Plasma levels of nitrite/nitrate and platelet cGMP levels are decreased in patients with atrial fibrillation

Coronary microvascular dysfunction, arrythmias, and sudden cardiac death: A literature review

The coronary vascular system has a unique structure and function that is adaptive to myocardial demand. It is composed of a continuous network of vessels receding in size from epicardial arteries to the microvascular circulation. Failure to meet myocardial demand results in ischemia, angina, and adverse myocardial outcomes. It is evident that 50 % of patients with angina have a non-obstructive coronary disease and 66 % of these patients have coronary microvascular dysfunction (CMD). The impact of CMD on the atria and ventricles is exhibited through its association with atrial fibrillation and distortion of ventricular repolarization. Ultimately, this influence increases the risk of mortality, morbidity, and sudden cardiac arrest. CMD serves as an independent risk for atrial fibrillation, increases ventricular electrical inhomogeneity, and contributes to the progression of cardiac disease. The underlying pathogenesis may be attributed to oxidative stress evident through reactive oxygen species, impaired vasoactive function, and structural disorders such as fibrotic changes. Myocardial ischemia, brought about by a demand-supply mismatch in CMD, may create a milieu for ventricular arrythmia and sudden cardiac arrest through distortion of ventricular repolarization parameters such as QT dispersion and corrected QT dispersion.

microRNAs as Biomarkers of Endothelial Dysfunction and Therapeutic Target in the Pathogenesis of Atrial Fibrillation

The pathophysiology of atrial fibrillation (AF) may involve atrial fibrosis/remodeling and dysfunctional endothelial activities. Despite the currently available treatment approaches, the progression of AF, its recurrence rate, and the high mortality risk of related complications underlay the need for more advanced prognostic and therapeutic strategies. There is increasing attention on the molecular mechanisms controlling AF onset and progression points to the complex cell to cell interplay that triggers fibroblasts, immune cells and myofibroblasts, enhancing atrial fibrosis. In this scenario, endothelial cell dysfunction (ED) might play an unexpected but significant role. microRNAs (miRNAs) regulate gene expression at the post-transcriptional level. In the cardiovascular compartment, both free circulating and exosomal miRNAs entail the control of plaque formation, lipid metabolism, inflammation and angiogenesis, cardiomyocyte growth and contractility, and even the maintenance of cardiac rhythm. Abnormal miRNAs levels may indicate the activation state of circulating cells, and thus represent a specific read-out of cardiac tissue changes. Although several unresolved questions still limit their clinical use, the ease of accessibility in biofluids and their prognostic and diagnostic properties make them novel and attractive biomarker candidates in AF. This article summarizes the most recent features of AF associated with miRNAs and relates them to potentially underlying mechanisms.

Dietary exposure to nitrites and nitrates in association with type 2 diabetes risk: Results from the NutriNet-Santé population-based cohort study

BACKGROUND

Nitrites and nitrates occur naturally in water and soil and are commonly ingested from drinking water and dietary sources. They are also used as food additives, mainly in processed meats, to increase shelf life and to avoid bacterial growth. Experimental studies suggested both benefits and harmful effects of nitrites and nitrates exposure on type 2 diabetes (T2D) onset, but epidemiological and clinical data are lacking. We aimed to study these associations in a large population-based prospective cohort study, distinguishing foods and water-originated nitrites/nitrates from those from food additives.

METHODS AND FINDINGS

Overall, 104,168 adults from the French NutriNet-Santé cohort study (2009 to 2021, 79.1% female, mean age [SD] = 42.7 [14.5]) were included. Associations between self-reported exposure to nitrites and nitrates (evaluated using repeated 24-h dietary records, linked to a comprehensive food composition database and accounting for commercial names/brands details of industrial products) and risk of T2D were assessed using cause-specific multivariable Cox proportional hazard models adjusted for known risk factors (sociodemographic, anthropometric, lifestyle, medical history, and nutritional factors). During a median follow-up duration of 7.3 years (interquartile range: [3.2; 10.1] years), 969 incident T2D cases were ascertained. Total nitrites and foods and water-originated nitrites were both positively associated with a higher T2D risk (HRtertile 3 vs.1 = 1.27 (95% CI 1.04 to 1.54), Ptrend = 0.009 and 1.26 (95% CI 1.03 to 1.54), Ptrend = 0.02, respectively). Participants with higher exposure to additives-originated nitrites (i.e., above the sex-specific median) and specifically those having higher exposure to sodium nitrite (e250) had a higher T2D risk compared with those who were not exposed to additives-originated nitrites (HR higher consumers vs. non-consumers = 1.53 (95% CI 1.24 to 1.88), Ptrend < 0.001 and 1.54 (95% CI 1.26 to 1.90), Ptrend < 0.001, respectively). There was no evidence for an association between total, foods and water-originated, or additives-originated nitrates and T2D risk (all Ptrend = 0.7). No causal link can be established from this observational study. Main limitations include possible exposure measurement errors and the lack of validation versus specific nitrites/nitrates biomarkers; potential selection bias linked to the healthier behaviors of the cohort's participants compared to the general population; potential residual confounding linked to the observational design, as well as a self-reported, yet cross-checked, case ascertainment.

CONCLUSIONS

The findings of this large prospective cohort did not support any potential benefits for dietary nitrites and nitrates. They suggested that a higher exposure to both foods and water-originated and additives-originated nitrites was associated with higher T2D risk in the NutriNet-Santé cohort. This study provides a new piece of evidence in the context of current debates about updating regulations to limit the use of nitrites as food additives. The results need to be replicated in other populations.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03335644 (https://clinicaltrials.gov/ct2/show/NCT03335644).

Comparison of frequency of silent cerebral infarction as assessed by serum neuron specific enolase in patients with non-valvular atrial fibrillation: Warfarin versus direct oral anticoagulant

BACKGROUND

Cerebral infarction in patients with atrial fibrillation (AF) may clinically vary from being silent to catastrophic. Silent cerebral infarction (SCI) is the neuronal injury in the absence of clinically appearent stroke or transient ischaemic attack. Serum neuron specific enolase (NSE) is suggested to be a valid surrogate biomarker that allows to detect recent neuronal injury. We aimed to evaluate the incidence of recent SCI by positive NSE levels in patients with non-valvular AF (NVAF) on oral anticoagulants.

METHODS

Blood samples for NSE were collected from 197 consecutive NVAF patients. NSE levels of greater than 12 ng/ml was considered as positive and suggestive of SCI.

