantly higher values of plaque thickness (p = 0.0005), plaque burden (p = 0.0004), and higher total plaque volume (p = 0.0005) than NVP. The remodeling index was not significantly different between the groups (p = 0.6), but the eccentricity index was (0.24 ± 0.14 compared to 0.14 ± 0.17, p = 0.023). Linear regression analysis revealed a significant correlation between plaque burden and plaque components in VP (r = 0.76, p <0.0001 for necrotic core; r = 0.62, p = 0.0008 for fibro-fatty tissue; and r = 0.5, p = 0.01 for fibrotic tissue volume). Culprit plaques located in the right coronary artery presented significantly larger plaque burden volumes (91.17 ± 4.88 mm3 vs. 83.35 ± 8.47 mm3, p = 0.04), larger volumes of necrotic core (82.03 ± 47.85 mm3 vs. 45.84 ± 43.72 mm3, p = 0.02) and fibrofatty tissue (53.23 ± 31.92 mm3 vs. 23.76 ± 20.90 mm3, p = 0.02) than the ones situated in the left coronary artery.

Conclusions: VPs from the culprit lesions exhibit a different phenotype than non-vulnerable ones, and vulnerability features are present in a significantly larger extent in VPs from the right coronary artery as compared to those from the left coronary artery.

Influence of tube potential on quantitative coronary plaque analyses by low radiation dose computed tomography: a phantom study

Previous studies have shown that employing the low dose computed tomography (CT) technique based on low tube potential reduces the radiation dose required for the coronary artery examination protocol. However, low tube potential may adversely influence the CT number of plaque composition. Therefore, we aimed to determine whether quantitative atherosclerotic plaque analysis by a multi-slice, low radiation dose CT protocol using 80 kilovolts (kV) yields results comparable to those of the standard 120 kV protocol. Artificial plaque samples (n = 17) composed of three kinds of plaque were scanned at 120 and 80 kV. Relative low-density and medium-density plaque component volumes obtained by three protocols (80 kV, 60 Hounsfield units [HU] threshold; 120 kV, 60 HU threshold; and 80 kV, 82 HU threshold) were compared. Using the 60 HU threshold, relative volume of the low-density plaque component obtained at 80 kV was lower than that obtained at 120 kV (27 ± 3% vs. 51 ± 5%, P < 0.001), whereas relative volume of the medium-density plaque component obtained at 80 kV was higher than that obtained at 120 kV (73 ± 3% vs. 48 ± 5%, P < 0.001). By contrast, no significant difference in relative volume obtained at 80 kV (82 HU threshold) versus 120 kV (60 HU threshold) was observed for either low-density (52 ± 5% vs. 51 ± 5%) or medium-density (48 ± 5% vs. 48 ± 5%) plaque component. Low tube potential may affect the accuracy of quantitative atherosclerotic plaque analysis. For our phantom test, 82 HU was the optimal threshold for scanning at 80 kV.

Original Research. Transluminal Contrast Attenuation Gradient Is Associated with Coronary Plaque Vulnerability — a Computed Tomography Angiography-based Study

The aim of this study was to demonstrate that the transluminal contrast attenuation gradient (TAG), a new CT imaging-derived marker of functional significance of a coronary stenosis, is directly associated with the vulnerability degree of atheromatous coronary plaques. Material and methods: This is a prospective study on 21 patients with 30 atheromatous plaques in the coronary arteries, who underwent cardiac computed tomography angiography (CCTA) for assessment of coronary plaques. Results: Twelve plaques were classified as vulnerable (40%) and 18 plaques (60%) as non-vulnerable. Plaques associated with a TAG value above 10 HU exhibited in a significantly higher proportion CCTA markers of plaque vulnerability, as compared to plaques in which the attenuation gradient was below 10 HU. TAG values >10 HU were associated with a higher amount of plaque volume (107.4 ± 91.2 mm3 vs. 56.0 ± 37.5 mm3, p = 0.009), necrotic core (32.5 ± 36.9 mm3 vs. 3.1 ± 3.2 mm3, p = 0.0003), and fibro-fatty tissue (17.7 ± 16.3 mm3 vs. 4.0 ± 2.6 mm3, p = 0.0002), as compared to those lesions with TAG values below 10 HU. Linear regression analysis revealed a significant correlation between TAG values and CCTA features of plaque instability: necrotic core (r = −0.73, p <0.0001), fibrofatty tissue (r = −0.63, p = 0.0002), and plaque volume (r = −0.48, p = 0.006). Conclusions: In patients with coronary artery disease, contrast attenuation gradient along the coronary plaques, determined by CCTA, correlates with CT markers of plaque vulnerability. Vulnerable coronary plaques are associated with a higher functional significance than the stable ones with a similar anatomic profile.

