Prothrombotic State In Atrial Fibrillation Research Articles

Refining the Prothrombotic State in Atrial Fibrillation with Left Atrial Appendage 3D Echocardiography

Refining the Prothrombotic State in Atrial Fibrillation with Left Atrial Appendage 3D Echocardiography

Biomarkers of prothrombotic state in atrial fibrillation

Biomarkers of prothrombotic state in atrial fibrillation

Relationship between lipoproteins, thrombosis, and atrial fibrillation.

The prothrombotic state in atrial fibrillation (AF) occurs as a result of multifaceted interactions, known as Virchow’s triad of hypercoagulability, structural abnormalities, and blood stasis. More recently, there is emerging evidence that lipoproteins are implicated in this process, beyond their traditional role in atherosclerosis. In this review, we provide an overview of the various lipoproteins and explore the association between lipoproteins and AF, the effects of lipoproteins on haemostasis, and the potential contribution of lipoproteins to thrombogenesis in AF. There are several types of lipoproteins based on size, lipid composition, and apolipoprotein category, namely: chylomicrons, very low-density lipoprotein, low-density lipoprotein (LDL), intermediate-density lipoprotein, and high-density lipoprotein. Each of these lipoproteins may contain numerous lipid species and proteins with a variety of different functions. Furthermore, the lipoprotein particles may be oxidized causing an alteration in their structure and content. Of note, there is a paradoxical inverse relationship between total cholesterol and LDL cholesterol (LDL-C) levels, and incident AF. The mechanism by which this occurs may be related to the stabilizing effect of cholesterol on myocardial membranes, along with its role in inflammation. Overall, specific lipoproteins may interact with haemostatic pathways to promote excess platelet activation and thrombin generation, as well as inhibiting fibrinolysis. In this regard, LDL-C has been shown to be an independent risk factor for thromboembolic events in AF. The complex relationship between lipoproteins, thrombosis and AF warrants further research with an aim to improve our knowledge base and contribute to our overall understanding of lipoprotein-mediated thrombosis.

Association of NT-proBNP and GDF-15 with markers of a prothrombotic state in patients with atrial fibrillation off anticoagulation

We investigated whether growth differentiation factor-15 (GDF-15), also known as macrophage inhibitory cytokine-1 (MIC-1), levels are associated with a prothrombotic state in atrial fibrillation (AF) as compared to N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin I (cTnI-hs). In 103 patients with AF assessed off anticoagulation (age: 71.0 [65.0–76.0] years; CHA2DS2-VASc score: 4.6 ± 1.7), we measured endogenous thrombin potential (ETP), plasma fibrin clot permeability (Ks, a measure of clot density) and clot lysis time (CLT) and other hemostatic parameters, along with GDF-15, NT-proBNP, and cTnI-hs. GDF-15 positively correlated with ETP and CLT (r = 0.25, P = 0.01 and R = 0.56, P < 0.0001, respectively) but not with Ks, von Willebrand factor, thrombin-activatable fibrinolysis inhibitor, plasminogen, antiplasmin or tissue-type plasminogen activator antigen. NT-proBNP showed a stronger association with ETP (r = 0.60, P < 0.0001) and a similar correlation with CLT (R = 0.53, P < 0.0001), while cTnI-hs correlated solely with CLT (R = 0.25, P = 0.01). After adjustment for clinical and laboratory parameters, GDF-15 was a better independent predictor of CLT (unstandardized coefficient B 0.009; 95% confidence interval [CI] 0.006–0.012) than NT-proBNP (B 0.007; 95% CI 0.004–0.010, R (2) = 0.51; P < 0.0001); while among the three biomarkers, only NT-proBNP was an independent predictor of ETP. Elevated GDF-15 and NT-proBNP independently predict impaired fibrin clot lysability, while NT-proBNP is a key predictor of heightened thrombin formation in AF. Our findings suggest that a predictive value of NT-proBNP and GDF-15 in AF could be in part attributed to their association with prothrombotic blood alterations.Graphic

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.

