Platelet activation, haemorheology and thrombogenesis in acute atrial fibrillation: a comparison with permanent atrial fibrillation

Short-Term Oral Anticoagulation Versus Antiplatelet Therapy Following Transcatheter Left Atrial Appendage Closure

Background:

The impact of antithrombotic therapy on coagulation system activation after left atrial appendage closure (LAAC) remains unknown. This study sought to compare changes in coagulation markers associated with short-term oral anticoagulation (OAC) versus antiplatelet therapy (APT) following LAAC.

Methods:

Prospective study including 78 atrial fibrillation patients undergoing LAAC with the Watchman device. F1+2 (prothrombin fragment 1+2) and TAT (thrombin-antithrombin III) were assessed immediately before the procedure, and at 7, 30, and 180 days after LAAC.

Results:

Forty-eight patients were discharged on APT (dual: 31, single: 17) and 30 on OAC (direct anticoagulants: 26, vitamin K antagonists: 4), with no differences in baseline-procedural characteristics between groups except for higher spontaneous echocardiography contrast in the OAC group. OAC significantly reduced coagulation activation within 7 days post-LAAC compared with APT (23% [95% CI, 5%–41%] versus 82% [95% CI, 54%–111%] increase for F1+2, P =0.007; 52% [95% CI, 15%–89%] versus 183% [95% CI, 118%–248%] increase for TAT, P =0.048), with all patients in both groups progressively returning to baseline values at 30 and 180 days. Spontaneous echocardiography contrast pre-LAAC was associated with an enhanced activation of the coagulation system post-LAAC (144 [48–192] versus 52 [24–111] nmol/L, P =0.062 for F1+2; 299 [254–390] versus 78 [19–240] ng/mL, P =0.002 for TAT). Device-related thrombosis occurred in 5 patients (6.4%), and all of them were receiving APT at the time of transesophageal echocardiography (10.2% versus 0% if OAC at the time of transesophageal echocardiography, P =0.151). Patients with device thrombosis exhibited a greater coagulation activation 7 days post-LAAC ( P =0.038 and P =0.108 for F1+2 and TAT, respectively).

Conclusions:

OAC (versus APT) was associated with a significant attenuation of coagulation system activation post-LAAC. Spontaneous echocardiography contrast pre-LAAC associated with enhanced coagulation activation post-LAAC, which in turn increased the risk of device thrombosis. These results highlight the urgent need for randomized trials comparing OAC versus APT post-LAAC.

Paroxysmal atrial fibrillation is associated with early coagulation activity regardless of risk factors for embolism

BACKGROUND

Paroxysmal atrial fibrillation (PAF) is associated with an increased incidence of embolic events, even in patients with no embologenic risk factors. This fact raises the question for the hypercoagulability in PAF as a state closely related to the arrhythmia itself, independent of other well established embologenic risk factors. The scarce data on that topic predisposed our aim that was to study coagulation activity in the early hours (up to the twenty-fourth hour) of the disease.

METHODS

Fifty-one non-anticoagulated patients (26 men, 25 women; mean age 59.84±1.60 years) and 52 controls (26 men, 26 women; mean age 59.50±1.46 years) were consequently selected for the study. Plasma coagulation activity of factor II (FII), factor V (FV) and factor X (FX) was examined.

RESULTS

In the PAF group, there was a higher activity of FII (167.81±9.12% vs. 100.43±5.77%, P<0.001), FV (198.47±10.88% vs. 121.53±4.79%, P<0.001) and FX (193.20±11.85 vs. 116.20±5.86, P<0.001). The deviations were independent of age, sex, body mass index, presence of hypertension and CHA<inf>2</inf>DS<inf>2</inf>-VASc risk score (P>0.05). PAF duration was a significant predictor of FII activity (r=0.83, P<0.001) but no correlation was established between FV and FX activity and the arrhythmia duration (r=0.10, P>0.05; r=0.11, P>0.05, respectively).

CONCLUSIONS

We established high coagulation activity during the first twenty-four hours of PAF. The observed deviations in the studied parameters give us reason to consider PAF a procoagulant state independent of the well-established prothrombotic risk factors, even in its early clinical manifestation.

