***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background and Purpose — The increased risk of stroke and thromboembolism in atrial fibrillation ( AF ) may be related to a prothrombotic or hypercoagulable state , with abnormalities of hemostasis and platelet activation . To investigate the role of platelets in AF and the influence of antithrombotic therapy , we developed and then applied a new assay to detect the absolute amount of P-selectin per platelet ( pP-selectin ) based on cell lysis . Thus , pP-selectin in AF patients was compared with that of healthy controls and also with plasma soluble P-selectin ( sP-selectin ) and & bgr;-thromboglobulin as established indices of platelet activation . Methods mdash ; We studied 122 patients ( mean [ SD ] age , 71 [ 9 ] years ; 65 men ) with chronic AF of > 6 weeks ’ duration : 34 were not on antithrombotic therapy , 30 were taking aspirin ( 75 to 300 mg/d ) , and 58 were fully anticoagulated with warfarin .  pP-selectin was compared with sP-selectin and  plasma & bgr;-thromboglobulin levels ( enzyme-linked immunosorbent assay ) . Results were compared with those of 23 healthy controls ( mean [ SD ] age , 74 [ 9 ] years ; 7 men ) in sinus rhythm . Results — pP-selectin was significantly lower in AF patients on no antithrombotic therapy ( P ∓0.03 ) than in healthy controls , but sP-selectin and & bgr;-thromboglobulin levels were not significantly different and did not differ in patients taking aspirin or warfarin .  However , pP-selectin was lower in patients with AF on aspirin than in those on warfarin ( P < 0.05 ) . pP-selectin/sP-selectin correlated significantly in healthy controls ( r ∓0.47 , P ∓0.03 ) but inversely ( r ∓−0.43 , P ∓0.03 ) in AF patients on no antithrombotic therapy . Conclusions — Lower levels of pP-selectin may represent a depletion of pP-selectin after platelet activation in AF . Aspirin further decreases pP-selectin levels compared with warfarin . On the basis of the principle of platelet lysis , we demonstrate that it is possible to determine the amount of P-selectin per platelet , which may be regulated in the megakaryocyte through a cyclooxygenase-dependent pathway Microalbuminuria is the best predictor of diabetic nephropathy development in patients with type II diabetes mellitus ( DM ) . It is also accepted as an indicator of diabetic microangiopathy . Increased activation of platelets has been suggested to be involved in the pathogenesis of vascular complications . In light of these findings , this study was design ed to investigate the association of microalbuminuria — an indicator glycemic control and microangiopathy — with mean platelet volume ( MPV ) . Subjects underwent laboratory analyses and their  MPV , HbA1c , serum creatinine , fasting , and postpr and ial blood glucose levels and 24-hour urine albumin levels  were recorded . All statistical analyses were performed using SPSS v13.0 for Windows XP . Mann – Whitney U-test , student 's t-test , spearman correlation analysis , ROC analysis , categorical regression analysis , and chi-square test were used for statistical evaluations . The study included 354 patients with type II DM . The median MPV value of microalbuminuria-positive patients was 9 ( 8–9.5 ) fl while MPV of patients without microalbuminuria was 8.5 ( 8–9.2 ) fl and the difference was statistically significant ( p = 0.004 ) . We determined positive correlation between MPV and 24-hour urine microalbuminuria ( r = 0.14 , p = 0.009 ) . There were no significant differences between patients with HbA1c levels below and above 7 % in terms of MPV ( p > 0.05 ) . We determined no correlation between MPV and HbA1c levels ( r = −0.36 , p = 0.64 ) . This study determined a significant positive relationship between microalbuminuria — a microvascular complication of diabetes — and MPV . No significant correlation was identified between poor glycemic control and MPV in diabetic patients . However , we are in the opinion that the association between poor glycemic control and MPV in type II diabetic patients should be investigated in prospect i ve studies with larger sample INTRODUCTION Atrial fibrillation ( AF ) is associated with impaired coronary flow by means of Thrombolysis in Myocardial Infa rct ion ( TIMI ) frame count ( TFC ) . Mean platelet volume ( MPV ) is elevated in patients with AF . In the present study we aim ed to investigate the relationship between MPV and TFC in patients with AF in the absence of obstructive coronary artery disease ( CAD ) . METHODS This observational study enrolled 185 AF patients and 189 control subjects , all with angiographically documented normal coronary arteries .  