Persistent Prothrombotic State in Atrial Fibrillation Despite Use of Novel Oral Anti-Coagulants

Background: Oral anticoagulants such as warfarin have been conventionally used for the management of atrial fibrillation (AF). Despite the effectiveness of warfarin, its use in AF patients requiring anticoagulation is suboptimal with an even greater underuse seen in elderly patients who are at higher risk of stroke. New oral anticoagulants such as rivaroxaban(R), apixaban (A), dabigitran (D) and edoxaban (E) have been approved to manage thrombotic and cardiovascular disorders including AF. The newer anticoagulants do not require continuous monitoring like warfarin and are much more convenient for patients with AF.Objective: To profile the baseline level of circulating thrombotic biomarkers plasminogen activator inhibitor (PAI-1), von Willebrand Factor (vWF), microparticle bound tissue factor (MP-TF) and prothrombin fragment 1.2 (F1.2) in patients with AF. Additionally, the effect of novel oral anticoagulants (R, A, D and E) on the levels of thrombotic biomarkers in patients with AF is assessed.Materials and Methods: Citrated blood samples were drawn from 30 patients (21 male and 9 female; mean age 59.1) prior to ablation surgery for AF at Loyola University Medical Center in Maywood, Illinois. Citrated blood was spun at 3000 rpm to obtain platelet poor plasma. Normal plasma samples from healthy controls (24 male and 24 female; mean age 33) were purchased from a commercial source (George King Biomedical, Overland Park, KS). The plasma samples were analyzed using a biochip array (Randox, London, UK) for metabolic syndrome biomarkers including PAI-1 and ELISA kits for vWF, MP-TF (Hyphen BioMed, Nueville-Sur-Oise, France) and prothrombin F1.2 (Siemens, Newark, DE).Results: Compared to the control group, circulating levels of vWF, MP-TF and PAI-1 were statistically increased in patients with AF (P<0.0001, P<0.0001, and P=0.0014, respectively). Circulating levels of prothrombin F1.2 showed no difference between the AF and the control group (P=0.2696). AF patients (n=30) were divided into two groups based on their usage (Group 1, n=17) and non-usage (Group 2, n=10) of any novel oral anticoagulant (R, A, D and E). Three patients on warfarin were excluded from this section of data analysis. A statistical increase in vWF (P=0.0018) and MP-TF (P=0.0039) remained in those taking novel oral anticoagulants compared to group 2. No difference was seen in PAI-1 (P=0.333) or F1.2 (P=0.31) between groups 1 and 2. Percent change from the normal mean was also calculated for PAI-1, vWF, MP-TF and F1.2 in group 1 (78%, 61.1%, 142%, 8.9%, respectively) and group 2 (113.6%, 16.9%, 31.7%, 41.4%, respectively) as seen in table 1.Discussion: Elevated levels of PAI-1, vWF and MP-TF seen in AF patients compared to normal provide insight into an additional risk of thrombogenesis associated with AF which is not targeted by current anticoagulant medications. Most AF patients are assessed using a stroke risk stratification scale (CHA2DS2VASc) to determine if anti-coagulants should be used to prevent stroke associated with AF. Patients in group 1 had a mean CHA2DS2VASc score of 1.15 compared to 2.18 see in group 2. This data supports studies which suggest that including levels of prothrombotic biomarkers to current risk stratification scales could be more effective in assessing the risk of stroke of patients with AF. This data also suggests that although very effective in lowering prothrombin F1.2 levels in AF, the newer anticoagulants, R,A,D and E still leave additional prothrombotic biomarkers unaffected. These unaffected biomarkers could be the potential target of future drug therapies which could lower the risk of stroke in patients with AF even more than the use of newer anticoagulants alone. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

High-Sensitivity C-Reactive Protein and Risk of Stroke in Atrial Fibrillation (from the Reasons for Geographic and Racial Differences in Stroke Study)

