Atrial fibrillation impairs endothelial function of forearm vessels in humans

Progressive increase in vascular access blood flow after percutaneous transluminal angioplasty in patients on hemodialysis

Percutaneous transluminal angioplasty (PTA) is the gold standard for treating stenoses with dysfunctional vascular access. Recently, we found that vascular access blood flow (VABF) measured immediately after PTA increased over time without the need for additional procedures in the patients who underwent PTA. Therefore, this study was conducted to confirm an increase in VABF after PTA and identify the factors associated with it. Patients on chronic hemodialysis at a single institution were retrospectively reviewed and those with accesses that had a measurement of VABF immediately after PTA and within 1 month from PTA were included in the study. The relationship between clinical parameters and changes in VABF were analyzed using paired t-test and linear regression. A total of 47 PTA accesses (fistulas, 26; grafts,21) were included. The mean VABF on the day of PTA and the following measurement were 796.9 ± 329.1 mL/min and 1105.1 ± 410.3 mL/min, respectively. In the univariate analysis, the diameter of the balloon catheter used in the PTA and serum uric acid (SUA) level were significantly associated with an increase in VABF. Atrial fibrillation was a significant factor for the percentage change in vascular access. In the multivariate analysis, SUA level, balloon catheter diameter, and atrial fibrillation remained independent factors for changes in VABF and percentage change in VABF, respectively. The study identified progressive increases in the VABF after PTA without additional procedures. SUA level, balloon catheter diameter used in PTA, and atrial fibrillation were independently associated with changes in VABF.

Mechanisms of Quercetin against atrial fibrillation explored by network pharmacology combined with molecular docking and experimental validation

Atrial fibrillation (AF) is a common atrial arrhythmia for which there is no specific therapeutic drug. Quercetin (Que) has been used to treat cardiovascular diseases such as arrhythmias. In this study, we explored the mechanism of action of Que in AF using network pharmacology and molecular docking. The chemical structure of Que was obtained from Pubchem. TCMSP, Swiss Target Prediction, Drugbank, STITCH, Pharmmapper, CTD, GeneCards, DISGENET and TTD were used to obtain drug component targets and AF-related genes, and extract AF and normal tissue by GEO database differentially expressed genes by GEO database. The top targets were IL6, VEGFA, JUN, MMP9 and EGFR, and Que for AF treatment might involve the role of AGE-RAGE signaling pathway in diabetic complications, MAPK signaling pathway and IL-17 signaling pathway. Molecular docking showed that Que binds strongly to key targets and is differentially expressed in AF. In vivo results showed that Que significantly reduced the duration of AF fibrillation and improved atrial remodeling, reduced p-MAPK protein expression, and inhibited the progression of AF. Combining network pharmacology and molecular docking approaches with in vivo studies advance our understanding of the intensive mechanisms of Quercetin, and provide the targeted basis for clinical Atrial fibrillation treatment.

Homocysteine and atrial fibrillation: novel evidences and insights

Atrial fibrillation (AF) is one of the most prevalent rhythm disorders worldwide, with around 37.574 million cases around the globe (0.51 % global population).  Different studies showed a high informative value of different biomarkers, including such related to the systemic inflammation, biomechanical stress and fibrosis. In this review article we aimed to study only the relation of homocysteine to the AF development. Homocysteine is a sulfur-containing amino acid, that is produced in the process of methionine metabolism. Which is a non-canonical amino acid, that is derived from the food proteins. From the scientific point of view there is a relation between hyperhomocysteinemia and myocardial fibrosis, but these mechanisms are complicated and not sufficiently studied. Homocysteine regulates activity of the ion channels through their redox state. Elevated homocysteine level can condition electrical remodeling of the cardiomyocytes through the increase of sodium current and change in the function of rapid sodium channels, increase of inwards potassium current and decrease in amount of rapid potassium channels. High homocysteine concentration also leads to the shortening of the action potential, loss of the rate adaptation of the action potential and persistent circulation of the re-entry waves. In a series of experimental studies on mice there was an association found between the homocysteine level and activity of vascular inflammation. Elevation of homocysteine level is an independent factor of the thromboembolic events and AF relapses. Population studies showed, that homocysteine is an independent risk factor for AF. So, homocysteine is an interesting target for up-stream therapy.

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.