RESULTS

Patients were mainly female with a mean age of 69 years. Ninety-eight of them (49.7%) were taking warfarin. Mean INR level was 2.3 ± 0.9. Mean CHA₂DS₂-VASc score of the study population was 3.5 ± 1.5. Seventy-two patients (36.5%) were found to have NSE elevation. They were more likely to have history of chronic heart failure and previous stroke/TIA. Increased left atrial diameter and higher CHA₂DS₂-VASc were other factors associated with SCI. Patients on DOACs and patients taking aspirin on top of oral anticoagulant treatment were less likely to have SCI. Multivariate analysis demonstrated that increased left atrial diameter (OR: 2.5; 95% CI: 1.52-4; p < 0.001) and use of warfarin (OR: 2.8; 95% CI: 1.37-5.61; p = 0.005) were detected as independent predictors of SCI.

CONCLUSIONS

Our study revealed that DOACs were associated with significantly reduced SCIs compared with warfarin, probably due to more effective and consistent therapeutic level of anticoagulation.

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.

Atrial Cardiomyopathy: Pathophysiology and Clinical Consequences

Around the world there are 33.5 million patients suffering from atrial fibrillation (AF) with an annual increase of 5 million cases. Most AF patients have an established form of an atrial cardiomyopathy. The concept of atrial cardiomyopathy was introduced in 2016. Thus, therapy of underlying diseases and atrial tissue changes appear as a cornerstone of AF therapy. Furthermore, therapy or prevention of atrial endocardial changes has the potential to reduce atrial thrombogenesis and thereby cerebral stroke. The present manuscript will summarize the underlying pathophysiology and remodeling processes observed in the development of an atrial cardiomyopathy, thrombogenesis, and atrial fibrillation. In particular, the impact of oxidative stress, inflammation, diabetes, and obesity will be addressed.

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.

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.

Blood Orange Juice Consumption Increases Flow-Mediated Dilation in Adults with Overweight and Obesity: A Randomized Controlled Trial

BACKGROUND

Epidemiological studies have indicated an inverse association between citrus fruit consumption and cardiovascular disease (CVD) risk. There is, however, a paucity of data concerning effects of blood orange juice (BOJ) intake on endothelial function and cardiovascular risk biomarkers.

OBJECTIVES

We examined short-term effects of BOJ on endothelial function, blood pressure, lipid profile, and inflammatory markers in healthy participants of European origin who were overweight or obese.

METHODS

In a randomized, controlled, single-blind, crossover trial, 15 men and women (age: 28.7 ± 6.5 y; BMI: 28.3 ± 3.1 kg/m2) consumed BOJ or a sugar-matched control drink (CD) (200 mL twice daily) for 2 wk with a washout period of 1 wk. Endothelial function, measured as flow-mediated dilation (FMD) (primary outcome), and the secondary outcomes blood pressure, anthropometric measures, lipid profile, inflammatory markers, markers of vasodilation and vasoconstriction, and urinary flavanone metabolites were evaluated prior to and at the end of each treatment period following an overnight fast. Changes between treatments over time were assessed using repeated-measures ANOVA.

RESULTS

The results demonstrate a significant increase in FMD following BOJ consumption (pre: 8.15% ± 2.92%; post: 10.2% ± 3.31%; P = 0.002) compared with CD (pre: 8.11% ± 2.52%; post: 7.77% ± 2.43%; time × treatment interaction: P = 0.001). Concurrent significant increases in urinary hesperetin-3'-glucuronide and hesperetin-7-glucuronide were observed following BOJ supplementation only (time × treatment interaction: P ≤ 0.01). Baseline blood pressure, lipid profile, high-sensitivity C-reactive protein, and endothelin-1 were generally within healthy ranges and unaffected by the intervention.

CONCLUSIONS

A 2-wk consumption of BOJ exerted favorable effects on endothelial function in healthy women and men who were overweight or obese, which is likely mediated by the combined actions of anthocyanin and flavanone metabolites on mechanisms that contribute to enhancing NO bioavailability. This trial was registered at clinicaltrials.gov as NCT03611114.

Fine air pollution particles induce endothelial senescence via redox-sensitive activation of local angiotensin system

Fine dust (FD) is a form of air pollution and is responsible for a wide range of diseases. Specially, FD is associated with several cardiovascular diseases (CVDs); long-term exposure to FD was shown to decrease endothelial function, but the underlying mechanism remains unclear. We investigated whether exposure to FD causes premature senescence-associated endothelial dysfunction in endothelial cells (ECs) isolated from porcine coronary arteries. The cells were treated with different concentrations of FD and senescence associated-beta galactosidase (SA-β-gal) activity, cell cycle progression, expression of endothelial nitric oxide synthase (eNOS), oxidative stress level, and vascular function were evaluated. We found that FD increased SA-β-gal activity, caused cell cycle arrest, and increased oxidative stress, suggesting the premature induction of senescence; on the other hand, eNOS expression was downregulated and platelet aggregation was enhanced. FD exposure impaired vasorelaxation in response to bradykinin and activated the local angiotensin system (LAS), which was inhibited by treatment with the antioxidant N-acetyl cysteine (NAC) and angiotensin II receptor type 1 (AT₁) antagonist losartan (LOS). NAC and LOS also suppressed FD-induced SA-β-gal activity, increased EC proliferation and eNOS expression, and improved endothelial function. These results demonstrate that FD induces premature senescence of ECs and is associated with increased oxidative stress and activation of LAS. This study can serve as a pharmacological target for prevention and/or treatment of air pollution-associated CVD.

Cross-Sectional Associations between Homoarginine, Intermediate Phenotypes, and Atrial Fibrillation in the Community-The Gutenberg Health Study

Homoarginine has come into the focus of interest as a biomarker for cardiovascular disease. Atrial fibrillation (AF) causes a substantial increase in morbidity and mortality. Whether circulating homoarginine is associated with occurrence or persistence of AF and may serve as a new predictive biomarker remains unknown. We measured plasma levels of homoarginine in the population-based Gutenberg health study (3761 patients included, of them 51.7% males), mean age 55.6 ± 10.9 years-old. Associations between homoarginine and intermediate electrocardiographic and echocardiographic phenotypes and manifest AF were examined. Patients with AF (124 patients, of them 73.4% males) had a mean age 64.8 ± 8.6 years-old compared to a mean age of 55.3 ± 10.9 in the population without AF (p-value < 0.001) and showed a less beneficial risk factor profile. The median homoarginine levels in individuals with and without AF were 1.9 μmol/L (interquartile range (IQR) 1.5–2.5) and 2.0 μmol/L (IQR 1.5–2.5), respectively, p = 0.56. In multivariable-adjusted regression analyses homoarginine was not statistically significantly related to electrocardiographic variables. Among echocardiographic variables beta per standard deviation increase was −0.12 (95% confidence interval (CI) −0.23–(−0.02); p = 0.024) for left atrial area and −0.01 (95% CI −0.02–(−0.003); p = 0.013) for E/A ratio. The odds ratio between homoarginine and AF was 0.91 (95% CI 0.70–1.16; p = 0.45). In our large, population-based cross-sectional study, we did not find statistically significant correlations between lower homoarginine levels and occurrence or persistence of AF or most standard electrocardiographic phenotypes, but some moderate inverse associations with echocardiographic left atrial size and E/A. Homoarginine may not represent a strong biomarker to identify individuals at increased risk for AF. Further investigations will be needed to elucidate the role of homoarginine and cardiac function.

