Early changes in arterial structure and function following statin initiation: quantification by magnetic resonance imaging

Association Between Aortic Wall Parameters on Multidetector Computed Tomography and Ruptured Plaques By Nonobstructive General Angioscopy

BACKGROUND

Nonobstructive general angioscopy (NOGA) can identify vulnerable plaques in the aortic lumen that serve as potential risk factors for cardiovascular events such as embolism. However, the association between computed tomography (CT) images and vulnerable plaques detected on NOGA remains unknown.

METHODS AND RESULTS

We investigated 101 patients (67±11 years; women, 13.8%) who underwent NOGA and contrast-enhanced CT before or after 90 days in our hospital. On CT images, the aortic wall thickness, aortic wall area (AWA), and AWA in the vascular area were measured at the thickest point from the 6th to the 12th thoracic vertebral levels. Furthermore, the association between these measurements and the presence or absence of NOGA-derived aortic plaque ruptures (PRs) at the same vertebral level was assessed. NOGA detected aortic PRs in the aortic lumens at 145 (22.1%) of the 656 vertebral levels. The presence of PRs was significantly associated with greater aortic wall thickness (3.3±1.7 mm versus 2.1±1.2 mm), AWA (1.33±0.68 cm2 versus 0.89±0.49 cm2), and AWA in the vascular area (23.2%±9.3% versus 17.2%±7.6%) (P<0.001 for all) on the CT scans compared with the absence of PRs. The frequency of PRs significantly increased as the aortic wall thickness increased. Notably, a few NOGA-derived PRs were detected on CT in near-normal intima.

CONCLUSIONS

The presence of NOGA-derived PRs was strongly associated with increased aortic wall thickness, AWA, and AWA in the vascular area, measured using CT. NOGA can detect PRs in the intima that appear almost normal on CT scans.

Assessment of Therapeutic Response to Statin Therapy in Patients With Intracranial or Extracranial Carotid Atherosclerosis by Vessel Wall MRI: A Systematic Review and Updated Meta-Analysis

Background and Aims: Statin therapy is an essential component of cardiovascular preventive care. In recent years, various vessel wall MRI (VW-MRI) techniques have been used to monitor atherosclerosis progression or regression in patients with extracranial or intracranial large-artery atherosclerosis. We aimed to perform a systematic review and meta-analysis on the effects of statin therapy on plaque evolution as assessed by VW-MRI.

Materials and Methods: Prospective studies investigating carotid and intracranial atherosclerotic plaques in patients on statin therapy monitored by serial VW-MRI were systematically identified in the literature. The plaque burden and lipid-rich necrotic core (LRNC) volume of carotid plaque and the imaging features of intracranial plaques were extracted and summarized. For studies investigating carotid artery wall volume and LRNC volume, combined estimates were derived by meta-analysis.

Results: The study identified 21 studies of carotid plaque and two studies of intracranial plaque. While 16 studies investigating carotid plaques that included 780 patients by High-resolution VW-MRI were included in the meta-analysis. There was no significant change in carotid wall volume from baseline to 12 months. A significant change in LRNC volume was observed at > 12 months compared with baseline (Effect = −10.69, 95% CI = −19.11, −2.28, P < 0.01), while no significant change in LRNC volume at 3–6 months or 7–12 months after statin therapy initiation in 6 studies. Increases in fibrous tissue and calcium and reduction in neovascularization density of the plaque were seen in 2/3 studies (including 48/59 patients), 1/3 studies (including 17/54 patients), and 2/2 studies (including 71 patients) after statin therapy, respectively. Two studies with 257 patients in intracranial atherosclerosis showed that statins could effectively decrease wall volume and plaque enhancement volume.

Conclusions: Collective data indicated that statins could potentially stabilize carotid plaques by significantly reducing LRNC with 1 year of therapy as shown on serial carotid VW-MRI. There was no significant decrease in wall volume, which nonetheless indicated that plaque composition changes might be more sensitive to response monitoring than wall volume. It is likely that more sensitive, clinically relevant, and preferably quantitative indicators of therapeutic effects on intracranial vessel plaque morphology will be developed in the future.

Aortic Distensibility Can Predict Events in Patients With Premature Coronary Artery Disease: A Cardiac Magnetic Resonance Study

Noninvasive assessment of aortic distensibility (AD) is feasible with cardiac magnetic resonance (CMR). We investigated the relationship between AD (assessed by CMR) and coronary artery disease (CAD) severity (assessed by the SYNTAX score) in patients with premature CAD. We recruited 125 patients with CAD confirmed by coronary angiography (males were <55 years old and females <65 years old). We excluded patients with significant aortic disease or contraindications to CMR. We also recruited 25 age- and sex-matched healthy patients as controls. One-year follow-up was also carried out. Aortic distensibility at the aortic root (AR) and descending aorta (DA) was significantly (P < .001 for both) lower in the patient group. There was a significant negative correlation between SYNTAX score and AD at the AR (r = -0.56; P < .001) and DA (r = -0.34; P < .001), but insignificant correlation with distensibility at the ascending aorta (AA; r = -0.03; P = .81). AR, AA, and DA distensibility, as well as left ventricular ejection fraction were predictors of adverse events. The severity of CAD in young patients is associated with decreased AD, especially at the level of the AR. Aortic distensibility can predict adverse events in these patients.

A promising tool to tackle the risk of cerebral vascular disease, the emergence of novel carotid wall imaging

Stroke is a heterogeneous vascular disease. Carotid artery atherosclerosis is associated with almost one-quarter of ischemic strokes. Moreover, a large percentage of preventable strokes are currently attributed to carotid atherosclerosis. Over the past three decades, the management of carotid artery disease has evolved. The benefits of carotid revascularization alongside medical therapy have early been recognized. Nonetheless, the debate regarding the optimal strategy is still ongoing, particularly in patients with asymptomatic carotid artery disease. One of the challenges is the use of luminal stenosis to quantify the severity of the carotid artery disease and to guide decision-making regarding invasive revascularization. Characterizing carotid atherosclerotic plaque is a promising tool to identify vulnerable plaque. Certain features such as large lipid core have already been linked to acute vascular events, not only at the plaque level but also to predict systemic cardiovascular events. Recently, a quantitative T2 mapping magnetic resonance imaging technique was developed and validated against histology. The ability to accurately quantify plaque lipid content using this technique opens several new opportunities. In this review articles, we will discuss the current challenges in the management of carotid artery disease and the future roles of T2 mapping to aid therapeutic options. These roles may include how to determine the mode of invasive carotid revascularization in symptomatic patients. Moreover, there may be a rational to use T2 mapping as a risk stratification tool in asymptomatic patients with carotid artery stenosis. It may also provide an opportunity to stage atherosclerosis and identify patients with coronary atherosclerosis who may benefit maximally from intensive lipid interventions.