Atrial electromechanical duration prolongs in patients with erectile dysfunction

Background: It is well known that erectile dysfunction (ED) is associated with increased risk of atrial fibrillation (AF) development. On the other hand, prolongation of the duration of atrial electromechanical delay (AEMD) is known to be a precursor for AF development. We aimed to evaluate AEMD in patients with ED patients without documented AF.Methods: Total of 68 outpatients with previously documented vascular ED and 44 participants without ED were enrolled to the current study. Sixty-eight patients with ED called as ED group and 44 participants without ED served as control group. We performed International Index of Erectile Function (IIEF-5) questionnaire for all participants to determine the disease severity of ED groups and to diagnose ED in control groups. Patients with a IIEF-5 score ≥22 were defined as having normal erectile functions. Both intra- and inter-AEMD were measured with tissue Doppler imaging. P-wave dispersion (PWD) was measured on a 12-lead electrocardiogram.Results: Basal characteristics were similar between the two groups. PWD, inter- and right intra-AEMD were significantly prolonged in patients with ED, compared to the control group (p = .02, p < .001 and p < .001, respectively). In the correlation analysis, IIEF-5 score was significantly negative correlated with systolic blood pressure, right intra- and inter-AEMD (r = -0.37, p = .02; r= -0.27, p = .02; r = -0.39, p = .001, respectively).Conclusions: According to current study results, AEMD is significantly correlated with ED severity and may be useful to stratify ED patients to the high-risk group for future development of AF as a cheap and easy method.

P wave dispersion in patients with erectile dysfunction

Background and aims

P wave dispersion (PWD) has been reported to be a non-invasive electrocardiographic predictor for atrial fibrillation. The aim of this study is to evaluate PWD between men with erectile dysfunction (ED) and healthy controls in order to investigate whether PWD was prolonged in patients with ED and related to severity of the disease.

Methods

This study included a total of 72 men (42 patients with ED and 30 healthy controls). Demographic data and clinical features were recorded on admission. An electrocardiographic evaluation was obtained to measure PWD values for both patients and controls.

Results

Maximum P wave duration was 108.5 ± 4.7 and 108.3 ± 4.3 in ED group and control group, respectively (p = 0.748). Minumum P wave duration was significantly higher in the control group than in the ED group. PWD was 48.1 ± 5.9 in the ED group. As a result, PWD was prolonged in patients with ED (48.1 ± 5.9 vs. 38.0 ± 3.9, p < 0.05). A significant negative correlation was observed between IIEF score and PWD values (p < 0.05, r = −0.662).

Conclusions

Patients with ED exhibited prolonged PWD values compared with normal controls. In addition, PWD was found to be associated with severity of the disease.

Does an imbalance in circulating vascular endothelial growth factors (VEGFs) cause atrial fibrillation in patients with valvular heart disease?

Background

The pathogenesis of atrial fibrillation (AF) remains unclear. Vascular endothelial growth factors (VEGFs) can stimulate fibrosis within the atrium and ventricle. We hypothesized that there is a relationship between the serum VEGFs/soluble vascular endothelial growth factor receptor (sVEGFRs) levels and AF in patients with valvular heart disease (VHD). This provides a new paradigm for studying AF.

Methods

The plasma levels of VEGF-A, VEGF-C, sVEGFR-1 and sVEGFR-2 were detected by enzyme-linked immunosorbent assay (ELISA). A total of 100 people, consisting of AF patients (long-standing, persistent AF; n=49), sinus rhythm (SR) patients (n=31) and healthy controls (n=20), were included in this study.

Results

The plasma levels of VEGF-A were significantly higher in AF patients compared to healthy control (P<0.05). The plasma levels of sVEGFR-1 were significantly higher in AF compared to SR (P<0.05). The plasma levels of sVEGFR-2 were significantly lower in AF patients compared to SR patients and healthy controls (both P<0.05). There was a significant and negative correlation between AF and the sVEGFR-2 levels in the groups (r=-0.432, P=0.000).

Conclusions

An imbalance in VEGFs and sVEGFRs may contribute to AF by breaking the balance of angiogenesis and lymphangiogenesis. Additionally, sVEGFR-2 may be an important biomarker of AF.

Improvement of peripheral microcirculation after cardioversion of atrial fibrillation

BACKGROUND

Near-infrared spectroscopy (NIRS) is a noninvasive method to measure regional tissue oxygenation (rSO₂ ). In patients with atrial fibrillation (AF), cardiac output and endothelial function are altered. Peripheral tissue oxygenation may therefore be reduced. This study aims to describe the peripheral tissue oxygenation of the feet before and after synchronized electrical cardioversion (CV) of patients with AF using NIRS.

METHODS

Patients with AF undergoing CV were included and screened for peripheral arterial disease (PAD), diabetes mellitus (DM), and peripheral neuropathy (PN). NIRS was performed before and after CV under continuous ECG and monitoring of peripheral oxygen saturation. NIRS was registered on the dorsoplantar and plantar area of both feet. Capillary blood gas analysis was performed and left ventricular ejection fraction (LVEF) was determined.

RESULTS

Twelve patients (five women, seven men, age 70.8 ± 10.8 years) participated. None had history of PAD. DM was present in three (25%) patients. Two patients (16.7%) had PN. CV was successful in 11 patients. Overall, rSO₂ improved significantly in all patients after CV (P = .0003). Mean improvement was 7.17%. There were no significant changes in body temperature, ankle-brachial index, sO₂ , pO₂ , pCO₂ , pH, or lactate after CV. Heart rate was significantly lower (P < .0001) and LVEF significantly higher (P = .0123) after CV.

