A cross-sectional and diurnal study of thrombogenesis among patients with chronic atrial fibrillation

Cardioembolic stroke and endothelial dysfunction in men aged between 30 and 50 years

Introduction. Stroke in young adults is associated with high-level socioeconomic components, and patients face the lifelong effects of the vascular catastrophe. Young patients with cardioembolic stroke make up an important subgroup of ischemic stroke patients globally. A key to optimizing treatment and preventing relapses is identifying the causes and risk factors for ischemic stroke in young adults.

Aim. To assess risk factors and endothelial function status in young men with cardioembolic stroke

Material and methods. A total of 19 patients aged 30-50 years with cardioembolic stroke underwent clinical and instrumental examinations. All patients were admitted to the Yaroslavl Vascular Center before the COVID-19 pandemic. The severity of clinical symptoms and stroke were assessed using the NIHSS scales, Modified Rankin Scale, and Rivermead Mobility Index. The main risk factors for IS including the presence of high- or moderate-risk sources of cardioembolism were reviewed. All patients underwent brain neuroimaging, ultrasound imaging, electrocardiogram, echocardioscopy, and laboratory blood testing. An ultrasound guided tourniquet test was performed to assess the brachial artery endothelial vasomotor function. 

Results. The average age of patients with cardioembolic stroke was 43.2 ± 6.4 years. Mechanical valve prostheses (21.1%) and isolated atrial fibrillation (42.0%) are the most common sources of cardioembolism. Other commonly identified risk factors included hypertension (73.7%), dyslipidemia (42.1%), smoking (52.6%), and prior acute myocardial infarction (42.1%). The ultrasound guided tourniquet test showed normal dilation of the brachial artery in 26.3% patients, insufficient dilatation in 42.1% patients and vasoconstriction in 31.6% patients. Statistically significant associations between the main vascular risk factors, serum markers of endothelial dysfunction and ultrasound guided tourniquet test indices were identified.

Conclusion. This study demonstrated a variety of risk factors for cardioembolic stroke in young men. Lifestyle modification is responsible for the occurrence of traditional risk factors in young adults.

The association of coagulation and atrial fibrillation: a systematic review and meta-analysis

AIMS

While atrial fibrillation (AF) is suggested to induce a prothrombotic state, increasing thrombotic risk, it is also hypothesized that coagulation underlies AF onset. However, conclusive evidence is lacking. With this systematic review and meta-analysis, we aimed to summarize and combine the evidence on the associations between coagulation factors with AF in both longitudinal and cross-sectional studies.

METHODS AND RESULTS

We systematically searched for longitudinal cohort and cross-sectional studies investigating AF and thrombosis. For longitudinal studies, pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated. For cross-sectional studies, we determined pooled standardized mean differences (SMDs) and 95% CIs. A total of 17 longitudinal and 44 cross-sectional studies were included. In longitudinal studies, we found significant associations between fibrinogen (HR 1.05, 95% CI 1.00-1.10), plasminogen activator inhibitor 1 (PAI-1) (HR 1.06, 95% CI 1.00-1.12), and D-dimer (HR 1.10, 95% CI 1.02-1.19) and AF incidence. In cross-sectional studies, we found significantly increased levels of fibrinogen (SMD 0.47, 95% CI 0.20-0,74), von Willebrand factor (SMD 0.96, 95% CI 0.28-1.66), P-selectin (SMD 0.31, 95% CI 0.08-0.54), ß-thromboglobulin (SMD 0.82, 95% CI 0.61-1.04), Platelet Factor 4 (SMD 0.42, 95% CI 0.12-0.7), PAI-1 (1.73, 95% CI 0.26-3.19), and D-dimer (SMD 1.74, 95% CI 0.36-3.11) in AF patients, as opposed to controls.

CONCLUSION

These findings suggest that higher levels of coagulation factors are associated with prevalent and incident AF. These associations are most pronounced with prevalent AF in cross-sectional studies. Limited evidence from longitudinal studies suggests a prothrombotic state underlying AF development.

Soluble Platelet Release Factors as Biomarkers for Cardiovascular Disease

Platelets are the main players in thrombotic diseases, where activated platelets not only mediate thrombus formation but also are involved in multiple interactions with vascular cells, inflammatory components, and the coagulation system. Although in vitro reactivity of platelets provides information on the function of circulating platelets, it is not a full reflection of the in vivo activation state, which may be relevant for thrombotic risk assessment in various disease conditions. Therefore, studying release markers of activated platelets in plasma is of interest. While this type of study has been done for decades, there are several new discoveries that highlight the need for a critical assessment of the available tests and indications for platelet release products. First, new insights have shown that platelets are not only prominent players in arterial vascular disease, but also in venous thromboembolism and atrial fibrillation. Second, knowledge of the platelet proteome has dramatically expanded over the past years, which contributed to an increasing array of tests for proteins released and shed from platelets upon activation. Identification of changes in the level of plasma biomarkers associated with upcoming thromboembolic events allows timely and individualized adjustment of the treatment strategy to prevent disease aggravation. Therefore, biomarkers of platelet activation may become a valuable instrument for acute event prognosis. In this narrative review based on a systematic search of the literature, we summarize the process of platelet activation and release products, discuss the clinical context in which platelet release products have been measured as well as the potential clinical relevance.

Endothelial function in patients with atrial fibrillation

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

Biomarkers in patients with Takotsubo cardiomyopathy compared to patients with acute anterior ST-elevation myocardial infarction

Background: Takotsubo cardiomyopathy (TTC) is a syndrome of acute non-coronary heart failure with similar symptoms and electrocardiograms to acute anterior ST-elevation myocardial infarction (STEMI). Little is known about the pathophysiology of TTC. We assessed admission plasma concentrations of biomarkers reflecting neuroendocrine response (copeptin, mid-regional-pro-adrenomedullin, pro-atrial-natriuretic-peptide, soluble thrombomodulin (sTM), syndecan-1) and inflammation (suppression-of-tumorigenicity 2 (ST2), high-sensitive C-reactive-protein) in TTC patients and compared to patients with acute anterior STEMI.Materials and methods: Twenty TTC patients were matched with 40 STEMI patients by age, gender and left ventricular ejection fraction. Blood was sampled upon hospital admission immediately before acute coronary angiography.Results: The groups had similar comorbidities. TTC patients had higher plasma concentrations of sTM: 7.94 (5.89;9.61) vs. 6.42 (5.50;7.82)ng/ml, p = 0.04 and ST2 (53 (32;157) vs. 45 (31;55)ng/ml, p = 0.008) and higher heart rate: 101 ([Formula: see text]33) vs. 76([Formula: see text]14)bpm, p = 0.0001, but lower concentrations of copeptin (10.4 (7.6;39) vs. 92.3 (13;197)pmol/l, p < 0.05) and troponin T (348 (98;759) vs. 1190 (261;4105)ng/l, p = 0.04).Conclusion: TTC patients had higher plasma concentrations of sTM and ST2, higher heart rate and lower copeptin and troponin T concentrations compared to acute anterior STEMI patients. This study contributes to the hypothesis that TTC patients have endothelial cell damage and are hemodynamically more stable than patients with acute anterior STEMI on admission.