Molecular and Nonmolecular Magnetic Resonance Coronary and Carotid Imaging

Atherosclerosis is the leading cause of cardiovascular morbidity and mortality. Over the past 2 decades, increasing research attention is converging on the early detection and monitoring of atherosclerotic plaque. Among several invasive and noninvasive imaging modalities, magnetic resonance imaging (MRI) is emerging as a promising option. Advantages include its versatility, excellent soft tissue contrast for plaque characterization and lack of ionizing radiation. In this review, we will explore the recent advances in multicontrast and multiparametric imaging sequences that are bringing the aspiration of simultaneous arterial lumen, vessel wall, and plaque characterization closer to clinical feasibility. We also discuss the latest advances in molecular magnetic resonance and multimodal atherosclerosis imaging.

T2 mapping MRI technique quantifies carotid plaque lipid, and its depletion after statin initiation, following acute myocardial infarction

BACKGROUND & AIMS

A recently-validated, highly-sensitive T2 mapping magnetic resonance (MRI) technique accurately quantifies carotid plaque lipid. The aims of this study were to determine: (i) the extent of carotid plaque lipid in patients with acute coronary syndromes (ACS); (ii) the effects of initiation of high-intensity statin on plaque lipid content and (iii) whether plaque lipid content is related to standard or 'functional' blood lipid measurements.

METHODS

Statin naïve subjects presenting with ACS underwent carotid artery MRI at 3 T scanner to quantify plaque lipid. Patients were subsequently commenced on high dose statin as part of clinical care and underwent a second MRI after three months. Plaque composition was measured using objective semi-automated techniques.

RESULTS

23 out of 24 patients had measurable lipid. Three months after statin initiation there was a significant reduction in carotid lipid percentage [from 10.3% (7.2-14.2) to 7.4% (5.4-10.0), p = 0.002] and a significant increase in fibrous percentage [from 83.3% ± 6.6-85.5% ± 4.8, p = 0.039]. None of the studied functional blood biomarkers were related to either baseline carotid plaque lipid content or its propensity to change with statin treatment.

CONCLUSIONS

T2-mapping demonstrated depleted carotid plaque lipid following the initiation of high-intensity statin treatment. Standard or 'functional' blood biomarkers were dissociated from plaque lipid content or changes with treatment. These findings further reinforce the importance of disease characterisation over risk factor assessment. Subject to clinical trial findings, quantification of plaque lipid may provide the basis for an approach to identify patients suitable for intensive lipid reduction regimes.

Dynamic change of carotid intraplaque hemorrhage volume in subjects with mild carotid stenosis

BACKGROUND AND PURPOSE

Early detection of intraplaque hemorrhage (IPH) in the carotid artery is important as it is correlated with an increased risk of cerebral ischemic events. We examined changes in IPH with magnetic resonance imaging (MRI) over an extended follow-up period in patients with mild carotid stenosis.

MATERIALS AND METHODS

From November 2013 to November 2015, we retrospectively reviewed cerebral MRI of 2036 patients, including magnetization-prepared rapid acquisition with gradient-echo (MPRAGE) sequences obtained with a 3.0 T (T) MRI unit. An experienced neuroradiologist reviewed all studies and found 38 patients with carotid IPH and carotid stenosis that were categorized as mild (<30%), according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria. Twenty-five patients agreed to join this study and signed informed consent for (MPRAGE) sequence imaging. We used semi-automated software to measure IPH volume on both the initial and follow up scans.

RESULTS

The median follow-up time of patients with mild carotid stenosis and IPH was 33.3 months. IPH volume increased in 10 of 27 carotid arteries (37.0%), with a mean volume increase of 42.6 ± 44.0 mm³. IPH volume decreased in 17 of 27 carotid arteries (63%), with a mean volume decrease of 17.2 ± 22.8 mm³. Two patients without IPH at baseline showed IPH development on follow-up imaging. There were no significant differences in patient demographics between the two groups.

CONCLUSIONS

Carotid IPH volume in subjects with mild carotid stenosis can change over time and may not be correlated with any typical patient demographics.

Translating the effects of statins: from redox regulation to suppression of vascular wall inflammation

Vascular oxidative stress is a key feature of atherogenesis, and targeting vascular redox signalling is a rational therapeutic goal in vascular disease pathogenesis. 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors or statins are potent lipid-lowering drugs that improve cardiovascular outcomes. It is now widely accepted that cardiovascular disease prevention by statins is dependent not only on their lipid lowering effects, but also on their beneficial effects on vascular redox signalling. Cell culture and animal models have provided important findings on the effects of statins on vascular redox and nitric oxide bioavailability. Recent evidence from studies on human vessels has further enhanced our understanding of the "pleiotropic" effects of statins on vascular wall. Reversal of endothelial dysfunction in human vessels by statins is dependent on the mevalonate pathway and Rac1 inhibition. These critical steps are responsible for reducing NADPH-oxidase activity and improving tetrahydrobiopterin bioavailability and nitric oxide synthase (NOS) coupling in human vessels. However, mevalonate pathway inhibition has been also held responsible for some of the side effects observed after statin treatment. In this review we summarise the existing knowledge on the effects of statins on vascular biology by discussing key findings from basic science as well as recent evidence from translational studies in humans. Finally, we discuss emerging aspects of statin pleiotropy, such as their effects on adipose tissue biology and adipokine synthesis that may light additional mechanistic links between statin treatment and improvement of clinical outcome in primary and secondary prevention.