Role of the CHADS2 Score in the Evaluation of Carotid Atherosclerosis in Patients with Atrial Fibrillation Undergoing Carotid Artery Ultrasonography

Objective

This study investigated the characteristics of carotid atherosclerosis in patients with atrial fibrillation (AF) and determined the feasibility and significance of the CHADS₂ score in predicting the degree of carotid atherosclerosis.

Methods

Consecutive patients (n = 109) with nonvalvular AF were registered and classified into two groups, the paroxysmal AF group (n = 59) and persistent AF group (n = 50). Fifty healthy patients, matched by sex and age, were considered the control group. All patients were examined using carotid ultrasound and velocity vector imaging (VVI).

Results

Compared with the control group, the mean intimal-medial thickness in the paroxysmal AF group (0.56 ± 0.11 versus 0.61 ± 0.10, respectively, P < 0.05) and the persistent AF group (0.56 ± 0.11 versus 0.64 ± 0.13, respectively, P < 0.001) was significantly increased. The plaque index (PI) in the persistent AF group was significantly higher than that observed in the paroxysmal AF group (1.05 ± 1.33 versus 1.42 ± 1.47, respectively, P < 0.001). Regarding the VVI indices, those reflecting the long-axis longitudinal motion function of carotid arteries were significantly decreased in both AF groups. Compared with the control group, a significantly lower total longitudinal displacement (tLoD) index was observed in the persistent AF group (0.73 ± 0.66 versus 0.31 ± 0.23, respectively, P < 0·0001) and the paroxysmal AF group (0.73 ± 0.66 versus 0.34 ± 0.17, P < 0·0001). The CHADS₂ score was related to indicators reflecting the structure and function of the carotid artery.

Conclusions

Carotid arterial structure and function were significantly altered in patients with AF. The degree of carotid atherosclerosis depended on the duration of AF. The CHADS₂ score may be useful as a predictor of the extent of carotid atherosclerosis in patients with AF.

Plasma Nitrate and Incidence of Cardiovascular Disease and All-Cause Mortality in the Community: The Framingham Offspring Study

BACKGROUND

Nitrate is a dietary component as well as an endogenously formed metabolite and source of the signaling molecule nitric oxide. Harmful as well as beneficial effects of nitrate have been advocated. Data regarding the prognostic relevance of plasma nitrate are limited. The aim of this study was to evaluate the prospective association of plasma nitrate with cardiovascular disease (CVD) and all-cause mortality.

METHODS AND RESULTS

We assayed plasma nitrate in 2855 Framingham Offspring Study participants (mean age 59 years, 54% women) by gas chromatography-mass spectrometry and evaluated its association with all-cause mortality and incident CVD. On follow-up (median 17.3 years), 775 participants died and 522 developed new-onset CVD (of 2546 participants free of CVD at baseline). In multivariable models adjusting for standard risk factors, plasma nitrate was associated with an increased risk of death in participants (hazard ratio per unit increase in log-nitrate 1.21; 95% confidence interval, 1.04-1.40 [P=0.015]). The strength of the association was attenuated by additional adjustment for estimated glomerular filtration rate (hazard ratio, 1.16; 95% confidence interval, 1.00-1.35 [P=0.057]). In contrast, no evidence was found for an association of plasma nitrate with incident CVD (multivariable-adjusted hazard ratio per unit increase log-nitrate 1.08; 95% confidence interval, 0.89-1.31 [P=0.42]).

CONCLUSIONS

In our prospective community-based investigation, a higher plasma nitrate concentration was associated with all-cause mortality but not with incident CVD. The association of nitrate with mortality may at least in part be attributable to its association with renal function.

Post-operative atrial fibrillation examined using whole-genome RNA sequencing in human left atrial tissue

Background

Both ambulatory atrial fibrillation (AF) and post-operative AF (poAF) are associated with substantial morbidity and mortality. Analyzing the tissue-specific gene expression in the left atrium (LA) can identify novel genes associated with AF and further the understanding of the mechanism by which previously identified genetic variants associated with AF mediate their effects.

Methods

LA free wall samples were obtained intraoperatively immediately prior to mitral valve surgery in 62 Caucasian individuals. Gene expression was quantified on mRNA harvested from these samples using RNA sequencing. An expression quantitative trait loci (eQTL) analysis was performed, comparing gene expression between different genotypes of 1.0 million genetic markers, emphasizing genomic regions and genes associated with AF.

Results

Comparison of whole-genome expression between patients who later developed poAF and those who did not identified 23 differentially expressed genes. These included genes associated with the resting membrane potential modified by potassium currents, as well as genes within Wnt signaling and cyclic GMP metabolism. The eQTL analysis identified 16,139 cis eQTL relationships in the LA, including several involving genes and single nucleotide polymorphisms (SNPs) linked to AF. A previous relationship between rs3744029 and MYOZ1 expression was confirmed, and a novel relationship between rs6795970 and the expression of the SCN10A gene was identified.

Conclusions

The current study is the first analysis of the human LA expression landscape using high-throughput RNA sequencing. Several novel genes and variants likely involved in AF pathogenesis were identified, thus furthering the understanding of how variants associated with AF mediate their effects via altered gene expression.

Trial registration

ClinicalTrials.gov ID: NCT00833313, registered 5. January 2009

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-017-0270-5) contains supplementary material, which is available to authorized users.

Predictive Role of Coagulation, Fibrinolytic, and Endothelial Markers in Patients with Atrial Fibrillation, Stroke, and Thromboembolism: A Meta-Analysis, Meta-Regression, and Systematic Review

Background

The pathophysiological mechanism associated with the higher prothrombotic tendency in atrial fibrillation (AF) is complex and multifactorial. However, the role of prothrombotic markers in AF remains inconclusive.

Material/Methods

We conducted a meta-analysis of observational studies evaluating the association of coagulation activation, fibrinolytic, and endothelial function with occurrence of AF and clinical adverse events. A comprehensive subgroup analysis and meta-regression was performed to explore potential sources of heterogeneity.