Paroxysmal Atrial Fibrillation: Insight Into the Intimate Mechanisms of Coagulation

Background

Atrial fibrillation (AF) is a hypercoagulable state. However, the intimate mechanisms leading to impaired coagulation and the timing of their activation are unclear. The aim of the study was to investigate the factors that initiate the coagulation cascade in the early hours (up to 48 h) of clinical manifestation of paroxysmal atrial fibrillation (PAF).

Methods

Tissue factor (TF) level, coagulation activity of factor VII (FVIIa), factor XII (FXIIa) and factor XI (FXIa) were measured in plasma of 51 non-anticoagulated patients (26 men and 25 women, aged 59.84 ± 11.42 years) and 52 controls (26 men and 26 women, aged 59.50 ± 10.53 years) by enzyme-linked immunoassays and kinetic assays.

Results

TF was higher in the PAF group (268.63 ± 90.62 pg/mL vs. 170.21 ± 66.19 pg/mL, P < 0.001) as well as FVIIa (170.82±59.39% vs. 95.17±37.90%, P < 0.001), FXIIa (218.31±84.04% vs. 148.41±53.94%, P < 0.001) and FXIa (178.41±55.94% vs. 111.75±37.33%, P < 0.001). Regression analysis showed that in the first 6 h of the disease, increase in time led to increase in FXIIa (r = 0.25, P < 0.05), FXIa (r = 0.75, P < 0.05), TF level (r = 0.25, P < 0.05) and FVIIa (r = 0.25, P < 0.05).

Conclusion

Hemocoagulation changes were observed even < 6 h after the onset of the disease. They suggest that PAF has an early tendency for hypercoagulability, with the involvement of the intrinsic and extrinsic pathways of coagulation.

Effects of Rivaroxaban on Biomarkers of Coagulation and Inflammation: A Post Hoc Analysis of the X-VeRT Trial

Introduction  This X-VeRT (eXplore the efficacy and safety of once-daily oral riVaroxaban for the prevention of caRdiovascular events in patients with nonvalvular aTrial fibrillation scheduled for cardioversion) substudy evaluated the effects of treatment with rivaroxaban or a vitamin-K antagonist (VKA) on levels of biomarkers of coagulation (D-dimer, thrombin–antithrombin III complex [TAT] and prothrombin fragment [F1.2]) and inflammation (high sensitivity C-reactive protein [hs-CRP] and high-sensitivity interleukin-6 [hs-IL-6]) in patients with atrial fibrillation (AF) who were scheduled for cardioversion and had not received adequate anticoagulation at baseline (defined as, in the 21 days before randomization: no oral anticoagulant; international normalized ratio <2.0 with VKA treatment; or <80% compliance with non-VKA oral anticoagulant treatment).

Methods  Samples for biomarker analysis were taken at baseline ( n  = 958) and treatment completion (42 days after cardioversion; n  = 918). The influence of clinical characteristics on baseline biomarker levels and the effect of treatment on changes in biomarker levels were evaluated using linear and logistic models.

Results  Baseline levels of some biomarkers were significantly associated with type of AF (D-dimer and hs-IL-6) and with history of congestive heart failure (hs-CRP, D-dimer, and hs-IL-6). Rivaroxaban and VKA treatments were associated with reductions from baseline in levels of D-dimer (−32.3 and −37.6%, respectively), TAT (−28.0 and −23.1%, respectively), hs-CRP (−12.5 and −17.9%, respectively), and hs-IL-6 (−9.2 and −9.8%, respectively). F1.2 levels were reduced from baseline in patients receiving a VKA (−53.0%) but not in those receiving rivaroxaban (2.7%).

Conclusion  Anticoagulation with rivaroxaban reduced levels of key inflammation and coagulation biomarkers to a similar extent as VKAs, with the exception of F1.2. Further investigation to confirm the value of these biomarkers in patients with AF is merited.

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.

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.

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.

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.

