Impaired flow mediated dilatation as evidence of endothelial dysfunction in chronic atrial fibrillation: relationship to plasma von Willebrand factor and soluble E-selectin levels

E-Selectin and Asymmetric Dimethylarginine Levels in Adult Cyanotic Congenital Heart Disease: Their Relation to Biochemical Parameters, Vascular Function, and Clinical Status

Background and Aim: Patients with cyanosis secondary to congenital heart disease (CHD) are characterized by erythrocytosis and increased blood viscosity, which contribute to endothelial dysfunction, increased arterial stiffness, and impaired vascular function, which may affect the final clinical presentation. Asymmetric dimethylarginine (ADMA) and e-selectin (e-sel) are valuable biomarkers for endothelial and vascular dysfunction. Their concentration levels in blood serum have the potential to be an accessible tool that reflects the severity of the disease. We aimed to assess e-sel and ADMA levels and their relationship with the clinical status and endothelial and vascular function. Methods: A cross-sectional study, including 36 adult CHD cyanotic patients [(17 males) (42.3 ± 16.3 years)] with an arterial blood oxygen saturation less than 92% and 20 healthy controls [(10 males) (38.2 ± 8.5 years)], was performed. All the patients underwent a clinical examination, blood testing, and cardiopulmonary tests. Their endothelial function was assessed using the intima media thickness and flow-mediated dilatation. Vascular function, using applanation tonometry methods, was determined using the aortic systolic pressure, aortic pulse pressure, augmentation pressure, augmentation index, pulse pressure amplification, and pulse wave velocity. Results: The concentrations of e-sel and ADMA were significantly higher in the patients with CHD. The E-sel levels correlated positively with red blood cells, hemoglobin concentration, hematocrit, and augmentation pressure; they correlated negatively with blood oxygen saturation, the forced expiratory one-second volume, forced vital capacity, and oxygen uptake. The ADMA levels were found to correlate only with age. Conclusions: The E-sel level, unlike ADMA concentration, reflects the severity of erythrocytosis and hypoxia and, thus, the physical status of patients with cyanotic CHD.

Atrial fibrillation, hypertension, and the cerebral vasodilatory reserve

Schematic representation for the cascade model of atrial fibrillation, hypertension, the cerebral vasodilatory reserve, and cognitive decline.

The effect of hypertension on cerebrovascular carbon dioxide reactivity in atrial fibrillation patients

Atrial fibrillation (AF) and hypertension (HTN) are both associated with impaired cerebrovascular carbon dioxide reactivity (CVRCO2), an indicator of cerebral vasodilatory reserve. We hypothesised that CVRCO2 would be lower in patients with both AF and HTN (AF + HTN) compared to normotensive AF patients, due to an additive effect of AF and HTN on CVRCO2. Forty AF (68 ± 9 years) and fifty-seven AF + HTN (68 ± 8 years) patients underwent transcranial Doppler ultrasound measurement of middle cerebral artery blood velocity (MCA Vm) during stepped increases and decreases in end-tidal carbon dioxide (PETCO2). A cerebrovascular conductance index (CVCi) was calculated as the ratio of MCA Vm and mean arterial pressure (MAP). CVRCO2 was determined from the linear slope for MCA Vm and MCA CVCi vs PETCO2. Baseline MAP was higher in AF + HTN than AF (107 ± 9 vs. 98 ± 9 mmHg, respectively; p < 0.001), while MCA Vm was not different (AF + HTN:49.6 [44.1-69.0]; AF:51.7 [45.2-63.3] cm.s-1; p = 0.075), and CVCi was lower in AF + HTN (0.46 [0.42-0.57] vs. 0.54 [0.44-0.63] cm.s-1.mmHg-1; p < 0.001). MCA Vm CVRCO2 was not different (AF + HTN: 1.70 [1.47-2.19]; AF 1.74 [1.54-2.52] cm/s/mmHg-2; p = 0.221), while CVCi CVRCO2 was 13% lower in AF + HTN (0.013 ± 0.004 vs 0.015 ± 0.005 cm.s-1.mmHg-1; p = 0.047). Our results demonstrate blunted cerebral vasodilatory reserve (determined as MCA CVCi CVRCO2) in AF + HTN compared to AF alone. This may implicate HTN as a driver of further cerebrovascular dysfunction in AF that may be important for the development of AF-related cerebrovascular events and downstream cognitive decline. We demonstrated reduced cerebrovascular CO2 responsiveness in atrial fibrillation with hypertension (AF+HTN) vs. atrial fibrillation (AF). Furthermore, AF per se (as opposed to normal sinus rhythm) predicts reduced cerebrovascular CO2 responsiveness. Our findings suggest additional cerebrovascular dysfunction in AF+HTN vs. AF.

Fibrinaloid Microclots and Atrial Fibrillation

Atrial fibrillation (AF) is a comorbidity of a variety of other chronic, inflammatory diseases for which fibrinaloid microclots are a known accompaniment (and in some cases, a cause, with a mechanistic basis). Clots are, of course, a well-known consequence of atrial fibrillation. We here ask the question whether the fibrinaloid microclots seen in plasma or serum may in fact also be a cause of (or contributor to) the development of AF. We consider known 'risk factors' for AF, and in particular, exogenous stimuli such as infection and air pollution by particulates, both of which are known to cause AF. The external accompaniments of both bacterial (lipopolysaccharide and lipoteichoic acids) and viral (SARS-CoV-2 spike protein) infections are known to stimulate fibrinaloid microclots when added in vitro, and fibrinaloid microclots, as with other amyloid proteins, can be cytotoxic, both by inducing hypoxia/reperfusion and by other means. Strokes and thromboembolisms are also common consequences of AF. Consequently, taking a systems approach, we review the considerable evidence in detail, which leads us to suggest that it is likely that microclots may well have an aetiological role in the development of AF. This has significant mechanistic and therapeutic implications.

A microfluidic model to study the effects of arrhythmic flows on endothelial cells

Atrial fibrillation (AF) is the most common type of cardiac arrhythmia and an important contributor to morbidity and mortality. Endothelial dysfunction has been postulated to be an important contributing factor in cardiovascular events in patients with AF. However, how vascular endothelial cells respond to arrhythmic flow is not fully understood, mainly due to the limitation of current in vitro systems to mimic arrhythmic flow conditions. To address this limitation, we developed a microfluidic system to study the effect of arrhythmic flow on the mechanobiology of human aortic endothelial cells (HAECs). The system utilises a computer-controlled piezoelectric pump for generating arrhythmic flow with a unique ability to control the variability in both the frequency and amplitude of pulse waves. The flow rate is modulated to reflect physiological or pathophysiological shear stress levels on endothelial cells. This enabled us to systematically dissect the importance of variability in the frequency and amplitude of pulses and shear stress level on endothelial cell mechanobiology. Our results indicated that arrhythmic flow at physiological shear stress level promotes endothelial cell spreading and reduces the plasma membrane-to-cytoplasmic distribution of β-catenin. In contrast, arrhythmic flow at low and atherogenic shear stress levels does not promote endothelial cell spreading or redistribution of β-catenin. Interestingly, under both shear stress levels, arrhythmic flow induces inflammation by promoting monocyte adhesion via an increase in ICAM-1 expression. Collectively, our microfluidic system provides opportunities to study the effect of arrhythmic flows on vascular endothelial mechanobiology in a systematic and reproducible manner.

