Fibrin D-dimer and beta-thromboglobulin as markers of thrombogenesis and platelet activation in atrial fibrillation. Effects of introducing ultra-low-dose warfarin and aspirin

Fibrinaloid Microclots and Atrial Fibrillation

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

The Association between Coagulation and Atrial Fibrillation

The existing literature highlights the presence of numerous coagulation factors and markers. Elevated levels of coagulation factors are associated with both existing and newly diagnosed cases of atrial fibrillation (AF). However, this article summarizes the role of coagulation in the pathogenesis of AF, which includes fibrinogen and fibrin, prothrombin, thrombomodulin, soluble urokinase plasminogen activator receptor, von Willebrand factor, P-selectin, D-dimer, plasminogen activator inhibitor-1, and platelet activation. Coagulation irregularities play a significant role in the pathogenesis of AF.

Omega-3 Fatty Acids and Markers of Thrombosis in Patients with Atrial Fibrillation

Omega-3 fatty acids (n-3 FAs) are associated with a lower risk of ischemic stroke in patients with atrial fibrillation (AF). Antithrombotic mechanisms may in part explain this observation. Therefore, we examined the association of n-3 FAs with D-dimer and beta-thromboglobulin (BTG), markers for activated coagulation and platelets, respectively. The n-3 FAs eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), docosapentaenoic acid (DPA) and alpha-linolenic acid (ALA) were determined via gas chromatography in the whole blood of 2373 patients with AF from the Swiss Atrial Fibrillation cohort study (ClinicalTrials.gov Identifier: NCT02105844). In a cross-sectional analysis, we examined the association of total n-3 FAs (EPA + DHA + DPA + ALA) and the association of individual fatty acids with D-dimer in patients with detectable D-dimer values (n = 1096) as well as with BTG (n = 2371) using multiple linear regression models adjusted for confounders. Median D-dimer and BTG levels were 0.340 ug/mL and 448 ng/mL, respectively. Higher total n-3 FAs correlated with lower D-dimer levels (coefficient 0.94, 95% confidence interval (Cl) 0.90-0.98, p = 0.004) and lower BTG levels (coefficient 0.97, Cl 0.95-0.99, p = 0.003). Likewise, the individual n-3 FAs EPA, DHA, DPA and ALA showed an inverse association with D-dimer. Higher levels of DHA, DPA and ALA correlated with lower BTG levels, whereas EPA showed a positive association with BTG. In patients with AF, higher levels of n-3 FAs were associated with lower levels of D-dimer and BTG, markers for activated coagulation and platelets, respectively. These findings suggest that n-3 FAs may exert antithrombotic properties in patients with AF.

DOACs vs Vitamin K Antagonists During Cardiac Rhythm Device Surgery: A Multicenter Propensity-Matched Study

BACKGROUND

There is a paucity of data comparing vitamin K antagonists (VKAs) to direct oral anticoagulants (DOACs) at the time of cardiac implantable electronic device (CIED) surgery. Furthermore, the best management of DOACs (interruption vs continuation) is yet to be determined.

OBJECTIVES

This study aimed to compare the incidence of device-related bleeds and thrombotic events based on anticoagulant type (DOAC vs VKA) and regimen (interrupted vs uninterrupted).

METHODS

This was an observational multicenter study. We included patients on chronic oral anticoagulation undergoing CIED surgery. Patients were matched using propensity scoring.

RESULTS

We included 1,975 patients (age 73.8 ± 12.4 years). Among 1,326 patients on DOAC, this was interrupted presurgery in 78.2% (n = 1,039) and continued in 21.8% (n = 287). There were 649 patients on continued VKA. The matched population included 861 patients. The rate of any major bleeding was higher with continued DOAC (5.2%) compared to interrupted DOAC (1.7%) and continued VKA (2.1%) (P = 0.03). The rate of perioperative thromboembolism was 1.4% with interrupted DOAC, whereas no thromboembolic events occurred with DOAC or VKA continuation (P = 0.04). The use of dual antiplatelet therapy, DOAC continuation, and male sex were independent predictors of major bleeding on a multivariable analysis.

CONCLUSIONS

In this large real-world cohort, a continued DOAC strategy was associated with a higher bleeding risk compared to DOAC interruption or VKA continuation in patients undergoing CIED surgery. However, DOAC interruption was associated with increased thromboembolic risk. Concomitant dual antiplatelet therapy should be avoided whenever clinically possible. A bespoke approach is necessary, with a strategy of minimal DOAC interruption likely to represent the best compromise.

Sepsis-induced coagulopathy is associated with new episodes of atrial fibrillation in patients admitted to critical care in sinus rhythm

Background

Sepsis is a life-threatening disease commonly complicated by activation of coagulation and immune pathways. Sepsis-induced coagulopathy (SIC) is associated with micro- and macrothrombosis, but its relation to other cardiovascular complications remains less clear. In this study we explored associations between SIC and the occurrence of atrial fibrillation (AF) in patients admitted to the Intensive Care Unit (ICU) in sinus rhythm. We also aimed to identify predictive factors for the development of AF in patients with and without SIC.

Methods

Data were extracted from the publicly available AmsterdamUMCdb database. Patients with sepsis and documented sinus rhythm on admission to ICU were included. Patients were stratified into those who fulfilled the criteria for SIC and those who did not. Following univariate analysis, logistic regression models were developed to describe the association between routinely documented demographics and blood results and the development of at least one episode of AF. Machine learning methods (gradient boosting machines and random forest) were applied to define the predictive importance of factors contributing to the development of AF.

Results

Age was the strongest predictor for the development of AF in patients with and without SIC. Routine coagulation tests activated Partial Thromboplastin Time (aPTT) and International Normalized Ratio (INR) and C-reactive protein (CRP) as a marker of inflammation were also associated with AF occurrence in SIC-positive and SIC-negative patients. Cardiorespiratory parameters (oxygen requirements and heart rate) showed predictive potential.