Endocardial Changes in Nonvalvular Atrial Fibrillation Without Atrial Thrombus-Thrombomodulin and Tissue Factor Pathway Inhibitor

Atrial fibrillation (AF) is a well-known cause for thromboembolism. Although blood stasis in the left atrium and hypercoagulable state of the blood have been emphasized as important mechanisms, limited attention has been paid to the endocardial changes in maintaining the balance of local coagulation, which may also contribute to the thrombus formation in AF. In the present study, left atrial appendage samples were obtained at heart surgery from nonvalvular AF and non-AF patients without atrial thrombus. Immunohistochemistry for endocardial markers including thrombomodulin (TM) and tissue factor pathway inhibitor (TFPI) was performed and semiquantitatively graded. In immunohistochemistry analysis, decreased expression of TM was found in patients with nonvalvular AF compared with those without AF ( P < .001). There was no difference in TFPI expression between the 2 groups ( P = .213). Patients with TM score of 0 or 1 seemed to have larger left atrial diameter (LAD) than those with TM score of 2 or 3 (44.0 (7.9) vs 40.6 (3.9); P = .009), while no relationship between LAD and TFPI expression was found (43.4 (7.0) vs 42.9 (7.8); P = .485). In conclusion, TM expression in the atrial endocardium is decreased in nonvalvular AF without atrial thrombus, while TFPI expression is not. Downregulated TM expression might be associated with enlarged LAD.

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 AND 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.

Update on ADAMTS13 and VWF in cardiovascular and hematological disorders

Endothelial cells (EC) respond to injury by releasing numerous factors, including von Willebrand factor (VWF). High circulating levels of unusually large VWF multimers (UL-VWFM) have strong procoagulant activity and facilitate platelet adhesion and aggregation by interacting with platelets after an acute event superimposed on peripheral arterial disease and coronary artery disease. ADAMTS13-a disintegrin-like metalloproteinase with thrombospondin motif type 1 member 13-regulates a key physiological process of coagulation in the circulation by cleaving VWF multimers into small, inactive fragments. Low levels of ADAMTS13 in the blood may play a role in cardiovascular and hematological disorders, and clarifying its role may help improve disease management. The genetic, pharmacological, physiological, and pathological aspects related to ADAMTS13/VWF have been extensively investigated. Here, we provide an update on recent findings of the relationship between ADAMTS13 and hematological/cardiovascular disorders, including thrombotic thrombocytopenic purpura, arterial thrombosis, thrombotic microangiopathy, myocardial infarction, ischemic stroke, heart failure, and hypertension.

Evaluating the Atrial Myopathy Underlying Atrial Fibrillation: Identifying the Arrhythmogenic and Thrombogenic Substrate

Atrial disease or myopathy forms the substrate for atrial fibrillation (AF) and underlies the potential for atrial thrombus formation and subsequent stroke. Current diagnostic approaches in patients with AF focus on identifying clinical predictors with the evaluation of left atrial size by echocardiography serving as the sole measure specifically evaluating the atrium. Although the atrial substrate underlying AF is likely developing for years before the onset of AF, there is no current evaluation to identify the preclinical atrial myopathy. Atrial fibrosis is 1 component of the atrial substrate that has garnered recent attention based on newer MRI techniques that have been applied to visualize atrial fibrosis in humans with prognostic implications regarding the success of treatment. Advanced ECG signal processing, echocardiographic techniques, and MRI imaging of fibrosis and flow provide up-to-date approaches to evaluate the atrial myopathy underlying AF. Although thromboembolic risk is currently defined by clinical scores, their predictive value is mediocre. Evaluation of stasis via imaging and biomarkers associated with thrombogenesis may provide enhanced approaches to assess risk for stroke in patients with AF. Better delineation of the atrial myopathy that serves as the substrate for AF and thromboembolic complications might improve treatment outcomes. Furthermore, better delineation of the pathophysiologic mechanisms underlying the development of the atrial substrate for AF, particularly in its earlier stages, could help identify blood and imaging biomarkers that could be useful to assess risk for developing new-onset AF and suggest specific pathways that could be targeted for prevention.

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.

Von Willebrand Factor Plasma Levels Variability In Nonvalvular Atrial Fibrillation

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

Plasma CX3CL1 levels and long term outcomes of patients with atrial fibrillation: the West Birmingham Atrial Fibrillation Project

BACKGROUND

There is growing evidence that chemokines are potentially important mediators of the pathogenesis of atherosclerotic disease. Major atherothrombotic complications, such as stroke and myocardial infarction, are common among atrial fibrillation (AF) patients. This increase in risk of adverse events may be predicted by a score based on the presence of certain clinical features of chronic heart failure, hypertension, age 75 years or greater, diabetes and stroke (the CHADS2 score). Our objective was to assess the prognostic value of plasma chemokines CCL2, CXCL4 and CX3CL1, and their relationship with the CHADS2 score, in AF patients.

METHODS

Plasma CCL2, CXCL4 and CX3CL1 were measured in 441 patients (59% male, mean age 75 years, 12% paroxysmal, 99% on warfarin) with AF. Baseline clinical and demographic factors were used to define each subject's CHADS2 score. Patients were followed up for a mean 2.1 years, and major adverse cardiovascular and cerebrovascular events (MACCE) were sought, being the combination of cardiovascular death, acute coronary events, stroke and systemic embolism.

RESULTS

Fifty-five of the AF patients suffered a MACCE (6% per year). Those in the lowest CX3CL1 quartile (≤ 0.24 ng/ml) had fewest MACCE (p = 0.02). In the Cox regression analysis, CX3CL1 levels >0.24 ng/ml (Hazard ratio 2.8, 95% CI 1.02-8.2, p = 0.045) and age (p = 0.042) were independently linked with adverse outcomes. The CX3CL1 levels rose directly with the CHADS2 risk score (p = 0.009). The addition of CX3CL1 did not significantly increased the discriminatory ability of the CHADS2 clinical factor-based risk stratification (c-index 0.60 for CHADS2 alone versus 0.67 for CHADS2 plus CX3CL1 >0.24 ng/ml, p = 0.1). Aspirin use was associated with lower levels of CX3CL1 (p = 0.0002) and diabetes with higher levels (p = 0.031). There was no association between CXCL4 and CCL2 plasma levels and outcomes.