CONCLUSIONS

In patients with AF, peripheral tissue oxygen saturation improves significantly after successful CV. This suggests that patients with PAD may not only benefit from interventional or surgical improvement of arterial vascularization, but also from CV in case of AF.

Relationship between Impairment of the Vascular Endothelial Function and the CHA2DS2-VASc Score in Patients with Sinus Rhythm and Non-valvular Atrial Fibrillation

Objective and methods There is little information concerning the influence of the heart rhythm on the vascular endothelial function in patients with non-valvular atrial fibrillation (AF) compared with studies concerning sinus rhythm (SR). The present study included paroxysmal (n=184) or chronic (n=53) AF patients without heart failure and control subjects with SR (n=79) matched for age, gender and the CHA₂DS₂-VASc score. Paroxysmal AF was defined as episodes that terminated spontaneously within 7 days, while chronic AF was defined as longstanding AF that was refractory to cardioversion for 12 months or longer. There were no significant differences in the numbers of patients receiving renin-angiotension-aldosterone system inhibitors or statins among the three groups. Results Among the 237 AF patients (155 men, mean age 64±9 years, mean CHA₂DS₂-VASc score 1.8±1.4), the flow-mediated dilatation (FMD) was 5.4%±2.6% in the paroxysmal AF group, 4.3%±2.1% in the chronic AF group and 6.5%±3.5% in the SR group. There were significant differences among the 3 groups (all, p<0.05). Nitroglycerin-induced dilatation (NMD) was noted in 14.6%±6.5% of the paroxysmal AF group, 16.5%±9.1% of the chronic AF group and 12.7%±5.9% of the SR group, with no significant differences among the 3 groups. There was a significant negative correlation between the CHA₂DS₂-VASc scores and the FMDs value in all 3 groups (paroxysmal AF group:r=-0.322, p<0.01; chronic AF group:r=-0.291, p<0.05; SR group:r=-0.326, p<0.01). Conclusion In comparison with SR, the frequency and duration of AF episodes appear to cause deterioration of the vascular endothelial function.

Platelet Reactivity Is Independent of Left Atrial Wall Deformation in Patients with Atrial Fibrillation

It has been documented recently that left atrial (LA) deformation in AF patients (while in AF) is predictive of subsequent stroke risk. Additionally, diminished LA deformation during AF correlates with the presence of LA blood stasis. Given that endothelial function is dependent on laminar blood flow, the present study sought to investigate the effect of diminished LA deformation (during AF) on platelet reactivity and inflammation in AF patients. Patients (n = 17) hospitalised with AF underwent echocardiography (while in AF) for determination of peak positive LA strain (LASp). Whole blood impedance aggregometry was used to measure extent of ADP-induced aggregation and subsequent inhibitory response to the nitric oxide (NO) donor, sodium nitroprusside. Platelet thioredoxin-interacting protein (Txnip) content was determined by immunohistochemistry. LASp tended (p = 0.078) to vary inversely with CHA2DS2VASc scores. However, mediators of inflammation (C-reactive protein, Txnip) did not correlate significantly with LASp nor did extent of ADP-induced platelet aggregation or platelet NO response. These results suggest that the thrombogenic risk associated with LA stasis is independent of secondary effects on platelet aggregability or inflammation.

Successful catheter ablation decreases platelet activation and improves endothelial function in patients with atrial fibrillation

BACKGROUND

Nonvalvular atrial fibrillation (AF) confers a five-fold increased risk of stroke. Whether catheter ablation (CA) subsequently decreases prothrombotic risk is unknown.

OBJECTIVE

The purpose of this study was to assess the long-term effects of CA for AF on prothrombotic risk.

METHODS

Fifty-seven patients undergoing CA for AF were prospectively studied. Platelet activation (CD62P [platelet P-selectin] and PAC-1 [glycoprotein IIb/IIIa] expression) and endothelial function (asymmetric dimethylarginine [ADMA] levels) were measured at baseline and 6-months postablation.

RESULTS

Thirty-seven (65%) patients remained in sinus rhythm (SR group) and 20 (35%) sustained AF recurrence (AF recurrence group) at 6-months. Patients with AF-recurrence were older, had a higher proportion of hypertension and long-standing persistent AF. There were no significant differences in CD62P (P = .3), PAC-1 (P = .1) and ADMA (P = .7) levels at baseline between the two groups. In the SR group, markers of platelet activation decreased significantly at 6-month follow-up compared to baseline; log CD62P % 0.79 ± 0.28 vs 1.03 ± 0.27 (P <.05) and log PAC-1 % 0.22 ± 0.58 vs 0.89 ± 0.31 (P <.01). This was not significant in the AF-recurrence group (P = .8, log CD62P; P = .1, log PAC-1). For endothelial function, ADMA levels decreased significantly at 6-months compared to baseline in the SR group (log ADMA μM/L 0.15 ± 0.02 vs 0.17 ± 0.04; P <.05), but did not alter significantly in the AF-recurrence group (P = .4, log ADMA).