Conclusion

Higher INR, elevated CRP, increased heart rate and more severe respiratory failure are risk factors for occurrence of AF in critical illness, suggesting an association between cardiac, respiratory and immune and coagulation pathways. However, age was the most dominant factor to predict the first episodes of AF in patients admitted in sinus rhythm with and without SIC.

Carbohydrate antigen 125 in atrial fibrillation

Atrial fibrillation is the most common arrhythmia in clinical settings. It is associated with an increased risk of death, stroke, and peripheral vascular embolism. Catheter ablation (CA) is an effective treatment for patients with AF. However, many studies have reported suboptimal outcomes, as AF recurrence rates often remain high after CA. Therefore, there is a need for early identification of patients who are prone to recurrence and require anti-inflammatory and/or antiarrhythmic treatment after CA. In recent years, Prediction of AF and AF recurrence after CA has become a hot topic in clinical practice. A lot of biomarkers (Such as B-type natriuretic peptide, N-terminal pro-BNP, high sensitivity C reactive protein etc.) have been identified as markers for predicting the risk of AF and AF recurrence after CA. Although these markers have been shown to predict AF and AF recurrence after CA, there are currently no relevant guidelines to indicate which of these markers have absolute predictive value. Therefore, Finding the appropriate indicators that can efficiently and accurately predict AF recurrence after AF ablation is important to provide the best treatment for each patient. These indicators still need exploration. Carbohydrate antigen 125 (CA-125) is a tumor marker suitable for the screening, diagnosis, and monitoring of ovarian malignant tumors. It has been widely studied in patients with heart failure. In recent years, the role of CA-125 in AF has been widely studied, and we provide a review in this article. It is wide availability and low cost provide additional advantages for its rapid implementation. This article reviews the role of CA-125 in patients with atrial fibrillation.

Relationship between baseline D-dimer and prognosis in Japanese patients with venous thromboembolism: Insights from the J'xactly study

Background

D-dimer is a biomarker of fibrin production and degradation, and changes in D-dimer concentration suggest fibrin clot formation, which is associated with thromboembolism and hypercoagulable states. Thus, an elevated D-dimer concentration could be a useful prognostic predictor for patients with venous thromboembolism (VTE).

Methods and results

In this subanalysis of the J'xactly study, a prospective multicenter study conducted in Japan, we examined the clinical outcomes of 949 patients with VTE stratified by baseline D-dimer concentration. The median D-dimer concentration was 7.6 μg/ml (low D-dimer group: <7.6 μg/ml [n = 473, 49.8%]; high D-dimer group: ≥7.6 μg/ml [n = 476, 50.2%]). The mean age of the patients was 68 years, and 386 patients (40.7%) were male. Compared with the low D-dimer group, the high D-dimer group had more frequent pulmonary embolism with or without deep vein thrombosis (DVT), proximal DVT, atrial fibrillation, or diabetes mellitus, and underwent intensive treatment with 30 mg/day rivaroxaban. The incidence of composite clinically relevant events (recurrence or exacerbation of symptomatic VTE, acute coronary syndrome [ACS], ischemic stroke, death from any cause, or major bleeding) was higher in the high D-dimer group than in the low D-dimer group (11.1% vs. 7.5% per patient-year; hazard ratio, 1.46; 95% confidence interval, 1.05-2.04; p = 0.025). There was no significant difference between the high and low D-dimer groups in the incidence of VTE (2.8% vs. 2.5% per patient-year, respectively; p = 0.788), ACS (0.4% per patient-year vs. not observed, respectively; p = 0.078), or major bleeding (4.0% vs. 2.1% per patient-year, respectively; p = 0.087), but there was a significant difference in the incidence of ischemic stroke (1.0% per patient-year vs. not observed, respectively; p = 0.004).

Conclusion

Elevated D-dimer concentration may be an important prognostic predictor in Japanese patients with VTE.Clinical Trial Registration: UMIN CTR, UMIN000025072 (https://www.umin.ac.jp/ctr/index.htm).

Atrial fibrillation and stroke

INTRODUCTION

Stroke is one of the leading causes of mortality and morbidity globally. Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. It is set to reach epidemic proportions. AF is associated with a five-fold increase in risk of stroke. Strokes caused by AF more often are fatal or result in severe disability. Even though the incidence of stroke has been significantly reduced by oral anticoagulation, AF is thought to account for a significant proportion of cryptogenic strokes where no etiology is identified.

AREAS COVERED

This article reviews the literature related to AF and stroke, pathophysiological insights, diagnosis of AF in stroke patients, and its management (Graphical Abstract).

EXPERT OPINION

The pathophysiology of thrombogenesis that links AF and stroke is not well understood and is an area of active research to identify new therapeutic targets to prevent AF and stroke. As the nature of AF and stroke is multifaceted, an integrated care approach to managing AF and stroke is increasingly essential.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Drugs in phase I and II clinical development for the prevention of stroke in patients with atrial fibrillation

INTRODUCTION

Atrial fibrillation is the most frequently diagnosed cardiac arrhythmia globally and is associated with ischemic stroke and heart failure. Patients with atrial fibrillation are typically prescribed long-term anticoagulants in the form of either vitamin K antagonists or non-vitamin K antagonist oral anticoagulants; however, both carry a potential risk of adverse bleeding.

AREAS COVERED

This paper sheds light on emerging anticoagulant agents which target clotting factors XI and XII, or their activated forms - XIa and XIIa, respectively, within the intrinsic coagulation pathway. The authors examined data available on PubMed, Scopus, and the clinical trials registry of the United States National Library of Medicine (www.clinicaltrials.gov).