Intracoronary Shear Stress and CT Characteristics of Vulnerable Coronary Plaques

Vulnerable coronary plaques are associated with a significant risk for rupture, and the ability to detect their characteristic features is of extreme importance, as timely detection of rupture-prone plaques could lead to the appropriate initiation of adequate therapeutic measures and prevent the evolution to an acute coronary event. The most common features of vulnerability in coronary plaques are represented by the presence of low density atheroma, a thin fibrous cap, spotty calcifications, and positive remodeling. However, there is still a huge amount of information to be learned about the role of local forces, represented by the shear stress, on the plaque vulnerability. This clinical update aims to present the most recent advances in the field of knowledge regarding the relation between shear stress and plaque vulnerability, starting from the hypothesis that shear stress significantly correlates with the CT features of plaque vulnerability and can represent a new marker of vulnerability in coronary artery plaques.

A Comparative Preliminary Study on CT Contrast Attenuation Gradient Versus Invasive FFR in Patients with Unstable Angina

The aim of this preliminary study was to assess the effectiveness of transluminal contrast attenuation gradient (TAG) determined by computed tomographic angiography (CTA), for the evaluation of the functional significance of coronary artery stenoses in patients with acute coronary syndromes produced by vulnerable coronary plaques, and to demonstrate the correlation between this new parameter and the vulnerability markers of the culprit lesions.

Material and methods: This is a preliminary pilot study on 10 patients with acute coronary syndromes – unstable angina type, who underwent CTA for the assessment of coronary lesions, followed by invasive angiography and the determination of fractional flow reserve (FFR) prior to a revascularization procedure. Patients were divided into 2 groups, according to their FFR values: Group 1 consisted of 6 patients with an FFR value <0.8 (functionally significant lesion), and Group 2 consisted of 4 patients who presented an FFR value >0.8 (functionally non-significant lesion).

Results: FFR values were 0.64 ± 0.07, 95% CI: 0.5–0.7 in Group 1, and 0.86 ± 0.05, 95% CI: 0.7–0.9 in Group 2. Plaques associated with an FFR<0.8 presented a higher amount of plaque volume (192.7 ± 199.7 mm3 vs. 42.1 ± 27.3 mm3, p = 0.1), necrotic core (66.7 ± 72.9 mm3 vs. 10.0 ± 9.3 mm3, p = 0.1), and fibro-fatty tissue (29.7 ± 37.4 mm3 vs. 6.2 ± 3.8 mm3, p = 0.2). At the same time, TAG significantly correlated with the presence of a functionally significant lesion. Coronary lesions associated with low FFR presented significantly higher values of TAG along the plaque as compared with lesions with FFR values >0.8 (TAG values 22.1 ± 5.8 HU vs. 11.7 ± 2.5 HU, p = 0.01). Linear regression identified a significant correlation between TAG and FFR values as a measure of functional significance of the lesion (r = 0.7, p = 0.01).

Conclusions: Contrast attenuation gradient along the culprit lesion, determined by CTA, correlates with the FFR values and with CT markers of plaque vulnerability, indicating that the presence of vulnerability features inside a coronary plaque could increase the functional significance of a coronary lesion.

Early Detection and Treatment of the Vulnerable Coronary Plaque

Early identification and treatment of the vulnerable plaque, that is, a coronary artery lesion with a high likelihood of rupture leading to an acute coronary syndrome, have gained great interest in the cardiovascular research field. Postmortem studies have identified clear morphological characteristics associated with plaque rupture. Recent advances in invasive and noninvasive coronary imaging techniques have empowered the clinician to identify suspected vulnerable plaques in vivo and paved the way for the evaluation of therapeutic agents targeted at reducing plaque vulnerability. Local treatment of vulnerable plaques by percutaneous coronary intervention and systemic treatment with anti-inflammatory and low-density lipoprotein–lowering drugs are currently being investigated in large randomized clinical trials to assess their therapeutic potential for reducing adverse coronary events. Results from these studies may enable a more patient-tailored strategy for the treatment of coronary artery disease.