CONCLUSION

There is an independent association between low plasma CX3CL1 levels and low risk of major cardiovascular events in AF patients, as well as a linear association between CX3CL1 plasma levels and CHADS2-defined cardiovascular risk. The potential for CX3CL1 in refining risk stratification in AF patients merits consideration.

Biochemical predictors of cardiac rhythm at 1 year follow-up in patients with non-valvular atrial fibrillation

C-reactive protein (CRP) is increased in patients with atrial fibrillation (AF) and it might predict the lack of sinus rhythm maintenance in the long term follow-up. Scarce data have been reported relating endothelial dysfunction and/or haemostatic or platelet markers to sinus rhythm maintenance in AF patients. We aimed to determine whether some biochemical markers including soluble thrombomodulin (sTM), soluble P-selectin, thrombin-antithrombin (TAT) complex and CRP levels could predict sinus rhythm maintenance at 1 year follow-up in non-valvular AF patients. 130 patients (70 males, mean age 67 ± 13 years) with newly diagnosed AF naïve of antithrombotic or antiplatelet therapy were studied. Baseline CRP, P-selectin, sTM and TAT levels were compared to those of 20 matched-healthy subjects in sinus rhythm. AF patients had significantly higher plasma CRP (10.5 ± 2.2 vs 3.25 ± 0.3 mg/l, p = 0.001), P-selectin (219 ± 141 vs 126 ng/ml, p = 0.01), and TAT (54 ± 237 vs 2.7 ± 3.3 ng/l, p = 0.001) levels compared with controls. Soluble TM levels, although higher than controls, did not reach statistical significance. Multivariate regression analyses showed that elevated CRP (OR = 4.8, p = 0.02) and sTM (OR = 1.05, p = 0.04) were the only two predictors of lack of sinus rhythm at 1 year follow-up. An altered inflammatory, haemostatic, endothelial and platelet environment exists in newly diagnosed AF patients. CRP and sTM levels might be used as biochemical markers to predict the status of cardiac rhythm at 1 year follow-up in some AF patients.

Increased plasma soluble thrombomodulin levels in cardioembolic stroke

Soluble thrombomodulin (sTM) has been proposed as a potential marker of ischemic stroke. Results from previous studies remain controversial among different populations. We performed an analysis of plasma levels of sTM in Thai patients with acute ischemic stroke and determined whether sTM levels correlate with stroke subtypes, severity, and risk factors. Ninety-three patients and 76 controls were enrolled. Blood samples were obtained within 24 hours after stroke onset. Plasma sTM levels, measured using quantitative enzyme-linked immunosorbent assay, were significantly higher in patients than controls (P < .005), with the mean ± standard deviation (SD) levels of 3.08 ± 1.05 and 2.57 ± 1.15 ng/mL, respectively. Plasma levels of sTM in patients with cardioembolic subtype were significantly higher than in patients with other stroke subtypes, with the mean ± SD levels of 3.79 ± 1.26, 2.38 ± 0.68 (P < .009), and 2.38 ± 0.44 (P < .05) ng/mL for cardioembolism, large artery atherosclerosis, and small artery occlusion, respectively. Plasma sTM levels were not associated with stroke severity and risk factors of stroke; however, there was a slight relationship between high sTM levels and the presence of atrial fibrillation in the patient group. In conclusion, plasma sTM levels were increased in Thai patients with cardioembolic stroke and may be a potential marker during the acute phase.

New peptide pENW (pGlu-Asn-Trp) inhibits platelet activation by attenuating Akt phosphorylation

Platelets play a key role in hemostasis and in the initiation and propagation of thrombus formation. New peptide pGlu-Asn-Trp (pENW), initially extracted from snake venom, shows a concentration-dependent antithrombotic activity, significantly attenuated thrombus formation in the arterial and venous vessel systems. This study was designed to further reveal the mechanisms underlying its antithrombotic effect by focusing on its in vitro antiplatelet effect after precluding its influence on coagulation factors. It showed that pENW concentration-dependently inhibited ADP-, collagen- and platelet activating factor (PAF)-induced platelet aggregation, inversely depending upon the intensity of stimulation induced by agonists. Furthermore, data obtained by ELISA and flow cytometry presented that pENW also suppressed ADP-mediated serotonin secretion and P-selectin expression in a concentration-dependent manner. As shown by Western blot assay, ADP-induced platelet Akt phosphorylation was attenuated by the priming incubation with pENW, demonstrating the influence on platelet intracellular signaling. It provided the explaining information for its activity of inhibiting platelet activation in vitro. These results suggested pENW attenuated thrombus formation in part by inhibiting platelet activation instead of coagulation factors, presented evidence of pENW interfering intracellular signaling system in the process of platelet activation and indicated the possibility that pENW could potentially be developed as a novel therapeutic agent in the prevention and treatment of thrombotic disorders.

Intracardiac expression of markers of endothelial damage/dysfunction, inflammation, thrombosis, and tissue remodeling, and the development of postoperative atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is a common complication of coronary artery bypass grafting (CABG), and may have an inflammatory and/or thrombotic etiology. We sought to determine the expression of inflammatory (interleukin [IL]-6), thrombotic (tissue factor and von Willebrand factor [VWF]) and remodeling (matrix metalloproteinase [MMP]-9 and tissue inhibitor of metalloproteinase [TIMP]-1) markers by left atrial appendage (LAA) and right atrial appendage (RAA) tissue in the prediction of postoperative AF. We determined whether the tissue expression of markers of certain different pathophysiologic mechanisms predicted the development of AF after CABG.

METHODS

LAA and RAA tissue was excised during CABG in 100 patients free of AF and inflammation. Tissue marker expression was quantified by immunohistochemistry and was related to 30-day postoperative AF.

RESULTS

Overall, there were no significant differences in staining intensity of any marker between LAA tissue and RAA tissue. However, more intense expression of VWF by LAA tissue predicted the 30 patients with postoperative AF as compared with those free of AF (P = 0.006). IL-6, MMP-9 and TIMP-1 expression by RAA and LAA epicardial tissue was stronger than expression by endocardium or cardiomyocytes (all P < 0.025) but failed to predict AF.

CONCLUSION

In this study, one of the largest to investigate tissue expression of pathophysiologic markers in relation to postoperative AF, we show that more intense expression of VWF by LAA tissue is a significant predictor of postoperative AF. This points towards a possible role of endothelial damage/dysfunction (as reflected by VWF changes) in the pathogenesis of postoperative AF.

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.