CONCLUSION

Catheter ablation and successful maintenance of SR leads to a decrease in platelet activation and improvement in endothelial function in patients with AF. These findings suggest that AF is an important determinant of the prothrombotic state and that this may be reduced by successful catheter ablation.

Improvement of cerebral oxygen saturation after successful electrical cardioversion of atrial fibrillation

AIMS

Cerebral and microvascular perfusion is reduced in atrial fibrillation (AF). Maintenance of brain perfusion is important in acute disease and long-term course. Assessment of brain perfusion and oxygenation is difficult in clinical practice. Our study aimed to determine changes in cerebral tissue oxygen saturation (SctO2) with bedside near-infrared spectroscopy (NIRS).

METHODS AND RESULTS

Twenty patients (mean age 67.7 ± 10.2 years, 50% men) in whom electrical cardioversion (CV) was successful were prospectively studied. Ten patients (mean age 64.2 ± 7.7 years, 80% men) in whom CV was not successful served as control group. Bilateral SctO2, mean arterial pressure (MAP), arterial oxygen saturation (SaO2), and heart rate were recorded and changes of all parameters before and after CV were compared between the groups. Our results show an increase in SctO2 after successful CV that was significantly higher compared with patients who remained in AF (right SctO2 3.25 ± 2.5 vs. -0.13 ± 0.52%, P = 0.001; left SctO2 4.27 ± 3.56 vs. -0.38 ± 2.4%, P < 0.001). Neither arterial blood pressure nor SaO2 changes differed significantly between the two groups. No correlation could be detected between the significant increase of SctO2 after successful CV and arterial blood pressure, SaO2, or heart rate.

CONCLUSION

Cerebral tissue oxygen saturation increases significantly after restoration of sinus rhythm. Near-infrared spectroscopy monitoring can identify changes of SctO2 after successful CV of AF independent from standard monitoring parameters (MAP, SaO2). Near-infrared spectroscopy can be used to detect cerebral oxygen saturation deficits in AF patients or patients at high risk for AF. Clinical applications may include monitoring during ablation procedures and in critical care.

Effect of lipid lowering on new-onset atrial fibrillation in patients with asymptomatic aortic stenosis: the Simvastatin and Ezetimibe in Aortic Stenosis (SEAS) study

BACKGROUND

Lipid-lowering drugs, particularly statins, have anti-inflammatory and antioxidant properties that may prevent atrial fibrillation (AF). This effect has not been investigated on new-onset AF in asymptomatic patients with aortic stenosis (AS).

METHODS

Asymptomatic patients with mild-to-moderate AS (n = 1,421) were randomized (1:1) to double-blind simvastatin 40 mg and ezetimibe 10 mg combination or placebo and followed up for a mean of 4.3 years. The primary end point was the time to new-onset AF adjudicated by 12-lead electrocardiogram at a core laboratory reading center. Secondary outcomes were the correlates of new-onset AF with nonfatal nonhemorrhagic stroke and a combined end point of AS-related events.

RESULTS

During the course of the study, new-onset AF was detected in 85 (6%) patients (14.2/1,000 person-years of follow-up). At baseline, patients who developed AF were, compared with those remaining in sinus rhythm, older and had a higher left ventricular mass index a smaller aortic valve area index. Treatment with simvastatin and ezetimibe was not associated with less new-onset AF (odds ratio 0.89 [95% CI 0.57-1.97], P = .717). In contrast, age (hazard ratio [HR] 1.07 [95% CI 1.05-1.10], P < .001) and left ventricular mass index (HR 1.01 [95% CI 1.01-1.02], P < .001) were independent predictors of new-onset AF. The occurrence of new-onset AF was independently associated with 2-fold higher risk of AS-related outcomes (HR 1.65 [95% CI 1.02-2.66], P = .04) and 4-fold higher risk of nonfatal nonhemorrhagic stroke (HR 4.04 [95% CI 1.18-13.82], P = .03).

CONCLUSIONS

Simvastatin and ezetimibe were not associated with less new-onset AF. Older age and greater left ventricular mass index were independent predictors of AF development. New-onset AF was associated with a worsening of prognosis.

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.

Persistent atrial fibrillation is not associated with thrombomodulin level increase in efficiently anticoagulated patients

INTRODUCTION

Atrial fibrillation (AF) is the most common arrhythmia and leads to a five-fold increased risk of stroke compared to persons with sinus rhythm. A soluble form of thrombomodulin (sTM) is a recognized marker of endothelial dysfunction and may contribute to the hypercoagulable state in AF. The aim of the study was to evaluate plasma concentration of sTM in persistent AF patients before and after sinus rhythm recovery following direct current cardioversion (CV).