EXPERT OPINION

Therapies targeting factors XI or XII can yield anticoagulant efficacy with the potential to reduce adverse bleeding. Advantages for targeting factor XI or XII include a wider therapeutic window and reduced bleeding. Long-term follow-up studies and a greater understanding of the safety and efficacy are required. Atrial fibrillation is a chronic disease and therefore the development of oral formulations is key.

Weighted gene co‑expression network analysis to identify key modules and hub genes associated with atrial fibrillation

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia and significantly increases the risks of morbidity, mortality and health care expenditure; however, treatment for AF remains unsatisfactory due to the complicated and incompletely understood underlying mechanisms. In the present study, weighted gene co‑expression network analysis (WGCNA) was conducted to identify key modules and hub genes to determine their potential associations with AF. WGCNA was performed in an AF dataset GSE79768 obtained from the Gene Expression Omnibus, which contained data from paired left and right atria in cardiac patients with persistent AF or sinus rhythm. Differentially expressed gene (DEG) analysis was used to supplement and validate the results of WGCNA. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were also performed. Green and magenta modules were identified as the most critical modules associated with AF, from which 6 hub genes, acetyl‑CoA Acetyltransferase 1, death domain‑containing protein CRADD, gypsy retrotransposon integrase 1, FTX transcript, XIST regulator, transcription elongation factor A like 2 and minichromosome maintenance complex component 3 associated protein, were hypothesized to serve key roles in the pathophysiology of AF due to their increased intramodular connectivity. Functional enrichment analysis results demonstrated that the green module was associated with energy metabolism, and the magenta module may be associated with the Hippo pathway and contain multiple interactive pathways associated with apoptosis and inflammation. In addition, the blue module was identified to be an important regulatory module in AF with a higher specificity for the left atria, the genes of which were primarily correlated with complement, coagulation and extracellular matrix formation. These results suggest that may improve understanding of the underlying mechanisms of AF, and assist in identifying biomarkers and potential therapeutic targets for treating patients with AF.

Altered profile of circulating microparticles in nonvalvular atrial fibrillation

Background

Nonvalvular atrial fibrillation (AF) is the most common cardiac arrhythmia, and it is associated with the prothrombotic state. Circulating microparticles (cMPs) are membrane vesicles that are shed from many cell types in response to cell activation and cell apoptosis. Several studies reported that cMPs may play a role in the hypercoagulable state that can be observed in patients with AF. The aim of this study was to determine the levels of total cMPs and characterize their cellular origins in AF patients.

Methods

Atotal of 66 AF patients and 33 healthy controls were enrolled. This study investigated total cMP levels and their cellular origin in AF patients using polychromatic flow cytometry.

Results

AF patients had significantly higher levels of total cMPs (median 36.38, interquartile range [IQR] 21.16‐68.50 × 10⁵ counts/mL vs median 15.21, IQR 9.91‐30.86 × 10⁵ counts/mL; P = 0.004), platelet‐derived MPs (PMPs) (median 10.61, IQR 6.55‐18.04 × 10⁵ counts/mL vs median 7.83, IQR 4.44‐10.26 × 10/mL; P = 0.009), and endothelial‐derived MPs (EMPs CD31+ CD41−) (median 2.94, IQR 1.78‐0.60 × 10⁵ counts/mL vs median 1.16, IQR 0.71‐2.30 × 10⁵ counts/mL; P = 0.001) than healthy controls after adjusting for potential confounders. Phosphatidylserine positive MP (PS + MP) levels were similar compared between AF patients and healthy controls.

Conclusion

The results of this study revealed a marked increase in total cMP levels, and evidence of elevated endothelial damage and platelet activation, as demonstrated by increased PMP and EMP levels, in AF patients. Additional study is needed to further elucidate the role of cMPs (PMPs and EMPs) in the pathophysiology of and the complications associated with AF.

Risk Assessment of Stroke in Patients with Atrial Fibrillation: Current Shortcomings and Future Directions

Atrial fibrillation is a well-known risk factor for cardioembolic stroke; a number of risk stratification scoring systems have been developed to help differentiate which patients would stand to benefit from anticoagulation. However, these scoring systems cannot be utilized in patients whose atrial fibrillation has not been diagnosed. As implantable cardiac monitors become more prevalent, it becomes possible to identify occult, subclinical atrial fibrillation. With this data, it is also possible to examine the relationship between episodes of paroxysmal atrial fibrillation and thromboembolism and the total burden of paroxysmal atrial fibrillation and thromboembolic risk. The data gleaned from these devices provides insight and raises questions regarding the underlying mechanism of thromboembolism in atrial fibrillation, and in doing so, exposes shortcomings in the present clinical use of current risk scoring systems, specifically, the inability to account for atrial fibrillation burden and to apply scores at all in subclinical atrial fibrillation.

The prothrombotic state in atrial fibrillation: pathophysiological and management implications

Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia and is associated with significant morbidity and mortality. There is plenty of evidence available to support the presence of a prothrombotic or hypercoagulable state in AF, but the contributory factors are multifactorial and cannot simply be explained by blood stasis. Abnormal changes in atrial wall (anatomical and structural, as ‘vessel wall abnormalities’), the presence of spontaneous echo contrast to signify abnormal changes in flow and stasis (‘flow abnormalities’), and abnormal changes in coagulation, platelet, and other pathophysiologic pathways (‘abnormalities of blood constituents’) are well documented in AF. The presence of these components therefore fulfils Virchow’s triad for thrombogenesis. In this review, we present an overview of the established and professed pathophysiological mechanisms for thrombogenesis in AF and its management implications.

Phosphatidylserine-exposing blood cells and microparticles induce procoagulant activity in non-valvular atrial fibrillation

BACKGROUND

The definitive role of phosphatidylserine (PS) in the prothrombotic state of non-valvular atrial fibrillation (NVAF) remains unclear. Our objectives were to study the PS exposure on blood cells and microparticles (MPs) in NVAF, and evaluate their procoagulant activity (PCA).

