In situcontrol of graphene oxide dispersions with a small impedance sensor.

Carbon-based nanomaterials (CBNs), such as graphene and carbon nanotubes, display advanced physical and chemical properties, which has led to their widespread applications. One of these applications includes the incorporation of CBNs into cementitious materials in the form of aqueous dispersions. The main issue that arises in this context is that currently no established protocol exists as far as characterizing the dispersions. In the present article, an innovative method for quick evaluation and quantification of graphene oxide (GO) dispersions is proposed. The proposed method is electrical impedance spectroscopy (EIS) with an impedance sensor. The novelty lies on the exploitation of a small sensor for on-site (field) direct dielectric measurements with the application of alternating current. Five different concentrations of GO dispersions were studied by applying EIS and for various accumulated ultrasonic energies. The low GO concentration leads to high impedance values due to low formed current network. Two opposing mechanisms were revealed during the accumulation of ultrasonic energy, that are taking place simultaneously: breakage of the agglomerates that facilitates the flow of the electric current due to the formation of a better dispersed network, nevertheless the surface hydrophilic structure of the GO is damaged with the high accumulated ultrasonic energy. The dielectric measurements were exploited to express an appropriate quantitative 'quality index' to facilitate with the dispersion control of the nanostructures. An intermediate concentration of GO is suggested (about 0.15 wt% of the binder materials) to be optimal for the specific engineering application, ultrasonicated at approximately 30 to 65 kJ. The investigated methodology is highly novel and displays a high potential to be applied in-field applications where CBNs must be incorporated in building materials.

Cardiac Imaging in Chronic Kidney Disease Patients.

Cardiovascular disease is highly prevalent and it is associated with high morbidity and mortality rates in patients with chronic kidney disease (CKD). The implementation of various imaging modalities may help to risk stratify these patients with a potential ease on the burden of complications and the rising costs of care. In this article we review some of the modern imaging techniques to diagnose cardiac disease in patients affected by CKD.

Anti-Inflammatory Treatment With Colchicine in Acute Myocardial Infarction: A Pilot Study.

BACKGROUND: Inflammatory processes have been identified as key mediators of the deleterious effects of ischemia/reperfusion in ST-segment-elevation myocardial infarction. Colchicine is a substance with potent anti-inflammatory properties, suitable for safe use in patients with cardiovascular disease. The purpose of this study was to test the hypothesis that a short course of colchicine treatment could lead to reduced infarct size. METHODS AND RESULTS: Patients presenting with ST-segment-elevation myocardial infarction ≤12 hours from pain onset (treated with primary percutaneous coronary intervention) were randomly assigned to colchicine or placebo for 5 days. The primary outcome parameter was the area under the curve of creatine kinase-myocardial brain fraction concentration. A subset of patients underwent cardiac MRI with late gadolinium enhancement 6 to 9 days after the index ST-segment-elevation myocardial infarction. One hundred fifty-one patients were included (60 in the MRI substudy). The area under the creatine kinase-myocardial brain fraction curve was 3144 (interquartile range [IQR], 1754-6940) ng·h(-1)·mL(-1) in the colchicine group in comparison with 6184 (IQR, 4456-6980) ng·h(-1)·mL(-1) in controls (P<0.001). Indexed MRI-late gadolinium enhancement-defined infarct size was 18.3 (IQR, 7.6-29.9) mL/1.73 m(2) in the colchicine group versus 23.2 (18.5-33.4) mL/1.73 m(2) in controls (P=0.019). The relative infarct size (as a proportion to left ventricular myocardial volume) was 13.0 (IQR, 8.0-25.3) % and 19.8 (IQR, 13.7-29.8) %, respectively (P=0.034). CONCLUSIONS: These results suggest a potential benefit of colchicine in ST-segment-elevation myocardial infarction, but further clinical trials are necessary to draw secure conclusions, especially considering the fact that the present study was not powered to assess clinical end points. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01936285.

Electrochemical Impedance as an Assessment Tool for the Investigation of the Physical and Mechanical Properties of Graphene-Based Cementitious Nanocomposites.