MATERIAL AND METHODS

In 45 effectively anticoagulated consecutive patients, with persistent non-valvular AF, and normal left ventricular function, CV was performed. Blood samples for sTM assessment were collected twice: 24 hours before and 24 hours after CV.

RESULTS

In 43 patients sinus rhythm was obtained. The mean plasma sTM level was significantly lower in AF patients compared to the control group with sinus rhythm and without anticoagulation (38.5 ±9.9 ng/ml vs. 44.1 ±9.1 ng/ml, p = 0.04). Plasma sTM levels did not change 24 hours after successful CV (36.7 ±9.5 ng/ml vs. 38.5 ±9.9 ng/ml, p = 0.16).

CONCLUSIONS

Plasma sTM concentration was lower in patients with persistent AF and normal left ventricle systolic function than in patients with sinus rhythm, presumably due to chronic oral anticoagulant therapy in the AF group. CV has no impact on sTM plasma level evaluated 24 hours after sinus rhythm restoration.

Improved endothelial function in patients with atrial fibrillation through maintenance of sinus rhythm by successful catheter ablation

BACKGROUND

Although atrial fibrillation (AF) is a risk factor for endothelial dysfunction (ED), the effect of catheter ablation (CA) on AF-associated ED has not been evaluated. The aims of this study are to determine if the degree of ED predicts the outcome of AF ablation and to evaluate whether ED can be improved through restoring sinus rhythm (SR) by successful CA.

METHODS

This study prospectively enrolled 80 subjects who underwent CA for AF (paroxysmal AF = 61, persistent AF = 19). Eighty subjects with no history of AF were enrolled as controls, all of whom were matched by age, gender, body mass index, and atherosclerotic risk factor distribution. Brachial artery flow-mediated dilatation (FMD) was measured at baseline, and at 1 month and 6 months post CA in AF subjects who remained in SR. Among controls, FMD was measured at baseline and at 6 months. We used high sensitivity C-reactive protein (hs-CRP), interleukin-6, soluble E- or P-selectin, and endothelin-1 as biomarker indices for inflammation and/or ED.

RESULTS

Compared with controls, AF subjects had lower FMD at baseline (FMD(baseline), P < 0.001). After successful CA, FMD was significantly improved at 1 month and 6 months, nearly approaching control levels. A multivariate analysis revealed that FMD(baseline), hs-CRP, and left atrial volume (LAV) were independent predictors for arrhythmia recurrence after CA. Other biomarkers were not related to rhythm outcome.

CONCLUSION

AF subjects have significantly impaired FMD, which can be reversed through maintenance of SR by successful CA. FMD(baseline), hs-CRP, and LAV are important predictors for AF recurrence after CA.

Assessment of endothelial (dys)function in atrial fibrillation

Atrial fibrillation (AF) is associated with an increased risk of mortality and morbidity from stroke and thromboembolism. Endothelial damage or dysfunction may contribute to this increased risk of thromboembolism via the mediation of a prothrombotic or hypercoagulable state. However, the precise pathophysiological mechanism(s) relating endothelial (dys)function to AF and thromboembolism are yet to be fully elucidated. This review article aims to provide a comprehensive overview of endothelial (dys)function and AF, as well as the merits and limitations of the different methods used to assess endothelial function in AF.

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.

Exercise metaboreflex activation and endothelial function impairment in atrial fibrillation

Exercising muscle hypoperfusion stimulates afferents (metaboreceptors) involved in the regulation of ventilation. Atrial fibrillation (AF), particularly when combined with diseases causing endothelial (ED) impairment, such as hypertension (HP) and diabetes mellitus (DM), depresses the ED activity and enhances exercise hyperventilation. The relationship between these two functions and the underlying mechanisms have not been explored previously. In lone AF or AF associated with HP or DM (12 subjects in each cohort), we investigated the brachial artery flow-mediated dilatation (ED function) and ventilation during the recovery phase of handgrip (metaboreflex) exercise for subjects receiving placebo or oral vitamin C (double-blind crossover), both before and after cardioversion (CV) to sinus rhythm. Baseline ED impairment was increasingly more severe and the ergoreflex activity more pronounced in AF + HP and AF + DM compared with lone AF. Vitamin C and CV significantly improved both flow-mediated dilatation and metaboreflex activity in lone AF and AF + HP, and vitamin C did not produce any additive effect when administered after CV. In AF + DM, neither vitamin C nor CV was effective. This study provides the following information: AF generates oxidative injury, which is less when the arrhythmia is lone AF and greater when the arrhythmia is associated with HP. In DM, the oxidative injury generated by AF is refractory to a rather weak antioxidant, like vitamin C, or the baseline damage is such as to prevent any additive influence of AF. In AF, a cause-effect link exists between ED dysfunction and metaboreflex activity. Ventilatory advantages of CV seem to be inversely related with the extension of the underlying ED oxidative impairment.