METHODS

NVAF patients without (n = 60) and with left atrial thrombi (n = 18) and controls (n = 36) were included in our study. Exposed PS was analyzed with flow cytometry and confocal microscopy. PCA was evaluated using clotting time, factor Xa (FXa), thrombin and fibrin formation.

RESULTS

PS⁺ blood cells and MPs were significantly higher in NVAF patients without and with left atrial thrombi (both P < 0.01) than in controls. Patients with left atrial thrombi showed increased PS⁺ platelets, neutrophils, erythrocytes and MPs compared with patients without thrombi (all P < 0.05). Moreover, in patients with left atrial thrombi, MPs primarily originated from platelets (56.1%) followed by leukocytes (21.9%, including MPs from neutrophils, monocytes and lymphocytes), erythrocytes (12.2%) and endothelial cells (8.9%). Additionally, PS⁺ blood cells and MPs contributed to markedly shortened coagulation time and dramatically increased FXa/thrombin/fibrin (all P < 0.001) generation in both NVAF groups. Furthermore, blockade of exposed PS on blood cells and MPs with lactadherin inhibited PCA by approximately 80%. Lastly, we found that the amount of PS⁺ platelets and MPs was positively correlated with thrombus diameter (all p < 0.005).

CONCLUSIONS

Our results suggest that exposed PS on blood cells and MPs play a procoagulant role in NVAF patients. Blockade of PS prior to thrombus formation might be a novel therapeutic approach in these patients.

Elevated levels of D-dimers increase the risk of ischaemic and haemorrhagic stroke

Elevated D-dimer levels are reportedly associated with coronary artery disease. It was the study objective to investigate the association of baseline D-dimer levels with strokes that occurred in the European Prospective Investigation into Cancer and Nutrition-Italy cohort. Using a nested case-cohort design, a centre-–stratified sample of 832 subjects (66 % women, age 35–71) was selected as subcohort and compared with 289 strokes in a mean follow-up of nine years. D-dimers were measured by an automated latex-enhanced immunoassay (HemosIL-IL). The multivariable hazard ratios were estimated by a Cox regression model using Prentice method. Individuals with elevated D-dimer levels had significantly higher risk of incident stroke. It was evident from the second quartile (D-dimers > 100 ng/ml) and persisted almost unchanged for higher D-dimers (hazard ratio [HR] 2.10, 95 % confidence interval [CI]: 1.28–3.47; 2.42, 95 %CI: 1.44–4.09 and 2.10, 95 %CI: 1.27–3.48 for the second, third or fourth quartile compared with the lowest quartile, respectively). The association was independent of several confounders, including triglycerides and C-reactive protein. No differences were observed in men and women (P for interaction= 0.46), in hypertensive or non-hypertensive subjects (P for interaction= 0.88) or in subjects with low (< 1 mg/l) or elevated (≥ 1 mg/l) C-reactive protein (P for interaction=0.35). After stratification for stroke type, the hazard ratio for every standard deviation increase was statistically significant both for ischaemic (1.21; 95 %CI: 1.01 to 1.45) and haemorrhagic (1.24; 95 %CI: 1.00 to 1.65) strokes. In conclusion, our data provide clear evidence that elevated levels of D-dimers are potential risk factors not only for ischaemic but also for haemorrhagic strokes.

Von Willebrand Factor: Multimeric Structure and Functional Activity in Patients With Atrial Fibrillation With and Without Oral Anticoagulation

von Willebrand factor (vWF) is a multimeric glycoprotein present in blood plasma. It is synthesized in megakaryocytes and endothelial cells, secreted into circulation in the form of high-molecular-weight multimers (HMWMs), and cleaved into shorter, less active multimers by ADAMTS13. It is essential for platelet adhesion and aggregation. Previous studies have investigated the relationship between vWF levels and thromboembolic events with little regard to vWF multimeric structure. Patients with atrial fibrillation (AF) exhibit higher plasma vWF and lower ADAMTS13 levels. One hundred seven patients with AF, 51 anticoagulated and 56 nonanticoagulated, were eligible for the study. Plasma samples were analyzed for vWF antigen, vWF activity, and ADAMTS13; vWF multimers were analyzed by Western blot in 1% to 1.3% sodium dodecyl sulfate agarose gel electrophoresis. Patients with AF without oral anticoagulation (OAC) had significantly higher vWF plasma levels (154.00 [75-201] UI/dL) and vWF activity (60.00% [20%-210%]) compared to patients with OAC (133.50 [90-192] UI/dL, P = <.001; 50.00% [20%-160%], P = .02). Both were specially decreased in patients treated with acenocumarin. Patients without OAC also showed lower ADAMTS13 levels and presence of vWF HMWMs. Patients with AF show higher plasma levels and vWF activity. Moreover, treatment with traditional OAC (acenocumarin) significantly reduced vWF levels. Patients without OAC might have an increased risk of thrombotic events showing lower ADAMTS13 and higher vWF levels. Patients with stroke had higher plasma levels, vWF activity, and HMWMs. Our study suggests that increased vWF levels and presence of HMWMs could be related to cerebrovascular disease and may represent useful biomarkers for stroke in AF.

Elevated NT-proBNP is associated with unfavorably altered plasma fibrin clot properties in atrial fibrillation

BACKGROUND

Dense fibrin clot formation and hypofibrinolysis have been reported in atrial fibrillation (AF). It is unclear which factors affect fibrin clot properties in AF.