The relation between inflammation and prothrombotic state in atrial fibrillation (AF) is well recognized. This suggests a potential role for high-sensitivity C-reactive protein (hs-CRP), a marker of systemic inflammation, in improving prediction of stroke in participants with AF. Cox proportional hazard analysis was used to examine the risk of stroke in 25,841 participants (40% black and 55% women) with and without AF who were enrolled in the Reasons for Geographic and Racial Differences in Stroke study from 2003 to 2007. Baseline AF (n= 2,132) was ascertained by electrocardiogram and self-reported history of previous physician diagnosis. Stroke events were identified and adjudicated during 8.3years of follow-up. A total of 655 incident strokes occurred during follow-up. In a model adjusted for sociodemographics, traditional stroke risk factors, and use of aspirin and warfarin, higher levels of hs-CRP were associated with increased overall stroke risk (hazard ratio [HR] 1.30, 95% confidence interval [CI] 1.10 to 1.54, and HR 1.06, 95% CI 1.01 to 1.12 for hs-CRP >3mg/L and per 1-SD increase, respectively). Higher levels of hs-CRP continued to be associated with incident stroke in participants without AF (HR 1.31, 95% CI 1.09 to 1.57, and HR 1.06, 95% CI 1.01 to 1.12 for hs-CRP >3mg/L and per 1-SD increase, respectively) but not in those with AF (HR 1.22, 95% CI 0.78 to 1.91, and HR 1.01, 95% CI 0.82 to 1.23 for hs-CRP >3mg/L and per 1-SD increase, respectively). In conclusion, although hs-CRP was significantly associated with stroke risk in this population, it seems to be limited to those without AF. These findings suggest a limited value of hs-CRP in improving stroke risk stratification in subjects with AF.

Effect of asymmetrical dimethylarginine for predicting pro-thrombotic risk in atrial fibrillation

Atrial fibrillation (AF) is responsible for some thromboembolic events. Asymmetrical dimethylarginine(ADMA) increases in atrial fibrillation(AF) animals with dysfunction of endothelium, but its role in pro-thrombotic state of AF was unknown. The aim of our study was to explore the role of ADMA in predicting the pro-thrombotic state in AF and to reveal its mechanism. One hundred and thirty-eight patients in the First Affiliated Hospital, Sun Yat-sen University, from 2010 to 2012, were enrolled (persistent atrial fibrillation group, PAF, n=80; paroxysmal atrial fibrillation group, Paf, n=30; sinus rhythm, SR, n=28). Plasma ADMA levels were detected by ELISA-kits. CHADS2 and CHA2DS2-VASc scores were estimated for each patient.14 Beagles (pacing group, n=8; sham group, n=6) were subjected to rapid atrial pacing (RAP). ADMA level was detected after 4 weeks of RAP. ADMA level was elevated significantly in patients with atrial fibrillation especially in patients with persistent atrial fibrillation, and showed a significant linear correlation to CHADS2 and CHA2DS2-VASc score. With ADMA, ROC area under the curve was 0.865 in CHADS2 score ≥2 and was 0.959 in CHA2DS2-VASc score ≥2 (P<0.001 respectively). After 4 weeks of RAP, ADMA level was elevated compared to sham group and before operation. ADMA showed a linear correlation with atrial fibrillation susceptibility(r=0.686, P=0.007). ADMA levels are elevated both in AF patients and RAP beagles. ADMA correlates with stroke risk concerning with CHADS2/CHA2DS2-VASc score. ADMA may become a new biomarker for predicting pro-thrombotic risk in AF.

Stroke in atrial fibrillation and improving the identification of ‘high‐risk’ patients: the crossroads of immunity and thrombosis

Stroke in atrial fibrillation and improving the identification of ‘high‐risk’ patients: the crossroads of immunity and thrombosis

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

BackgroundThere 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.MethodsWe 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.ResultsA 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).ConclusionsIncreased 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.