Antithrombotics in atrial fibrillation and coronary disease

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia and approximately 18-45% of AF patients have concomitant coronary artery disease (CAD). Several studies have demonstrated that oral anticoagulation is the mainstay of therapy for stroke prevention in AF. Similarly, antiplatelet therapy including aspirin and P2Y12 inhibitor is recommended in the management of acute coronary syndrome and stable CAD. Despite the high prevalence of CAD with AF, practice guidelines are scarce on the appropriate antithrombotic regimen due to lack of large-scale randomized clinical trials. The use of direct thrombin and factor Xa inhibitors for stroke prevention in AF has also complicated the possible combinations of antithrombotic therapies. This review aims to discuss the available evidence regarding aspirin as an antithrombotic strategy, the role of novel anticoagulants and the specific clinical situations where aspirin may be beneficial in patients with AF and CAD.

Embryology and Anatomy of the Left Atrial Appendage: Why Does Thrombus Form?

The left atrial appendage (LAA) is a long tubular structure that opens into the left atrium. In patients with atrial fibrillation, the LAA develops mechanical dysfunction and fibroelastotic changes on the endocardial surface. The complex anatomy of the LAA makes it a good site for relative blood stasis. In addition, systemic factors exacerbate the hypercoagulable state, eventually resulting in endothelial dysfunction, release of tissue factor, and production of inflammatory cytokines and oxidative free radicals, and eventually initiating the coagulation cascade. Thus, the LAA is susceptible to thrombus formation and is the most common source of systemic thromboembolism.

A bioclinical pattern for the early diagnosis of cardioembolic stroke

Background and Scope. Early etiologic diagnosis of ischemic stroke subtype guides acute management and treatment. We aim to evaluate if plasma biomarkers can predict stroke subtypes in the early phase from stroke onset. Methods. Plasma N-terminal prohormone of brain natriuretic peptide (NT-proBNP), D-dimer, C-reactive protein, serum albumin, and globulin levels have been investigated in 114 consecutive patients presenting at the emergency room within 6 hours of the ischemic stroke onset. Plasma levels of biomarkers have been correlated with stroke aetiology (based on TOAST criteria) by multivariable logistic regression analysis, adjusted for several covariates. Results. Of the 114 patients, 34 (30%) had cardioembolic stroke, 27 (23%) atherothrombotic stroke, 19 (17%) lacunar stroke, and 34 (30%) stroke of undetermined origin. Patients with cardioembolic stroke had significantly higher levels of NT-proBNP and lower globulin/albumin (G/A) ratio compared with the other subgroups. At multiple logistic regression NT-proBNP > 200 pg/mL, G/A ratio > 0.70, and NIHSS score were independent predictors of cardioembolic stroke with high accuracy of the model, either including (AUC, 0.91) or excluding (AUC, 0.84) atrial fibrillation. Conclusions. A prediction model that includes NT-proBNP, G/A ratio, and NIHSS score can be useful for the early etiologic diagnosis of ischemic stroke.

Cost-Effective Medicines for Stroke Prophylaxis in Patients with Atrial Fibrillation

Non-valvular atrial fibrillation is the most common arrhythmia encountered in clinical practice and is associated with substantial healthcare costs. The risk of thromboembolic stroke is 3-5 times higher in patients with atrial fibrillation compared with the general population. Until the recent emergence of direct thrombin (factor IIa) and factor Xa inhibitors, antithrombotic therapy for atrial fibrillation was achieved with antiplatelet agents or vitamin K antagonists, which are considered cost-effective strategies when compared to no treatment. Now newer agents, such as the direct thrombin inhibitor dabigatran, can lower thromboembolic events and reduce the risk of fatal and intracerebral hemorrhage compared with warfarin, in addition to eliminating the need for costly therapeutic monitoring. Multiple analyses have shown that dabigatran, when compared with warfarin therapy that achieves a time in therapeutic range (TTR) consistent with previous large-scale trials, is a cost-effective approach to antithrombotic therapy in atrial fibrillation, ranging from $16,385 to $86,000 per quality-adjust life-year (QALY) gained. It has been shown to be especially cost-effective (QALY < $50,000) for high stroke-risk patients, those with a CHADS₂ score of > 3 (barring excellent INR control) and for lower-risk patients with a CHADS₂ of 2 but concomitant high risk of hemorrhage. In addition, factor Xa inhibitors, such as rivaroxaban (recently approved by the Federal Drug Administration [FDA]) and apixaban, may exhibit the same cost savings as dabigatran in terms of reduction of bleeding and elimination of therapeutic level monitoring costs. Going forward, the use of these agents and their role in thromboembolic stroke prophylaxis will need to be evaluated on a patient-by-patient basis, balancing consideration of the patient?s stroke and bleeding risks, as well as quality of life post-therapy.