Carotid Intima-Media Thickness as a Cardiovascular Risk Factor and Imaging Pathway of Atherosclerosis

Assessment of carotid intima-media thickness (IMT) has emerged as a simple and noninvasive technique for measuring atherosclerotic burden. Although serum biomarkers have been linked to the risk of developing atherosclerosis, carotid IMT has the theoretical advantage of directly visualizing a final consequence of the disease itself, namely atherosclerosis in the vessel wall. The current widespread application of carotid IMT measurements has been based on the validity, standardization, and reproducibility of the measurement and the evidence that an increased carotid IMT can be regarded as an attractive biomarker of atherosclerosis and of increased cardiovascular risk, potentially useful as a therapeutic target in those at increased cardiovascular risk. The utilization of carotid IMT measurements as a surrogate end point in clinical trials evaluating a specific drug intervention may result in considerably smaller efforts and costs than when using a hard end point such as myocardial infarction, stroke, or death. In addition, the use of carotid IMT measurement as a screening tool in clinical practice in association with traditional risk factors may improve risk classification and decisions regarding therapeutic interventions. However, although carotid IMT may be correlated with clinical outcomes, changes in surrogate end points over time that result from a particular therapy may not necessarily be predictive of future cardiovascular events. Therefore, it is necessary to perform more clinical studies to clearly define the relationship between the modifications in carotid IMT and the changes in cardiovascular events. In an era of economic burden, when there is a clear combination of limited resources with high expense of innovation in drug development, carotid IMT represents a reasonable, worthwhile surrogate trial end point with a history of nearly 30 years of technical progress and clinical research. Current data strongly suggest that carotid IMT will continue to successfully be used as a valuable tool in clinical atherosclerosis research.

The relationship between coronary artery distensibility and fractional flow reserve

Discordance between angiography-based anatomical assessment of coronary stenosis severity and fractional flow reserve (FFR) has been attributed to several factors including lesion length and irregularity, and the myocardial territory supplied by the target vessel. We sought to examine if coronary arterial distensibility is an independent contributor to this discordance. There were two parts to this study. The first consisted of “in silico” models of 26 human coronary arteries. Computational fluid dynamics-derived FFR was calculated for fully rigid, partially distensible and fully distensible models of the 26 arteries. The second part of the study consisted of 104 patients who underwent coronary angiography and FFR measurement. Distensibility at the lesion site (Distensibility_MLA) and for the reference vessel (Distensibility_Ref) was determined by analysing three-dimensional angiography images during end-systole and end-diastole. Computational fluid dynamics-derived FFR was 0.67±0.19, 0.70±0.18 and 0.75±0.17 (P<0.001) in the fully rigid, partially distensible and fully distensible models respectively. FFR correlated with both Distensibility_MLA (r = 0.36, P<0.001) and Distensibility_Ref (r = 0.44, P<0.001). Two-way ANCOVA analysis revealed that Distensibility_MLA (F (1, 100) = 4.17, p = 0.031) and percentage diameter stenosis (F (1, 100) = 60.30, p < 0.01) were both independent predictors of FFR. Coronary arterial distensibility is a novel, independent determinant of FFR, and an important factor contributing to the discordance between anatomical and functional assessment of stenosis severity.

Plaque imaging to refine indications for emerging lipid-lowering drugs

Statins have been effective in reducing adverse cardiovascular events. Their benefits have been proportional to the level of plasma LDL-cholesterol reduction and seem to extend to patients with 'normal' levels of cholesterol at outset. Statins are also inexpensive and have a favourable side-effect profile. As a result, they are used widely (almost indiscriminately) in patients with atherosclerotic vascular disease, and in those at risk of disease. Next generation lipid-modifying drugs seem unlikely to offer the same simplicity of application. The recent trials of new classes of lipid modifying drugs underline the need for a risk stratification tool which is not based on patients' category of diagnosis (for example, post-myocardial infarction) but based on the characterization of disease in that individual patient. Mechanistic staging, a process that matches the target of the drug action with an identifiable disease characteristic, may offer an opportunity to achieve more precise intervention. The upshots of this targeted approach will be greater efficacy, requiring smaller clinical trials to demonstrate effectiveness; a reduced number needed to treat to yield benefits and more cost-effective prescribing. This will be important, as purchasers require ever more rigorous demonstration of both efficacy and cost-effectiveness. In this context, we will discuss available pharmacological strategies of lipid reduction in anti-atherosclerotic treatment and how plaque imaging techniques may provide an ideal method in stratifying patients for new lipid-modifying drugs.

Assessment of atherosclerosis in large vessel walls: A comprehensive review of FDG-PET/CT image acquisition protocols and methods for uptake quantification

There is growing evidence showing the importance of fluorodeoxyglucose positron emission tomography (FDG-PET) in the evaluation of vessel wall inflammation and atherosclerosis. Although this imaging modality has been increasingly used, there are various methods for image acquisition and evaluating FDG uptake activity in the vessel walls and atherosclerotic lesions, including qualitative visual scaling, semi-quantitative, and quantitative evaluations. Using each of these image acquisition protocols and measurement methods may result in different findings. In this review, we are going to describe the various image acquisition methods and common measurement strategies reflected in the literature and discuss their advantages and flaws.

Carotid atherosclerotic plaque stenosis: the stabilizing role of statins

BACKGROUND

Both pathophysiology and treatments of carotid atherosclerotic plaque stenosis represent two interesting fields of strong scientific investigation. Among different drugs, safety and efficacy of statin treatment have been widely investigated and proved.

MATERIALS AND METHODS

This narrative review is based on the material searched for and obtained via MEDLINE and PubMed up to March 2014. The search terms we used were: 'carotid plaque, intima-media thickness, plaque burden, stroke' in combination with 'statins, pleiotropic effects, HMG-CoA reductase inhibitors, lipid-lowering drugs'.

RESULTS

Carotid stenosis represents both a useful parameter to evaluate the atherosclerotic burden and a target for therapeutic (medical or surgical) decisions. Statins do not only improve the lipid profile, but also induce some 'pleiotropic' anti-inflammatory activities that contribute to carotid plaque stabilization. Statin-mediated protective activities are under active investigation at subclinical levels with the potential benefit of advanced imaging techniques. However, considering that some new techniques (excepted B-mode ultrasound) remain quite expensive, they can have for the moment an important role in research, but not in the clinical field.

CONCLUSIONS

Emerging evidence suggests that statin treatment improves carotid atherosclerosis, inducing a partial regression of plaque inflammation and size. Innovative imaging techniques might also ameliorate the identification of patients at high risk of cerebrovascular and coronary events, for which preventive statin treatments might be essential.