Pathophysiology and clinical relevance of atrial myopathy

Atrial myopathy is a condition that consists of electrical, structural, contractile, and autonomic remodeling of the atria and is the substrate for development of atrial fibrillation, the most common arrhythmia. Pathophysiologic mechanisms driving atrial myopathy are inflammation, oxidative stress, atrial stretch, and neurohormonal signals, e.g., angiotensin-II and aldosterone. These mechanisms initiate the structural and functional remodeling of the atrial myocardium. Novel therapeutic strategies are being developed that target the pathophysiologic mechanisms of atrial myopathy. In this review, we will discuss the pathophysiology of atrial myopathy, as well as diagnostic and therapeutic strategies.

Relationship of Warfarin and Apixaban with Vascular Function in Patients with Atrial Fibrillation

INTRODUCTION

Atrial fibrillation (AF) is associated with endothelial damage/dysfunction. Herein, we tested the hypothesis that brachial artery flow-mediated dilation (FMD) is superior in AF patients taking apixaban compared to warfarin.

METHODS

AF patients on apixaban (n = 46; 67 [7] years; mean [standard deviation]; 15 women) and warfarin (n = 27; 73 [9] years (p < 0.01); 11 women) were recruited. Duplex Doppler ultrasound imaging was undertaken during baseline (2 min), cuff inflation (5 min), and following cuff deflation (3 min). FMD was defined as peak increase in brachial artery diameter following cuff deflation and analysed as percentage change in diameter, as a ratio of FMD, shear rate area under the curve (SRAUC; FMD-to-SRAUC), and using SRAUC as a covariate (FMDSR).

RESULTS

Baseline artery diameter (4.96 [1.14] vs. 4.89 [0.88] mm), peak diameter (5.12 [1.17] vs. 5.14 [0.93] mm), and FMDSR (3.89 [3.62] vs. 4.80 [3.60] %) were not different between warfarin and apixaban (p > 0.05; analysis of covariance with age, CHA2DS2-VASc, years since AF diagnosis, number of diabetics, alcohol drinkers, and units of alcohol consumed per week as covariates). Stepwise multiple regression identified independent association of fibrillation, hypertension, and increased age with FMD.

CONCLUSION

AF patients on warfarin and apixaban exhibit similar endothelium-dependent vasodilation. Increased blood pressure negatively impacts vasodilator capacity in AF patients.

Impaired retinal micro-vascular function in patients with atrial fibrillation

BACKGROUND

Cardiovascular (CV) risk factors and CV diseases, in particular heart failure, are strongly associated with impaired microvascular retinal endothelial function. Whether atrial fibrillation (AF) contributes to vascular dysfunction is not clear. Therefore, the aim of this study was to investigate the impact of AF on retinal microvascular function.

METHODS

In this study, vascular function was measured non-invasively with flicker-light induced vasodilatation of retinal arterioles (FIDart%). Patients with a history of AF and risk factors for heart failure (HF) or heart failure (n = 69; age 67.9 ± 9.2 years, 71% male, 35% HFrEF, 56% paroxysmal, 25% persistent, 19% permanent AF), as well as age, sex and ejection fraction matched patients with absent history of AF (n = 66; age 63.4 ± 10.6 years, 67% male, 47% HFrEF) were included. Patients with AF were further divided into those with paroxysmal AF (in sinus rhythm - AFSR: n = 38, age 71.4 ± 9.2, 73% male), and those with AF at the time of the study visit.

RESULTS

Retinal microvascular function was impaired in patients with AF compared to patients without AF (FIDart% 1.1% [0.3-2.8] vs. 2.7% [1.3-5.1], p < 0.001). Patients currently in AF have poorer retinal microvascular function (FIDart% 0.8% [0.1-1.9) compared to patients with a history of AF but currently in SR at the time of retinal function measurement (1.5% [0.6-4.9] p = 0.017). In patients with AF, impaired retinal vascular function was independently associated with larger left atrial volume (mean 49.8 ± 18.4), even after correction for confounding factors in different models (SCR = -0. 251 to -0.256, p = 0.035-0.01).

CONCLUSIONS

AF in patients with heart failure is associated with impaired vascular function, even if currently in sinus rhythm. The association of retinal microvascular dysfunction with left atrial volume, a surrogate for elevated cardiac filling pressures, may further highlight the important interplay between the vasculature and elevated filling pressures in the development of AF.

Unveiling the Role of Endothelial Dysfunction: A Possible Key to Enhancing Catheter Ablation Success in Atrial Fibrillation

Atrial fibrillation, a prevalent type of arrhythmia, is increasingly contributing to the economic burden on healthcare systems. The development of innovative treatments, notably catheter ablation, has demonstrated both impressive and promising outcomes. However, these treatments have not yet fully replaced pharmaceutical approaches, primarily due to the relatively high incidence of atrial fibrillation recurrence post-procedure. Recent insights into endothelial dysfunction have shed light on its role in both the onset and progression of atrial fibrillation. This emerging understanding suggests that endothelial function might significantly influence the effectiveness of catheter ablation. Consequently, a deeper exploration into endothelial dynamics could potentially elevate the status of catheter ablation, positioning it as a primary treatment option for atrial fibrillation.

Ischemia with Nonobstructive Coronary Artery Disease and Atrial Cardiomyopathy-Two Sides of the Same Story?

Ischemia with nonobstructive coronary artery disease (INOCA) is increasingly recognized as a significant cause of angina, myocardial remodeling, and eventually heart failure (HF). Coronary microvascular dysfunction (CMD) is a major endotype of INOCA, and it is caused by structural and functional alterations of the coronary microcirculation. At the same time, atrial cardiomyopathy (ACM) defined by structural, functional, and electrical atrial remodeling has a major clinical impact due to its manifestations: atrial fibrillation (AF), atrial thrombosis, stroke, and HF symptoms. Both these pathologies share similar risk factors and have a high comorbidity burden. CMD causing INOCA and ACM frequently coexist. Thus, questions arise whether there is a potential link between these pathologies. Does CMD promote AF or the reverse? Which are the mechanisms that ultimately lead to CMD and ACM? Are both part of a systemic disease characterized by endothelial dysfunction? Lastly, which are the therapeutic strategies that can target endothelial dysfunction and improve the prognosis of patients with CMD and ACM? This review aims to address these questions by analyzing the existing body of evidence, offering further insight into the mechanisms of CMD and ACM, and discussing potential therapeutic strategies.

Atrial fibrillation is an independent risk factor for new-onset myocardial infarction: a prospective study

BACKGROUND

Atrial fibrillation (AF) and myocardial infarction (MI) share common cardiovascular risk factors, therefore coexistence of AF and MI is very common, in addition, both AF and MI aggravate and exacerbate each other through multiple pathological processes. The aim of this study is to investigate whether AF increases the risk of new-onset MI.

METHODS

In total 171,086 participants from an industrial city in North China were selected and enrolled in this prospective cohort study, participants were divided into the AF group or the non-AF group according to their medical history. 1542 participants from the AF group were propensity-matched with 4626 participants from the non-AF group. All the participants were followed up every 2 years from June 2006 to December 2020, the median follow-up was 14.25 years and the endpoint of this study was new-onset MI. The association between AF and new-onset MI was analysed by using both univariate and multivariate Cox proportional hazards regression analysis.

RESULTS

New-onset MI was documented in 56 cases from the AF group and 98 cases from the non-AF group, respectively, the cumulative incidence of new-onset MI in the AF group (3.73%) was significantly higher than that in the non-AF group (2.23%) (p < 0.01). In a univariate analysis, AF was associated with an increased risk of new-onset MI (hazard ratio: 1.73, 95% confidence interval: 1.24-2.40), in two multivariable-adjusted analyses, AF was still associated with an increased risk of new-onset MI (hazard ratio: 1.78, 95% confidence interval, 1.28-2.47).