This investigation explores the potential of electrochemical impedance spectroscopy (EIS) in evaluating graphene-based cementitious nanocomposites, focusing on their physical and structural properties, i.e., electrical resistivity, porosity, and fracture toughness. EIS was employed to study cement mixtures with varying graphene nanoplatelet (xGnP) concentrations (0.05-0.40% per dry cement weight), whereas flexural tests assessed fracture toughness and porosimetry analyses investigated the structural characteristics. The research demonstrated that the electrical resistivity initially decreased with increasing xGnP content, leveling off at higher concentrations. The inclusion of xGnPs correlated with an increase in the total porosity of the cement mixtures, which was indicated by both EIS and porosimetry measurements. Finally, a linear correlation emerged between fracture toughness and electrical resistivity, contributing also to underscore the use of EIS as a potent non-destructive tool for evaluating the physical and mechanical properties of conductive nano-reinforced cementitious nanocomposites.

Dispersion of Multi-Walled Carbon Nanotubes into White Cement Mortars: The Effect of Concentration and Surfactants.

Multi-wall carbon nanotubes (MWCNTs) exhibit exceptional mechanical and electrical properties and can be used to improve the mechanical and piezoelectric properties of cement-based materials. In the present study, the effect of different MWCNT concentrations as well as different types of surfactants and a superplasticizer were examined to reinforce, at the nanoscale, a white cement mortar typically used for the restoration of monuments of cultural heritage. It was shown that sodium dodecylbenzenesulfonate (SDBS) and Triton X-100 surfactants slightly decreased the white cement mortars' electrical resistivity (by an average of 10%), however, the mechanical properties were essentially decreased by an average of 60%. The most suitable dispersion agent for the MWCNTs proved to be the superplasticizer Ceresit CC198, and its optimal concentration was investigated for different MWCNT concentrations. Carboxylation of the MWCNT surface with nitric acid did not improve the mechanical performance of the white cement nanocomposites. The parametric experimental study showed that the optimum combination of 0.8 wt% of cement superplasticizer and 0.2 wt% of cement MWCNTs resulted in a 60% decrease in the electrical resistivity; additionally, the flexural and compressive strengths were both increased by approximately 25% and 10%, respectively.

Piezoresistive Properties of Natural Hydraulic Lime Binary Pastes with Incorporated Carbon-Based Nanomaterials under Cyclic Compressive Loadings.

Natural Hydraulic Limes (NHL) are extensively used for the restoration of Monuments of Cultural Heritage, often combined with pozzolanic materials, such as natural pozzolans and metakaolin etc. In the present study, five (5) different cases of binary lime-based pastes composed of a specific type of NHL (NHL5) and metakaolin as pozzolanic addition were examined, that were reinforced with carbon nanostructures, namely graphene and carbon nanotubes. For the first time in restoration mortars, the incorporation of carbon nanostructures was investigated, aiming to produce materials with adequate piezoresistive response, so that they have the potential to be exploited for in situ structural health monitoring. The compressive strength, flexural strength, electrical resistance and piezoresistive response of the composite pastes was examined. The results showed that all modified carbon nanostructures lead to a significant reduction in electrical resistance. The pastes reinforced with 2D nanostructures (graphene family) displayed up to 30% increase in compressive strength and the pastes reinforced with 1D nanostructures (carbon nanotubes) displayed enhanced flexural strength (up to 100% increase). Piezoresistivity was attained for almost all investigated pastes, nevertheless the graphene oxide (GO) was considered as optimal reinforcement as the sensing ability of such pastes was found to be almost proportional to the applied compressive load level.

The prognostic role of late gadolinium enhancement on cardiac magnetic resonance in patients with nonischemic cardiomyopathy and reduced ejection fraction, implanted with cardioverter defibrillators for primary prevention. A systematic review and meta-analysis.