"Inflammation and arterial stiffness in humans"

Arterial stiffness is an established marker of cardiovascular morbidity and mortality and a potential therapeutic target. While hypertension and aging are established factors contributing to arterial stiffness, the role of inflammation in stiffening of the arteries is less well understood. We summarize existing literature regarding inflammation and arterial stiffness, including a discussion of the potential mechanisms by which inflammation may lead to arterial stiffening and studies assessing: (1) The association between subclinical inflammation and arterial stiffness in the general population; (2) The presence of increased arterial stiffness in primary inflammatory diseases; (3) The effect of anti-inflammatory therapy on arterial stiffness in primary inflammatory disease including the effect of statins; (4) Experimental evidence of immunization-induced arterial stiffening in normal adults. We discuss potential opportunities to assess the impact of anti-inflammatory interventions on arterial stiffness in subjects without primary inflammatory conditions. We also review the effect of inflammation on wave reflections.

Carotid magnetic resonance imaging for monitoring atherosclerotic plaque progression: a multicenter reproducibility study

This study sought to determine the multicenter reproducibility of magnetic resonance imaging (MRI) and the compatibility of different scanner platforms in assessing carotid plaque morphology and composition. A standardized multi-contrast MRI protocol was implemented at 16 imaging sites (GE: 8; Philips: 8). Sixty-eight subjects (61 ± 8 years; 52 males) were dispersedly recruited and scanned twice within 2 weeks on the same magnet. Images were reviewed centrally using a streamlined semiautomatic approach. Quantitative volumetric measurements on plaque morphology (lumen, wall, and outer wall) and plaque tissue composition [lipid-rich necrotic core (LRNC), calcification, and fibrous tissue] were obtained. Inter-scan reproducibility was summarized using the within-subject standard deviation, coefficient of variation (CV) and intraclass correlation coefficient (ICC). Good to excellent reproducibility was observed for both morphological (ICC range 0.98-0.99) and compositional (ICC range 0.88-0.96) measurements. Measurement precision was related to the size of structures (CV range 2.5-4.9 % for morphology, 36-44 % for LRNC and calcification). Comparable measurement variability was found between the two platforms on both plaque morphology and tissue composition. In conclusion, good to excellent inter-scan reproducibility of carotid MRI can be achieved in multicenter settings with comparable measurement precision between platforms, which may facilitate future multicenter endeavors that use serial MRI to monitor atherosclerotic plaque progression.

Design of the rosuvastatin pretreatment to reduce embolization during Carotid Artery Stenting trial

BACKGROUND

Carotid artery stenting (CAS) is a worldwide diffuse intervention, but may be associated with distal plaque component embolization, and sometimes major and minor stroke. Statin use has been demonstrated to reduce atherosclerotic plaque burden, but its effect in reducing distal embolization during carotid stenting has not yet been well validated.

AIMS

With the Rosuvastatin Pretreatment to Reduce Embolization during Carotid Artery Stenting trial, we aim to discover if a pretreatement with high doses of rosuvastatin in dyslipidemic patients is able to reduce periprocedural cerebral ischemic complications following carotid stenting.

METHODS

This is a phase III prospective, randomized controlled trial. All consecutive patients with asymptomatic carotid stenosis at least 80% will be randomized to a 6-week rosuvastatin treatment followed by carotid stenting, and to direct carotid stenting. Carotid stenting will be performed following common practice with distal or proximal embolic protection. The primary efficacy end point of the trial will be the prevalence of 'relevant' embolization during CAS, as a surrogate end point for cerebral ischemic complications. Other laboratory and clinical data will be registered and patients will be followed up to 1 year. In order to obtain the expected superiority of statin pretreatment on primary end point, a population of 130 patients will be enrolled into the study.

CONCLUSION

In conclusion, with the Rosuvastatin Pretreatment to Reduce Embolization during Carotid Artery Stenting trial, we want to evaluate whether a high dose of rosuvastatin for 6 weeks before CAS in asymptomatic patients with severe carotid stenosis is able to reduce the rate of plaque embolization during the procedure, thus suggesting a possible reduction in cerebral ischemic complications.

Endothelial dysfunction in conduit arteries and in microcirculation. Novel therapeutic approaches

The vascular endothelium not only is a single monolayer of cells between the vessel lumen and the intimal wall, but also plays an important role by controlling vascular function and structure mainly via the production of nitric oxide (NO). The so called "cardiovascular risk factors" are associated with endothelial dysfunction, that reduces NO bioavailability, increases oxidative stress, and promotes inflammation contributing therefore to the development of atherosclerosis. The significant role of endothelial dysfunction in the development of atherosclerosis emphasizes the need for efficient therapeutic interventions. During the last years statins, angiotensin-converting enzyme inhibitors, angiotensin-receptor antagonists, antioxidants, beta-blockers and insulin sensitizers have been evaluated for their ability to restore endothelial function (Briasoulis et al., 2012). As there is not a straightforward relationship between therapeutic interventions and improvement of endothelial function but rather a complicated interrelationship between multiple cellular and sub-cellular targets, research has been focused on the understanding of the underlying mechanisms. Moreover, the development of novel diagnostic invasive and non-invasive methods has allowed the early detection of endothelial dysfunction expanding the role of therapeutic interventions and our knowledge. In the current review we present the available data concerning the contribution of endothelial dysfunction to atherogenesis and review the methods that assess endothelial function with a view to understand the multiple targets of therapeutic interventions. Finally we focus on the classic and novel therapeutic approaches aiming to improve endothelial dysfunction and the underlying mechanisms.

Sustained acceleration in carotid atherosclerotic plaque progression with intraplaque hemorrhage: a long-term time course study

OBJECTIVES

This study sought to determine the immediate and long-term effects of intraplaque hemorrhage (IPH) on plaque progression in the carotid artery.

BACKGROUND

Previous studies have associated IPH in the carotid artery with more rapid plaque progression. However, the time course and long-term effect remain unknown. Carotid magnetic resonance imaging is a noninvasive imaging technique that has been validated with histology for the accurate in vivo detection of IPH and measurement of plaque burden.