The determinants of stroke phenotypes were different from the predictors (CHADS2 and CHA2DS2-VASc) of stroke in patients with atrial fibrillation: a comprehensive approach

Background

Atrial fibrillation (AF) is a leading cause of fatal ischemic stroke. It was recently reported that international normalized ratio (INR) levels were associated with infarct volumes. However, factors other than INR levels that affect stroke phenotypes are largely unknown. Therefore, we evaluated the determinants of stroke phenotypes (pattern and volume) among patients with AF who were not adequately anticoagulated.

Methods

We analyzed data pertaining to consecutive AF patients admitted over a 6-year period with acute MCA territory infarcts. We divided the patients according to DWI (diffusion-weighted imaging) lesion volumes and patterns, and the relationship between stroke predictors (the CHADS₂ and CHA₂DS₂-VASc score), systemic, and local factors and each stroke phenotype were then evaluated.

Results

The stroke phenotypes varied among 231 patients (admission INR median 1.06, interquartile range (IQR) 1.00-1.14). Specifically, (1) the DWI lesion volumes ranged from 0.04-338.62 ml (median 11.86 ml; IQR, 3.07-44.20 ml) and (2) 46 patients had a territorial infarct pattern, 118 had a lobar/deep pattern and 67 had a small scattered pattern. Multivariate testing revealed that the CHADS₂ and CHA₂DS₂-VASc score were not related to either stroke phenotype. Additionally, the prior use of antiplatelet agents was not related to the stroke phenotypes. Congestive heart failure and diastolic dysfunction were not associated with stroke phenotypes.

Conclusions

The results of this study indicated that the determinants of stroke phenotypes were different from the predictors (i.e., CHADS2 and CHA₂DS₂-VASc score) of stroke in patients with AF.

Cardioembolic stroke in atrial fibrillation-rationale for preventive closure of the left atrial appendage

Atrial fibrillation is the most common cardiac arrhythmias, and a major cause of morbidity and mortality due to cardioembolic stroke. The left atrial appendage is the major site of thrombus formation in non-valvular atrial fibrillation. Loss of atrial systole in atrial fibrillation and increased relative risk of associated stroke point strongly toward a role for stasis of blood in left atrial thrombosis, although thrombus formation is multifactorial, and much more than blood flow irregularities are implicated. Oral anticoagulation with vitamin-K-antagonists is currently the most effective prophylaxis for stroke in atrial fibrillation. Unfortunately, this treatment is often contraindicated, particularly in the elderly, in whom risk of stroke is high. Moreover, given the risk of major bleeding, there is reason to be skeptical of the net benefit when warfarin is used in those patients. This work reviews the pathophysiology of cardioembolic stroke and critically spotlights the current status of preventive anticoagulation therapy. Various techniques to exclude the left atrial appendage from circulation were discussed as a considerable alternative for stroke prophylaxis.

Mechanisms of thrombogenesis in atrial fibrillation: Virchow's triad revisited

Atrial fibrillation is the most common sustained cardiac arrhythmia, which is associated with a high risk of stroke and thromboembolism. Increasing evidence suggests that the thrombogenic tendency in atrial fibrillation is related to several underlying pathophysiological mechanisms. Abnormal changes in flow are evident by stasis in the left atrium, and seen as spontaneous echocontrast. Abnormal changes in vessel walls-essentially, anatomical and structural defects-include progressive atrial dilatation, endocardial denudation, and oedematous or fibroelastic infiltration of the extracellular matrix. Additionally, abnormal changes in blood constituents are well described, and include haemostatic and platelet activation, as well as inflammation and growth factor changes. These changes result in the fulfilment of Virchow's triad for thrombogenesis, and accord with a prothrombotic or hypercoagulable state in this arrhythmia. In this Review, we present an overview of the established and purported mechanisms for thrombogenesis in atrial fibrillation.