Endothelial dysfunction and exercise performance in lone atrial fibrillation or associated with hypertension or diabetes: different results with cardioversion

Endothelial dysfunction and underperfusion of exercising muscle contribute to exercise intolerance, hyperventilation, and breathlessness in atrial fibrillation (AF). Cardioversion (CV) improves endothelial function and exercise performance. We examined whether CV is equally beneficial in diabetes and hypertension, diseases that cause endothelial dysfunction and are often associated with AF. Cardiopulmonary exercise and pulmonary and endothelial (brachial artery flow-mediated dilation) function were tested before and after CV in patients with AF alone ( n = 18, group 1) or AF with hypertension ( n = 19, group 2) or diabetes ( n = 19, group 3). Compared with group 1, peak exercise workload, O2 consumption (V̇o2), O2 pulse, aerobic efficiency (ΔV̇o2/ΔWR), and ratio of brachial diameter changes to flow changes (Δ D/ΔF) were reduced in group 2 and, to a greater extent, in group 3; exercise ventilation efficiency (V̇e/V̇co2 slope) and dead space-to-tidal volume ratio (Vd/Vt) were similar among groups. CV had less effect on peak workload (+7% vs. +18%), peak V̇o2 (+12% vs. +17%), O2 pulse (+33% vs. +50%), ΔV̇o2/ΔWR (+7% vs. +12%), V̇e/V̇co2 slope (−6% vs. −12%), Δ D/ΔF (+7% vs. +10%), and breathlessness (Borg scale) in group 2 than in group 1 and was ineffective in group 3. The antioxidant vitamin C, tested in eight additional patients in each cohort, improved flow-mediated dilation in groups 1 and 2 before, but not after, CV and was ineffective in group 3, suggesting that the oxidative injury is least in lone AF, greater in hypertension with AF, and greater still in diabetes with AF. Comorbidities that impair endothelial activity worsen endothelial dysfunction and exercise intolerance in AF. The advantages of CV appear to be inversely related to the extent of the underlying oxidative injury.

Effects of oral beraprost sodium, a prostaglandin I2 analogue, on endothelium dependent vasodilatation in the forearm of patients with coronary artery disease

1. Previous clinical studies with prostaglandin I(2) (PGI(2)) analogue beraprost sodium suggested the potential effects on protection of cardiovascular events in patients with peripheral artery disease. Although the mechanism is not well known, experimental studies have shown protective effects of endothelial cells. This study was designed to examine the effects of beraprost sodium on vascular endothelial function in the forearm of patients with coronary artery disease. 2. Beraprost sodium (120 microg/day) was orally administered to 14 coronary artery disease patients for 4 weeks and then stopped for 4 weeks. Eleven control patients did not receive beraprost sodium treatment. Reactive hyperemia was induced in the forearm, endothelium-dependent vasodilatation was assessed by plethysmography, and urinary 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)) was measured at baseline, 4 weeks and 8 weeks. 3. Both groups had similar reactive hyperemic responses at baseline. In the control group, reactive hyperemic response and urinary 8-iso-PGF(2alpha) remained unchanged for 8 weeks. In the beraprost group, maximum forearm blood flow increased significantly (P = 0.01) after 4 weeks of treatment and returned to baseline at 8 weeks. Duration of hyperemia increased significantly (P = 0.003) after 4 weeks, and remained greater than baseline at 8 weeks (P = 0.02). Urinary 8-iso-PGF(2alpha) decreased significantly (P = 0.03) after 4 weeks, and tended to be lower at 8 weeks (P = 0.07). Changes in reactive hyperemia correlated weakly but significantly with changes in 8-iso-PGF(2alpha) (P < 0.001). 4. Beraprost sodium decreased oxidative stress and improved forearm endothelium-dependent vasodilatation in coronary artery disease patients. The favorable effects on vascular endothelium could potentially lead to a decrease in vascular events.

Angiogenic factors in atrial fibrillation: a possible role in thrombogenesis?

BACKGROUND

The precise pathophysiological processes underlying the prothrombotic or hypercoagulable state in atrial fibrillation (AF) remain uncertain. We hypothesized a relationship between abnormal endothelial damage/dysfunction, coagulation, and angiogenic factors, thereby contributing to increased thrombogenicity.

METHODS

Plasma levels of von Willebrand factor (vWF, an index of endothelial damage/dysfunction) and tissue factor (TF, an index of coagulation), as well as the angiogenic factors, vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2), were measured by enzyme-linked immunosorbant assay (ELISA) in 59 chronic AF patients. Data were compared to 40 age- and sex-matched healthy controls in sinus rhythm.

RESULTS

Plasma vWF, VEGF and Ang-2 were significantly higher in AF patients compared to healthy controls (P=0.005, P=0.0055 and P<0.0001 respectively) but there were no significant differences in plasma Ang-1 or TF levels between the two groups (P=0.925 and P=0.121 respectively). Significant correlations were found between VEGF and vWF levels (Spearman, r=0.262, P=0.011) and between VEGF and Ang-2 (r=0.333, P=0.001).