CONCLUSIONS

AF is an independent risk factor for new-onset MI in an industrial population of North China.

Integrated Analysis of the microRNA–mRNA Network Predicts Potential Regulators of Atrial Fibrillation in Humans

Atrial fibrillation (AF) is a form of sustained cardiac arrhythmia and microRNAs (miRs) play crucial roles in the pathophysiology of AF. To identify novel miR–mRNA pairs, we performed RNA-seq from atrial biopsies of persistent AF patients and non-AF patients with normal sinus rhythm (SR). Differentially expressed miRs (11 down and 9 up) and mRNAs (95 up and 82 down) were identified and hierarchically clustered in a heat map. Subsequently, GO, KEGG, and GSEA analyses were run to identify deregulated pathways. Then, miR targets were predicted in the miRDB database, and a regulatory network of negatively correlated miR–mRNA pairs was constructed using Cytoscape. To select potential candidate genes from GSEA analysis, the top-50 enriched genes in GSEA were overlaid with predicted targets of differentially deregulated miRs. Further, the protein–protein interaction (PPI) network of enriched genes in GSEA was constructed, and subsequently, GO and canonical pathway analyses were run for genes in the PPI network. Our analyses showed that TNF-α, p53, EMT, and SYDECAN1 signaling were among the highly affected pathways in AF samples. SDC-1 (SYNDECAN-1) was the top-enriched gene in p53, EMT, and SYDECAN1 signaling. Consistently, SDC-1 mRNA and protein levels were significantly higher in atrial samples of AF patients. Among negatively correlated miRs, miR-302b-3p was experimentally validated to suppress SDC-1 transcript levels. Overall, our results suggested that the miR-302b-3p/SDC-1 axis may be involved in the pathogenesis of AF.

Endothelial function and atrial fibrillation: A missing piece of the puzzle?

Endothelial dysfunction, a term used to describe both the physical damage and dysregulated physiology of this endothelial lining, is an increasingly recognized pathophysiological state shared by many cardiovascular diseases. Historically, the role of endothelial dysfunction in atrial fibrillation (AF) was thought to be limited to mediating atrial thromboembolism. However, there is emerging evidence that endothelial dysfunction both promotes and maintains atrial arrhythmic substrate, predicts adverse outcomes, and identifies patients at high risk of recurrence following cardioversion and ablation therapy. Treatments targeted at improving endothelial function also represent a promising new therapeutic paradigm in AF. This review summarizes the current understanding of endothelial function in AF.

Endothelial dysfunction in patients with lone atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is the most common tachyarrhythmia in patients with cardiovascular diseases (CVDs) and may have significant complications such as stroke. The present study aims to evaluate endothelial dysfunction in patients with lone atrial fibrillation (LAF) through flow-mediated dilation (FMD) in the brachial artery, as a non-invasive method for evaluating functional and structural markers of endothelial dysfunction.

METHODS

In this case-control study, 43 patients with LAF were selected. 51 age and sex-matched healthy individuals were selected as the control group. The brachial artery diameter of the subjects in both groups was measured through FMD. The obtained data were analyzed by SPSS software.

RESULTS

Patients with LAF and healthy subjects did not have any difference in terms of gender, heart rate (HR), and systolic blood pressure (SBP) (P > 0.05 for all). FMD of the patients with AF was significantly lower (P = 0.04) than FMD of the healthy controls.

CONCLUSION

Our findings showed that LAF was associated with systemic endothelial dysfunction. AF plays an important and independent role in reducing FMD.

Blood-brain barrier disruption in atrial fibrillation: a potential contributor to the increased risk of dementia and worsening of stroke outcomes?

Atrial fibrillation (AF) has become one of the most significant health problems worldwide, warranting urgent answers to currently pending questions on the effects of AF on brain function. Recent evidence has emerged to show an association between AF and an increased risk of developing dementia and worsening of stroke outcomes. A healthy brain is protected by the blood–brain barrier (BBB), which is formed by the endothelial cells that line cerebral capillaries. These endothelial cells are continuously exposed to shear stress (the frictional force generated by blood flow), which affects endothelial cell structure and function. Flow disturbances as experienced during AF can disrupt the BBB and leave the brain vulnerable to damage. Investigating the plausible mechanisms in detail, linking AF to cerebrovascular damage is difficult in humans, leading to paucity of available clinical data. Here, we discuss the available evidence for BBB disruption during AF due to altered cerebral blood flow, and how this may contribute to an increased risk of dementia and worsening of stroke outcomes.

Cerebrovascular Dysfunction in Atrial Fibrillation

It is now well established that besides being the most common sustained arrhythmia, atrial fibrillation (AF) is a major healthcare burden. Risk of debilitating stroke is increased in AF patients, but even in the absence of stroke, this population is at heightened risk of cognitive decline, depression, and dementia. The reasons for this are complex, multifactorial, and incompletely understood. One potential contributing mechanism is cerebrovascular dysfunction. Cerebral blood flow is regulated by chemical, metabolic, autoregulatory, neurogenic, and systemic factors. The dysfunction in one or more of these mechanisms may contribute to the elevated risk of cognitive decline and cerebrovascular events in AF. This short review presents the evidence for diminished cerebral blood flow, cerebrovascular carbon dioxide reactivity (i.e., cerebrovascular vasodilatory reserve), cerebral autoregulation, and neurovascular coupling in AF patients when compared to control participants in sinus rhythm. Further work is needed to understand the physiological mechanisms underpinning these observations and their clinical significance in atrial fibrillation patients.

Neurovascular coupling and cerebral autoregulation in atrial fibrillation

The risk of cognitive decline and stroke is increased by atrial fibrillation (AF). We sought to determine whether neurovascular coupling and cerebral autoregulation are blunted in people with AF in comparison with age-matched, patients with hypertension and healthy controls. Neurovascular coupling was assessed using five cycles of visual stimulation for 30 s followed by 30 s with both eyes-closed. Cerebral autoregulation was examined using a sit-stand test, and a repeated squat-to-stand (0.1 Hz) manoeuvre with transfer function analysis of mean arterial pressure (MAP; input) and middle cerebral artery mean blood flow velocity (MCA V_m; output) relationships at 0.1 Hz. Visual stimulation increased posterior cerebral artery conductance, but the magnitude of the response was blunted in patients with AF (18 [8] %; mean [SD]) and hypertension (17 [8] %), in comparison with healthy controls (26 [9] %) (P < 0.05). In contrast, transmission of MAP to MCA V_m was greater in AF patients compared to hypertension and healthy controls, indicating diminished cerebral autoregulation. We have shown for the first time that AF patients have impaired neurovascular coupling responses to visual stimulation and diminished cerebral autoregulation. Such deficits in cerebrovascular regulation may contribute to the increased risk of cerebral dysfunction in people with AF.