METHODS AND RESULTS

We investigated plasma fibrin clot permeability (K_s), clot lysis time (CLT), endogenous thrombin potential (ETP) as well as other coagulation and fibrinolysis parameters along with N-terminal pro-B-type natriuretic peptide (NT-proBNP) in 160 AF patients (median age, 70.5years). Previous stroke (n=15; 9.4%) was associated with decreased K_s (P=0.04) and longer CLT (P=0.005), together with higher antiplasmin (P=0.03) and lower tissue-type plasminogen activator (P=0.01). Lower K_s (P=0.04) and tendency towards longer CLT (P=0.10) were observed in patients with a left atrium diameter>40mm. Patients with a CHA₂DS₂-VASc score of 3 or more (82.5%) were characterized by higher thrombin-activatable fibrinolysis inhibitor antigen (P=0.009). K_s was inversely correlated with log NT-proBNP (r=-0.34, P<0.0001), plasminogen activator inhibitor-1 (PAI-1) antigen (r=-0.24, P=0.002) and C-reactive protein (r=-0.18, P=0.02), while CLT was positively correlated with log NT-proBNP (R=0.61, P<0.0001) and ETP (r=0.37, P<0.0001), which were interrelated (r=0.59, P<0.0001). After adjustment for potential confounders, PAI-1 (odds ratio [OR]: 1.14; 95% confidence interval [CI]: 1.02-1.26) was the only independent predictor of low K_s (the lowest quartile,≤6×10^-9cm²), while NT-proBNP (OR: 1.21; 95% CI: 1.12-1.31) and PAI-1 (OR: 1.30; 95% CI: 1.12-1.51) both predicted prolonged CLT (the top quartile,≥109min).

CONCLUSION

In AF patients prothrombotic fibrin clot properties assessed ex vivo are determined by PAI-1 and NT-proBNP and this phenotype is associated with prior ischemic stroke.

Prediction of New-Onset and Recurrent Atrial Fibrillation by Complete Blood Count Tests: A Comprehensive Systematic Review with Meta-Analysis

Background

Atrial fibrillation (AF) is one of the most critical and frequent arrhythmias precipitating morbidities and mortalities. The complete blood count (CBC) test is an important blood test in clinical practice and is routinely used in the workup of cardiovascular diseases. This systematic review with meta-analysis aimed to determine the strength of evidence for evaluating the association of hematological parameters in the CBC test with new-onset and recurrent AF.

Material/Methods

We conducted a meta-analysis of observational studies evaluating hematologic parameters in patients with new-onset AF and recurrent AF. A comprehensive subgroup analysis was performed to explore potential sources of heterogeneity.

Results

The literature search of all major databases retrieved 2150 studies. After screening, 70 studies were analyzed in the meta-analysis on new-onset AF and 23 studies on recurrent AF. Pooled analysis on new-onset AF showed platelet count (PC) (weighted mean difference (WMD)=WMD of −26.39×10⁹/L and p<0.001), mean platelet volume (MPV) (WMD=0.42 FL and p<0.001), white blood cell (WBC) (WMD=−0.005×10⁹/L and p=0.83), neutrophil to lymphocyte ratio (NLR) (WMD=0.89 and p<0.001), and red blood cell distribution width (RDW) (WMD=0.61% and p<0.001) as associated factors. Pooled analysis on recurrent AF revealed PC (WMD=−2.71×10⁹/L and p=0.59), WBC (WMD=0.20×10⁹/L (95% CI: 0.08 to 0.32; p=0.002), NLR (WMD=0.37 and p<0.001), and RDW (WMD=0.28% and p<0.001).

Conclusions

Hematological parameters have significant ability to predict occurrence and recurrence of AF. Therefore, emphasizing the potential predictive role of hematological parameters for new-onset and recurrent AF, we recommend adding the CBC test to the diagnostic modalities of AF in clinical practice.

Laboratory assessment of anti-thrombotic therapy in heart failure, atrial fibrillation and coronary artery disease: insights using thrombelastography and a micro-titre plate assay of thrombogenesis and fibrinolysis

As heart failure, coronary artery disease and atrial fibrillation all bring a risk of thrombosis, anti-thrombotic therapy is recommended. Despite such treatment, major cardiovascular events such as myocardial infarction and stroke still occur, implying inadequate suppression of thrombus formation. Accordingly, identification of patients whose haemostasis remains unimpaired by treatment is valuable. We compared indices for assessing thrombogenesis and fibrinolysis by two different techniques in patients on different anti-thrombotic agents, i.e. aspirin or warfarin. We determined fibrin clot formation and fibrinolysis by a microplate assay and thromboelastography, and platelet marker soluble P selectin in 181 patients with acute or chronic heart failure, coronary artery disease who were taking either aspirin or warfarin. Five thromboelastograph indices and four microplate assay indices were different on aspirin versus warfarin (p < 0.05). In multivariate regression analysis, only microplate assay indices rate of clot formation and rate of clot dissolution were independently related to aspirin or warfarin use (p ≤ 0.001). Five microplate assay indices, but no thrombelastograph index, were different (p < 0.001) in aspirin users. Three microplate assay indices were different (p ≤ 0.002) in warfarin users. The microplate assay indices of lag time and rate of clot formation were abnormal in chronic heart failure patients on aspirin, suggesting increased risk of thrombosis despite anti-platelet use. Soluble P selectin was lower in patients on aspirin (p = 0.0175) but failed to correlate with any other index of haemostasis. The microplate assay shows promise as a tool for dissecting thrombogenesis and fibrinolysis in cardiovascular disease, and the impact of antithrombotic therapy. Prospective studies are required to determine a role in predicting thrombotic risk.