Relation of Reduced Expression of MiR-150 in Platelets to Atrial Fibrillation in Patients With Chronic Systolic Heart Failure

Atrial fibrillation (AF) is associated with poor prognosis in patients with heart failure (HF). Although platelets play an important role in rendering a prothrombotic state in AF, the exact mechanism by which the effect is mediated is still debated. MicroRNAs (miRNAs), which have been shown to be involved in a variety of cardiovascular conditions, are abundant in platelets and in a cell-free form in the circulation. In the present study, we performed a genome-wide screen for miRNA expression in platelets of patients with systolic HF and in controls without cardiac disease, in pursuit of specific miRNAs that are associated with the presence of AF. MiRNA expression was measured in platelets from 50 patients with systolic HF and 50 controls, of which, samples from 41 patients with HF and 35 controls were used in the final analysis because of a quality control process. MiR-150 expression was 3.2-fold lower (p = 0.0003) in platelets of patients with HF with AF relative to those without AF. A similar effect was seen in serum samples from the same patients, in which miR-150 levels were 1.5-fold lower (p = 0.004) in patients with HF with AF. Furthermore, the serum levels of miR-150 were correlated to platelet levels in patients with AF (r = 0.65, p = 0.0087). In conclusion, miR-150 expression levels in platelets of patients with systolic HF with AF are significantly reduced and correlated to the cell-free circulating levels of this miRNA.

Microparticles Contribute to the Prothrombotic State in Atrial Fibrillation

Microparticles Contribute to the Prothrombotic State in Atrial Fibrillation

Circulating progenitor cells in patients with atrial fibrillation and their relation with serum markers of inflammation and angiogenesis

The pathophysiological inter-relationships and underlying 'drivers' of a prothrombotic state in atrial fibrillation (AF) are complex but may include endothelial abnormalities. Circulating progenitor cells (CPCs) have been recently described as a cell population that may promote repair of endothelial damage. We hypothesised abnormalities in this cell population, alongside abnormal markers of endothelial damage/dysfunction (von Willebrand factor, soluble E-selectin), apoptosis (soluble Fas, soluble Fas ligand), angiogenesis (vascular endothelial growth factor) and inflammation (interleukin-6) in 135 consecutive AF patients (14 with lone AF), who were compared to 33 'disease controls' and 13 healthy controls. We also explored whether restoration of sinus rhythm would alter these indices. No significant differences in research indices were observed between AF and disease controls, apart from soluble Fas levels (p<0.001). Median CPC levels in lone AF were higher compared to 'non-lone AF' (that is, AF patients with co-morbidities) [p<0.001], apparently because of difference in age and presence of co-morbidities. There was an increase in CPC counts (p=0.007), but in not other markers following DC cardioversion. CPCs increased significantly in the 17 patients who were successfully cardioverted into sinus rhythm (p=0.003). In a stepwise multiple regression analysis, age (p=0.014), hyperlipidaemia (p=0.001) and use of statins (but not AF) was predictive of CPC counts (p=0.014). In conclusion, AF is unlikely to be independently associated with abnormalities in CPCs. Successful cardioversion is associated with a modest but significant increase in CPCs.

Accumulation of risk factors enhances the prothrombotic state in atrial fibrillation

Accumulation of risk factors enhances the prothrombotic state in atrial fibrillation

The endothelium and atrial fibrillation

Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia, which confers a high risk of mortality and morbidity from stroke and thromboembolism. The precise mechanisms by which AF causes thromboembolism and subsequent cerebrovascular events have attracted much research interest, and are yet to be fully elucidated. Nonetheless, it is well recognised that AF fulfils Virchow's triad for thrombogenesis, with abnormal flow conditions with loss of atrial contractility and an irregularly irregular cardiac output, (i. e. flow abnormalities), as well as structural heart disease with endocardial damage (i. e. abnormal vessel wall) and abnormalities in platelet and haemostatic variables (i. e. abnormal blood constituents). This review is to summarise the evidence so far for the role of coagulation and fibrinolytic components, platelets and inflammation (that is blood constituents) in the generation of the prothrombotic state in AF, with particular focus on the endothelium and AF.