Results

A literature search of major databases retrieved 1703 studies. After screening, a total of 71 studies were identified. Pooled analysis showed the association of coagulation markers (D-dimer (weighted mean difference (WMD)=197.67 and p<0.001), fibrinogen (WMD=0.43 and p<0.001), prothrombin fragment 1–2 (WMD=0.53 and p<0.001), antithrombin III (WMD=23.90 and p=0.004), thrombin-antithrombin (WMD=5.47 and p=0.004)); fibrinolytic markers (tissue-type plasminogen activator (t-PA) (WMD=2.13 and p<0.001), plasminogen activator inhibitor (WMD=11.44 and p<0.001), fibrinopeptide-A (WMD=4.13 and p=0.01)); and endothelial markers (von Willebrand factor (WMD=27.01 and p<0.001) and soluble thrombomodulin (WMD=3.92 and p<0.001)) with AF.

Conclusions

The levels of coagulation, fibrinolytic, and endothelial markers have been reported to be significantly higher in AF patients than in SR patients.

Platelets Cellular and Functional Characteristics in Patients with Atrial Fibrillation: A Comprehensive Meta-Analysis and Systematic Review

BACKGROUND This systematic review with meta-analysis aimed to determine the strength of evidence for evaluating the association of platelet cellular and functional characteristics including platelet count (PC), MPV, platelet distribution width (PDW), platelet factor 4, beta thromboglobulin (BTG), and p-selectin with the occurrence of atrial fibrillation (AF) and consequent stroke. MATERIAL AND METHODS We conducted a meta-analysis of observational studies evaluating platelet characteristics in patients with paroxysmal, persistent and permanent atrial fibrillations. A comprehensive subgroup analysis was performed to explore potential sources of heterogeneity. RESULTS Literature search of all major databases retrieved 1,676 studies. After screening, a total of 73 studies were identified. Pooled analysis showed significant differences in PC (weighted mean difference (WMD)=-26.93 and p<0.001), MPV (WMD=0.61 and p<0.001), PDW (WMD=-0.22 and p=0.002), BTG (WMD=24.69 and p<0.001), PF4 (WMD=4.59 and p<0.001), and p-selectin (WMD=4.90 and p<0.001). CONCLUSIONS Platelets play a critical and precipitating role in the occurrence of AF. Whereas distribution width of platelets as well as factors of platelet activity was significantly greater in AF patients compared to SR patients, platelet count was significantly lower in AF patients.

Atrial Fibrillation and Risk of ST-Segment-Elevation Versus Non-ST-Segment-Elevation Myocardial Infarction: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

It has recently been reported that atrial fibrillation (AF) is associated with an increased risk of myocardial infarction (MI). However, the mechanism underlying this association is currently unknown. Further study of the relationship of AF with the type of MI (ST-segment-elevation MI [STEMI] versus non-ST-segment-elevation MI [NSTEMI]) might shed light on the potential mechanisms.

METHODS AND RESULTS

We examined the association between AF and incident MI in 14 462 participants (mean age, 54 years; 56% women; 26% blacks) from the Atherosclerosis Risk in Communities (ARIC) study who were free of coronary heart disease at baseline (1987-1989) with follow-up through December 31, 2010. AF cases were identified from study visit ECGs and by review of hospital discharge records. Incident MI and its types were ascertained by an independent adjudication committee. Over a median follow-up of 21.6 years, 1374 MI events occurred (829 NSTEMIs, 249 STEMIs, 296 unclassifiable MIs). In a multivariable-adjusted model, AF (n=1545) as a time-varying variable was associated with a 63% increased risk of MI (hazard ratio,1.63; 95% confidence interval, 1.32-2.02). However, AF was associated with NSTEMI (hazard ratio, 1.80; 95% confidence interval, 1.39-2.31) but not STEMI (hazard ratio, 0.49; 95% confidence interval, 0.18-1.34; P for hazard ratio comparison=0.004). Combining the unclassifiable MI group with either STEMI or NSTEMI did not change this conclusion. The association between AF and MI, total and NSTEMI, was stronger in women than in men (P for interaction <0.01 for both).

CONCLUSIONS

AF is associated with an increased risk of incident MI, especially in women. However, this association is limited to NSTEMI.

Association of hemostatic markers with atrial fibrillation: a meta-analysis and meta-regression

BACKGROUND

There is growing evidence that indicates the presence of a prothrombotic state in atrial fibrillation (AF). However, the role of hemostatic markers in AF remains inconclusive.

METHODS

We conducted a meta-analysis of observational studies to evaluate the association between hemostatic markers and AF. A meta-regression was performed to explore potential sources of heterogeneity.

RESULTS

A total of 59 studies met our inclusion criteria for the meta-analysis. For platelet activation, increased circulating platelet factor-4, β-thromboglobulin (BTG) and P-selectin were significantly higher in AF cases compared with controls (standardized mean difference [SMD][95% confidence interval (CI)]: 1.72[0.96-2.49], 1.61[1.03-2.19] and 0.50[0.23-0.77], respectively). For coagulation activation, increased levels of plasma D-dimer, fibrinogen, thrombin-antithrombin, prothrombin fragment 1+2, and antithrombin-III were significantly associated with AF (SMD[95% CI]: 1.82[1.38-2.26], 0.72[0.55-0.89], 0.42[0.13-0.72], 1.00 [0.00-1.99] and 1.38[0.16-2.60], respectively). For fibrinolytic function, tissue-type plasminogen activator and plasminogen activator inhibitor-1 were significantly increased in AF cases compared with controls (SMD[95% CI]: 0.86[0.04-1.67] and 0.87[0.28-1.47], respectively) but the associations became nonsignificant after performing subgroup analysis by anticoagulants treatment status. For endothelial function, increased von Willebrand factor was significantly associated with AF (SMD, 0.79; 95% CI, 0.60-0.99); however, no association was observed for soluble thrombomodulin (SMD, 0.60; 95% CI, -0.13-1.33).

CONCLUSIONS

Increased circulating hemostatic factors (PF-4, BTG, P-selectin, D-dimer, fibrinogen, TAT, F1+2, AT- III, and vWf) are significantly associated with AF. Future research is necessary to elucidate the precise mechanism of the prothrombotic state and how hemostatic markers promote thromboembolism in AF.

Redox control of cardiac remodeling in atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice and is a potential cause of thromboembolic events. AF induces significant changes in the electrophysiological properties of atrial myocytes and causes alterations in the structure, metabolism, and function of the atrial tissue. The molecular basis for the development of structural atrial remodeling of fibrillating human atria is still not fully understood. However, increased production of reactive oxygen or nitrogen species (ROS/RNS) and the activation of specific redox-sensitive signaling pathways observed both in patients with and animal models of AF are supposed to contribute to development, progression and self-perpetuation of AF.

SCOPE OF REVIEW

The present review summarizes the sources and targets of ROS/RNS in the setting of AF and focuses on key redox-sensitive signaling pathways that are implicated in the pathogenesis of AF and function either to aggravate or protect from disease.