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

Background

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

Material/Methods

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

Results

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

Conclusions

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

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

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

Clinical Stroke prevention in atrial fibrillation

Oral anticoagulation therapy has reduced the risk of ischaemic stroke and improved the outcomes for patients with atrial fibrillation considerably. The emergence of the non-vitamin K oral anticoagulants as alternatives to vitamin K antagonists has significantly changed the practice of stroke prevention in atrial fibrillation. As the main complication with antithrombotic therapy is bleeding, physicians should always balance the risk of ischaemic stroke against intracranial haemorrhage and intervene where appropriate to reduce both risks. Individual approach is often mandatory due to heterogeneity of the risks and patient preferences. The purpose of this review is to summarise the current knowledge of the oral anticoagulation therapy in atrial fibrillation patients and guide physicians with the management of anticoagulants based on data from clinical trials and systematic reviews.

Advances in anticoagulation management of patients undergoing cardioversion of nonvalvular atrial fibrillation

Atrial fibrillation (AF) is a major cause of stroke. The restoration of sinus rhythm through cardioversion, either chemical or electrical is a common practice. Interestingly, there is an incremental increase from the baseline risk for embolisation in the immediate post-cardioversion period, with most events occurring within 10 days from cardioversion. Especially patients with recent onset AF show the lowest rates of antithrombotic therapy, while having a high stroke risk. Despite the increased risk for embolisation, anticoagulation in patients undergoing cardioversion of atrial fibrillation is often inadequate. Moreover, since the implementation of non-vitamin K antagonists oral anticoagulants (DOACs) there are several therapeutic approaches for pericardioversion anticoagulant therapy and not all suits to all patients. In addition, the extensive use of transesophageal echocardiography provides an alternative strategy, especially useful for patients of high haemorrhagic risk. In this review article, we aim to provide an update on the anticoagulation strategies for patients undergoing cardioversion of non-valvular atrial fibrillation in the advent of the use of DOACs.

Early Changes in the Antithrombin and Thrombin-Antithrombin Complex in Patients With Paroxysmal Atrial Fibrillation

Background

Data on coagulation changes in paroxysmal atrial fibrillation (PAF) are scarce. The aim of this study was to examine plasma antithrombin (AT) levels and activity as well as thrombin-antithrombin (TAT) complex levels in the early hours of the clinical manifestation of PAF.

Methods

Fifty-one patients (26 men and 25 women; mean age 59.84 ± 1.60 years) were consecutively selected with PAF duration < 24 hours, and 52 controls (26 men and 26 women; mean age 59.50 ± 1.46 years) matched the patients in terms of gender, age and comorbidities. Plasma levels and activity of AT and levels of the covalent TAT complex were studied once in each study participant.

Results

AT plasma levels in PAF patients were statistically significantly lower compared to controls (164.69 ± 10.51 vs. 276.21 ± 8.29 μg/mL, P < 0.001). Plasma activity of the anticoagulant was also significantly lower in PAF (71.33±4.87 vs. 110.72±3.09%, P < 0.001). TAT complex concentration in plasma was higher in the patient group (5.32 ± 0.23 vs. 3.20 ± 0.14 μg/L, P < 0.001).

Conclusion

We can say that PAF is associated with significantly reduced AT levels and activity and increased levels of TAT complex during the first 24 hours after its manifestation. These changes indicate a reduced activity of AT anticoagulant system, which is a probable prerequisite for the established enhanced coagulation (high TAT complex levels).

Emerging Tools for Stroke Prevention in Atrial Fibrillation

Ischaemic strokes resulting from atrial fibrillation (AF) constitute a devastating condition for patients and their carers with huge burden on health care systems. Prophylactic treatment against systemic embolization and ischaemic strokes is the cornerstone for the management of AF. Effective stroke prevention requires the use of the vitamin K antagonists or non-vitamin K oral anticoagulants (NOACs). This article summarises the latest developments in the field of stroke prevention in AF and aims to assist physicians with the choice of oral anticoagulant for patients with non-valvular AF with different risk factor profile.

Exposure-response for biomarkers of anticoagulant effects by the oral direct thrombin inhibitor AZD0837 in patients with atrial fibrillation

AIMS

AZD0837 is a novel oral anticoagulant investigated in clinical studies for stroke prevention in patients with atrial fibrillation (AF). It is bioconverted to its active form, AR-H067637, a potent, specific and reversible thrombin inhibitor. The effects on coagulation biomarkers were correlated with the pharmacokinetic (PK) exposure of AR-H067637 to guide selection of the effective dose regimen for a confirmatory efficacy study in AF patients.

METHODS

Blood samples were obtained from 601 AF patients randomized to one of four doses of AZD0837 (blinded treatment) or dose-adjusted vitamin K antagonists (VKA, open treatment) for 3-9 months. A pharmacodynamic model was developed to describe the time course of the AR-H067637 exposure dependent effects and the effect of VKA on fibrin D-dimer. The thrombin generation measured ex vivo in venous plasma was also investigated.

RESULTS

The PK exposure of AR-H067637 was stable with an interindividual variability of 33% and no or minor influence of patient demographics or comedications. For AZD0837, D-dimer levels decreased with more rapid onset than for VKA. The decrease in D-dimer levels correlated with steady-state plasma concentrations (C(ss)) of AR-H067637, with a maximum decrease of baseline D-dimer levels estimated to approximately 60% for both AZD0837 and VKA therapy. The effect on thrombin generation correlated closely with the plasma concentration of AR-H067637.

CONCLUSIONS

The effects on thrombin generation and fibrin D-dimer levels correlated with the plasma concentration of its active form and provided comparable effects to well-controlled VKA therapy at an exposure at least corresponding to the 300 mg once daily dose of AZD0837.

D-Dimer elevation and adverse outcomes

d-Dimer is a biomarker of fibrin formation and degradation. While a d-dimer within normal limits is used to rule out the diagnosis of deep venous thrombosis and pulmonary embolism among patients with a low clinical probability of venous thromboembolism (VTE), the prognostic association of an elevated d-dimer with adverse outcomes has received far less emphasis. An elevated d-dimer is independently associated with an increased risk for incident VTE, recurrent VTE, and mortality. An elevated d-dimer is an independent correlate of increased mortality and subsequent VTE across a broad variety of disease states. Therefore, medically ill subjects in whom the d-dimer is elevated constitute a high risk subgroup in which the prospective evaluation of the efficacy and safety of antithrombotic therapy is warranted.