BACKGROUND: Previous studies suggest that late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) is associated with arrhythmic events in patients with nonischemic cardiomyopathy (NICM), while others have questioned the role of left ventricular ejection fraction (LVEF) as a sole predictor of future events. OBJECTIVES: To evaluate the role of LGE on CMR in identifying patients with NICM and reduced LVEF for whom a benefit from defibrillator implantation for primary prevention is not anticipated, thus they are mainly exposed to potential risks. METHODS: Major electronic databases were searched for studies reporting the incidence of appropriate device therapy (ADT), sudden cardiac death (SCD), and cardiac death based on the presence of LGE on CMR, among patients with NICM and reduced LVEF, implanted with a cardioverter defibrillator for primary prevention. RESULTS: Eleven studies (1652 patients, 947 with LGE) were included in the final analysis. LGE presence was strongly associated with ADT (logOR: 1.95, 95%CI: 1.21-2.69) and cardiac death (logOR: 0.91, 95%CI: 0.14-1.68), but not with SCD (logOR: 0.26, 95%CI: -1.09-1.6). Diagnostic accuracy analysis demonstrated that contrast enhancement is a sensitive marker of future ADT and cardiac death (93%, 95%CI: 85.8-96.7%; 82.9%, 95%CI: 70.6-90.7%; respectively), with moderate specificity ( 44%, 95%CI: 27.2-62.6%; 37.7%, 95%CI: 23.4-54.6%; respectively). CONCLUSION: LGE is a highly sensitive predictor of ADT and cardiac death in NICM patients implanted with a defibrillator for primary prevention. However, due to moderate specificity, derivation of a cutoff with adequate predictive values and probably a multifactorial approach are needed to improve discrimination of patients who will not benefit from ICDs.

Effects of Acute Triiodothyronine Treatment in Patients with Anterior Myocardial Infarction Undergoing Primary Angioplasty: Evidence from a Pilot Randomized Clinical Trial (ThyRepair Study).

Background: Thyroid hormone has a differential action on healthy and ischemic heart. Triiodothyronine (T3) administration improved postischemic cardiac function while it limited apoptosis in experimentally induced ischemia. Thus, the present study investigated the potential effects of acute liothyronine (LT3) treatment in patients with anterior myocardial infarction. Methods: This study is a pilot, randomized, double-blind, placebo-controlled trial (ThyRepair study). We randomized 52 patients and analyzed data from 37 patients (n = 16 placebo and n = 21 LT3), per prespecified per protocol analysis. We excluded three patients who had died of cardiovascular causes (one in placebo and two in LT3 arm), four with small infarct size below a pre-specified threshold (in the placebo arm), and the rest, who lacked follow-up data. LT3 treatment started after stenting as an intravenous (i.v.) bolus injection of 0.8 µg/kg of LT3 followed by a constant infusion of 0.113 µg/kg/h i.v. for 48 hours. All patients had cardiac magnetic resonance (CMR) at hospital discharge and 6 months follow-up. The primary end point was CMR left ventricular (LV) ejection fraction (LVEF) and secondary endpoints were LV volumes, infarct volume (IV), and safety. Results: The CMR LVEF% at 6 months was 53.6 ± 9.5 for the LT3-treated group and 48.6 ± 11 for placebo, p = 0.15. Acute LT3 treatment resulted in a significantly lower LV end-diastolic volume index (92.2 ± 16.8 mL/m2 vs. 107.5 ± 22.2, p = 0.022) and LV systolic volume index (47.5 ± 13.9 mL/m2 vs. 61.3 ± 21.7, p = 0.024) at hospital discharge, but not at 6 months. There was no statistically significant difference in CMR IV at hospital discharge between the groups (p = 0.24). CMR IV tended to be lower in the LT3-treated group at 6 months (18.7 ± 9.5 vs. 25.9 ± 11.7, in placebo, p = 0.05). Serious, life-threatening events related to LT3 treatment were not observed. A tendency for an increased incidence of atrial fibrillation (AF) was found in the LT3 group during the first 48 hours (19% for T3 group vs. 5% for placebo, p = 0.13). Conclusion: This pilot randomized, placebo-controlled trial study suggests potential favorable effects (acute cardiac dilatation and 6-month IV) as well as potential concerns regarding a higher risk of AF after LT3 administration early after myocardial infarction, which should be tested in a larger scale study.