Temporal changes in circulating P-selectin, plasminogen activator inhibitor-1, magnesium, and creatine kinase after percutaneous coronary intervention

OBJECTIVE

This study aims to determine the mechanisms underlying restenosis and ischemia-reperfusion injury of the myocardium after percutaneous coronary intervention (PCI).

METHODS

The present study examined serial changes (5 min, 30 min, 2 h, 6 h, and 24 h after PCI) in circulating P-selectin, plasminogen activator inhibitor-1 (PAI-1), magnesium (Mg), and creatine kinase-myocardial band fraction (CK-MB) levels, which may be associated with restenosis and myocardial injury in patients undergoing PCI. The occurrence rates of major adverse cardiovascular events were collected over a six-month follow-up.

RESULTS

PCI induced an early elevation of P-selectin, which correlated positively with the inflation pressure used in the PCI procedure. PCI also caused a significant and sustained decrease in serum Mg in PCI patients, without an effect on PAI-1. An increase in CK-MB was observed in PCI patients, although values were within normal reference range. In addition, elevated P-selectin and decreased Mg measured shortly after the coronary angioplasty procedure were associated with recurrent treatment and heart failure, respectively.

CONCLUSIONS

Our study demonstrates that PCI induces temporal changes of P-selectin, Mg, and CK-MB, which may be involved in restenosis and ischemia-reperfusion injury. These findings highlight the need for using antiplatelet therapy and Mg to reduce the risks associated with PCI.

A study of blood soluble P-selectin, fibrinogen, and von Willebrand factor levels in idiopathic and lone atrial fibrillation

AIMS

A prothrombotic state with elevated levels of soluble P-selectin (sP-sel), fibrinogen, von Willebrand factor (vWf), and other haemostatic indices has been reported in some patients with atrial fibrillation (AF). Whether these changes are due to AF itself or coexistent cardiovascular diseases remains a matter of debate. Therefore, in the present study, the differences in plasma levels of sP-sel, fibrinogen, and vWf between patients with idiopathic/lone AF and sex-, age-, and risk factor-matched controls were investigated to determine whether AF itself might be associated with a hypercoagulable state.

METHODS AND RESULTS

Ninety consecutive patients (63 males, 54.1 ± 10.1 years) with idiopathic AF were studied, 60 (43 males, 48.8 ± 7.5 years) of whom were diagnosed as lone AF. Plasma sP-sel and vWf were measured by enzyme-linked immunosorbent assay. Plasma fibrinogen was measured by chromometry. These indices in AF patients were compared with those in sex-, age- and risk factor-matched controls. Compared with the controls, patients with idiopathic AF had higher levels of sP-sel (AF vs. control: 33.4 ± 7.4 vs. 29.2 ± 6.5 ng/mL, P < 0.001) and fibrinogen (AF vs. control: 3.3 ± 0.9 vs. 3.0 ± 0.6 g/L, P = 0.02), but not vWf, whether with the adjustment of covariates or not. As for those < 60 years, between lone AF and age-matched controls, significant difference existed in the levels of sP-sel (AF vs. control: 34.5 ± 7.3 vs. 30.2 ± 7.3 ng/mL, P = 0.002), but not in those of fibrinogen and vWf, whether with the adjustment of covariates or not.

CONCLUSIONS

Both platelet activation and abnormal changes in coagulation were suggested in idiopathic AF and a platelet activation state in lone AF. This supports the notion that AF per se contributes to a state of hypercoagulation.

Relationship of circulating endothelial progenitor cells to the recurrence of atrial fibrillation after successful conversion and maintenance of sinus rhythm

AIMS

To determine whether the number of circulating endothelial progenitor cells (EPCs) in patients with persistent atrial fibrillation (AF) predicts arrhythmia recurrence after direct current cardioversion (DCCV).

METHODS AND RESULTS

The numbers of circulating CD34+/KDR+ EPCs were determined with flow cytometry in 51 consecutive patients with persistent AF [the mean age: 67 +/- 1.3 years, male (65%)] prior to DCCV and were compared with that of age- and sex-matched controls, and cohorts of patients with coronary artery disease and ischaemic stroke. The AF recurrence rate at 1 year was also determined. The EPCs in patients with persistent AF, patients with coronary artery disease, and patients with ischaemic stroke were significantly lower than that of the age- and sex-matched controls (P < 0.01). One year after successful DCCV, patients with high EPC count (50th to 100th percentile) had a higher recurrence rate of AF when compared with those with low EPC count (less than 50th percentile) (73 vs. 40%, P = 0.02). Cox regression analysis revealed the high EPC count was the only independent predictors for the AF recurrence (HR: 2.29, P = 0.047).

CONCLUSION

The number of EPCs is reduced in patients with persistent AF and predicts the recurrence of AF after successful DCCV.

Changes in plasma von Willebrand factor and ADAMTS13 levels associated with left atrial remodeling in atrial fibrillation

INTRODUCTION

Previous studies have shown raised plasma von Willebrand factor (VWF) levels in patients with atrial fibrillation (AF). However, little is known about changes of VWF associated with VWF-cleaving protease (ADAMTS13) in AF. The aim of this study was to examine the relationship between changes in plasma VWF and ADAMTS13 levels, and left atrial remodeling in AF patients.

MATERIALS AND METHODS

We measured plasma VWF and ADAMTS13 antigen levels in 70 paroxysmal AF (PAF) patients, 56 chronic AF (CAF) patients, and 55 control subjects.

RESULTS

Plasma VWF levels (mU/ml) were significantly higher in CAF and PAF patients compared with the controls (2103 +/- 743, 1930 +/- 676, 1532 +/- 555, respectively, P < 0.0001 in CAF vs. controls, P = 0.001 in PAF vs. control), while ADAMTS13 levels (mU/ml) were significantly lower in CAF and PAF patients compared with the controls (795 +/- 169, 860 +/- 221, 932 +/- 173, respectively, P = 0.0002 in CAF vs. controls, P = 0.04 in PAF vs. control). The VWF/ADAMTS13 ratio was significantly higher in patients with CAF than PAF or controls (2.81 +/- 1.30, 2.34 +/- 0.92, 1.73 +/- 0.83, respectively; P = 0.01 in CAF vs. PAF, P < 0.0001 in CAF vs. controls). There was a significant correlation between the VWF/ADAMTS13 ratio and left atrial diameter (positive correlation; r = 0.275, P = 0.0002) and left atrial appendage flow velocity (negative correlation; r = -0.345, P = 0.0018).

CONCLUSIONS

These findings suggest that the imbalance between plasma VWF and ADAMTS13 levels caused by left atrial remodeling might be closely associated with intra-atrial thrombus formation in AF patients.