A greater burden of atrial fibrillation is associated with worse endothelial dysfunction in hypertension

Atrial fibrillation (AF) and hypertension often co-exist and both are associated with endothelial dysfunction. We hypothesised that AF would further worsen endothelium-dependent flow-mediated dilatation (FMD) in hypertension patients compared to those without AF. In a cross-sectional comparison, we measured brachial artery diameter at rest and during reactive hyperaemia following 5 min of arterial occlusion in two patient groups: AF (and hypertension) (n = 61) and hypertension control groups (n = 33). The AF (and hypertension) subgroups: permanent AF (n = 30) and paroxysmal AF (n = 31) were also assessed. The permanent AF patients received heart rate and blood pressure (BP) control optimisation and were then followed up after eight weeks for repeat FMD testing. There was no significant difference in FMD between AF (and hypertension) group and hypertension control group (4.6%, 95% CI [2.6-5.9%] vs 2.6%, 95% CI [1.9-5.3%]; p = 0.25). There was a significant difference in FMD between permanent AF and paroxysmal AF groups (3.1%, 95% CI [2.3-4.8%] vs 5.9%, 95% CI [4.0-8.1%]; p = 0.02). Endothelium-dependent FMD response showed a non-significant improvement trend following eight weeks of heart rate and BP optimisation (3.1%, 95% CI [2.3-4.8%] (baseline) vs 5.2%, 95% CI [3.9-6.5%] (follow up), p = 0.09). Presence of AF generally does not incrementally worsen endothelial dysfunction in hypertension patients, although the duration and frequency of AF (paroxysmal AF to permanent AF) does lead to worsening endothelial function. Eight weeks of BP optimisation did not significantly improve endothelial dysfunction as measured by FMD.

Inflammatory activation and endothelial dysfunction markers in patients with permanent atrial fibrillation: a cross-sectional study

In recent years a growing body of evidence supported the role of inflammation in the initiation, maintenance and outcome of atrial fibrillation (AF). Nevertheless, despite a large amount of information, whether AF or the underlying structural heart disease (SHD) is the cause of the inflammatory process is still under debate. We, therefore, sought to determine if the inflammatory process reflect an underlying disease or the arrhythmia ‘per se’. We evaluated plasma levels of soluble Interleukin 2 Receptor Alpha (sIL-2Rα), TNF-α and IL-18 in 100 consecutive patients with permanent AF, (43 with a SHD and 57 without a SHD) compared to 121 age and sex-matched controls which had normal sinus rhythm. We also evaluated the endothelial function in both groups of patients using reactive hyperemia index (RHI) values measured by Endo-PAT2000. Compared to controls, AF patients showed higher circulating levels of inflammatory markers and a lower mean value of RHI. At multiple logistic regression analysis, the inflammatory markers and RHI were significantly associated with AF presence, whereas ROC curve analysis had good sensitivity and specificity in inflammatory variables and RHI for AF presence. No significant association was observed in the group of permanent AF patients, between inflammatory markers and the presence of an underlying SHD. These findings could help to clarify the role of inflammation in subjects with AF and suggest that the markers of systemic inflammation are not associated with the underlying cardiovascular disease, rather with the atrial fibrillation ‘per se’.

Endothelial function in patients with atrial fibrillation

Atrial fibrillation (AF) is the most common heart arrhythmia and is associated with poor outcomes. The adverse effects of AF are mediated through multiple pathways, including endothelial dysfunction, as measured by flow-mediated dilatation. Flow-mediated dilatation has demonstrated endothelial dysfunction in several conditions and is associated with poor outcomes including mortality, yet can be improved with medical therapy. It is thus a useful tool in assessing endothelial function in patients. Endothelial dysfunction is present in patients with AF and is associated with poor outcomes. These patients are generally older and have other co-morbidities such as hypertension, hypercholesterolaemia and diabetes. The precise process by which AF is affiliated with endothelial damage/dysfunction remains elusive. This review explores the endothelial structure, its physiology and how it is affected in patients with AF. It also assesses the utility of flow mediated dilatation as a technique to assess endothelial function in patients with AF. Key MessagesEndothelial function is affected in patients with atrial fibrillation as with other cardiovascular conditions.Endothelial dysfunction is associated with poor outcomes such as stroke, myocardial infarction and death, yet is a reversible condition.Flow-mediated dilatation is a reliable tool to assess endothelial function in patients with atrial fibrillation.Patients with atrial fibrillation should be considered for endothelial function assessment and attempts made to reverse this condition.

Accumulated nocturnal hypoxemia predict arterial endothelial function in patients with sleep-disordered breathing with or without chronic heart failure

ABTSRACT

Sleep-disordered breathing (SDB) is often accompanied with the chronic heart failure (CHF). Hypoxemia due to pulmonary congestion from CHF and concurrent SDB might synergistically impair endothelial function and worsen the prognosis. However, the main factors affecting deterioration of endothelial function are unknown and whether the influence of hypoxemia differs in SDB patients with and without CHF remains unclear. Fifty-three patients (CHF group, n = 23; non-CHF group, n = 30) underwent polysomnography to evaluate their SDB and flow-mediated vasodilation (FMD) measurements to assess arterial endothelial function. We examined the relationships between FMD and SDB-related parameters, including our original index of accumulated hypoxemia by SDB throughout one-night sleep: the time desaturation summation index (TDS), calculated as follows: (100% - averaged arterial oxygen saturation during sleep) × total sleep time. The mean age in the CHF and non-CHF groups was 59.0 ± 13.5 and 57.7 ± 11.4 years, respectively. Although the FMD in the 2 groups were not significantly different, well-known adverse factors for FMD such as serum lipid profiles, blood pressure levels, and conventional indices of SDB were worse in the non-CHF group. Only the TDS was not significantly different between 2 groups and associated with FMD as shown by the univariate analysis (CHF: p < 0.05, non-CHF: p < 0.01) and multivariate analysis (CHF: p < 0.05, non-CHF: p < 0.01). Accumulated hypoxemia (TDS) rather than the frequency of hypoxemia might more influence on the endothelial function irrespective of the cardiac state. Removal of accumulation of nocturnal hypoxemia might be a target for treatment equally in the patients with and without CHF.

Deciphering Endothelial Dysfunction in the HIV-Infected Population

Cardiovascular disease (CVD), as a possible consequence of endothelial dysfunction, is prevalent among HIV-infected patients despite successful administration of antiretroviral drugs. This warrants the routine clinical assessment of endothelial function in HIV-positive patients to circumvent potential CVD events. Several different non-invasive strategies have been employed to assess endothelial function in clinical research studies yielding inconsistencies among these reports. This review summarises the different techniques used for assessing endothelial function, with a focus on proposed blood-based biomarkers, such as endothelial leukocyte adhesion molecule-1 (E-selectin), soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), von Willebrand factor (vWF), TNF-α, interleukin 6 (IL6) and soluble thrombomodulin (sTM). The identification of suitable blood-based biomarkers, especially those that can be measured using a point-of-care device, would be more applicable in under-resourced countries where the prevalence of HIV is high.

α-galactosidase A deficiency promotes von Willebrand factor secretion in models of Fabry disease

Fabry disease results from loss of activity of the lysosomal enzyme α-galactosidase A (GLA), leading to the accumulation of globoseries glycosphingolipids in vascular endothelial cells. Thrombosis and stroke are life-threatening complications of Fabry disease; however, the mechanism of the vasculopathy remains unclear. We explored the relationship between GLA deficiency and endothelial cell von Willebrand factor (VWF) secretion in in vivo and in vitro models of Fabry disease. Plasma VWF was significantly higher at two months and increased with age in Gla-null compared to wild-type mice. Disruption of GLA in a human endothelial cell line by siRNA and CRISPR/Cas9 resulted in a 3-fold and 5-fold increase in VWF secretion, respectively. The increase in VWF levels was associated with decreased endothelial nitric oxide synthase (eNOS) activity in both in vitro models. Pharmacological approaches that increase nitric oxide bioavailability or decrease reactive oxygen species completely normalized the elevated VWF secretion in GLA deficient cells. In contrast, the abnormality was not readily reversed by recombinant human GLA or by inhibition of glycosphingolipid synthesis with eliglustat. These results suggest that GLA deficiency promotes VWF secretion through eNOS dysregulation, which may contribute to the vasculopathy of Fabry disease.