CONCLUSIONS

Raised VEGF in association with Ang-2 and vWF may reflect a link between abnormal endothelial damage/dysfunction and angiogenic factors. These may act together to alter TF expression and endothelial integrity, thereby contributing to the prothrombotic state in AF.

Exercise hyperventilation, dyspnea sensation, and ergoreflex activation in lone atrial fibrillation

Lone atrial fibrillation may be associated with daily life disability and exercise limitation. The extracardiac pathophysiology of these effects is poorly explored. In 35 subjects with lone atrial fibrillation (mean age 67 +/- 7 yr), we investigated pulmonary function, symptom-limited cardiopulmonary exercise performance, muscle ergoreflex (handgrip exercise) contribution to ventilation, and brachial artery flow-mediated dilation (as a measure of endothelial function) before and after (average interval 20 +/- 5 days) restoring sinus rhythm with external cardioversion. Respiratory volumes and lung diffusing capacity at rest were within normal limits during both atrial fibrillation and after restoring sinus rhythm. Cardioversion was associated with the following changes: a decrease of the slope of exercise ventilation vs. CO2 production (from 35 +/- 5 to 29 +/- 3; P <0.01) and of dyspnea sensation (Borg score from 4 to 2) and an increase of peak oxygen uptake (Vo2; from 16 +/- 4 to 20 +/- 5 ml.min(-1).kg(-1); P <0.01), Vo2 at anaerobic threshold (from 11 +/- 2 to 13 +/- 2 ml.min(-1).kg(-1); P <0.05), and O2 pulse (from 8 +/- 3 to 11 +/- 3 ml/beat; P <0.01). After cardioversion, the observed improvement in ventilatory efficiency was accompanied by a significant peak end-tidal CO2 increase (from 33 +/- 2 to 37 +/- 2 mmHg; P <0.01) and no changes in dead space-to-tidal volume ratio (from 0.23 +/- 0.03 to 0.23 +/- 0.02; P=not significant). In addition, the ergoreflex contribution to ventilation was remarkably attenuated, and the brachial artery flow-mediated dilatation was significantly augmented (from 0.32 +/- 0.07 to 0.42 +/- 0.08 mm; P <0.01). Ten patients had atrial fibrillation relapse and, compared with values after restoration of regular sinus rhythm, invariably showed worsening of endothelial function, exercise ventilatory efficiency, and muscle ergoreflex contribution to ventilation. In subjects with lone atrial fibrillation, an impairment in ventilatory efficiency appears to be involved in the pathophysiology of exercise limitation, and to be primarily related with a demodulated peripheral control of ventilation.

Analysis of pravastatin to prevent recurrence of atrial fibrillation after electrical cardioversion

To test the hypothesis that a statin could reduce the recurrence rate of atrial fibrillation after electrical cardioversion (EC), we performed an open, controlled multicenter study. Patients (n = 114) who had atrial fibrillation >48 hours and who were scheduled for EC were randomized to receive 40 mg of pravastatin once daily for 3 weeks before and 6 weeks after EC or no drug in addition to standard therapy. Pravastatin did not reduce the recurrence rate of atrial fibrillation after EC.

REDUCED HIGH SERUM HEPATOCYTE GROWTH FACTOR LEVELS AFTER SUCCESSFUL CARDIOVERSION IN PATIENTS WITH ATRIAL FIBRILLATION

1. Serum hepatocyte growth factor (HGF) is considered to be a potent marker of vascular endothelial injury. The present study was designed to examine serum HGF levels in atrial fibrillation and after successful direct current (DC) cardioversion. 2. We measured serum HGF levels before and 7 days and 1 month after DC cardioversion in 39 patients with atrial fibrillation in whom sinus rhythm was maintained for at least 7 days after DC cardioversion and in 30 age- and sex-matched normal control subjects with sinus rhythm. We also measured acetylcholine-induced changes in forearm blood flow (FBF) using venous occlusive plethysmography in 10 patients. 3. Serum HGF levels were significantly higher in the atrial fibrillation patients (both lone atrial fibrillation and with underlying heart disease) than in the controls (0.16 +/- 0.07 vs 0.10 +/- 0.04 ng/mL; P < 0.001). Seven days after successful DC cardioversion, the patients' serum HGF levels had decreased significantly (0.16 +/- 0.07 vs 0.12 +/- 0.06 ng/mL; P < 0.05) and in the 24 patients maintaining sinus rhythm 1 month after DC cardioversion, serum HGF levels decreased to control values (0.10 +/- 0.08 ng/mL at 1 month). Serum HGF levels of the 15 patients who had relapsed into atrial fibrillation 1 month after DC cardioversion tended to decrease 7 days after DC cardioversion, but increased again 1 month after DC cardioversion. Percentage changes in FBF between baseline and the highest dose of acetylcholine before and after DC cardioversion were 180 +/- 98 and 323 +/- 196%, respectively (P = 0.0051). The rate of increase in FBF at the highest dose of acetylcholine between before and after DC cardioversion correlated negatively with the rate of decrease in serum HGF levels between before and after DC cardioversion (r = -0.837; P = 0.0025). 4. This study is the first to demonstrate that serum HGF levels increase in atrial fibrillation and decrease after successful DC cardioversion. This may reflect the fact that atrial fibrillation induces vascular endothelial injury.