MAJOR CONCLUSIONS

NADPH oxidases and various mitochondrial monooxygenases are major sources of ROS during AF. Besides direct oxidative modification of e.g. ion channels and ion handling proteins that are crucially involved in action potential generation and duration, AF leads to the reversible activation of redox-sensitive signaling pathways mediated by activation of redox-regulated proteins including Nrf2, NF-κB, and CaMKII. Both processes are recognized to contribute to the formation of a substrate for AF and, thus, to increase AF inducibility and duration.

GENERAL SIGNIFICANCE

AF is a prevalent disease and due to the current demographic developments its socio-economic relevance will further increase. Improving our understanding of the role that ROS and redox-related (patho)-mechanisms play in the development and progression of AF may allow the development of a targeted therapy for AF that surpasses the efficacy of previous general anti-oxidative strategies. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation.

Atrial fibrillation and the risk of myocardial infarction

IMPORTANCE

Myocardial infarction (MI) is an established risk factor for atrial fibrillation (AF). However, the extent to which AF is a risk factor for MI has not been investigated.

OBJECTIVE

To examine the risk of incident MI associated with AF.

DESIGN, SETTING, AND PARTICIPANTS

A prospective cohort of 23,928 participants residing in the continental United States and without coronary heart disease at baseline were enrolled from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort between 2003 and 2007, with follow-up through December 2009.

MAIN OUTCOMES AND MEASURES

Expert-adjudicated total MI events (fatal and nonfatal).

RESULTS

Over 6.9 years of follow-up (median 4.5 years), 648 incident MI events occurred. In a sociodemographic-adjusted model, AF was associated with about 2-fold increased risk of MI (hazard ratio [HR], 1.96 [95% CI, 1.52-2.52]). This association remained significant (HR, 1.70 [95% CI, 1.26-2.30]) after further adjustment for total cholesterol, high-density lipoprotein cholesterol, smoking status, systolic blood pressure, blood pressure-lowering drugs, body mass index, diabetes, warfarin use, aspirin use, statin use, history of stroke and vascular disease, estimated glomerular filtration rate, albumin to creatinine ratio, and C-reactive protein level. In subgroup analysis, the risk of MI associated with AF was significantly higher in women (HR, 2.16 [95% CI, 1.41-3.31]) than in men (HR, 1.39 [95% CI, 0.91-2.10]) and in blacks (HR, 2.53 [95% CI, 1.67-3.86]) than in whites (HR, 1.26 [95% CI, 0.83-1.93]); for interactions, P = .03 and P = .02, respectively. On the other hand, there were no significant differences in the risk of MI associated with AF in older (≥75 years) vs younger (<75 years) participants (HR, 2.00 [95% CI, 1.16-3.35] and HR, 1.60 [95% CI, 1.11-2.30], respectively); for interaction, P = .44.

CONCLUSIONS AND RELEVANCE

AF is independently associated with an increased risk of incident MI, especially in women and blacks. These findings add to the growing concerns of the seriousness of AF as a public health burden: in addition to being a well-known risk factor for stroke, AF is also associated with increased risk of MI.

Inhibition of nitric oxide and antiphospholipid antibody-mediated thrombosis

The antiphospholipid syndrome (APS) is characterized by recurrent vascular thrombosis, thrombocytopenia, and fetal loss occurring in the presence of antiphospholipid antibodies (aPL). Along with arterial and venous thrombosis and pregnancy complications, patients with APS have an increased risk of myocardial infarction, stroke, and coronary artery disease, resulting from vascular cell dysfunction induced by aPL. Accumulating evidence to date indicates that interactions between circulating aPL and cell surface molecules of target cells, primarily endothelial cells and platelets, underlie the vascular disease phenotypes of APS. However, the molecular basis of APS is poorly understood. Nitric oxide produced by endothelial cells is a key determinant of vascular health that regulates several physiologic processes, including thrombosis, endothelial-leukocyte interaction, vascular cell migration, and the modulation of vascular tone. This review will discuss recent findings that indicate a novel mechanism by which aPL antagonize endothelial cell production of nitric oxide and thereby promote thrombosis.

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.

Tackling endothelial dysfunction by modulating NOS uncoupling: new insights into its pathogenesis and therapeutic possibilities

Endothelial nitric oxide synthase (eNOS) serves as a critical enzyme in maintaining vascular pressure by producing nitric oxide (NO); hence, it has a crucial role in the regulation of endothelial function. The bioavailability of eNOS-derived NO is crucial for this function and might be affected at multiple levels. Uncoupling of eNOS, with subsequently less NO and more superoxide generation, is one of the major underlying causes of endothelial dysfunction found in atherosclerosis, diabetes, hypertension, cigarette smoking, hyperhomocysteinemia, and ischemia/reperfusion injury. Therefore, modulating eNOS uncoupling by stabilizing eNOS activity, enhancing its substrate, cofactors, and transcription, and reversing uncoupled eNOS are attractive therapeutic approaches to improve endothelial function. This review provides an extensive overview of the important role of eNOS uncoupling in the pathogenesis of endothelial dysfunction and the potential therapeutic interventions to modulate eNOS for tackling endothelial dysfunction.

Platelet nitric oxide signaling system in patients with coronary artery disease

BACKGROUND

Coronary artery disease (CAD) is the leading cause of death worldwide, and the major cause of hospital admissions in the Western countries. The pathogenesis of CAD is closely related to nitric oxide release and formation. The purpose of this study was to investigate the status of platelets nitric oxide in patients with coronary artery disease.

METHODS

We measured platelets aggregation, cGMP, NO (nitrite/nitrate level), NO synthase activity, plasma NO, and ionized Ca(2+) in 40 healthy volunteers and 120 patients with myocardial infarction, unstable and stable angina, with 40 subjects in each group. The subjects' age mean range was from 40-51 years.

RESULTS

Platelets aggregation, NO, cGMP, NO synthase activity, plasma NO and ionized Ca(2+) have increased significantly (P <0.001) across the patients groups compared to controls. Platelets NO synthase activity (mean ± SD / U / 10(9) platelets) in healthy controls, MI, unstable angina and stable angina patients were 1.19 ± 0.56, 1.21 ± 0.64, 1.64 ± 0.98 and 1.57 ± 0.81 respectively. The cGMP (mean ± SD / pmole / 10(9) platelets) levels were 0.95 ± 0.41, 1.53 ± 0.64, 3.18 ± 0.77, and 5.12 ± 1.5 respectively.

CONCLUSIONS

The present study demonstrated that platelets aggregation, NO, cGMP, NO synthase activity, plasma NO, and ionized Ca(2+) profoundly increased in CAD. The increases in NO-cGMP components may have resulted as a compensatory response to ameliorate platelet activity and Ca(2+) levels in CAD patients.

Effect of Waon therapy on oxidative stress in chronic heart failure

BACKGROUND

A previous report by our team showed that Waon therapy, using a far infrared-ray dry sauna at 60°C, improves cardiac and vascular function in patients with chronic heart failure (CHF). The purpose of the present study was to clarify the effect of Waon therapy on oxidative stress in CHF patients and investigate its mechanism by animal experiments.