METHODS

Asymptomatic subjects with 50% to 79% carotid stenosis underwent carotid magnetic resonance imaging at baseline and then serially every 18 months for a total of 54 months. Subjects with IPH present in at least 1 carotid artery at 54 months were selected. Subsequently, presence/absence of IPH and wall volume were determined independently in all time points for both sides. A piece-wise progression curve was fit by using a linear mixed model to compare progression rates described as annualized changes in wall volume between periods defined by their relationship to IPH development.

RESULTS

From 14 subjects who exhibited IPH at 54 months, 12 arteries were found to have developed IPH during the study period. The progression rates were -20.5 ± 13.1, 20.5 ± 13.6, and 16.5 ± 10.8 mm(3)/year before, during, and after IPH development, respectively. The progression rate during IPH development tended to be higher than the period before (p = 0.080) but comparable to the period after (p = 0.845). The progression rate in the combined period during/after IPH development was 18.3 ± 6.5 mm(3)/year, which indicated significant progression (p = 0.008 compared with a slope of 0) and was higher than the period before IPH development (p = 0.018). No coincident ischemic events were noted for new IPH.

CONCLUSIONS

The development of IPH posed an immediate and long-term promoting effect on plaque progression. IPH seems to alter the biology and natural history of carotid atherosclerosis. Early identification of patients with IPH may prove invaluable in optimizing management to minimize future sequelae.

Aortic distensibility and aortic intima-media thickness in patients without clinical manifestation of atherosclerotic cardiovascular disease

BACKGROUND

There is growing evidence that aortic distensibility (AD) is a subclinical marker of early atherosclerosis. Aortic intima-media thickness (IMT) was an earlier marker than carotid IMT of preclinical atherosclerosis. In this study, we aimed to assess the relationship between thoracic aortic IMT and AD.

METHODS

We studied 192 patients (mean age: 45.5 ± 8.4 years) who underwent transesophageal echocardiography (TEE) for various indications. Four different grades were determined according to IMT of thoracic aorta (Grade 1 < 1 mm; 1 mm ≤ Grade 2 < 3 mm; 3 mm ≤ Grade 3 < 5 mm; 5 mm ≤ Grade 4). AD was calculated from the echocardiographically derived ascending aorta diameters and hemodynamic pressure measurements in all patients. High sensitive C-reactive protein (hsCRP) and other biochemical markers were measured using an automated chemistry analyzer.

RESULTS

TEE evaluation characterized thoracic aortic intimal morphology as grade 1 in 71 patients (37%), grade 2 in 57 patients (29.7%), grade 3 in 34 patients (17.7%), and grade 4 in 30 (15.6%) patients. The lowest AD level was observed in grade 4 group compared with grade 1 and grade 2 groups (P < 0.001, P = 0.009, respectively). AD level of grade 3 group was lower than grade 1 and grade 2 group (P < 0.001, P = 0.021, respectively). In multiple linear regression analysis, AD was independently associated with age (β = -0.138, P = 0.029), hsCRP (β = -0.209, P = 0.001), and aortic IMT (β = -0.432, P < 0.001).

CONCLUSION

AD is independently associated with age, thoracic aortic IMT, and hsCRP. Impaired elasticity index of the aorta might be an independent predictor for the severity of thoracic atherosclerosis.

Review: the physiological and computational approaches for atherosclerosis treatment

The cardiovascular disease has long been an issue that causes severe loss in population, especially those conditions associated with arterial malfunction, being attributable to atherosclerosis and subsequent thrombotic formation. This article reviews the physiological mechanisms that underline the transition from plaque formation in atherosclerotic process to platelet aggregation and eventually thrombosis. The physiological and computational approaches, such as percutaneous coronary intervention and stent design modeling, to detect, evaluate and mitigate this malicious progression were also discussed.

Effects of p38 mitogen-activated protein kinase inhibition on vascular and systemic inflammation in patients with atherosclerosis

OBJECTIVES

This study sought to determine the effects of a p38 mitogen-activated protein kinase inhibitor, losmapimod, on vascular inflammation, by (18)F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography imaging.

BACKGROUND

The p38 mitogen-activated protein kinase cascade plays an important role in the initiation and progression of inflammatory diseases, including atherosclerosis.

METHODS

Patients with atherosclerosis on stable statin therapy (n = 99) were randomized to receive losmapimod 7.5 mg once daily (lower dose [LD]), twice daily (higher dose [HD]) or placebo for 84 days. Vascular inflammation was assessed by FDG positron emission tomography/computed tomography imaging of the carotid arteries and aorta; analyses focused on the index vessel (the artery with the highest average maximum tissue-to-background ratio [TBR] at baseline). Serum inflammatory biomarkers and FDG uptake in visceral and subcutaneous fat were also measured.

RESULTS

The primary endpoint, change from baseline in average TBR across all segments in the index vessel, was not significantly different between HD and placebo (ΔTBR: -0.04 [95% confidence interval [CI]: -0.14 to +0.06], p = 0.452) or LD and placebo (ΔTBR: -0.02 [95% CI: -0.11 to +0.06], p = 0.579). However, there was a statistically significant reduction in average TBR in active segments (TBR ≥1.6) (HD vs. placebo: ΔTBR: -0.10 [95% CI: -0.19 to -0.02], p = 0.0125; LD vs. placebo: ΔTBR: -0.10 [95% CI: -0.18 to -0.02], p = 0.0194). The probability of a segment being active was also significantly reduced for HD when compared with placebo (OR: 0.57 [95% CI: 0.41 to 0.81], p = 0.002). Within the HD group, reductions were observed in placebo-corrected inflammatory biomarkers including high-sensitivity C-reactive protein (% reduction: -28% [95% CI: -46 to -5], p = 0.023) as well as FDG uptake in visceral fat (ΔSUV: -0.05 [95% CI: -0.09 to -0.01], p = 0.018), but not subcutaneous fat.

CONCLUSIONS

Despite nonsignificant changes for the primary endpoint of average vessel TBR, HD losmapimod reduced vascular inflammation in the most inflamed regions, concurrent with a reduction in inflammatory biomarkers and FDG uptake in visceral fat. These results suggest a systemic anti-inflammatory effect. (A Study to Evaluate the Effects of 3 Months Dosing With GW856553, as Assessed FDG-PET/CT Imaging; NCT00633022).