Retinal Vascular Geometry and the Prevalence of Atrial Fibrillation and Heart Failure in a Clinic-Based Sample

BACKGROUND

We aimed to examine the cross-sectional association between a range of retinal vascular geometric variables and the prevalence of atrial fibrillation (AF) and heart failure.

METHODS

The Australian Heart Eye Study (AHES) surveyed 1,680 participants presenting to a tertiary referral hospital for the evaluation of potential coronary artery disease by coronary angiography. Retinal vascular geometric variables (tortuosity, branching, and fractal dimension) were measured from retinal photographs using a computer-assisted program (Singapore I Vessel Assessment). Atrial fibrillation was determined based on a combination of: self-reported history of AF; self-reported use of rate-control and anti-arrhythmic medications; and/or screening electrocardiogram. Self-reported echocardiography-confirmed heart failure was also documented.

RESULTS

A total of 1,169 participants had complete information on retinal vascular geometric variables and AF and of these 104 (8.9%) had AF. Participants in the second tertile of fractal dimension (D_f) compared to those in the highest tertile (reference group), had 92% increased likelihood of having AF after multivariable adjustment. A threshold effect for D_f was identified, and participants below versus those above a D_f threshold value of 1.472, had greater odds of having AF: multivariable-adjusted OR 1.85 (95% CI 1.03-3.31). Measures of retinal tortuosity and branching were not associated with AF. Retinal vascular geometric variables were also not associated with prevalence of heart failure.

CONCLUSIONS

A sparser retinal microvascular network (lower D_f) was independently associated with greater likelihood of AF. Further studies are needed to investigate whether temporal changes to the retinal vascular geometry are predictive of AF in the longer term.

Endothelial function changes in paroxysmal atrial fibrillation and treatment with propafenone

Aim. To evaluate the changes of endothelial function in arterial hypertension (AH) patients with paroxysmal atrial fibrillation (AF) in treatment with propafenone (Propanorm, PRO.MED.CS Praha a. s.) in comparison with bisoprolol.

Material and methods. To the study, 62 AH patients included with paroxysmal AH, age 45-63 y. o. (mean age 54,5±3,7 y. o.). Patients were randomized to 2 groups: 32 of group 1 (main) for rhythm-control were taking propafenone (Propanorm, PRO.MED.CS Praha a. s.) 450 mg daily, and 30 of group 2 (comparison) were taking bisoprolol for rate control. The groups were comparable by gender, age, severity of AH and duration of arrhythmia. Changes in endothelium vascular motion function and biochemical markers of endothelial dysfunction were assessed at inclusion and in 12 months of therapy.

Results. Sinus rhythm retention in propafenone group facilitated the improvement of vascular motion function of endothelium — endothelium dependent vasodilatation of brachial artery showed tendency to rise significantly from 5,4±0,3% to 6,9±0,1% (р=0,01). In patients taking bisoprolol for pulse reduction during 12 months, there was negative tendency from 4,8±0,2% to 3,6±0,1% (р=0,003), that points on worsening of endothelial function with persistent AF. Repeat measurement of biochemical markers of endothelial dysfunction revealed that in 12 months there is raise of endothelin concentration in both groups. Value of the collagen-binding activeness of von Willebrand factor in 12 months significantly reduced from 131±12 to 118±6 U/dL (р<0,05) in those retaining sinus rhythm with propafenone, and increased from 135±11 U/dL to 147±12 U/dL in those with rate control by bisoprolol.

Conclusion. In AH patients with paroxysmal AF retention of sinus rhythm with propafenone facilitated the improvement of vascular motion function of endothelium and decrease of collagen binding activeness of von Willebrand factor.

Adverse cardiovascular outcomes in atrial fibrillation: Validation of the new 2MACE risk score

BACKGROUND

In addition to thromboembolism, atrial fibrillation (AF) may also predispose to major adverse cardiovascular events (MACE) attributable to coronary artery disease (CAD), including myocardial infarction (MI). The 2MACE score (2 points - Metabolic syndrome and Age≥75years, 1 point - MI/revascularization, Congestive heart failure/ejection-fraction <40%, and thrombo-Embolism) was recently proposed to help identify AF patients at risk of MACE. We assessed the predictive validity of the 2MACE score for MACE occurrence in AF patients free of CAD at baseline.

METHODS

Non-valvular AF patients (n=794) without CAD (mean-age, 62.5±12.1years, metabolic syndrome, 34.0%; heart failure/ejection-fraction <40%, 25.7%; thromboembolism, 9.7%) were prospectively followed for 5years, or until MACE (composite of non-fatal/fatal MI, revascularization and cardiovascular death). At inclusion, CAD was excluded by medical history, exercise-stress testing and/or coronary angiography. Also, the 2MACE score was determined.

RESULTS

At follow-up, 112 patients experienced MACE (2.8%/year). The 2MACE score demonstrated adequate discrimination (C-statistic, 0.699; 95% confidence interval [CI], 0.648-0.750; P<0.001) and calibration (Hosmer-Lemeshow P=0.79) for MACE. The score was significantly associated with MACE, with the adjusted Hazard Ratio (aHR) of 1.56 (95%CI, 1.35-1.73; P<0.001). As for individual outcomes, the score predicted MI (n=46; aHR, 1.49; 95%CI 1.23-1.80), revascularization (n=32; aHR, 1.41; 95%CI, 1.11-1.80) and cardiovascular death (n=34; aHR, 1.43; 95%CI, 1.14-1.81), all P<0.001.

CONCLUSIONS

The 2MACE score successfully predicts future MACE, including incident MI, coronary revascularization and cardiovascular death in AF patients free of CAD at baseline. It may have a role in risk-stratification and primary prevention of MACE in AF patients.

Preventive effect of rosiglitazone on liver injury in a mouse model of decompression sickness

BACKGROUND AND AIMS

Severe decompression sickness (DCS) is a multi-organ injury. This study investigated the preventive effects of rosiglitazone on liver injury following rapid decompression in mice and examined the underlying mechanisms.

METHODS

Mice were randomly divided into four groups: a control group, vehicle group, and rosiglitazone (5 and 10 mg·kg⁻¹) groups, the latter three being exposed to a pressure of 911 kPa. Haematoxylin and eosin staining, plasma levels of alanine transaminase (ALT), aspartate transaminase (AST) and lactate dehydrogenase and blood cell counts were used to evaluate liver injury at 30 min after rapid decompression. The expression of endothelial and inducible nitric oxide synthase (iNOS) and its phosphorylation were measured to uncover the underlying molecular mechanisms.

RESULTS

A significant increase in plasma ALT, red blood cells and platelets, and a decrease in neutrophils were observed in the vehicle group. Furthermore, the expression of iNOS, E-selectin and the total level of NO in hepatic tissue, and soluble E-selectin in the plasma were significantly elevated in the vehicle group. Rosiglitazone pre-treatment prevented the increases in ALT (and AST), soluble E-selectin concentration, red blood cells and platelet counts. Moreover, rosiglitazone reduced over-expression of iNOS and the NO level, prevented the fall in neutrophil count and promoted the phosphorylation of iNOS in the liver.

CONCLUSIONS

Pre-treatment with rosiglitazone ameliorated liver injury from severe DCS. This preventive effect may be partly mediated by stimulating endothelial NO production, improving endothelial function and limiting inflammatory processes.