Epicardial adipose tissue volume and coronary artery calcium to predict myocardial ischemia on positron emission tomography-computed tomography studies.

BACKGROUND: There appears to be an association of epicardial adipose tissue (EAT) with coronary artery disease (CAD) and its risk factors. EAT is assumed to influence CAD development by altering vasomotor tone and via toxic paracrine effects. The relationship of EAT to myocardial perfusion has not been studied. METHODS: Quantification of EAT and CAC was performed on positron emission tomography/computed tomography (PET/CT) studies in 45 subjects (77% intermediate pre-test probability of CAD) with mild-moderate myocardial ischemia (5-14% perfusion defect, n = 23), severe ischemia (≥15% defect, n = 22) and a control group with no ischemia matched for CAD risk factors (n = 52). RESULTS: EAT volume showed a better correlation with myocardial ischemia than total CAC (r = .47 vs r = .28, P < .01). EAT volume increased significantly from the control group to subjects with mild-moderate and severe ischemia (96.9, 124.5, and 143.9 cm(3), P < .01 for both ischemia groups vs controls). Total mean CAC was significantly higher in the severe ischemia group (676.3) than in control group (229.4) (P < .01). Multivariable logistic regression analyses showed that EAT volume was, but CAC was not, a significant predictor of ischemia after adjustment for age, sex, body mass index, and each other. EAT volume was a better predictor of ischemia than total CAC [area under the curve (AUC): .764 vs .6291, P = .04]. The combination of EAT + CAC (AUC = .7694) did not improve over EAT volume alone (P = .57). CONCLUSIONS: In this study, EAT volume assessed by CT was an independent predictor of ischemia on PET, and outperformed CAC score in a CAD naïve population at intermediate pre-test probability of disease.

Lessons of the month: Reemergence of rheumatic fever after a systemic streptococcal A infection: The role of cardiac MRI on the diagnosis of subclinical rheumatic carditis.

A 42-year-old man presented with fever, sore throat, rash and painful right knee swelling, preceded by self-medication with oral steroids. Blood and knee cultures yielded group A Streptococcus After 2 weeks of intravenous antibiotics and two arthroscopic knee debridements, he continued to experience spiking fevers, and electrocardiographic changes developed. We postulate that the patient suffered from the first presentation of acute rheumatic fever, following an invasive group A bacteraemic streptococcal infection. The possible role of cardiac magnetic resonance imaging in the diagnosis of rheumatic carditis is discussed.

Coronary aging in HIV-infected patients.

BACKGROUND: Human immunodeficiency virus (HIV)-infected patients often demonstrate accelerated aging processes. We investigated whether the vascular age of a cohort of stable HIV-infected patients receiving antiretroviral therapy (ART) was increased and sought out predictors of increased vascular age. METHODS: In this cross-sectional study, 400 HIV-infected patients (mean age, 48 years) attending a cardiometabolic clinic underwent cardiac computed tomography imaging to identify coronary artery calcium (CAC). Vascular age was estimated on the basis of the extent of CAC by means of previously published equations. RESULTS: Increased vascular age was observed in 162 patients (40.5%), with an average increase of 15 years (range, 1-43 years) over the chronological age. In univariable analyses, chronological age, male sex, systolic blood pressure, duration of ART, fasting glucose level, fasting serum triglyceride level, total cholesterol level, low-density and high-density lipoprotein cholesterol levels, hypertension, and the presence of the metabolic syndrome were associated with increased vascular age. In multivariable linear regression analyses, current CD4+ cell count was the only predictor of increased vascular age (beta = 0.51; P = .005). CONCLUSIONS: Increased vascular age is frequent among HIV-infected patients and appears to be associated with CD4+ cell count. If these findings were to be confirmed in prospective trials, a positive response to ART with an increase in CD4+ cell count may become a marker of increased risk of atherosclerosis development.