[Measurement of d-dimers in non-valvular atrial fibrillation. First prospective Tunisian study]

Atrial fibrillation can expose to thrombo-embolic complications. Many biomarkers have been tested to refine the stratification of thrombo-embolic risk. The study aim was to assess the interest of the d-dimer testing in this pathology. We conducted a prospective observational study including 50 cases and 19 controls, enrolled at the cardiology department of the Mongi Slim Hospital, from July to November 2012. The d-dimer assay was performed on mini-VIDAS(®) and analyzed according to clinical, echocardiographic and biological data. The mean age of patients was 61.8±10.6years. The mean CHA2DS2-VASc score was 2.58±1.31. The average of D-dimer levels was 590±506ng/ml in patients and 225.26±112.95ng/ml in controls (P=0.02). No significant difference has been found between the d-dimer level and age, sex, type and etiology of atrial fibrillation, the CHA2DS2-VASc score, the left atrial surface. Among patients on acenocoumarol, d-dimer levels was significantly higher in patients with an INR<2 compared to those with an INR≥2 (P=0.004). We identified a positive d-dimer threshold (300ng/ml) in patients distinguishing them significantly with controls (P<0.001). In conclusion, the measurement of d-dimers could help clinicians to identify patients with atrial fibrillation having an increased coagulability and, therefore, an increased thrombo-embolic risk. It could be complementary to the determination of INR in monitoring anticoagulation therapy: d-dimers level refines the thrombo-embolic risk and INR measurement assesses the level of anticoagulation and the bleeding risk.

Epidemiology, diagnosis, and management of atrial fibrillation in women

Atrial fibrillation (AF) is the most common arrhythmia and has become a serious public health problem. Moreover, epidemiological data demonstrate that incidence and prevalence of AF are increasing. Several differences in epidemiological patterns, clinical manifestations, and incidence of stroke have been reported between AF in women and in men, particularly in elderly women. Elderly women have higher blood pressure than men and a higher prevalence of heart failure with preserved ejection fraction, both independent risk factors for stroke. On the basis of the evidence on the higher stroke risk among AF in women, recently, female sex has been accepted as a risk factor for stroke and adopted to stratify patients, especially if they are not at high risk for stroke. This review focuses on available evidence on sex differences in AF patients, and examines factors contributing to different stroke risk, diagnosis, and prognosis of arrhythmia in women, with the aim to provide an analysis of the available evidence.

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.

Hypercoagulability, D-dimer and atrial fibrillation: an overview of biological and clinical evidence

Atrial fibrillation (AF) is the most common among the severe cardiac arrhythmias and carries a significant risk of mortality and morbidity in the general population. The most important complication is represented by development of one or more thrombi in the left atrium of the dyskinetic heart, and their successive cerebral and peripheral embolization. The pathophysiological basis of the thromboembolic complications in AF entails the presence of a hypercoagulable state, which is mirrored by increased concentrations of a variety of prothrombotic markers. D-dimer is universally considered the gold standard among the various biomarkers that reflect activation of coagulation, fibrinolysis, or both, and several studies have assessed its diagnostic and prognostic role in AF. With a few exceptions and despite a broad heterogeneity in the study designs, published data seem to demonstrate that D-dimer values may be associated with the presence of atrial thrombosis, may be predictive of primary adverse outcomes and death, may be correlated with cerebral infarction volume, and may also be a useful parameter for assessing the degree of hypercoagulability of AF patients after cardioversion. If larger prospective studies confirm these findings, D-dimer assessment may hence become an integral part of the clinical decision-making in patients with AF.

D-dimer and risk of thromboembolic and bleeding events in patients with atrial fibrillation--observations from the ARISTOTLE trial

BACKGROUND

D-dimer is related to adverse outcomes in arterial and venous thromboembolic diseases.

OBJECTIVES

To evaluate the predictive value of D-dimer level for stroke, other cardiovascular events, and bleeds, in patients with atrial fibrillation (AF) treated with oral anticoagulation with apixaban or warfarin; and to evaluate the relationship between the D-dimer levels at baseline and the treatment effect of apixaban vs. warfarin.

METHODS

In the ARISTOTLE trial, 18 201 patients with AF were randomized to apixaban or warfarin. D-dimer was analyzed in 14 878 patients at randomization. The cohort was separated into two groups; not receiving vitamin K antagonist (VKA) treatment and receiving VKA treatment at randomization.

RESULTS

Higher D-dimer levels were associated with increased frequencies of stroke or systemic embolism (hazard ratio [HR] [Q4 vs. Q1] 1.72, 95% confidence interval [CI] 1.14-2.59, P = 0.003), death (HR [Q4 vs. Q1] 4.04, 95% CI 3.06-5.33) and major bleeding (HR [Q4 vs. Q1] 2.47, 95% CI 1.77-3.45, P < 0.0001) in the no-VKA group. Similar results were obtained in the on-VKA group. Adding D-dimer level to the CHADS2 score improved the C-index from 0.646 to 0.655 for stroke or systemic embolism, and from 0.598 to 0.662 for death, in the no-VKA group. D-dimer level improved the HAS-BLED score for prediction of major bleeds, with an increase in the C-index from 0.610 to 0.641. There were no significant interactions between efficacy and safety of study treatment and D-dimer level.

CONCLUSION

In anticoagulated patients with AF, the level of D-dimer is related to the risk of stroke, death, and bleeding, and adds to the predictive value of clinical risk scores. The benefits of apixaban were consistent, regardless of the baseline D-dimer level.