Permanent atrial fibrillation impairs the function of circulating endothelial progenitor cells

OBJECTIVE

to determine whether functions of endothelial progenitor cells (EPCs) were impaired in patients with permanent atrial fibrillation (AF).

METHODS

35 patients with permanent AF (AF group) and 35 age and sex matched controls (control group) were collected. The numbers of circulating CD34⁺/KDR⁺ cells were determined with flow cytometry in the two groups. Cell proliferation, tube formation, nitric oxygen (NO) and vascular endothelial growth factor (VEGF) were assayed.

RESULTS

the numbers of CD34⁺/KDR⁺ cells were lower in the AF group than the control group (20.01 ± 12.66 /10⁵ vs 77.93 ± 58.93 /10⁵，p = 0.022). Colony formation unit (CFU) of EPCs were decreased in AF group compared to the control group（1.76 ± 0.59 CFU vs 3.45 ± 0.82 CFU, p = 0.0000). The AF group had lower cell proliferation ability than control group（0.401 ± 0.113 A vs 0.558 ± 0.130 A, p = 0.004). Tube formation ability was decreased in AF patients compared to controls（434.30 ± 96.22μm/mm² vs 568.09 ± 196.17μm/mm²，p = 0.041). AF patients had lower VEGF secretion than controls (27.35 ± 9.93 ng/L vs 41.86 ± 7.31 ng/L，p = 0.001），they also had lower NO secretion than controls（16.55 ± 6.92μmol/l vs 23.65 ± 5.48，p = 0.012).

CONCLUSIONS

proliferation, tube formation and paracrine of EPCs were reduced in patients with permanent AF.

Relations of Arterial Stiffness and Brachial Flow-Mediated Dilation With New-Onset Atrial Fibrillation: The Framingham Heart Study

The relations of measures of arterial stiffness, pulsatile hemodynamic load, and endothelial dysfunction to atrial fibrillation (AF) remain poorly understood. To better understand the pathophysiology of AF, we examined associations between noninvasive measures of vascular function and new-onset AF. The study sample included participants aged ≥45 years from the Framingham Heart Study offspring and third-generation cohorts. Using Cox proportional hazards regression models, we examined relations between incident AF and tonometry measures of arterial stiffness (carotid-femoral pulse wave velocity), wave reflection (augmentation index), pressure pulsatility (central pulse pressure), endothelial function (flow-mediated dilation), resting brachial arterial diameter, and hyperemic flow. AF developed in 407/5797 participants in the tonometry sample and 270/3921 participants in the endothelial function sample during follow-up (median 7.1 years, maximum 10 years). Higher augmentation index (hazard ratio, 1.16; 95% confidence interval, 1.02-1.32; P=0.02), baseline brachial artery diameter (hazard ratio, 1.20; 95% confidence interval, 1.01-1.43; P=0.04), and lower flow-mediated dilation (hazard ratio, 0.79; 95% confidence interval, 0.63-0.99; P=0.04) were associated with increased risk of incident AF. Central pulse pressure, when adjusted for age, sex, and hypertension (hazard ratio, 1.14; 95% confidence interval, 1.02-1.28; P=0.02) was associated with incident AF. Higher pulsatile load assessed by central pulse pressure and greater apparent wave reflection measured by augmentation index were associated with increased risk of incident AF. Vascular endothelial dysfunction may precede development of AF. These measures may be additional risk factors or markers of subclinical cardiovascular disease associated with increased risk of incident AF.

Biomarkers and the prediction of atrial fibrillation: state of the art

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice, and it places a substantial burden on the health care system. Despite improvements in our understanding of AF pathophysiology, we have yet to develop targeted preventive therapies. Recently, numerous biological markers have been identified to aid in the prediction of future AF events. Subclinical markers of atrial stress, inflammation, endothelial dysfunction, kidney dysfunction, and atherosclerosis have been linked to AF. The connection between these markers and AF is the identification of subclinical states in which AF propagation is likely to occur, as these conditions are associated with abnormal atrial remodeling and fibrosis. Additionally, several risk scores have been developed to aid in the identification of at-risk patients. The practicing clinician should be aware of these subclinical markers, as several of these markers improve the predictive abilities of current AF risk scores. Knowledge of these subclinical markers also provides clinicians with a better understanding of AF risk factors, and the opportunity to reduce the occurrence of AF by incorporating well-known cardiovascular disease risk factor modification strategies. In this review, we highlight several novel biological markers that have improved our understanding of AF pathophysiology and appraise the utility of these markers to improve our ability to predict future AF events.

Left ventricular native T1 time and the risk of atrial fibrillation recurrence after pulmonary vein isolation in patients with paroxysmal atrial fibrillation

BACKGROUND

Native T1 mapping has emerged as a noninvasive non-contrast magnetic resonance imaging (MRI) method to assess for diffuse myocardial fibrosis. However, LV native T1 time in AF patients and its clinical relevance are unclear.

METHODS

Fifty paroxysmal AF patients referred for PVI (60 ± 8 years, 37 male) and 11 healthy control subjects (57 ± 8 years, 10 male) were studied. All patients were in sinus rhythm during the MRI scan. Native T1 mapping images were acquired using a Modified Look-Locker imaging (MOLLI) sequence in 3 short-axis planes (basal, mid and apical slices) using an electrocardiogram triggered single-shot acquisition with a balanced steady-state free precession readout. Late gadolinium enhanced (LGE) MRI was acquired to evaluate for LV myocardial scar.

RESULTS

LV ejection fraction was similar between groups (AF: 61 ± 6%; controls: 60 ± 6%, p=0.75). No LV myocardial scar was observed in any patient on LGE. Myocardial native T1 time was greater in AF patients (1099 ± 52 vs 1042 ± 20 msec, p<0.001). During a median follow-up period of 326 days, 18 of 50 (36%) patients experienced recurrence of AF. Multivariate Cox proportional hazard analysis identified elevated native T1 time as an independent predictor of recurrence of AF (HR: 6.53, 95% CI: 1.25-34.3, p=0.026).

CONCLUSIONS

There are differences in the native LV myocardial T1 time between AF patients with preserved LV function referred for PVI and normal controls. Native T1 time is an independent predictor of recurrence of AF after PVI in patients with paroxysmal AF.

Endothelial dysfunction and oxidative stress in children with sleep disordered breathing: role of NADPH oxidase

OBJECTIVE

Oxidative stress plays a crucial role in impairing endothelial function in sleep disordered breathing (SDB) but the underlying mechanism is still undefined. The objective of this study was to evaluate the interplay between oxidative stress, assessed by serum isoprostanes (8-iso-PGF2α) and soluble NOX2-dp (sNOX2-dp), and endothelial function, assessed by flow-mediated dilation (FMD), in children with SDB and healthy controls (HC).

METHODS

One-hundred forty-four children including 45 with primary snoring (PS), 22 with obstructive sleep apnea (OSA) and 67 HC were recruited in this study; in 15 out of 22 OSA children FMD, serum 8-iso-PGF2α and sNOX2-dp were assessed before and after one month post adeno-tonsillectomy (AT).