Accumulation of risk factors enhances the prothrombotic state in atrial fibrillation

BACKGROUND

The present study was conducted to investigate the relation between the accumulation of the risk factors of thromboembolism and the levels of hemostatic markers in patients with nonvalvular atrial fibrillation (NVAF).

METHODS

Five hundred ninety-one NVAF patients and 129 control subjects were categorized into low, moderate or high risk of thromboembolism, according to CHADS(2) index. One point each was given to patients with advanced age (> or =75 years), hypertension, congestive heart failure, and diabetes mellitus, and 2 points, to those with prior ischemic stroke or transient ischemic attack. Patients with CHADS(2) score of 0, 1 or 2, and > or =3 were classified as low, moderate and high risk, respectively. Levels of hemostatic markers (platelet factor 4, beta-thromboglobulin, prothrombin fragment F1+2 and D-dimer) were determined.

RESULTS

Of 591 patients with NVAF, 302 were treated with warfarin (mean international normalized ratio 1.88). D-dimer levels increased as the risk level increased irrespective of warfarin use. Particularly, NVAF patients without receiving warfarin (n=289) had significantly higher D-dimer levels than control patients (e.g., for high risk patients, 175+/-144 vs 75+/-87 ng/ml, p<0.001), while NVAF patients receiving warfarin had intermediate levels (136+/-156 ng/ml). F1+2 levels increased as the risk level increased, and were significantly suppressed by warfarin. Levels of markers of platelet activation (platelet factor 4 and beta-thromboglobulin) were increased in NVAF patients but not affected by the risk level.

CONCLUSION

Coagulation and fibrinolytic activity is increased along with the accumulation of the risk factors of thromboembolism in NVAF patients.

Hyperviscosity as a possible risk factor for cerebral ischemic complications in atrial fibrillation patients

Recent studies have suggested that hyperviscosity is frequent in patients with atrial fibrillation (AF). The aims of this study were to evaluate if hemorheologic alterations play a role in the occurrence of cerebral ischemic events in patients with AF and to explore a possible association between inflammation and hyperviscosity in these patients. Sixty-two patients with AF with a history of >or=1 cerebral ischemic event and 94 patients with AF without cerebral ischemic events were studied. A control population included 130 age- and gender-matched healthy volunteers. Hemorheologic variables (whole-blood viscosity, plasma viscosity, the erythrocyte deformability index, and hematocrit), fibrinogen, and high-sensitivity C-reactive protein levels were assayed. An alteration in whole blood viscosity at 94.5 seconds(-1) and the erythrocyte deformability index were found more frequently in patients with previous ischemic events on univariate and multivariate analyses (odds ratio 3.19, p=0.023 and odds ratio 4.26, p=0.002, respectively) adjusted for age, gender, hypertension, diabetes, history of coronary artery disease, left ventricular dysfunction, smoking habit, dyslipidemia, hematocrit, fibrinogen, high-sensitivity C-reactive protein, and hemorheologic parameters. These results should stimulate prospective studies on the role of hemorheologic alterations in the occurrence of cerebral ischemic complications in patients with AF.

New approaches to anticoagulation in atrial fibrillation

Oral direct thrombin inhibitors (DTIs) are a potential alternative to vitamin K antagonists, such as warfarin, for anticoagulant therapy. The oral DTI at the most advanced stage of clinical development is ximelagatran, which is rapidly absorbed and bioconverted to the active form melagatran. Oral ximelagatran has been evaluated in randomized, controlled trials for several indications, including stroke prevention in atrial fibrillation (AF). Recently, two pivotal phase III trials demonstrated that fixed-dose oral ximelagatran, 36 mg twice daily without coagulation monitoring, prevents stroke and systemic embolic events in patients with nonvalvular AF as effectively as well-controlled, adjusted-dose warfarin. Oral ximelagatran was generally well tolerated and caused less total (major plus minor) bleeding than warfarin. In a minority of ximelagatran-treated patients, elevated serum alanine aminotransferase levels were reported, but were typically not associated with specific symptoms, and returned toward the pretreatment baseline whether treatment was continued or discontinued. In AF, oral ximelagatran promises a better benefit to risk ratio than warfarin.