Divergent effects of laughter and mental stress on arterial stiffness and central hemodynamics.

OBJECTIVE: To investigate the effect of laughter and mental stress on arterial stiffness and central hemodynamics. Arterial stiffness and wave reflections are independent predictors of cardiovascular risk. Chronic psychological stress is an independent risk factor for cardiovascular events, whereas acute stress deteriorates vascular function. METHODS: Eighteen healthy individuals were studied on three occasions, according to a randomized, single-blind, crossover, sham procedure-controlled design. The effects of viewing a 30-minute segment of two films inducing laughter or stress were assessed. Carotid-femoral pulse wave velocity was used as an index of arterial stiffness; augmentation index was used as a measure of wave reflections. RESULTS: Laughter decreased pulse wave velocity (by 0.30 m/sec, p = .01), and augmentation index (by 2.72%, p = .05). Conversely, stress increased pulse wave velocity (by 0.29 m/sec, p = .05) and augmentation index (by 5.1%, p = .005). Laughter decreased cortisol levels by 1.67 microg/dl (p = .02), soluble P-selectin by 26 ng/ml (p = .02) and marginally von Willebrand factor (by 2.4%, p = .07) and increased total oxidative status (by 61 micromol/L, p < .001). Stress decreased interleukin-6 (by 0.11 pg/ml, p = .04) and increased total oxidative status (by 44 micromol/L, p = .007). Soluble CD40 ligand and fibrinogen remained unchanged. CONCLUSIONS: Positive (laughter) and negative (stress) behavioral interventions have divergent acute effects on arterial stiffness and wave reflections. These findings have important clinical implications extending the spectrum of lifestyle modifications that can ameliorate arterial function.

Prognostic value of adenosine stress cardiovascular magnetic resonance in patients with low-risk chest pain.

BACKGROUND: Approximately 5% of patients with an acute coronary syndrome are discharged from the emergency room with an erroneous diagnosis of non-cardiac chest pain. Highly accurate non-invasive stress imaging is valuable for assessment of low-risk chest pain patients to prevent these errors. Adenosine stress cardiovascular magnetic resonance (AS-CMR) is an imaging modality with increasing application. The goal of this study was to evaluate the negative prognostic value of AS-CMR among low-risk acute chest pain patients. METHODS: We studied 103 patients, mean 56.7 + or - 12.3 years of age, with chest pain and no electrocardiographic evidence of ischemia and negative cardiac biomarkers of necrosis, who were admitted to the Cardiac Decision Unit of our institution. All patients underwent AS-CMR. A negative AS-CMR was defined as absence of all the following: regional wall motion abnormalities at rest; perfusion defects during stress (adenosine) and rest; and myocardial scar on late gadolinium enhancement images. The patients were followed for a mean of 277 (range 161-462) days. The primary end point was defined as the combination of cardiac death, nonfatal acute myocardial infarction, re-hospitalization for chest pain, obstructive coronary artery disease (>50% coronary stenosis on invasive angiography) and coronary revascularization. RESULTS: In 14 patients (13.6%), AS-CMR was positive. The remaining 89 patients (86.4%), who had negative AS-CMR, were discharged. No patient with negative AS-CMR reached the primary end-point during follow-up. The negative predictive value of AS-CMR was 100%. CONCLUSION: AS-CMR holds promise as a useful tool to rule out significant coronary artery disease in patients with low-risk chest pain. Patients with negative AS-CMR have an excellent short and mid-term prognosis.

The effect of heart rate on wave reflections may be determined by the level of aortic stiffness: clinical and technical implications.