METHODS AND RESULTS

Forty patients with CHF were divided into control (n=20) and Waon therapy (n=20) groups. All patients received standard optimal medications for CHF. Waon therapy group was treated with Waon therapy daily for 4 weeks. After 4 weeks of Waon therapy, concentrations of hydroperoxide and brain natriuretic peptide (BNP) decreased significantly (hydroperoxide, 422±116 to 327±88U.CARR, P<0.001; BNP, 402±221 to 225±137pg/ml, P<0.001), and the nitric oxide metabolites increased (71.2±35.4 to 92.0±40.5mmol/L, P<0.05). In contrast, none of these variables changed over the 4-week interval in the control group. Furthermore, animal experiments were performed using TO-2 cardiomyopathic hamsters. On immunohistochemistry, cardiac expression of 4-hydroxy-2-nonenal, a marker of oxidative stress, was decreased in the 4-week Waon therapy compared to untreated hamsters. On Western blotting, cardiac expressions of heat shock protein (HSP) 27, manganese superoxide dismutase and HSP32, which reduce oxidative stress, were significantly upregulated in the 4-week Waon therapy compared to untreated hamsters.

CONCLUSIONS

Waon therapy decreases oxidative stress in patients and hamsters with heart failure.

Lysophosphatidic acid level and the incidence of silent brain infarction in patients with nonvalvular atrial fibrillation

Lysophosphatidic acid (LPA), which is proposed to play an important role in normal physiological situations such as wound healing, vascular tone, vascular integrity and reproduction, may be involved in the etiology of some diseases such as atherosclerosis, cancer, obesity or myocardial infarction. Abnormal findings, including silent brain infarction (SBI), are frequently observed by magnetic resonance imaging (MRI) in patients with nonvalvular atrial fibrillation (NVAF). However, whether there is a relationship between LPA level and the prevalence of SBI has not been extensively studied. In the present study, the association between them was investigated. 235 patients with NVAF, 116 cases of SBI without NVAF and 120 cases of healthy volunteers (control group), who did not receive any antithrombotic therapy, were enrolled in this study. Plasma LPA levels in the NVAF with SBI group were significantly higher than that in the control group (p < 0.01), NVAF without SBI group (p < 0.01) and SBI without NVAF group (p < 0.01). The LPA levels are lower in the control group than in the NVAF without SBI and SBI without NVAF groups (p < 0.01), however, the latter two groups did not significantly differ from each other for LPA levels (p > 0.05) There were significant differences in the positive rate of platelet activation between each of the groups (p < 0.01). The positive rate of platelet activation was significantly higher in the NVAF with SBI group. We suggest that LPA might be a novel marker for estimation of the status of platelet activation and the risk factor for SBI onset in NVAF patients. We expected that plasma LPA levels could predict the occurrence of SBI in NVAF patients.

Risk of "silent stroke" in patients older than 60 years: risk assessment and clinical perspectives

With the increasing size of the elderly population and evolving imaging technology, silent brain infarction (SBI) has garnered attention from both the public and the physicians. Over 20% of the elderly exhibit SBI, and the prevalence of SBI increases steadily with age, ie, 30%–40% in those older than 70 years. Well-known cardiovascular risk factors such as hypertension has been identified as a risk factor of SBI (odds ratio [OR] = 3.47) Besides this, blood pressure (BP) reactivity to mental stress, morning BP surges, and orthostatic BP changes have been demonstrated to contribute to the presence of SBI. Further, a metabolic syndrome not only as a whole syndrome (OR =2.18) but also as individual components could have an influence on SBI. Increased C-reactive protein and interleukin-6, coronary artery disease, body mass index, and alcohol consumption have also been associated with SBI. The ORs and possible mechanisms have been discussed in this article. Overt stroke, dementia, depression, and aspiration pneumonia were all associated with SBI. (overt stroke: hazard ratio [HR] =1.9, 95% confidence interval [CI]: 1.2–2.8; dementia: HR =2.26, 95% CI: 1.09–4.70). We also looked into their close relationship with SBI in this review.

Systemic vascular cell adhesion molecule-1 predicts the occurrence of post-operative atrial fibrillation

BACKGROUND

Post-operative atrial fibrillation occurs in 30% of patients after on-pump heart surgery and is associated to elevated inflammatory markers. We have evaluated if the systemic biomarkers of inflammation and endothelial damage, vascular cell adhesion molecule-1 (VCAM-1) and soluble thrombomodulin may help in identifying patients prone to development of post-operative atrial fibrillation.

METHODS

One hundred and forty-four patients in sinus rhythm submitted to elective coronary artery bypass surgery. Systemic inflammatory, oxidative stress and endothelial damage markers were measured at baseline and 72 h after surgery. During the procedure, a sample of the right atrial appendage was obtained for histochemistry. Electrocardiogram was monitored for 72 h after surgery for event adjudication.

RESULTS

22% of the patients developed post-operative atrial fibrillation. Baseline systemic inflammatory markers did not differ between patients with or without post-operative atrial fibrillation. However, baseline plasma VCAM-1 and thrombomodulin levels were significantly higher in patients who developed post-operative atrial fibrillation. After adjustment for age, gender, comorbidities and concurrent medication, circulating VCAM-1 remained as an independent predictor for post-operative atrial fibrillation development. No association was observed between systemic plasma VCAM-1 and VCAM-1 tissue expression in the right atrial appendage.

CONCLUSIONS

In patients undergoing coronary artery bypass surgery, elevated VCAM-1 levels predict a higher risk for post-operative atrial fibrillation. Plasma VCAM-1 elevation is not related to its expression in the right atria, suggesting that systemic endothelial damage rather than local changes pre-exist in patients who develop the arrhythmia.