Multimodal cardiovascular magnetic resonance quantifies regional variation in vascular structure and function in patients with coronary artery disease: relationships with coronary disease severity

BACKGROUND

Cardiovascular magnetic resonance (CMR) of the vessel wall is highly reproducible and can evaluate both changes in plaque burden and composition. It can also measure aortic compliance and endothelial function in a single integrated examination. Previous studies have focused on patients with pre-identified carotid atheroma. We define these vascular parameters in patients presenting with coronary artery disease and test their relations to its extent and severity.

METHODS AND RESULTS

100 patients with CAD [single-vessel (16%); two-vessel (39%); and three-vessel (42%) non-obstructed coronary arteries (3%)] were studied. CAD severity and extent was expressed as modified Gensini score (mean modified score 12.38 ± 5.3). A majority of carotid plaque was located in the carotid bulb (CB). Atherosclerosis in this most diseased segment correlated modestly with the severity and extent of CAD, as expressed by the modified Gensini score (R = 0.251, P < 0.05). Using the AHA plaque classification, atheroma class also associated with CAD severity (rho = 0.26, P < 0.05). The distal descending aorta contained the greatest plaque, which correlated with the degree of CAD (R = 0.222; P < 0.05), but with no correlation with the proximal descending aorta, which was relatively spared (R = 0.106; P = n. s.). Aortic distensibility varied along its length with the ascending aorta the least distensible segment. Brachial artery FMD was inversely correlated with modified Gensini score (R = -0.278; P < 0.05). In multivariate analysis, distal descending aorta atheroma burden, distensibility of the ascending aorta, carotid atheroma class and FMD were independent predictors of modified Gensini score.

CONCLUSIONS

Multimodal vascular CMR shows regional abnormalities of vascular structure and function that correlate modestly with the degree and extent of CAD.

Coronary artery distensibility assessed by 3.0 Tesla coronary magnetic resonance imaging in subjects with and without coronary artery disease

Coronary vessel distensibility is reduced with atherosclerosis and normal aging, but direct measurements have historically required invasive measurements at cardiac catheterization. Therefore, we sought to assess coronary artery distensibility noninvasively using 3.0 Telsa coronary magnetic resonance imaging (MRI) and to test the hypothesis that this noninvasive technique can detect differences in coronary distensibility between healthy subjects and those with coronary artery disease (CAD). A total of 38 healthy, adult subjects (23 men, mean age 31 ± 10 years) and 21 patients with CAD, diagnosed using x-ray angiography (11 men, mean age 57 ± 6 years) were studied using a commercial whole-body MRI system. In each subject, the proximal segment of a coronary artery was imaged for the cross-sectional area measurements using cine spiral MRI. The distensibility (mm Hg(-1) × 10(3)) was determined as (end-systolic lumen area - end-diastolic lumen area)/(pulse pressure × end-diastolic lumen area). The pulse pressure was calculated as the difference between the systolic and diastolic brachial blood pressure. A total of 34 healthy subjects and 19 patients had adequate image quality for coronary area measurements. Coronary artery distensibility was significantly greater in the healthy subjects than in those with CAD (mean ± SD 2.4 ± 1.7 mm Hg(-1) × 10(3) vs 1.1 ± 1.1 mm Hg(-1) × 10(3), respectively, p = 0.007; median 2.2 vs 0.9 mm Hg(-1) × 10(3)). In a subgroup of 10 patients with CAD, we found a significant correlation between the coronary artery distensibility measurements assessed using MRI and x-ray coronary angiography (R = 0.65, p = 0.003). In a group of 10 healthy subjects, the repeated distensibility measurements demonstrated a significant correlation (R = 0.80, p = 0.006). In conclusion, 3.0-Tesla MRI, a reproducible noninvasive method to assess human coronary artery vessel wall distensibility, is able to detect significant differences in distensibility between healthy subjects and those with CAD.

Carotid plaque regression following 6-month statin therapy assessed by 3T cardiovascular magnetic resonance: comparison with ultrasound intima media thickness

BACKGROUND

Cardiovascular magnetic resonance (CMR) allows volumetric carotid plaque measurement that has advantage over 2-dimensional ultrasound (US) intima-media thickness (IMT) in evaluating treatment response. We tested the hypothesis that 6-month statin treatment in patients with carotid plaque will lead to plaque regression when measured by 3 Tesla CMR but not by IMT.

METHODS

Twenty-six subjects (67 ± 2 years, 7 females) with known carotid plaque (> 1.1 mm) and coronary or cerebrovascular atherosclerotic disease underwent 3T CMR (T1, T2, proton density and time of flight sequences) and US at baseline and following 6 months of statin therapy (6 had initiation, 7 had increase and 13 had maintenance of statin dosing). CMR plaque volume (PV) was measured in the region 12 mm below and up to 12 mm above carotid flow divider using software. Mean posterior IMT in the same region was measured. Baseline and 6-month CMR PV and US IMT were compared. Change in lipid rich/necrotic core (LR/NC) and calcification plaque components from CMR were related to change in PV.

RESULTS

Low-density lipoprotein cholesterol decreased (86 ± 6 to 74 ± 4 mg/dL, p = 0.046). CMR PV decreased 5.8 ± 2% (1036 ± 59 to 976 ± 65 mm3, p = 0.018). Mean IMT was unchanged (1.12 ± 0.06 vs. 1.14 ± 0.06 mm, p = NS). Patients with initiation or increase of statins had -8.8 ± 2.8% PV change (p = 0.001) while patients with maintenance of statin dosing had -2.7 ± 3% change in PV (p = NS). There was circumferential heterogeneity in CMR plaque thickness with greatest thickness in the posterior carotid artery, in the region opposite the flow divider. Similarly there was circumferential regional difference in change of plaque thickness with significant plaque regression in the anterior carotid region in region of the flow divider. Change in LR/NC (R = 0.62, p = 0.006) and calcification (R = 0.45, p = 0.03) correlated with PV change.

CONCLUSIONS

Six month statin therapy in patients with carotid plaque led to reduced plaque volume by 3T CMR, but ultrasound posterior IMT did not show any change. The heterogeneous spatial distribution of plaque and regional differences in magnitude of plaque regression may explain the difference in findings and support volumetric measurement of plaque. 3T CMR has potential advantage over ultrasound IMT to assess treatment response in individuals and may allow reduced sample size, duration and cost of clinical trials of plaque regression.