BACKGROUND: Augmentation Index (AIx) is related to cardiovascular diseases, risk, and mortality. AIx is associated with heart rate but the effect of aortic stiffness on this relationship has not been studied. The purpose of our study was to investigate the relationship between AIx and heart rate at different aortic stiffness levels. METHODS: The study consisted of 425 normotensive and untreated hypertensive subjects. Wave reflections and pulse-wave velocity (PWV) were determined by the Sphygmocor and the Complior systems, respectively. RESULTS: AIx was independently associated with heart rate, age, gender, height, mean blood pressure (BP) and the effective reflection site distance (ERD). The population was divided into three groups of those with different PWV levels (tertiles). The regression lines for AIx with heart rate differed significantly between the 3rd and the other two tertiles of PWV (P = 0.039 for slopes and P = 0.002 for intercepts). This difference remained significant even after adjustment for age, gender, height, mean BP, and distance of wave reflections. CONCLUSIONS: A significantly stronger correlation of AIx with heart rate was observed in subjects with higher levels of aortic stiffness as compared to those with lower levels; namely, the same increase in the heart rate between subjects, induced a greater decrease in the AIx at higher compared to lower PWV levels. The correction of AIx for heart rate should be reconsidered based on the aortic stiffness level. This finding has implications for interventional studies that aim to improve central hemodynamics but simultaneously affect heart rate. Further studies that show acute modifications of heart rate at different arterial stiffness levels are required to support these findings.

Epicardial Adipose Tissue: Another Tassel in the Complex Fabric of Atherosclerosis.

Atherosclerosis affects the majority of adult individuals in industrialized nations and it is beginning to affect even traditionally spared populations. The classic view has been that the precipitating events are intraluminal. However, good evidence supports the possibility that at least part of the atherosclerosis burden may be the consequence of extra-luminal noxious stimuli. Additionally, the epidemic of obesity, insulin resistance and diabetes mellitus has generated a strong interest in the potential role of visceral adipose tissue as an extra-luminal promoter of atherosclerosis. The epicardial space is filled with adipose tissue with an embryological origin similar to that of abdominal visceral fat. Both fats are highly inflamed in obese patients, patients with the metabolic syndrome and in those with established coronary artery disease. Additionally they are capable of secreting large quantities of pro-inflammatory cytokines and free fatty acids but also anti-inflammatory adipokines like adiponectin. In this manuscript we review the current evidence supporting the role of epicardial adipose tissue in the development of atherosclerosis and its complications.

Relation of habitual cocoa consumption to aortic stiffness and wave reflections, and to central hemodynamics in healthy individuals.

The effect of habitual cocoa consumption on arterial stiffness and wave reflection indexes, as well as on peripheral and central blood pressure, was assessed in 198 healthy subjects. In conclusion, higher cocoa intake was an independent determinant of low arterial stiffness and wave reflection indexes and was also independently associated with significantly lower central (aortic) pulse pressure.

Detecting human coronary inflammation by imaging perivascular fat.

Early detection of vascular inflammation would allow deployment of targeted strategies for the prevention or treatment of multiple disease states. Because vascular inflammation is not detectable with commonly used imaging modalities, we hypothesized that phenotypic changes in perivascular adipose tissue (PVAT) induced by vascular inflammation could be quantified using a new computerized tomography (CT) angiography methodology. We show that inflamed human vessels release cytokines that prevent lipid accumulation in PVAT-derived preadipocytes in vitro, ex vivo, and in vivo. We developed a three-dimensional PVAT analysis method and studied CT images of human adipose tissue explants from 453 patients undergoing cardiac surgery, relating the ex vivo images with in vivo CT scan information on the biology of the explants. We developed an imaging metric, the CT fat attenuation index (FAI), that describes adipocyte lipid content and size. The FAI has excellent sensitivity and specificity for detecting tissue inflammation as assessed by tissue uptake of 18F-fluorodeoxyglucose in positron emission tomography. In a validation cohort of 273 subjects, the FAI gradient around human coronary arteries identified early subclinical coronary artery disease in vivo, as well as detected dynamic changes of PVAT in response to variations of vascular inflammation, and inflamed, vulnerable atherosclerotic plaques during acute coronary syndromes. Our study revealed that human vessels exert paracrine effects on the surrounding PVAT, affecting local intracellular lipid accumulation in preadipocytes, which can be monitored using a CT imaging approach. This methodology can be implemented in clinical practice to noninvasively detect plaque instability in the human coronary vasculature.