Increased von Willebrand factor in acute stroke patients with atrial fibrillation

Plasma level of von Willebrand factor (vWF) is a useful marker not only for endothelial dysfunction, but also for left atrial thrombogenesis. We measured plasma levels of vWF antigen and other coagulation and fibrinolysis markers in 183 consecutive patients with acute ischemic stroke and compared these data between patients with and without atrial fibrillation (AF). vWF correlated with severity, outcome, and infarct size and were significantly higher in the AF group than in the non-AF group. The positive correlations of vWF with plasmin-alpha2 plasmin inhibitor complex and soluble fibrin monomer complex, and higher levels of vWF in patients with than without spontaneous echo contrast, indicate thrombogenesis in the left atrium. Plasma levels of vWF may reflect thrombogenesis in patients with AF.

The feasibility of tissue Doppler acceleration as a new predictor of thrombogenesis in the left atrial appendage associated with nonvalvular atrial fibrillation

BACKGROUND

Tissue acceleration utilizing the tissue Doppler imaging (TDI) technique is a new marker of ventricular contraction. We evaluated whether the left atrial appendage (LAA) wall acceleration was associated with thrombosis in patients with nonvalvular atrial fibrillation (NVAF).

METHODS

Seven NVAF patients with thromboembolism (TE), eight without TE, and eight with normal sinus rhythm (NSR) were studied using transesophageal echocardiography. TDI was used to evaluate the LAA wall acceleration.

RESULTS

There was a decrease in the peak flow velocity in the TE group compared with the other two groups. There was greater LAA expansion in NVAF with TE groups (with TE [8.9 +/- 2.1 cm(2)] compared with the group without TE [7.3 +/- 2.8 cm(2)]), but the difference was not statistically significant; the difference was statistically significant compared with the NSR group (5.3 +/- 1.2 cm(2); P = 0.0035). The average of the continuous 40-frames area where tissue Doppler acceleration (TDA) was >0.024 cm/sec(2) was significantly lower in the TE group (0.12 +/- 0.05 cm(2)) compared to the group without TE (0.33 +/- 0.17 cm(2); P = 0.0017) and NSR group (0.30 +/- 0.13 cm(2); P = 0.0042), although wall velocity was not significantly different comparing the two NVAF groups. Furthermore, peak flow velocity of LAA was well correlated with LAA wall acceleration (r = 0.864, P < 0.0001).

CONCLUSIONS

LAA wall acceleration obtained utilizing the TDI technique may be a new predictor of thrombogenesis in patients with NVAF.

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.

Levels of circulating procoagulant microparticles in nonvalvular atrial fibrillation

Circulating procoagulant microparticles (MPs) arising from cell activation or fragmentation during apoptosis retain procoagulant properties and are increased in severe thrombotic states. We investigated whether circulating procoagulant MP levels would be increased in nonvalvular atrial fibrillation (AF). Using a hospital case-control study design, circulating procoagulant MP levels were measured in 45 patients with permanent and/or persistent AF who were not receiving anticoagulant therapy and 90 age-matched control subjects (45 with cardiovascular risk factors and 45 without). Annexin V-positive MP levels (expressed as nanomoles per liter of phosphatidylserine equivalent) were higher in patients with AF (median 9.3, interquartile range 6.8 to 17.3 nmol/L) than in control subjects with cardiovascular risk factors (median 4.9, interquartile range 3.7 to 8.4 nmol/L) and control subjects without cardiovascular risk factors (median 3.2, interquantile range 2.3 to 4.6 nmol/L; p<0.001). Platelet-derived MPs (captured with antiglycoprotein Ib) and endothelial-derived MPs (captured with anti-CD31) were similar in patients with AF and control subjects with cardiovascular risk factors but were significantly higher than in control subjects without cardiovascular risk factors. On multiple regression analysis, the presence of AF was a strong predictor of annexin V-positive MP level (p<.001). In conclusion, circulating procoagulant MPs are increased in persistent and/or permanent AF and might reflect a hypercoagulable state that could contribute to atrial thrombosis and thromboembolism.

Chronobiology of hemostasis and inferences for the chronotherapy of coagulation disorders and thrombosis prevention

The hemostatic system in its multiple components displays an intricate organization in time which is characterized by circadian (approximately 24-hour), circaseptan (approximately 7-day), menstrual (approximately monthly), and circannual (approximately yearly) bioperiodicities. The interaction of the rhythms of the variables participating in hemostasis determine transient risk states of thromboembolic events, including myocardial infarction and stroke, and of hemorrhage and hemorrhagic events, each with a unique timing. The circadian staging of the rhythms in vascular, cellular, and coagulation factors that favors blood coagulation and thrombosis coincides with the daily minimum in fibrinolytic activity; as a result there is elevated risk in the morning of acute myocardial infarction and stroke. Similar hemostatic rhythms may determine the epidemiology of thromboembolic and hemorrhagic events during the week, month and year. This article focuses on the large-amplitude circadian rhythms operative in the hemostatic system. Their implication for preventive and curative pharmacotherapy of hemostatic disorders is presented, with discussion of related problems.

Self-limited bursts of atrial fibrillation following successful cardioversion

BACKGROUND

To evaluate if self-limited episodes of atrial fibrillation after DC cardioversion predict recurrence of persistent atrial fibrillation. To evaluate the incidence and duration of such episodes as well as their change over time.

METHODS

Consecutive patients with persistent atrial fibrillation, scheduled for direct current cardioversion were prospectively included in the study. Ambulatory ECG Holter monitoring (24 h) was performed one, three and 6 weeks after successful cardioversion.

RESULTS

A total of 84 patients were prospectively included in the study. Sinus rhythm was restored in 74 patients (88%). At 6 weeks of follow-up 40 patients out of 74 (54%) had sinus rhythm, and 34 patients (46%) had relapsed into persistent atrial fibrillation. Eight out of these 34 patients (24%) had bursts of atrial fibrillation at their first Holter recording, compared to 12 patients out of 40 (30%) in sinus rhythm at 6 weeks (p>0.05). On the first, second and third Holter recording 21 patients out of 51 (41%), 21 patients out of 43 (49%) and 15 out of 40 patients (38%) had self-limited bursts of atrial fibrillation, respectively. The incidence or duration of episodes did not vary over time during the 6 weeks of follow-up.

CONCLUSION

In patients successfully converted to sinus rhythm self-limited bursts of atrial fibrillation do not predict recurrence of persistent atrial fibrillation during 6 weeks of follow up. Brief self-limited episodes of atrial fibrillation are common, and the incidence and duration of such episodes are constant during a 6 weeks period after DC cardioversion.