Vascular imaging with positron emission tomography

Atherosclerosis is an inflammatory disease that causes most myocardial infarctions, strokes and acute coronary syndromes. Despite the identification of multiple risk factors and widespread use of drug therapies, it still remains a global health concern with associated costs. Although angiography is established as the gold standard means of detecting coronary artery stenosis, it does not image the vessel wall itself, reporting only on its consequences such as luminal narrowing and obstruction. MRI and computed tomography provide more information about the plaque structure, but recently positron emission tomography (PET) imaging using [(18) F]-fluorodeoxyglucose (FDG) has been advocated as a means of measuring arterial inflammation. This results from the ability of FDG-PET to highlight areas of high glucose metabolism, a feature of macrophages within atherosclerosis, particularly in high-risk plaques. It is suggested that the degree of FDG accumulation in the vessel wall reflects underlying inflammation levels and that tracking any changes in FDG uptake over time or with drug therapy might be a way of getting an early efficacy readout for novel anti-atherosclerotic drugs. Early reports also demonstrate that FDG uptake is correlated with the number of cardiovascular risk factors and possibly even the risk of future cardiovascular events. This review will outline the evidence base, shortcomings and emerging applications for FDG-PET in vascular imaging. Alternative PET tracers and other candidate imaging modalities for measuring vascular inflammation will also be discussed.

Carotid MRI: a tool for monitoring individual response to cardiovascular therapy?

Stroke remains a leading cause of morbidity and mortality. While stroke-related mortality has declined over the past four decades, data indicate that the mortality rate has begun to plateau. This change in trend may be attributable to variation in individual response to therapies that were derived from population-based studies. Further reductions in stroke mortality may require individualized care governed by directly monitoring the effects of cardiovascular therapy. In this article, carotid MRI is considered as a tool for monitoring in vivo carotid atherosclerotic disease, a principal etiology of stroke. Carotid MRI has been previously utilized to identify specific plaque features beyond luminal stenosis that are predictive of transient ischemic attack and stroke. To gain perspective on the possibility of monitoring plaque change within the individual, clinical trials and natural history studies that have used serial carotid MRI are considered. Data from these studies indicate that patients with a lipid-rich necrotic core with or without intraplaque hemorrhage may represent the desired phenotype for monitoring treatment effects in the individual. Advances in tissue-specific sequences, acquisition resolution, scan time, and techniques for monitoring inflammation and mechanical forces are expected to enable earlier detection of response to therapy. In so doing, cost-effective multicenter studies can be conducted to confirm the anticipated positive effects on outcomes of using carotid MRI for individualized care in patients with carotid atherosclerosis. In accordance, carotid MRI is poised to emerge as a powerful clinical tool for individualized management of carotid atherosclerotic disease to prevent stroke.

Imaging of atherosclerosis

It is now well recognized that the atherosclerotic plaques responsible for thrombus formation are not necessarily those that impinge most on the lumen of the vessel. Nevertheless, clinical investigations for atherosclerosis still focus on quantifying the degree of stenosis caused by plaques. Many of the features associated with a high-risk plaque, including a thin fibrous cap, large necrotic core, macrophage infiltration, neovascularization, and intraplaque hemorrhage, can now be probed by novel imaging techniques. Each technique has its own strengths and drawbacks. In this article, we review the various imaging modalities used for the evaluation and quantification of atherosclerosis.

Atherosclerosis regression and high-density lipoproteins

Atherosclerosis regression has been demonstrated clearly in animal experimental models and, to a lesser extent, in human clinical studies. Imaging techniques for study of the arterial wall are playing a key role in promoting our appreciation of regression. LDL lowering remains the mainstay of current lipid treatment, but given the multiple antiatherosclerotic functions of HDL, including reverse cholesterol transport, agents that target HDL may represent the next generation of treatment for atherosclerotic disease. Currently available agents, including nicotinic acid, have documented antiatherosclerotic effects and trials examining clinical outcomes in the context of contemporary LDL treatment are now underway. Future approaches to HDL treatment may include cholesteryl ester transfer protein inhibitors and apolipoprotein A-I mimetics.

Are changes in carotid intima-media thickness related to risk of nonfatal myocardial infarction? A critical review and meta-regression analysis

BACKGROUND

Carotid intima-media thickness (CIMT) is increasingly being used as a surrogate end point in randomized control trials (RCTs) of novel cardiovascular therapies. However, it remains unclear whether changes in CIMT that result from these therapies correlate with nonfatal myocardial infarction (MI).

METHODS

We performed a literature search of RCTs from 1990-2009 that used CIMT. Eligible RCTs (1) included quantitative and sequential assessments in CIMT at least 1 year apart and (2) reported nonfatal MI. Across RCTs, random-effects metaregression was employed to correlate differences in mean change in CIMT between treatment and control groups over time with the log odds ratios of developing nonfatal MI during follow-up.

RESULTS

Overall, we identified 28 RCTs with 15,598 patients. Differences in mean change in CIMT over time between treatment and control groups correlated with developing nonfatal MI during follow-up: for each 0.01 mm per year smaller rate of change in CIMT, the odds ratio for MI was 0.82 (95% CI, 0.69 to 0.96; P = .018). Results were similar in subgroups of RCTs with >1 year follow-up (P = .018) and those with at least 50 subjects in the treatment group (P = .019). However, there was no significant relationship between mean change in CIMT and nonfatal MI in RCTs evaluating statin therapy or those with high CIMTs at baseline (P > .20 in both instances).

CONCLUSIONS

Less progression in CIMT over time is associated with a lower likelihood of nonfatal MI in selected RCTs; however, these findings were inconsistent at times, suggesting caution in using CIMT as a surrogate end point.

Tyrosine polyethylene glycol (PEG)-micelle magnetic resonance contrast agent for the detection of lipid rich areas in atherosclerotic plaque

Vulnerable or high-risk atherosclerotic plaques often exhibit large lipid cores and thin fibrous caps that can lead to deadly vascular events when they rupture. In this study, polyethylene glycol (PEG)-micelles that incorporate a gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) amphiphile were used as an MR contrast agent. In an approach inspired by lipoproteins, the micelles were functionalized with tyrosine residues, an aromatic, lipophilic amino acid, to reach the lipid-rich areas of atherosclerotic plaque in a highly efficient manner. These micelles were applied to apolipoprotein E(-/-) (ApoE(-/-)) mice as a model of atherosclerosis. The abdominal aortas of the animals were imaged using T(1)-weighted (T(1)W) high-resolution MRI at 9.4T before and up to 48 h after the administration of the micelles. PEG-micelles modified with 15% tyrosine residues yielded a significant enhancement of the abdominal aortic wall at 6 and 24 h postinjection (pi) as compared to unmodified micelles. Fluorescence microscopy on histological sections of the abdominal aorta showed a correlation between lipid-rich areas and the distribution of the functionalized contrast agent in plaque. Using a simple approach, we demonstrated that lipid-rich areas in atherosclerotic plaque of ApoE(-/-) mice can be detected by MRI using Gd-DTPA micelles.