Dual-energy CT can detect malignant lymph nodes in rectal cancer

BACKGROUND

There is a need for an accurate and operator independent method to assess the lymph node status to provide the most optimal personalized treatment for rectal cancer patients. This study evaluates whether Dual Energy Computed Tomography (DECT) could contribute to the preoperative lymph node assessment, and compared it to Magnetic Resonance Imaging (MRI). The objective of this prospective observational feasibility study was to determine the clinical value of the DECT for the detection of metastases in the pelvic lymph nodes of rectal cancer patients and compare the findings to MRI and histopathology.

MATERIALS AND METHODS

The patients were referred to total mesorectal excision (TME) without any neoadjuvant oncological treatment. After surgery the rectum specimen was scanned, and lymph nodes were matched to the pathology report. Fifty-four histology proven rectal cancer patients received a pelvic DECT scan and a standard MRI. The Dual Energy CT quantitative parameters were analyzed: Water and Iodine concentration, Dual-Energy Ratio, Dual Energy Index, and Effective Z value, for the benign and malignant lymph node differentiation.

RESULTS

DECT scanning showed statistical difference between malignant and benign lymph nodes in the measurements of iodine concentration, Dual-Energy Ratio, Dual Energy Index, and Effective Z value. Dual energy CT classified 42% of the cases correctly according to N-stage compared to 40% for MRI.

CONCLUSION

This study showed statistical difference in several quantitative parameters between benign and malignant lymph nodes. There were no difference in the accuracy of lymph node staging between DECT and MRI.

Computed Tomography Biomarkers of Vulnerable Coronary Plaques

An unstable plaque has a high risk of thrombosis and at the same time for a fast progression of the stenosis degree. Also, “high-risk plaque” and “thrombosis-prone plaque” are used as synonym terms for characterization of a vulnerable plaque. The imaging biomarkers for vulnerable coronary plaques are considered to be spotty calcifications, active remodeling, low-density atheroma and the presence of a ring-like attenuation pattern, also known as the napkin-ring sign. Computed cardiac tomography can determine the plaque composition by assessing the plaque density, which is measured in Hounsfield units (HU). The aim of this manuscript was to provide an update about the most frequently used biomarkers of vulnerability in a vulnerable plaque with the help of computed cardiac tomography.

Wellens’ Syndrome Depicted by Coronary CT Angiography

Introduction: Wellens’ Syndrome is indicated by deeply inverted or biphasic T-waves in V2-V3 precordial leads without ST elevation or pathological Q waves, immediately following an episode of angina pectoris.

Case presentation: A case of Wellens’ syndrome depicted by coronary CT angiography (CTA) and invasive coronary angiography is reported.

Conclusion: Recognition of these ECG changes is important, due to the imminent danger of acute LAD occlusion. Patients with Wellens’ syndrome should undergo invasive coronary angiography without delay. Ischemia provocation tests (i.e. treadmill) are contraindicated in these patients.

Extracorporeal Life Support and New Therapeutic Strategies for Cardiac Arrest Caused by Acute Myocardial Infarction - a Critical Approach for a Critical Condition

This review summarizes the most recent developments in providing advanced supportive measures for cardiopulmonary resuscitation, and the results obtained using these new therapies in patients with cardiac arrest caused by acute myocardial infarction (AMI). Also detailed are new approaches such as extracorporeal cardiopulmonary resuscitation (ECPR), intra-arrest percutaneous coronary intervention, or the regional models for systems of care aiming to reduce the critical times from cardiac arrest to initiation of ECPR and coronary revascularization.

The Use of Biomarkers for the Early Detection of Vulnerable Atherosclerotic Plaques and Vulnerable Patients. A Review

Acute coronary syndromes represent the most severe consequences of atherosclerosis, most often triggered by the rupture of a coronary plaque, which, for various reasons, has become unstable. In many cases, these rupture-prone vulnerable plaques are difficult to diagnose, because they do not always cause significant obstruction noticeable by coronary angiography. Therefore, new methods and tools for the identification of vulnerable plaques have been proposed, many of which are currently under study. Various biomarkers have been suggested as predictors of a vulnerable plaque, as well as indicators of an increased inflammatory status associated with higher patient susceptibility for plaque rupture. Integration of such biomarkers into multiple biomarker platforms has been suggested to identify superior diagnostic algorithms for the early detection of the high-risk condition associated with an unstable plaque. The aim of this review is to summarize recent research related to biomarkers used for the early detection of vulnerable plaques and vulnerable patients.