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 (≥ 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 ≥ 3 were classified as low, moderate and high risk, respectively. Levels of hemostatic markers (platelet factor 4, β-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 β-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.

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

Background. The precise pathophysiological processes underlying the prothrombotic or hypercoagulable state in atrial fibrillation (AF) remain uncertain. We hypothesized a relationship between abnormal endothelial damage/dysfunction, coagulation, and angiogenic factors, thereby contributing to increased thrombogenicity.Methods. Plasma levels of von Willebrand factor (vWF, an index of endothelial damage/dysfunction) and tissue factor (TF, an index of coagulation), as well as the angiogenic factors, vascular endothelial growth factor (VEGF), angiopoietin‐1 (Ang‐1) and angiopoietin‐2 (Ang‐2), were measured by enzyme‐linked immunosorbant assay (ELISA) in 59 chronic AF patients. Data were compared to 40 age‐ and sex‐matched healthy controls in sinus rhythm.Results. Plasma vWF, VEGF and Ang‐2 were significantly higher in AF patients compared to healthy controls (P = 0.005, P = 0.0055 and P<0.0001 respectively) but there were no significant differences in plasma Ang‐1 or TF levels between the two groups (P = 0.925 and P = 0.121 respectively). Significant correlations were found between VEGF and vWF levels (Spearman, r = 0.262, P = 0.011) and between VEGF and Ang‐2 (r = 0.333, P = 0.001).Conclusions. Raised VEGF in association with Ang‐2 and vWF may reflect a link between abnormal endothelial damage/dysfunction and angiogenic factors. These may act together to alter TF expression and endothelial integrity, thereby contributing to the prothrombotic state in AF.

Relationship of interleukin-6 and C-Reactive protein to the prothrombotic state in chronic atrial fibrillation

ObjectivesWe sought to test the hypothesis that there is a relationship between inflammation and the prothrombotic state in atrial fibrillation (AF). BackgroundAtrial fibrillation is associated with a prothrombotic or hypercoagulable state, which may contribute to an increased risk of stroke and thromboembolism. Inflammation may be involved in the pathogenesis of AF, but the role of inflammation in the pathophysiology of the prothrombotic state of AF has not been studied in detail, despite evidence of a link between inflammation and arterial atherothrombotic disorders. MethodsWe measured plasma indexes of inflammation (C-reactive protein [CRP] and interleukin-6 [IL-6]) and the prothrombotic state, including markers of platelet activation (soluble P-selectin), endothelial damage/dysfunction (von Willebrand factor), the coagulation cascade (tissue factor [TF], fibrinogen), and indexes of blood rheology (plasma viscosity, plasma fibrinogen, and hematocrit) in 106 patients with chronic AF and 41 healthy control subjects included in a cross-sectional analysis. ResultsCompared with controls, AF patients had higher levels of IL-6 (p = 0.034), CRP (p = 0.003), TF (p = 0.019), and plasma viscosity (p = 0.045). Plasma IL-6 levels were higher among AF patients at “high” risk of stroke (p = 0.003). After adjusting for potential confounding clinical variables (e.g., vascular disease), AF remained significantly associated with a raised logarithmic transformation (log) of TF (p = 0.04), but the relationships between AF and log IL-6, log CRP, and plasma viscosity became nonsignificant. Among AF patients, log TF (p < 0.001) and high stroke risk (p = 0.003) were independent associates of log IL-6 (adjusted r2= 0.443), whereas log fibrinogen (p < 0.001) and plasma viscosity (p = 0.04) were independent associates of log CRP (adjusted r2= 0.259). ConclusionsIncreased plasma IL-6, CRP, and plasma viscosity support the case for the existence of an inflammatory state among “typical” populations with chronic AF. These indexes of inflammation are related to indexes of the prothrombotic state and may be related to the clinical variables of the patients (underlying vascular disease and co-morbidities), rather than simply to the presence of AF itself.