Effect of hyperthyroidism on the hypercoagulable state and thromboembolic events in patients with atrial fibrillation

OBJECTIVE

To clarify whether hyperthyroidism (HT) itself confers an additional effect on the hypercoagulable state and the risk of ischemic stroke among patients with hyperthyroid atrial fibrillation (AF).

METHODS

We prospectively evaluated plasma D-dimer levels and thromboembolic events among three groups of patients (hyperthyroid AF, n = 62; nonthyroid AF, n = 107, and HT without AF, n = 100). Plasma D-dimer levels were used to evaluate the hypercoagulable state.

RESULTS

The D-dimer level was significantly higher in patients with hyperthyroid AF than in nonthyroid AF (0.66 ± 0.06 vs. 0.34 ± 0.02 mg/l, p < 0.001) and HT without AF (0.66 ± 0.06 vs. 0.27 ± 0.02 mg/l, p < 0.001). During a 3-year follow-up, patients with hyperthyroid AF had a significantly higher incidence of ischemic stroke compared with patients with nonthyroid AF (hazard ratio, HR: 3.2, 95% confidence interval, CI: 1.01-5.59, p = 0.04). Cox regression analysis revealed that age (HR: 2.5, 95% CI: 1.01-1.21, p = 0.05), CHADS2-VAS score (HR: 5.5, 95% CI: 1.51-7.43, p = 0.01) and anticoagulation (HR: 0.45, 95% CI: 0.07-0.54, p = 0.01) were independent predictors of risk for the occurrence of ischemic stroke.

CONCLUSIONS

The present study suggests that HT may enhance the hypercoagulable state and the risk of ischemic stroke in patients with AF.

Female sex as an independent risk factor for stroke in atrial fibrillation: possible mechanisms

Atrial fibrillation (AF) is an independent risk factor for thromboembolism and stroke. Women with AF are at a higher overall risk for thromboembolic stroke when compared to men with AF. Recent evidence suggests that female sex, after adjusting for stroke risk profile and sex differences in utilisation of anticoagulation, is an independent stroke risk factor in AF. The inclusion of female sex has improved the accuracy of the CHADS2 stroke risk stratification schema (Congestive heart failure, Hypertension, Age 75 years or greater, Diabetes mellitus, and prior Stroke or TIA). The newly revised and validated schema, CHA2DS2-VASc, dichotomises age and incorporates female sex and vascular disease history. The pathophysiological mechanisms to explain this increased risk in women are not well understood. According to Virchow's triad, thrombosis that leads to stroke in AF should arise from three co-existing phenomena: structural abnormalities, blood stasis, and a hypercoagulable state. Herein, we explore the sex differences in the biological processes that lead to thrombus formation as applied to Virchow's Triad. The objective of this review is to describe the potential mechanisms behind the increased risk of stroke in AF associated with female sex.

Mean platelet volume in patients with nonvalvular atrial fibrillation

The procoagulant and prothrombotic states in patients with chronic atrial fibrillation are higher than those in patients with normal sinus rhythm. Mean platelet volume (MPV) which is a marker of platelet function and activation can reflect changes either in the level of platelet stimulation or the rate of platelet production. In this study, we aimed to assess and compare the hematologic parameters of routine complete blood count analysis in elderly patients with nonvalvular atrial fibrillation and control individuals with normal sinus rhythm. One hundred and seven consecutive patients with nonvalvular chronic atrial fibrillation and 112 age and sex-matched control individuals with normal sinus rhythm were retrospectively included in the study from the outpatient cardiology clinic. Hematological variables, including MPV, platelet count, red blood cell and white blood cell count were measured in all patients and control individuals. Presence of coronary artery disease, hypertension, sex, hyperlipidemia, diabetes mellitus, smoking status, hematocrit and platelet count were comparable between two groups (P>0.05 for all). However, MPV and white blood cell count were significantly higher in patients with atrial fibrillation compared to those without atrial fibrillation. Logistic regression analysis revealed that white blood cell count and MPV significantly and independently associated with atrial fibrillation. We have shown that MPV and white blood cell count is independently associated with chronic nonvalvular atrial fibrillation. To improve the clinical utility of MPV and role of inflammation in the pathogenesis of atrial fibrillation, further studies are needed to be carried out.

Association of D-dimer levels with all-cause mortality in a healthy adult population: findings from the MOLI-SANI study

Elevated D-dimer levels are reportedly associated with higher risk of total mortality in patients with different diseases. We investigated whether a similar association could be found in a large, apparently healthy population. A large sample of individuals (N=17,359, 47% men, age ≥ 35 years) free of clinically recognized cardiovascular and cancer disease, for whom baseline D-dimer level was available, were studied within the MOLI-SANI cohort, randomly recruited from the general adult population of Southern Italy. The cohort was followed for a median of 4.2 years (73,807 person-years). D-dimer was measured in fresh citrated plasma by an automated latex-enhanced immunoassay. Hazard ratios were calculated using three Cox-proportional hazard models. Two hundred and eighty deaths were recorded. When modeled as a continuous variable, D-dimer level at baseline showed a non-linear association with mortality, whose incidence increased only in the upper quartile of the distribution (D-dimer ≥ 221 ng/mL). Thus, the group of individuals with D-dimer <221 ng/mL (75% of the population) acted as the reference group, while the remaining individuals were subdivided in tertiles and compared with the former group. Multivariable hazard ratios for mortality were 1.06, 1.45 and 1.97, respectively (P for trend <0.0001) across the three categories of increasing D-dimer concentration. The association was slightly attenuated, but still highly significant (P for trend 0.0002), after further adjustment for white blood cell count and C-reactive protein. In conclusion, Elevated D-dimer levels were independently associated with increased risk of death from any cause in an apparently healthy adult population.