Diurnal, seasonal, and blood-processing patterns in levels of circulating fibrinogen, fibrin D-dimer, C-reactive protein, tissue plasminogen activator, and von Willebrand factor in a 45-year-old population

BACKGROUND

Circulating levels of fibrinogen, fibrin D-dimer, C-reactive protein (CRP), tissue plasminogen activator antigen (t-PA) and von Willebrand factor are associated with incident coronary heart disease. We describe cross-sectional diurnal, seasonal, and blood-processing patterns for these variables, and assess whether they represent important sources of variability that should be taken into account in epidemiological studies or for additional risk prediction in individuals.

METHODS AND RESULTS

A total of 9377 men and women aged 45 years were visited in their homes and blood-sampled for fibrinogen, D-dimer, CRP, t-PA, and von Willebrand factor. These variables were examined in relation to the time of blood sample collection, day of the year, and delay in processing. All variables exhibited statistically significant diurnal sinusoidality (P < or = 0.02). Our models predicted a peak rise for fibrinogen and von Willebrand factor at midday, with overall diurnal variations of 3% and 10%, respectively, after adjustment for standard cardiovascular risk factors. D-dimer exhibited a peak at 14:00 hours, CRP at 15:00 hours, and t-PA at 10:00 hours with diurnal variations of 10%, 34%, and 55%, respectively, after full adjustment. All variables except CRP showed seasonal heterogeneity. Greater delays in processing blood samples were associated with higher levels of t-PA in particular. The proportion of variation attributed to the diurnal, seasonal, and processing effects was 2% for fibrinogen and von Willebrand factor; 9% for D-dimer, 1% for CRP, and 16% for t-PA.

CONCLUSIONS

Temporal variations are important sources of heterogeneity that may bias the analysis of epidemiological studies and coronary heart disease risk prediction in individuals. Sample-processing delay is particularly important for t-PA.

Thoracic Aortic Plaque Enhances Hypercoagulability in Patients With Nonrheumatic Atrial Fibrillation

BACKGROUND

Patients with atrial fibrillation (AF) are at risk for thromboembolism, and coexistent cardiovascular diseases could affect their prothrombotic profiles. The relationship between plasma hemostatic markers and aortic atherosclerosis was determined in patients with AF or in sinus rhythm (SR).

METHODS AND RESULTS

Sixty patients with nonrheumatic AF and 46 patients in SR who underwent transesophageal echocardiography and did not receive anticoagulant therapy constituted the study group. Markers for platelet activity (platelet factor 4 and beta-thromboglobulin), thrombotic status (thrombin-antithrombin III complex and prothrombin fragment 1+2 (F1+2)) and fibrinolytic status (plasmin-alpha2-plasmin inhibitor complex (PIC) and D-dimer) were determined. Levels of F1+2, PIC and D-dimer were higher in AF patients with severe atheroma than in those without severe atheroma (p<0.05). In patients in SR, hemostatic markers were not significantly increased even if they had severe aortic atherosclerosis. AF (Odds ratio (OR) 4.06, p=0.04) and age>or=75 years (OR 3.98, p=0.02) were independently predictive of elevated D-dimer levels and severe atheroma was predictive of elevated F1+2 levels (OR 5.52, p=0.04).

CONCLUSIONS

Elderly patients with AF and severe aortic atherosclerosis might be in a prothrombotic state, and could benefit from intensive antithrombotic therapy.

Fluctuations in coagulation activity among patients with atrial fibrillation who are stably anticoagulated

Atrial fibrillation is an important independent risk factor for stroke and increases the risk of systemic embolism. The individual risk depends on several clinical, environmental and biological factors. Additionally, a hypercoagulable state with abnormalities of hemostasia, thrombosis and platelet function have been observed in atrial fibrillation. This arrhythmia is also influenced by a disrupted circadian rhythm of hypercoagulable status implicated in the genesis of cardiovascular and cerebral diseases. The beneficial effect of oral anticoagulation therapy in atrial fibrillation has been confirmed by several studies. However, circadian variations in the degree of anticoagulation in these patients have also been described. In this review, the authors analyze the factors that might condition diurnal variations in thrombogenesis, hypercoagulability, and the extent of anticoagulation in patients with atrial fibrillation.

The effects of direct current cardioversion for persistent atrial fibrillation on indices of endothelial damage/dysfunction

BACKGROUND

Atrial fibrillation is associated with increased thromboembolic risk, and this risk may occur even following cardioversion. Atrial fibrillation has been hypothesised to cause alterations in endothelial cell function through the influences of altered flow dynamics, and resultant endothelial dysfunction may be contributory to the generation of a prothrombotic state. The aim of this study was therefore to assess endothelial function before and after electrical cardioversion.

METHODS

We studied 30 consecutive patients undergoing elective cardioversion for AF and compared them with 20 healthy controls. Plasma levels of endothelial damage/dysfunction [von Willebrand factor (vWF), E-selectin (E-sel), soluble thrombomodulin (sTM)] and Circulating Endothelial Cells (CECs, an index of endothelial damage) in whole blood were measured in all subjects and on the AF group at baseline (pre-cardioversion) and at 2 h and 4 weeks following cardioversion.

RESULTS

Plasma levels of vWf were significantly increased in persistent AF at baseline compared to healthy controls (p<0.001). With restoration of sinus rhythm, vWF levels were significantly decreased at 4 weeks (p=0.0001), whilst levels of CECs (p=0.01) and sTM (p=0.022), although not increased at baseline, were significantly increased following cardioversion.

CONCLUSION

Although plasma vWF levels decreased post-cardioversion, suggesting some improvement in vascular endothelial function, the increases in sTM and CECs at 4 weeks may indicate endothelial injury sustained peri-cardioversion. This (delayed) injury and shedding of endothelial cells post-cardioversion may contribute to late thromboembolic risk.

Angiotensin II Type 1 Receptor Blocker Prevents Atrial Structural Remodeling in Rats with Hypertension Induced by Chronic Nitric Oxide Inhibition

The prevalence of atrial fibrillation (AF) increases in patients with hypertension. Angiotensin II is involved in structural atrial remodeling, which contributes to the onset and maintenance of AF in paced animal models. We investigated the role of angiotensin II in atrial structural remodeling in rats with hypertension. Ten-week-old male Wistar-Kyoto rats were randomly divided into 4 groups: a control group (no treatment), an Nomega-nitro-L-arginine methyl ester (L-NAME) group (administered L-NAME, an inhibitor of nitric oxide synthase, 1 g/l in drinking water), an L-NAME+candesartan group (L-NAME plus candesartan-an angiotensin II receptor blocker (ARB)-at 0.1 mg/kg/day), and an L-NAME + hydralazine group (L-NAME plus hydralazine at 120 mg/l in drinking water). Eight weeks after treatment, the L-NAME group showed significantly higher systolic blood pressure than the control group (197 +/- 12 vs.138 +/- 5 mmHg, p < 0.05). Candesartan or hydralazine with L-NAME reduced systolic blood pressure to baseline. Chronic inhibition of NO synthesis increased the extent of fibrosis and transforming growth factor-beta expression in atrial tissue, and both of these effects were prevented by candesartan, but not by hydralazine. Cardiac hypertrophy and dysfunction were induced in the L-NAME group, and these effects were also prevented by candesartan, but not by hydralazine. In contrast, the decrease in thrombomodulin expression in the atrial endocardium in hypertensive rats was restored by candesartan and hydralazine. The ARB prevented atrial structural remodeling, a possible contributing factor for the development of AF, in the hearts of rats with hypertension induced by long-term inhibition of NO synthesis.