Elevated plasma concentration of NO and cGMP may be responsible for the decreased platelet aggregation and platelet leukocyte conjugation in platelets hypo-responsive to catecholamines

Impaired responsiveness to epinephrine and other catecholamines (CA) were previously reported in platelets of 20 approximately 30% healthy Japanese and Koreans. In the present study, the possible mechanisms of different responsiveness to CA in platelets of CA hypo-responders (CA-HY) and CA good-responders (CA-GR) were investigated. Increased platelet-leukocyte conjugate (PLC) formations were observed with whole blood of CA-GR than with that of CA-HY in both non-stimulated [mean fluorescence intensity (MFI) values: 1.33 +/- 0.26 vs. 1.16 +/- 0.19] and ADP (MFI: 5.54 +/- 3.46 vs. 2.15 +/- 1.13) or TRAP (MFI: 5.11 +/- 2.32 vs. 3.38 +/- 1.47) activated states. The platelets of CA-GR, when stimulated with ADP (10 microM), released approximately twice the amount of ATP than those of CA-HY (0.88 +/- 0.65 and 0.45 +/- 0.36 nmole, respectively). Nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) levels were significantly higher in non-stimulated PRP of CA-HY than in that of CA-GR (70.3 +/- 24.1 microM and 14.1 +/- 4.9 nM vs. 41.1 +/- 15.8 microM and 6.7 +/- 2.4 nM, respectively). The platelet-monocyte conjugation induced with either ADP or TRAP was significantly reduced in CA-GR with the addition of linsidomine, a NO donor, (MFI: 2.78 +/- 0.43 vs. 3.73 +/- 0.90, or 4.28 +/- 0.95 vs. 5.76 +/- 1.33, respectively). Moreover, the degree of platelet aggregation and the ATP secretion induced by epinephrine in CA-GR were significantly retarded with the addition of either linsidomine or 8-Bromo-cGMP (a cGMP analog) with more substantial effects on ATP release than aggregation. The results suggested that elevated NO and/or cGMP plasma levels may be responsible for the lower platelet aggregation and PLC formation observed in CA-HY than that in CA-GR.

Nitric oxide overproduction derived from inducible nitric oxide synthase increases cardiomyocyte apoptosis in human atrial fibrillation

BACKGROUND

Inflammation and oxidant stress have been suggested to be involved in the structural remodeling in atrial fibrillation (AF), and inducible nitric oxide synthase (iNOS) is associated with inflammation and oxidant stress. To study whether iNOS could contribute to atrial remodeling in AF, we investigated the relationship between inflammation, oxidant stress, nitric oxide (NO) and its synthase, and cardiomyocytic apoptosis in the right atrium in human AF.

METHODS

Fifteen patients with permanent AF (PmAF) and 17 patients with sinus rhythm (SR), who underwent mitral valve replacement surgery were investigated. Western blotting and immunohistochemical staining were used to detect the expression of endothelial nitric oxide synthase (eNOS), iNOS and 3-nitrotyrosine (3NT; a biological marker of peroxynitrite) in the right atrium. The occurrence of cardiomyocytic apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL). Caspase 3 staining for the activated, cleaved protease was also performed. In addition, concentrations of NO(2)(-)/NO(3)(-) (NO(X)) both in plasma and in the right atrium were measured by a NO(X) Detection Kit. Finally, plasma levels of high-sensitivity C-reactive protein (hs-CRP) were routinely measured.

RESULTS AND CONCLUSIONS

Levels of hs-CRP were far more enhanced in patients with PmAF compared to the controls. Plasma levels of NO(X) were significantly lower in PmAF patients than SR patients, but the production of NO(X) in the local right atrium increased obviously. Furthermore, iNOS and 3NT expressions increased dramatically in the right atrium in PmAF patients, whereas the expression of eNOS did not change apparently. In addition, when patients were further divided into a higher hs-CRP group (> or =5 mg/L) and a lower hs-CRP group (<5 mg/L) according to the hs-CRP level, significant upregulation of iNOS was found in the higher hs-CRP group. Apoptosis index and caspase 3 staining were also prominently enhanced in PmAF patients compared with SR patients. More importantly, we demonstrated in this study that a higher expression of 3NT was associated with an increased expression of iNOS/eNOS (r=0.74, P<0.05) and an enhanced apoptosis index (r=0.69, P<0.05). In conclusion, the results presented novel evidence that imbalanced expression of iNOS/eNOS could contribute to protein nitration and cardiomyocyte apoptosis in human AF, in which condition inflammation may be an important participant.

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

BACKGROUND

Impaired endothelial-dependent flow-mediated dilatation (FMD) has been used to demonstrate endothelial dysfunction in a wide variety of cardiovascular disease, but previous studies have excluded patients with atrial fibrillation(AF). We therefore hypothesised that endothelial dysfunction exists in AF and that this could be demonstrated by impaired FMD, and related to plasma indices of endothelial damage/dysfunction [soluble E-selectin (sE-sel), von Willebrand factor (vWf), and soluble thrombomodulin (sTM)], as well as total body nitrate/nitrite product (NOx, a measure of endothelial nitric oxide production).

METHODS

We studied 40 patients with chronic permanent AF, who were compared to 26 sinus rhythm controls. Patients with AF were stable on rate-control and antithrombotic medication and were fasted for the study. High-resolution ultrasound was used to measure right brachial artery diameter at rest, during reactive hyperaemia (endothelium-dependent flow-mediated dilatation) and following endothelium-independent, GTN-mediated dilatation.

RESULTS

Baseline brachial artery diameter did not differ significantly between AF and healthy control subjects. FMD was significantly impaired in AF patients in comparison to healthy controls (8.9% in controls vs 0.0% in AF, p<0.0001). There was no significant difference in endothelium-independent (GTN-induced) dilatation between the groups. Only AF and male sex were independent predictors of impaired FMD on stepwise multiple regression analysis(p<0.0001). sE-sel and vWf were higher in AF than controls (p<0.05), and NOx levels did not reach significance (p=0.1416).

CONCLUSIONS

Endothelial dysfunction, as demonstrated by impairment of FMD and raised vWF and E-selectin, is present in AF. Such endothelial perturbation may contribute to the increased risk of stroke and thromboembolism in this common arrhythmia.

Soluble E-selectin, von Willebrand factor, soluble thrombomodulin, and total body nitrate/nitrite product as indices of endothelial damage/dysfunction in paroxysmal, persistent, and permanent atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is associated with a prothrombotic state, which is related to endothelial damage/dysfunction. Plasma levels of soluble E-selectin (sE-sel), von Willebrand factor (vWf), and soluble thrombomodulin (sTM) have been used as indexes of endothelial activation, damage/dysfunction, and endothelial damage, respectively. Nitric oxide is also made by a healthy endothelium, and a total body nitrate/nitrite product (NOx) is used as a measure of endothelial nitric oxide production. We hypothesized that the levels of these markers of endothelial function would be abnormal in patients with paroxysmal, persistent, and permanent AF.

METHODS

We studied 145 AF patients (paroxysmal AF, 35 patients; permanent AF, 50 patients; persistent AF, 60 patients) and 35 patients with "lone" AF. Plasma levels of sE-sel, vWf, and sTM (measured by enzyme-linked immunosorbent assay) and NOx (measured by a colorimetric assay based on the Griess reaction) were compared to 40 age-matched healthy control subjects in sinus rhythm.

RESULTS

Patients with AF had significantly higher plasma levels of vWf (p < 0.001) and sE-sel (p = 0.005) compared with control subjects, but sTM and NOx levels were not significantly different. Levels did not differ significantly among the clinical subgroups of patients with paroxysmal, persistent, and permanent AF. Patients with lone AF had significantly higher vWF levels (p = 0.003) and significantly lower sTM levels (p = 0.0361) compared to control subjects, but sE-sel and NOx levels were not significantly different. There were no significant differences in the AF study population in vWF, sE-sel or sTM levels after 4 weeks of warfarin treatment.