Relation of interleukin-6, C-reactive protein, and the prothrombotic state to transesophageal echocardiographic findings in atrial fibrillation

Atrial fibrillation (AF) is a major cause of morbidity and mortality from stroke due to thromboembolism from the fibrillating left atrium, including its appendage. We hypothesized that indexes of inflammation (as indicated by C-reactive protein and interleukin-6) and indexes of the prothrombotic state in AF that represent platelet activation (soluble P-selectin levels), endothelial damage or dysfunction (von Willebrand factor), coagulation (tissue factor and fibrinogen), and hemorrheology (plasma viscosity and hematocrit) would be related to the presence of thromboembolic predictors on transesophageal echocardiography in patients with long-term AF. To test this hypothesis, we recruited 37 patients with long-term AF who were receiving warfarin therapy with an international normalized ratio of ≥2.0 for ≥3 weeks before transesophageal echocardiography. Twenty-two patients had dense spontaneous echo contrast (SEC) visible in the left atrium or left atrial appendage, 10 had complex atheromatous plaque in the descending aorta, 11 had peak left atrial appendage velocities ≤0.2 m/s, and 3 had thrombus visible in the left atrial appendage. Twenty-eight patients had ≥1 transesophageal echocardiographic (TEE) risk factor for thromboembolism. Plasma levels of C-reactive protein (p = 0.03) and soluble P-selectin (p = 0.04) and hematocrit (p = 0.004) were higher among patients with AF with dense SEC than among those without. No significant associations were found for other TEE risk factors. Hematocrit was the only variable significantly associated with the presence of ≥1 TEE risk factor among patients with AF (p = 0.007) and the only independent associate of dense SEC after multivariate analysis (relative risk 1.4, 95% confidence interval 1.1 to 1.6) per 1% increase in hematocrit (p = 0.003, r 2 = 0.22). Although hematocrit was the only independent associate of dense SEC and ≥1 TEE risk factor, significant associations between dense SEC and the 2 indexes, C-reactive protein and soluble P-selectin, may indicate that mechanisms other than stasis are present with dense SEC. These observations support an “inflammatory hypothesis” in the pathogenesis of SEC that may have implications for thrombogenesis in AF.

Is thrombogenesis in atrial fibrillation related to matrix metalloproteinase-1 and its inhibitor, TIMP-1?

Decreased matrix metalloproteinase-1 (MMP-1) and increased levels of its inhibitor, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), reflect impaired matrix degradation with an increase in fibrosis. A prothrombotic state has been described in atrial fibrillation (AF), increasing the risk of stroke and thromboembolism. Because structural abnormalities and remodeling of atria have been observed in AF, we hypothesized that the prothrombotic state in AF may be related to abnormal indexes of matrix degradation. We studied 48 consecutive patients (30 men; age, 70.5+/-9.0 years) with chronic nonrheumatic AF who were not on anticoagulation. Plasma levels of MMP-1, TIMP-1, and prothrombin fragment 1+2 (F1+2, an index of thrombogenesis) were measured by enzyme-linked immunosorbent assay. M-mode, 2-dimensional, and Doppler echocardiographic studies were performed in all patients. Research indexes were compared with data from 32 control subjects in sinus rhythm who were of similar age and sex. Patients with AF had lower levels of MMP-1 (P=0.011) but increased levels of TIMP-1 (P=0.033) and F1+2 (P<0.001) and a higher ratio of TIMP-1 to MMP-1 (P=0.009) compared with control subjects. After adjustment for sex, age, hypertension, and diabetes, TIMP-1 levels and the ratio of TIMP-1 to MMP-1 correlated with F1+2 levels (r=0.24, P=0.038; and r=0.26, P=0.023, respectively). In multivariate analysis, there was no independent relationship between MMP-1, TIMP-1, or ratio of TIMP-1 to MMP-1 and the presence of AF. Patients with AF have evidence of impaired matrix degradation, but this was not independently associated with the presence of AF on multivariate analysis. However, an independent relationship was found between the MMP/TIMP system and prothrombotic state (assessed by F1+2 levels).