Effects of congestive heart failure on plasma von Willebrand factor and soluble P-selectin concentrations in patients with non-valvar atrial fibrillation

OBJECTIVE

To examine further the relations of plasma von Willebrand factor (vWf, an index of endothelial damage and dysfunction) and soluble P-selectin (sP-sel, an index of platelet activation) concentrations to the presence and onset of clinical congestive heart failure (CHF) and the degree of left ventricular (LV) dysfunction in patients taking part in the SPAF (stroke prevention in atrial fibrillation) study.

METHODS

Plasma concentrations of vWf and sP-sel were measured by enzyme linked immunosorbent assay (ELISA) in 1321 participants in the SPAF III study and related to the presence and onset of clinical CHF, as well as echocardiographic findings. Of the 1321 patients with atrial fibrillation (AF), 331 (25%) had a documented history of clinical heart failure, of which 168 cases were related to a new or recurrent episode of acute decompensated heart failure occurring within the preceding three months.

RESULTS

Mean plasma vWf was higher among patients with AF and CHF (154 (29) v 144 (31) IU/dl, p < 0.001), particularly those with acute or recent decompensated symptoms. Patients with severe LV dysfunction on two dimensional echocardiography and low fractional shortening also had significantly higher vWf concentrations than those with no LV dysfunction. CHF patients with clinical features--with (156 (28) IU/dl) and without (152 (31) IU/dl) LV dysfunction--also had higher mean vWf concentrations than patients with asymptomatic LV dysfunction (146 (31) IU/dl, p < 0.001). The presence of mitral regurgitation in CHF was associated with lower vWf concentrations. Plasma sP-sel concentrations were not affected by presence, onset, or severity of heart failure.

CONCLUSIONS

CHF may contribute to hypercoagulability and thrombotic risk in AF through increased endothelial damage and dysfunction. Patients with acute or recent decompensated features have the highest degree of endothelial damage and dysfunction. The presence of CHF clinical features was an important determinant of plasma vWf concentrations.

Dementia in subjects with atrial fibrillation: hemostatic function and the role of anticoagulation

BACKGROUND

Atrial fibrillation (AF) is associated with cognitive impairment and dementia, perhaps through encouraging a prothrombotic state and cardioembolism.

OBJECTIVES

We wished to test the hypotheses that hemostatic function is altered in subjects with AF who develop dementia, and that long-term warfarin anticoagulation is protective against this complication.

PATIENTS AND METHODS

Recruitment was from an observational cohort study of AF. Baseline assessment included measurement of plasma fibrinogen, fibrin D-dimer, prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complexes (TAT), von Willebrand factor and tissue plasminogen activator. We assessed cognitive function after 3 years' follow-up using the 13-item modified Telephone Interview for Cognitive Status (TICSm) and the short form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE).

RESULTS

Of the 218 subjects assessed, 145 (66%) were prescribed warfarin. Forty-nine (22%) met TICSm/IQCODE criteria for dementia. D-dimer, F1+2 and TAT levels were higher in AF subjects with dementia compared with those without (medians 81 vs. 60 ng mL(-1), P = 0.008; 0.76 vs. 0.49 nmol L(-1), P = 0.006; and 1.78 vs. 1.44 microg L(-1), P = 0.003, respectively). These associations became of borderline statistical significance following adjustment for age. Logistic regression showed a trend towards warfarin use being independently associated with reduced prevalence of dementia (odds ratio 0.52, P = 0.08).

CONCLUSIONS

We found evidence of increased thrombin generation and fibrin turnover in subjects with AF and dementia compared with those without dementia. Long-term warfarin use may be protective against the development of dementia in subjects with AF.

Tissue factor expression in atrial endothelia associated with nonvalvular atrial fibrillation: possible involvement in intracardiac thrombogenesis

INTRODUCTION

Tissue factor plays a key role in the extrinsic coagulation pathway and is induced by inflammatory cytokines. Atrial myocarditis has been detected recently in some patients with lone atrial fibrillation. Virchow's triad of low blood flow, hypercoagulability, and endothelial dysfunction, enhances thrombus formation. The present study was designed to elucidate the role of endothelial dysfunction in thrombogenesis associated with nonvalvular atrial fibrillation.

MATERIAL AND METHODS

We investigated tissue factor expression in the endothelia of left atrial appendages obtained from seven patients with nonvalvular atrial fibrillation and cardiogenic thromboembolism. Tissues were divided into 7-13 sections and compared with control specimens from four patients who died of noncardiac events. Expression of tissue factor, von Willebrand factor and tissue factor pathway inhibitor was evaluated by immunohistochemistry.

RESULTS

Histopathologically, inflammatory cells infiltrated the endocardium and all seven patients showed features of persistent myocarditis. Activated T cells [15.3+/-9.4 cells/high power field (HPF, mean+/-S.D.) vs. control 2.2+/-4.4/HPF (P=0.0294)] and a few macrophages [5.1+/-8.4 cells/HPF vs. control 2.4+/-3.5 cells/HPF (P=NS)] infiltrated the endocardium. Tissue factor was overexpressed in the endothelia particularly in tissues containing inflammatory cells and denuded matrix of the endocardium, compared with the control group. Von Willebrand factor, but not tissue factor pathway inhibitor, was also overexpressed in these tissues.

CONCLUSION

Tissue factor expression induced by local inflammation is involved in the pathogenesis of thrombosis in patients with nonvalvular atrial fibrillation.

Effects of the Oral Direct Thrombin Inhibitor Ximelagatran on P-Selectin Expression and Thrombin Generation in Atrial Fibrillation

This study investigated the pharmacodynamic effects of the oral direct thrombin inhibitor ximelagatran on platelet activation and thrombin generation in patients with nonvalvular atrial fibrillation. Using an open, group-matched study design, the effects of ximelagatran (36 mg twice daily for 5 days) were studied in 12 patients with permanent nonvalvular atrial fibrillation and in 12 healthy controls. After ximelagatran for 5 days, elevated platelet P-selectin expression in atrial fibrillation patients was lowered to that during coumarin treatment or in controls but had no effect in control subjects. Using the endogenous thrombin potential as a marker, ximelagatran decreased and delayed thrombin generation in both groups. In conclusion, direct thrombin inhibition with ximelagatran reduced elevated platelet P-selectin expression and inhibited thrombin generation.