Effects of high-dose modified-release nicotinic acid on atherosclerosis and vascular function: a randomized, placebo-controlled, magnetic resonance imaging study

OBJECTIVES

Our aim was to determine the effects of high-dose (2 g) nicotinic acid (NA) on progression of atherosclerosis and measures of vascular function.

BACKGROUND

NA raises high-density lipoprotein cholesterol (HDL-C) and reduces low-density lipoprotein cholesterol and is widely used as an adjunct to statin therapy in patients with coronary artery disease. Although changes in plasma lipoproteins suggest potential benefit, there is limited evidence of the effects of NA on disease progression when added to contemporary statin treatment.

METHODS

We performed a double-blind, randomized, placebo-controlled study of 2 g daily modified-release NA added to statin therapy in 71 patients with low HDL-C (<40 mg/dl) and either: 1) type 2 diabetes with coronary heart disease; or 2) carotid/peripheral atherosclerosis. The primary end point was the change in carotid artery wall area, quantified by magnetic resonance imaging, after 1 year.

RESULTS

NA increased HDL-C by 23% and decreased low-density lipoprotein cholesterol by 19%. At 12 months, NA significantly reduced carotid wall area compared with placebo (adjusted treatment difference: -1.64 mm(2) [95% confidence interval: -3.12 to -0.16]; p = 0.03). Mean change in carotid wall area was -1.1 +/- 2.6 mm(2) for NA versus +1.2 +/- 3.0 mm(2) for placebo. In both the treatment and placebo groups, larger plaques were more prone to changes in size (r = 0.4, p = 0.04 for placebo, and r = -0.5, p = 0.02 for NA).

CONCLUSIONS

In statin-treated patients with low HDL-C, high-dose modified-release NA, compared with placebo, significantly reduces carotid atherosclerosis within 12 months. (Oxford Niaspan Study: Effects of Niaspan on Atherosclerosis and Endothelial Function; NCT00232531).

Inflammation imaging in atherosclerosis

Inflammation is important at many stages of atherosclerotic plaque development. We highlight several imaging modalities that can quantify the degree of plaque inflammation noninvasively. Imaging of this type might allow testing of novel antiatherosclerosis drugs, identification of patients at risk of plaque rupture, and deeper insight into the biology of the disease. The imaging modalities are discussed in relation to their potential use in these areas.

Location of arterial stiffening differs in those with impaired fasting glucose versus diabetes: implications for left ventricular hypertrophy from the Multi-Ethnic Study of Atherosclerosis

OBJECTIVE

To determine whether middle-aged and older individuals with impaired fasting glucose (IFG), but no clinical evidence of cardiovascular disease, exhibit abnormal changes in proximal thoracic aortic stiffness or left ventricular (LV) mass when compared with healthy counterparts.

RESEARCH DESIGN AND METHODS

From the Multi-Ethnic Study of Atherosclerosis, 2,240 subjects with normal fasting glucose (NFG), 845 with IFG, and 414 with diabetes, all aged 45 to 85 years and without preexisting coronary artery disease, underwent MRI determinations of total arterial and proximal thoracic aortic stiffness and LV mass. The presence or absence of other factors known to influence arterial stiffness was assessed.

RESULTS

After adjustment for clinical factors known to modify arterial stiffness, proximal thoracic aortic stiffness was not increased in those with IFG compared with those with NFG (1.90 +/- 0.05 versus 1.91 +/- 0.04 10(-3) mmHg(-1), respectively, P = 0.83). After accounting for clinical factors known to influence LV mass, LV mass was increased in those with diabetes relative to those with NFG (150.6 +/- 1.4 versus 145.8 +/- 0.81 g, P < 0.0009) but not in those with IFG in comparison with NFG (145.2 +/- 1.03 versus 145.8 +/- 0.81 g, P = 0.56).

CONCLUSIONS

Middle-aged and older individuals with the pre-diabetes state of IFG do not exhibit abnormal proximal thoracic distensibility or LV hypertrophy relative to individuals with NFG. For this reason, an opportunity may exist in those with IFG to prevent LV hypertrophy and abnormal aortic stiffness that is observed in middle-aged and older individuals with diabetes.

In vivo quantification of carotid artery wall dimensions: 3.0-Tesla MRI versus B-mode ultrasound imaging

BACKGROUND

Our aim was to compare common carotid mean wall thickness (MWT) measurements by 3.0-T MRI with B-mode ultrasound common carotid intima-media thickness (CCIMT) measurements, a validated surrogate marker for cardiovascular disease.

METHODS AND RESULTS

B-mode ultrasound and 3.0-T MRI scans of the left and right common carotid arteries were repeated 3 times in 15 healthy younger volunteers (age, 26+/-2.6 years), 15 healthy older volunteers (age, 57+/-3.2 years), and 15 subjects with cardiovascular disease and carotid atherosclerosis (age, 63+/-9.8 years). MWT was 0.711 (SD, 0.229) mm and mean CCIMT was 0.800 (SD, 0.206) mm. MWT and CCIMT were highly correlated (r=0.89, P<0.001). The intraclass correlation coefficients for interscan and interobserver and intraobserver agreements of MRI MWT measurements were larger than 0.95 with small confidence intervals, indicating excellent reproducibility. Power calculations indicate that 89 subjects are required to detect a 4% difference in MRI MWT compared with 469 subjects to detect similar differences with ultrasound IMT in follow-up studies.

CONCLUSIONS

The study data for carotid MRI and ultrasound IMT showed strong agreement, indicating that both modalities measure the thickness of the intima and media. The advantage of MRI over ultrasound is that the measurement variability is smaller, enabling smaller sample sizes and potentially shorter study duration in cardiovascular prevention trials.