RESULTS

Compared with HC, OSA and PS children had significantly higher sNOX2-dp and serum 8-iso-PGF2α levels and lower FMD; compared with PS, FMD was significantly lower in OSA children. No significant difference for sNOX2-dp and serum 8-iso-PGF2α was observed between OSA and PS children. FMD was inversely correlated with sNOX2-dp levels (p<0.001) and with serum 8-iso-PGF2α (p<0.001). In multiple linear regression analysis, sNOX2-dp (p<0.001) and serum 8-iso-PGF2α (p<0.001) were the only independent predictive variables associated with FMD. AT significantly decreased sNOX2-dp and serum 8-iso-PGF2α levels (from 38.2±8.8 to 22.4±11.1 pg/ml, p<0.001, and from 281.4±69.7 to 226.0±66.4 pg/ml, p<0.001, respectively); conversely, FMD significantly increased after AT in OSA children (from 3.0±1.5 to 8.0±2.8%, p<0.001).

CONCLUSION

This study suggests that NOX2-derived oxidative stress is involved in artery dysfunction in SDB children. Such hypothesis is reinforced by FMD improvement after AT coincidentally with oxidative stress lowering.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02247167.

Atrial fibrillation: effects beyond the atrium?

Atrial fibrillation (AF) is the most common sustained clinical arrhythmia and is associated with significant morbidity, mostly secondary to heart failure and stroke, and an estimated two-fold increase in premature death. Efforts to increase our understanding of AF and its complications have focused on unravelling the mechanisms of electrical and structural remodelling of the atrial myocardium. Yet, it is increasingly recognized that AF is more than an atrial disease, being associated with systemic inflammation, endothelial dysfunction, and adverse effects on the structure and function of the left ventricular myocardium that may be prognostically important. Here, we review the molecular and in vivo evidence that underpins current knowledge regarding the effects of human or experimental AF on the ventricular myocardium. Potential mechanisms are explored including diffuse ventricular fibrosis, focal myocardial scarring, and impaired myocardial perfusion and perfusion reserve. The complex relationship between AF, systemic inflammation, as well as endothelial/microvascular dysfunction and the effects of AF on ventricular calcium handling and oxidative stress are also addressed. Finally, consideration is given to the clinical implications of these observations and concepts, with particular reference to rate vs. rhythm control.

Von Willebrand Factor Plasma Levels Variability In Nonvalvular Atrial Fibrillation

Atrial Fibrillation (AF) is the most common cardiac arrhythmia of clinical significance; it increases the risk of mortality due to stroke. The mechanisms behind cerebral thromboembolism in AF are associated with a prothrombotic state, demonstrated by higher levels of von Willebrand Factor (vWF), a multimeric glycoprotein that plays a crucial role in platelet adhesion and aggregation and it has been proposed as a biomarker of endothelial dysfunction. Plasma vWF levels are elevated in patients with nonvalvular Atrial Fibrillation (NVAF) associated to the presence of cardiovascular risk factors. The variability in vWF plasma levels in healthy subjects has a wide distribution, but there is no description available of the variability in AF patients and among types of AF. The aim of this study was to determine the variability of vWF plasma concentrations in patients with NVAF, associated to cardiovascular risk factors. Search strategy included PubMed and Ovid. Keywords used were "Atrial Fibrillation" and "von Willebrand Factor". It includes original articles, with analysis of plasma vWF levels by ELISA, without acute stroke. Review articles and meta-analysis were excluded. Reviewed studies include 22 trials and 6542 patients with nonvalvular AF associated to cardiovascular disease risk factors: age, sex, hypertension, heart failure, diabetes mellitus, prior stroke, coronary artery disease. Variability in vWF plasma levels was wide, with minimum values of 77 IU/dl and maximum values of 245 IU/dl and a mean of 146 IU/dl. Age of patients ranged between 54 and 78 years, and the percentage of males ranged between 23% and 80%. According to type of AF vWF levels were as follows, in paroxysmal AF: 92-264 IU/dl; persistent AF: 76-234 IU/dl; permanent AF: 91-247 IU/dl. The variability in vWF plasma levels is affected by risk factors and the AF type, however vWF levels in AF patients are higher when compared with healthy subjects.

Flow-mediated dilation is associated with cardiovascular events in non-valvular atrial fibrillation patients

BACKGROUND

Atrial fibrillation is associated with multiple atherosclerotic risk factors and predisposes to cardiovascular events (CVE). Endothelial dysfunction is associated with atherosclerosis and independently predicts CVE. The aim of the study was to evaluate the association between endothelial dysfunction, as assessed by flow-mediated dilation (FMD), and CVE in AF patients.

METHODS

We prospectively measured FMD in 514 non-valvular AF patients on anticoagulant treatment with vitamin K antagonists. Patients were followed-up for a mean time of 23.5 months. The main composite outcome of the study was the occurrence of stroke/TIA, myocardial infarction, urgent revascularization and cardiovascular death.

RESULTS

Median value of FMD was 4.6% [IQR 1.46-8.00]. A CVE occurred in 44 patients (8.56%):non-fatal myocardial infarction (MI) in 7, fatal MI in 2, stent/coronary artery by-pass graft (CABG) in 10, ischemic non-fatal stroke in 10, fatal stroke in 3, transient ischemic attack (TIA) in 1, and cardiovascular death in 11 patients. Patients who experienced a CVE showed significantly reduced FMD compared to those who did not (3.06% [IQR 0.00-6.00] vs 4.67% [IQR 1.58-8.22], p=0.027). During a mean follow-up of 23.5 months, the rate of CVE was significantly higher in subjects with FMD below median (<4.6%) than in those with FMD above median (27 vs 17, log-rank test p=0.006). COX analysis demonstrated that low FMD (below median) (HR: 2.20, CI 95%:1.13-4.28, p=0.020), age (HR: 1.08, CI 95%: 1.03-1.12, p<0.001), smoking (HR: 4.15, CI 95%: 1.63-10.6, p=0.003) and history of stroke/TIA (HR: 2.38, CI 95%: 1.13-5.04, p=0.023) independently predicted CVE.

CONCLUSIONS

In AF patients low FMD is associated with increased risk of CVE suggesting that impaired artery dilatation predisposes to atherosclerotic complications.

Brachial flow-mediated dilation and incident atrial fibrillation: the multi-ethnic study of atherosclerosis

OBJECTIVE

It is unknown whether endothelial dysfunction precedes atrial fibrillation (AF) development. The objective of this study was to examine the association of brachial flow-mediated dilation (FMD) with incident AF.

APPROACH AND RESULTS

A total of 2936 participants (mean age, 61±9.9 years; 50% women; 66% nonwhites) from the Multi-Ethnic Study of Atherosclerosis with available ultrasound brachial FMD measurements who were free of baseline AF were included in this analysis. Baseline (2000-2002) FMD was computed from the percentage difference (%FMD) in brachial artery diameter and maximum diameter during measured vasodilator response. AF was ascertained from hospitalization data including Medicare claims during a median follow-up of 8.5 years. Probability-weighted Cox proportional-hazards regression was used to compute hazard ratios and 95% confidence intervals for the association between FMD as a continuous variable (%FMD values per 1-SD increase) and incident AF. Incident AF was detected in 137 (4.7%) participants. Those with %FMD values below the sex-specific median value (median %FMD; men, 3.6%; women, 4.2%; incidence rate per 1000 person-years, 7.3; 95% confidence interval, 5.9-9.0) were more likely to develop AF than people whose %FMD values were above the median value (incidence rate per 1000 person-years, 4.5; 95% confidence interval, 3.4-5.8; log-rank P=0.0043). In a multivariable Cox regression analysis, each 1-SD increase in %FMD values (SD, 2.8%) was associated with less incident AF (hazard ratio, 0.84; 95% confidence interval, 0.70-0.99). These results were consistent across subgroups stratified by age, sex, and race/ethnicity.