Thrombomodulin and tissue factor pathway inhibitor in endocardium of rapidly paced rat atria

BACKGROUND

Atrial fibrillation (AF) is well known as one of the cardiogenic causes for thromboembolism. Although decreased flow and hypercoagulable state of the blood in the fibrillating atrium have been emphasized as the underlying mechanisms, endocardial dysfunction in maintaining the local coagulation balance could also contribute to the thrombogenesis in AF.

METHODS AND RESULTS

The paroxysmal AF model was created by rapid atrial pacing in anesthetized rats. To test the hypothesis that AF induces local coagulation imbalance by disturbing the atrial endocardial function, the gene expression of intrinsic anticoagulant factors, thrombomodulin (TM) and tissue factor pathway inhibitor (TFPI), were determined by means of ribonuclease protection assay, Western blotting, and immunohistochemistry. Rapid atrial pacing for 8 hours significantly decreased TM and TFPI mRNA levels in the left atrium but not in the ventricle, leading to the downregulation of their immunoreactive proteins. Immunohistochemical analysis revealed that TM and TFPI were expressed predominantly in the endocardial cells of the normal atrium, presumably preventing local blood coagulation, and that rapid atrial pacing induced the loss of TM and TFPI expression in the endocardium, leading to deficiency in anticoagulant barriers between the atria and the blood.

CONCLUSIONS

Rapid atrial pacing acutely downregulated the gene expression of TM and TFPI in the atrial endocardium, thereby inducing local coagulation imbalance on the internal surface of the atrial cavity. These results would support the validity of supplement of anticoagulant molecules deficient in AF.

Interleukin-6, tissue factor and von Willebrand factor in acute decompensated heart failure: relationship to treatment and prognosis

Arterial thrombotic and thromboembolic complications are increased in congestive heart failure (CHF), and are a particular problem in acute decompensated heart failure, which carries a poor prognosis. As interleukin-6 (IL-6) has been shown to induce the potent procoagulant tissue factor (TF) in experimental models, we hypothesized that the pro-inflammatory IL-6 may be one mechanism contributing to thrombosis in heart failure, mediated via endothelial expression of TF on activated/damaged cells [indicated by plasma von Willebrand factor (vWF)]. Seventy-seven patients (67% men, New York Heart Association class III-IV, 87%) with acute CHF were recruited, and were compared with 53 chronic stable CHF patients in sinus rhythm (66% men, New York Heart Association class III-IV, 2%) and 37 healthy controls (68% men). Acute CHF patients in sinus rhythm had elevated baseline levels of IL-6 (P < 0.0001), TF (P = 0.041) and vWF (P < 0.0001) (all measured by enzyme-linked immunosorbent assay) compared with both chronic CHF and healthy control groups. A correlation exists in acute CHF between baseline TF and IL-6 (Spearman r = 0.64, P < 0.0001). After 3 months treatment, with control or alleviation of heart failure symptoms in 40 patients, there was a fall in levels of IL-6 (P < 0.0001) and vWF (P < 0.0001), but levels still remained significantly higher than healthy controls. Patients who died at 6 months follow-up also had higher baseline levels of IL-6 (P = 0.008), TF (P = 0.037) and vWF (P = 0.039) when compared with those who remained alive. Elevated IL-6 may contribute to the thrombotic and thromboembolic complications in acute heart failure, in a process mediated via increased TF and vWF. Improvement of symptoms and plasma markers after treatment of acute CHF and prediction of prognosis by the markers may be useful in the clinical setting.

Prognostic value of plasma von Willebrand factor and soluble P-selectin as indices of endothelial damage and platelet activation in 994 patients with nonvalvular atrial fibrillation

BACKGROUND

Abnormal plasma markers of a prothrombotic state have been described in atrial fibrillation (AF), but no such marker has yet been shown to reliably predict future stroke or cardiovascular outcome in AF. We hypothesized that raised plasma levels of von Willebrand factor (vWf, an index of endothelial damage/dysfunction) and/or soluble P-selectin (sP-sel, an index of platelet activation) might predict vascular events in AF.

METHODS AND RESULTS

We measured vWf and sP-sel levels by ELISA in 994 participants receiving aspirin in the Stroke Prevention in Atrial Fibrillation III trial, at study entry or after 3 months, and related these indices to the subsequent incidence of stroke and vascular events. Plasma vWf levels were a significant predictor of both stroke (P=0.03) and vascular events (P<0.001), with the greatest risk for those with the highest levels of vWf. After adjustment for other clinical predictors, the relationship between vWf and stroke became nonsignificant, but vWf remained an independent predictor of vascular events (relative risk, 1.2 [95% CI, 1.0-1.4] per 20 IU/dL increase in vWf; P=0.02). No significant relationships were found between sP-sel levels and outcome.

CONCLUSIONS

Among patients with AF who received aspirin, raised levels of vWf (endothelial damage/dysfunction) were predictive of stroke and vascular events, but raised sP-sel levels (platelet activation) were not associated with increased cardiovascular risk. Endothelial damage/dysfunction (or vWf itself) may play an important role in the mechanisms behind stroke and cardiovascular outcome among aspirin-treated AF patients and might represent a target for novel therapies or an adjunctive aid to risk stratification in AF.

Diurnal and seasonal variation of stroke incidence in patients with cardioembolic stroke due to atrial fibrillation

A seasonal variation with an incidence peak during the colder period of the year, as well as a circadian distribution with a single peak of stroke onset in the morning hours are described in various countries. Cardioembolic stroke seems to be the most frequent stroke subtype among Greek patients. Atrial fibrillation is identified as the most frequent cause of stroke. Analysis of the temporal pattern of symptom onset in a series of over 300 Greek patients with first-ever cardioembolic acute stroke due to atrial fibrillation revealed a circannual distribution with a peak during winter and a decline of stroke occurrence during summer. Analysis of the diurnal variation of symptom onset in this stroke subgroup showed a distribution with 2 incidence peaks between 08:00-10:00 and 16:00-18:00. A relation between the second, however lower, frequency peak and the traditional Greek habit of afternoon sleep (siesta) could be assumed. Possible clustering of cardiologic events in patients with atrial fibrillation, especially during the time interval after awakening from night and afternoon sleep, could be a plausible explanation, which certainly deserves to be further investigated.