The inextricable axis of targeted diagnostic imaging and therapy: An immunological natural history approach

In considering the challenges of approaches to clinical imaging, we are faced with choices that sometimes are impacted by rather dogmatic notions about what is a better or worse technology to achieve the most useful diagnostic image for the patient. For example, is PET or SPECT most useful in imaging any particular disease dissemination? The dictatorial approach would be to choose PET, all other matters being equal. But is such a totalitarian attitude toward imaging selection still valid? In the face of new receptor targeted SPECT agents one must consider the remarkable specificity and sensitivity of these agents. (99m)Tc-Tilmanocept is one of the newest of these agents, now approved for guiding sentinel node biopsy (SLNB) in several solid tumors. Tilmanocept has a Kd of 3×10(-11)M, and it specificity for the CD206 receptor is unlike any other agent to date. This coupled with a number of facts, that specific disease-associated macrophages express this receptor (100 to 150 thousand receptors), that the receptor has multiple binding sites for tilmanocept (>2 sites per receptor) and that these receptors are recycled every 15 min to bind more tilmanocept (acting as intracellular "drug compilers" of tilmanocept into non-degraded vesicles), gives serious pause as to how we select our approaches to diagnostic imaging. Clinically, the size of SLNs varies greatly, some, anatomically, below the machine resolution of SPECT. Yet, with tilmanocept targeting, the SLNs are highly visible with macrophages stably accruing adequate (99m)Tc-tilmanocept counting statistics, as high target-to-background ratios can compensate for spatial resolution blurring. Importantly, it may be targeted imaging agents per se, again such as tilmanocept, which may significantly shrink any perceived chasm between the imaging technologies and anchor the diagnostic considerations in the targeting and specificity of the agent rather than any lingering dogma about the hardware as the basis for imaging approaches. Beyond the elements of imaging applications of these agents is their evolution to therapeutic agents as well, and even in the neo-logical realm of theranostics. Characteristics of agents such as tilmanocept that exploit the natural history of diseases with remarkably high specificity are the expectations for the future of patient- and disease-centered diagnosis and therapy.

Enhanced expression of hemoglobin scavenger receptor CD163 in accumulated macrophages within filtered debris between acute coronary syndromes and stable angina pectoris

Coronary intraplaque hemorrhage up-regulates hemoglobin scavenger receptor CD163 expression on macrophages, and has an association with vulnerable plaque development. During percutaneous coronary intervention, mechanical plaque disruption exposes potentially embolic atheromatous contents from culprit plaque.In 37 patients with stable angina pectoris (SAP, n = 20) or acute coronary syndrome (ACS, n = 17), atherothrombotic debris was collected using a filter-based distal embolic protection device. We immunohistochemically determined CD14-positive macrophages and CD163-positive macrophages in filtered debris. We also examined the relation of CD14- and CD163-positive macrophages with culprit plaque volume and components evaluated with ultrasonic tissue characterization (VH-IVUS).The only significant difference in clinical characteristics between the two groups was in hs-CRP. In ACS, the percentage of CD14- and CD163-positive macrophages to the whole cells (%CD14 and %CD163, respectively) was significantly higher than that in SAP (20.1 ± 8.2 versus 8.8 ± 6.8%, P < 0.001 and 32.6 ± 18.9 versus 9.0 ± 3.8%, P < 0.001, respectively). In IVUS indices of culprit plaque, the remodeling index was significantly higher in ACS than in SAP. However, necrotic core component (%NC) in ACS was significantly higher than that in SAP. Furthermore, fibrotic component (%Fibrous) in ACS was significantly lower than that in SAP (56.1 ± 4.7 versus 60.1 ± 3.3%, P = 0.03). %CD14 and %CD163 had a significant positive correlation with %NC (%CD14: r = 0.40, P = 0.01 and %CD163: r = 0.45, P = 0.01), but only %CD163 was negatively correlated with %Fibrous (%CD163: r = -0.48, P = 0.01).These findings suggest that the presence of CD14- and CD163-positive macrophages may reflect plaque inflammation, NC expansion, and plaque vulnerability in patients with coronary heart disease.