CONCLUSION

Endothelial perturbation exists in all clinical subgroups of patients with AF, including those with lone AF, which may contribute to the prothrombotic state seen in these patients.

Endothelial cell function during atrial fibrillation and after restoration of sinus rhythm

Beat-to-beat variation in blood flow dynamics during atrial fibrillation (AF) has been associated with evidence of endothelial dysfunction. The aim of the present work is to confirm endothelial dysfunction in patients with AF and test the hypothesis that endothelial dysfunction is reversible upon restoration of normal sinus rhythm. Endothelium-dependent (flow-mediated dilation [FMD]) and endothelium-independent (nitroglycerin-mediated dilation [NMD]) vasodilator function of the brachial artery were measured using high-resolution ultrasound in 46 patients with persistent AF who were scheduled for internal electrical cardioversion and in 25 control subjects. In patients who remained in sinus rhythm after cardioversion, these measurements were repeated after 24 hours (n = 32) and 1 month (n = 19). Compared with control subjects, patients (n = 32) showed lower FMD during AF (8.1 +/- 3.6% vs 12.2 +/- 3.2%, respectively, p <0.001) and similar NMD (17.0 +/- 3.5% vs 15.9 +/- 3.1%, respectively, p = 0.21). In 19 patients who remained in sinus rhythm, FMD increased at both 24 hours (8.0 +/- 3.9% vs 10.6 +/- 4.6%, p = 0.015) and 1 month (8.0 +/- 3.9% vs 13.6 +/- 5.3%, p <0.001). In contrast, NMD was not significantly altered at 24 hours or 1 month after sinus rhythm restoration (17.1 +/- 3.9% vs 17.2 +/- 4.0% vs 16.9 +/- 4.1%). In conclusion, AF is associated with impairment in endothelial function that improves after sinus rhythm restoration.

Effects of cardioversion of atrial fibrillation on endothelial function in hypertension or diabetes

BACKGROUND

Cardioversion (CV) to sinus rhythm corrects endothelial dysfunction secondary to atrial fibrillation (AF). As AF often complicates hypertension and diabetes (disorders associated with impaired endothelial function) the study probed whether these comorbidities to AF produced an additive effect and to what extent CV might be advantageous.

MATERIALS AND METHODS

Brachial artery flow-mediated dilatation (FMD) was evaluated before and after CV in 17 lone AF patients (group 1), 16 patients with AF + hypertension (group 2) and 17 patients with AF + diabetes type II (group 3), while in supine and head-up tilting (HUT) positions, as this is when endothelial vasodilation is emphasized as a counterbalance to neurogenic vasoconstriction.

RESULTS

After 2 weeks, CV in group 1 increased (P < 0.01) supine FMD (from 7.22-->9.50%) and restored its HUT potentiation (from 9.31-->17.22%). In group 2, FMD also improved significantly with CV (supine from 4.92-->7.11% and HUT from 5.29-->11.83%; P < 0.01). In group 3, CV did not promote significant FMD changes (supine from 5.12-->4.92% and HUT from 4.98-->4.73%). After 3 months, FMD improvement persisted in groups 1 and 2 with enduring sinus rhythm, but not in those with AF relapse. In group 3, FMD remained unchanged regardless of cardiac rhythm.

CONCLUSIONS

Cardioversion persistently increases supine shear stress endothelial responsiveness and restores the orthostatic modulation in AF alone or in association with hypertension, but not with diabetes. Differences in background endothelial impairment may explain the presence (hypertension) or the absence (diabetes) of an additive AF effect in comorbidities, as well as CV results.

Acute anticoagulation adjustment in patients with atrial fibrillation at risk for stroke: approaches, strategies, risks and benefits

The acute management of anticoagulation in patients with atrial fibrillation to prevent stroke and other thromboembolic complications includes the use of individualized strategies tailored to the patient and based on the situation (cardioversion, surgeries, dental procedures, cardiac interventions, other invasive procedures and initiation of, or adjustment to, warfarin dosing). The vast range of choices can cause confusion and few randomized controlled clinical trials in this area provide adequate guidance. Chronic anticoagulation management is more straightforward since clinical evidence is ample, randomized clinical trial data provides cogent informaiton and guidelines have been established. Acute management of anticoagulation in patients with atrial fibrillation to prevent thromboembolic complications is often unrecognized but is emerging as a crucial, but challenging, and increasingly complex aspect of the care of patients with atrial fibrillation. This review addresses issues regarding such patients who may be at risk for stroke and require acute adjustments of anticoagulation (in light of, or in lieu of, chronic anticoagulation). Several promising new strategies are considered in light of established medical care. This analysis provides practical recommendations based on available data and presents results from recent investigations that may provide insight into future strategies.

ESR techniques for the detection of nitric oxide in vivo and in tissues

Plasma levels of nitrite/nitrate may not accurately reflect endothelial nitric oxide synthase (eNOS) function because of interference by dietary nitrates. Nitrosyl hemoglobin (HbNO), a metabolic product of nitric oxide (NO*), may better correlate with bioavailable NO*, but it may depend on the activity of different NOS isoforms and may be affected by dietary nitrite/nitrate. This work examined the correlation between vascular endothelial NO* release and blood levels of HbNO. We measured HbNO in mouse blood using electron spin resonance (ESR) spectrometry, and we quantified vascular production of NO* using colloid Fe(DETC)2 and ESR. C57Blk/6 mice who were fed a high-nitrate diet had levels of plasma HbNO increased 10-fold, whereas those fed a low-nitrate diet had decreased HbNO levels from 0.58 +/- 0.02 to 0.48 +/- 0.01 microM. Therefore, a low-nitrate diet is essential when using HbNO as a marker of eNOS activity. Treatment with L-NAME and the eNOS-specific inhibitor L-NIO halved HbNO formation, which reflects the complete inhibition of NO* release by aorta endothelium. Treatment of mice with the selective inducible NOS (iNOS) inhibitor, 1400W, or the selective neuronal NOS (nNOS) inhibitor N-AANG did not alter either blood HbNO levels or vascular NO*. The relationship between HbNO and NO* production by the endothelium (0.23 microM HbNO to 5.27 microM/h of NO*/mg of dry weight aorta) was found to be identical for both C57Blk/6 mice and mice with vascular smooth muscle-targeted expression of p22phox associated with strong increase in eNOS activity. These results support the important role of eNOS in the formation of circulating HbNO, whereas iNOS and nNOS do not contribute to HbNO formation under normal conditions. These data suggest that HbNO can be used as a noninvasive marker of endothelial NO* production in vivo.