CONCLUSIONS

Smaller brachial FMD values are associated with higher rates of AF, suggesting a role for endothelial dysfunction in AF pathogenesis.

Endothelial dysfunction in metabolic and vascular disorders

Vascular endothelium has important regulatory functions in the cardiovascular system and a pivotal role in the maintenance of vascular health and metabolic homeostasis. It has long been recognized that endothelial dysfunction participates in the pathogenesis of atherosclerosis from early, preclinical lesions to advanced, thrombotic complications. In addition, endothelial dysfunction has been recently implicated in the development of insulin resistance and type 2 diabetes mellitus (T2DM). Considering that states of insulin resistance (eg, metabolic syndrome, impaired fasting glucose, impaired glucose tolerance, and T2DM) represent the most prevalent metabolic disorders and risk factors for atherosclerosis, it is of considerable scientific and clinical interest that both metabolic and vascular disorders have endothelial dysfunction as a common background. Importantly, endothelial dysfunction has been associated with adverse outcomes in patients with established cardiovascular disease, and a growing body of evidence indicates that endothelial dysfunction also imparts adverse prognosis in states of insulin resistance. In this review, we discuss the association of insulin resistance and T2DM with endothelial dysfunction and vascular disease, with a focus on the underlying mechanisms and prognostic implications of the endothelial dysfunction in metabolic and vascular disorders. We also address current therapeutic strategies for the improvement of endothelial dysfunction.

Predictive value of atrial high-rate episodes for arterial stiffness and endothelial dysfunction in dual-chamber pacemaker patients

BACKGROUND

Various pacing studies have demonstrated an association between right ventricular pacing (RVp) and atrial fibrillation (AF), even after preserving atrioventricular (AV) synchrony. We aimed to assess the interaction between arterial stiffness, endothelial function and atrial high-rate episodes (AHRE) in patients with dual-chamber pacemakers.

METHODS

We studied 101 patients with dual-chamber pacemakers incorporated with sophisticated AF detection and therapy algorithms. Macrovascular endothelial dysfunction (ED) was measured by the relative change in aortic augmentation index (AIx), using carotid artery applanation tonometry in response to inhaled salbutamol and sublingual glyceryl trinitrate. Microvascular ED was measured by cutaneous laser Doppler flowmetry (LDF) in response to acetylcholine (Ach, endothelium dependent) and sodium nitroprusside (SNP, endothelium independent). Arterial stiffness was measured using carotid-femoral pulse wave velocity (PWVcf). 'Reservoir pressure' (Pr, MATLAB) describes the aortic 'cushioning' properties.

RESULTS

Mean age of the cohort was 72.1 ± 10.8 years; men (n = 69) 68.3%. Of 101 dual-chamber pacemaker patients, 23.8% (n = 24) had AHRE detected on the baseline pacemaker interrogation. PP, PWVcf and Pr were significantly higher in patients with AHRE compared with those without AHRE. The change in AIx with salbutamol (∆% AIx Sal) and acetylcholine-induced changes in LDF (Δ%LDF Ach) were lower in patients with AHRE compared with those without AHRE. In patients with AHRE, significant correlations were observed between%Vp and Δ%LDF Ach (P = 0.03) as well as between PP and Δ%LDF Ach (P = 0.05). On multivariate analysis, PP, Pr, PWVcf and ∆% AIx Sal remained as independent predictors of AHRE.

CONCLUSION

In patients with dual-chamber pacemakers, both higher arterial stiffness and greater endothelial dysfunction independently predicted AHRE, irrespective of the degree (or mode) of pacing. Arterial stiffness and endothelial dysfunction may potentially contribute to the perpetuation of atrial arrhythmias beyond the adverse effects of ventricular pacing alone.

Prognostic role of plasma von Willebrand factor and soluble E-selectin levels for future cardiovascular events in a 'real-world' community cohort of patients with atrial fibrillation

BACKGROUND

Endothelial damage/dysfunction may contribute to a prothrombotic state in patients with atrial fibrillation (AF) and the increased risk of thromboembolism and cardiovascular events. Raised plasma von Willebrand factor (vWf), an established marker of endothelial damage/dysfunction, has been associated with stroke and vascular events, at least in a clinical trial population. Soluble E-selectin (sE-sel) is another biomarker of endothelial activation/dysfunction, with more limited data on prognostic outcomes in AF.

OBJECTIVE

To assess the relationship between the levels of vWf, sE-sel and clinical adverse outcomes (including stroke, MI and all-cause mortality) in a 'real-world' community cohort of patients with AF.

METHODS

We studied 423 patients (mean age 72·7 ± 8·4 years, 55·6% male) with nonvalvular AF, with a median follow-up of 19 (9-31) months. Plasma vWf and sE-sel levels were measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

There were 94 clinical adverse events (22·2%) observed during a median follow-up of 19 months. Patients with clinical events had significantly higher vWf (P < 0·001) and sE-sel levels at baseline (P < 0·001) compared with those who were event free. Kaplan-Meir analyses demonstrated that more clinical adverse events occurred in the upper tertile of vWf [upper vs. lowest tertile, RR 3·8, 95% CI (2·63-5·57), P < 0·001; upper vs. middle tertile, RR 10·5, 95% CI (5·33-20·60), P < 0·001]. Similarly, the highest tertile of sE-sel was associated with more adverse events [upper vs. lowest tertile, RR 3·7, 95% CI (2·51-5·31), P < 0·001; upper vs. middle tertile, RR 6·5, 95% CI (3·56-11·91), P < 0·001].

CONCLUSION

High plasma vWf and soluble E-selectin levels are associated with an increased risk of clinical adverse events (acute myocardial infarction, ischaemic stroke and all-cause mortality) in 'real-world' patients with AF. These soluble biomarkers may potentially aid clinical risk stratification in this common arrhythmia.

Atrial fibrillation pacing decreases intravascular shear stress in a New Zealand white rabbit model: implications in endothelial function

Atrial fibrillation (AF) is characterized by multiple rapid and irregular atrial depolarization, leading to rapid ventricular responses exceeding 100 beats per minute (bpm). We hypothesized that rapid and irregular pacing reduced intravascular shear stress (ISS) with implication to modulating endothelial responses. To simulate AF, we paced the left atrial appendage of New Zealand White rabbits (n = 4) at rapid and irregular intervals. Surface electrical cardiograms were recorded for atrial and ventricular rhythm, and intravascular convective heat transfer was measured by microthermal sensors, from which ISS was inferred. Rapid and irregular pacing decreased arterial systolic and diastolic pressures (baseline, 99/75 mmHg; rapid regular pacing, 92/73; rapid irregular pacing, 90/68; p < 0.001, n = 4), temporal gradients ([Formula: see text] from 1,275 ± 80 to 1,056 ± 180 dyne/cm(2) s), and reduced ISS (from baseline at 32.0 ± 2.4 to 22.7 ± 3.5 dyne/cm(2)). Computational fluid dynamics code demonstrated that experimentally inferred ISS provided a close approximation to the computed wall shear stress at a given catheter to vessel diameter ratio, shear stress range, and catheter position. In an in vitro flow system in which time-averaged shear stress was maintained at [Formula: see text] , we further demonstrated that rapid pulse rates at 150 bpm down-regulated endothelial nitric oxide, promoted superoxide (O 2 (.-) ) production, and increased monocyte binding to endothelial cells. These findings suggest that rapid pacing reduces ISS and [Formula: see text] , and rapid pulse rates modulate endothelial responses.