Plasma Levels of Nitrites/Nitrates in Patients with Chronic Atrial Fibrillation are Increased after Electrical Restoration of Sinus Rhythm

INTRODUCTION

Patients with persistent atrial fibrillation (AF) have hemodynamic changes, which impair endothelial cell function resulting in decreased nitric oxide (NO) production. The aim of this work was to assess endothelial function in AF patients before and at various time points after cardioversion.

METHODS

Forty-two patients with AF and 21 normal and age-adjusted healthy controls were studied. Nitrites and nitrates (NO(x)) and von Willebrand factor (vWf) concentrations were measured on blood samples taken just before cardioversion and over a 30 day period after the procedure.

RESULTS

Plasma levels of NO(x) in AF were significantly lower compared to healthy controls (p < 0.001), but after cardioversion gradually increased to approach to those of the healthy controls by the end of the first month of sustained sinus rhythm (p = 0.004). Interestingly plasma levels of NO(x) were negatively correlated to left atrial volume measured by ultrasonography (r = -0.34, p < 0.05). Plasma levels of vWf in AF patients were significantly higher compared to the healthy controls (p < 0.01) but with sustained sinus rhythm decreased (p = 0.02).

CONCLUSION

The parallel normalization of the NO(x) titers and vWf levels suggests that vascular endothelial function improves after 30 days of normal sinus rhythm.

Is the hypercoagulable state in atrial fibrillation mediated by vascular endothelial growth factor?

BACKGROUND AND PURPOSE

Tissue factor (TF; an initiator of coagulation) and vascular endothelial growth factor (VEGF; a marker of angiogenesis) are involved in the hypercoagulable state associated with malignancy. We investigated their roles in chronic atrial fibrillation (AF), a condition also associated with increased risk of stroke and thromboembolism, as well as a prothrombotic or hypercoagulable state.

METHODS

We studied 25 patients with AF (20 men; mean+/-SD age, 62+/-13 years) who were compared with 2 control groups in sinus rhythm: 30 healthy control subjects (17 men; mean age, 60+/-9 years) and 35 patient control subjects with coronary artery disease (CAD; 27 men; mean age, 60+/-12 years). Plasma levels of TF, VEGF, and the VEGF receptor sFlt-1 were measured by enzyme-linked immunosorbent assay.

RESULTS

VEGF, sFlt-1, and TF were significantly different between the 3 groups, with abnormal levels in AF and CAD patients compared with control subjects (P<0.001, P=0.022, and P=0.008, respectively). Among the AF patients, TF levels were significantly correlated with VEGF (Spearman's r=0.65, P<0.001) and sFlt (r=0.54, P=0.006) levels. Only TF and VEGF levels were significantly correlated in CAD patients (r=0.39, P=0.02). There were no significant correlations among the healthy control subjects.

CONCLUSIONS

Patients with chronic AF have high TF levels, in keeping with the prothrombotic state associated with this arrhythmia. The relationships between TF and VEGF and its receptor sFlt-1 in AF suggest a possible role for VEGF in the hypercoagulable state found in AF, as seen in malignancy and atherosclerosis.

Impaired exercise-induced vasodilatation in chronic atrial fibrillation--role of endothelium-derived nitric oxide

Exercise capacity is often reduced in patients with atrial fibrillation (AF), but very few studies have focused on changes in endothelial function as a potential mechanism for the exercise limitation. The present study used using venous occlusion plethysmography to investigate whether nitric oxide (NO)-mediated vasodilatation is attenuated during exercise in patients with AF by measuring forearm blood flow (FBF) in 10 patients at rest and immediately after 2 levels of rhythmic handgrip exercise, before and after inhibition of NO synthesis with N(G)-monomethyl-L-arginine (L-NMMA, 100 micromol). The measurements were repeated 1 day after restoration of sinus rhythm by cardioversion. FBF responses to graded doses of acetylcholine (ACh) were also observed before and after cardioversion. Heart rate decreased after cardioversion, but blood pressure did not change. FBF at rest was not affected by cardioversion, but at the highest level of exercise it increased from 28.4+/-2.3 ml x min(-1) x dl(-1) before to 39.4+/-3.2 ml x min(-1) x dl(-1) after cardioversion (p<0.05). L-NMMA significantly decreased FBF at rest (p<0.01) and depressed the increase in FBF response to exercise after (p<0.01), but not before cardioversion. The FBF response to ACh was also accelerated significantly after cardioversion. The present results provide new evidence that NO bioavailability is depressed at rest and during exercise in patients with AF.