MPV  was measured at baseline and  mean TFC  was assessed after diagnostic coronary angiography . RESULTS The MPV was 9.95±1.32 in the AF group and 9.02±1.16 in the control group ( p<0.001 ) . In AF patients , MPV was significantly correlated with mean TFC ( r=0.419 , p<0.001 ) , AF duration ( r=0.407 , p<0.001 ) , AF classification ( r=0.378 , p<0.001 ) , systemic hypertension ( r=0.165 , p=0.024 ) , diabetes mellitus ( r=0.233 , p=0.001 ) , left ventricular ejection fraction ( r=-0.347 , p<0.001 ) , and baseline use of diuretics ( r=0.177 , p=0.016 ) . In linear regression analysis , mean TFC , left ventricular ejection fraction and diabetes mellitus were found to be independently associated with MPV ( p<0.001 , p=0.028 and p=0.045 respectively ) . CONCLUSION Mean platelet volume seems to be independently associated with coronary blood flow in patients with atrial fibrillation in the absence of obstructive coronary artery disease OBJECTIVE --To determine whether chronic atrial fibrillation is associated with abnormalities in plasma fibrinogen , von Willebr and factor ( vWF ) ( a marker of endothelial disturbance ) , or fibrin D- dimer ( a measure of fibrin turnover ) ; and if so , whether such levels are related to haemodynamic disturbance ( enlarged left atrium , poor left ventricular function ) or existing treatment with warfarin or aspirin . To investigate the effects of introducing warfarin in patients with atrial fibrillation on fibrinogen and D- dimer levels . DESIGN --Cross sectional population sample controlled study and longitudinal study of patients undergoing anticoagulation .  SETTING --District general hospital . SUBJECTS--87 patients ( 44 men and 43 women of mean ( SEM ) age 63.0 ( 1.0 ) ) with chronic atrial fibrillation . At the time of the study , 37 were taking no antithrombotic medication ( group 1 ) , 31 were taking warfarin ( including two on warfarin and aspirin ) ( group 2 ) and 19 were taking aspirin alone ( group 3 ) . They were compared with 158 population controls from a r and om population sample ( the second Glasgow monitoring trends and determinants in cardiovascular disease study ) . As part of clinical treatment warfarin was introduced in 20 patients with chronic atrial fibrillation ( 14 men and six women of mean ( SEM ) ( range ) age 63.9 ( 2.35 ( 32 - 74 ) years ) . RESULTS --Plasma fibrinogen remained significantly increased in patients of group 1 ( no antithrombotic medication ) compared with that of the population controls ( median difference 1.23 g/l ; 95 % confidence interval ( CI ) 0.88 to 1.62 , P < 0.0001 ) . There was also a significant increase in plasma D-dimer levels ( median difference 77 ng/ml ; 95 % CI 38 to 122 , P < 0.01 ) and vWF ( median difference 63 IU/dl ; 95 % CI 38 to 89 , P < 0.0001 ) . There was no significant difference in plasma fibrinogen ( median difference 0.14 g/l ; 95 % CI -0.44 to 0.77 , P = 0.65 ) or vWF ( median difference 3.5 IU/dl ; 95 % CI - 41 to 41 , P = not significant in patients of group 2 ( warfarin treatment ) compared with that of patients in group 1 . Levels of D-dimer were significantly lower in group 2 ( median difference 90 ng/ml , 95 % CI 39 to 150 , P < 0.0001 ) than in group 1 . There were no significant differences in plasma fibrinogen ( median difference 0.08 g/l ; 95 % CI - 0.52 to 0.77 , P = 0.73 ) , D-dimer ( median difference - 34 ng/ml ; 95 % CI - 114 to 21.0 , P = 0.25 ) , or vWF ( median difference 2 % ; 95 % CI - 35 to 41 , P = not significant ) levels between patients of groups 1 and 3 . There were no significant correlations between the coagulation indices and left atrial volume or ventricular function . There was a significant positive correlation between plasma fibrin D-dimer and vWF levels in patients of groups 1 and 3 ( r = 0.52 , P < 0.001 ) . There was a significant reduction in median plasma fibrin D-dimer levels at 2 months after the introduction of warfarin ( 181 ng/ml v 80 ng/ml , P < 0.001 ) , but no effect on plasma fibrinogen . CONCLUSIONS --Increased median plasma fibrinogen and vWF levels were found in patients with chronic atrial fibrillation .  Plasma D-dimer levels were also increased in patients with chronic atrial fibrillation not receiving warfarin , suggesting increased intravascular thrombogenesis in such patients . Introduction of warfarin normalised circulating fibrin D- dimer levels , suggesting that warfarin treatment was effective in preventing excessive fibrin turnover , consistent with the antithrombotic effects of warfarin . These results suggest three possible thrombotic markers to assess patients with atrial fibrillation who are at high risk of thrombogenesis ; D-dimer also merits assessment as a measure of reduction in thrombotic risk in patients receiving warfarin Atrial fibrillation ( AF ) is strongly associated with thromboembolic complications , although the mechanism for the increased risk has not been fully explained . To determine whether AF might be associated with a hypercoagulable state , we studied hemostatic factors in subjects with or without AF in the Framingham Heart Study . In 3,577 subjects , we measured  fibrinogen , von Willebr and factor antigen , tissue plasminogen activator ( tPA ) antigen , and plasminogen activator inhibitor-1 antigen .  Forty-seven subjects had AF at the index clinic examination and 15 had AF on a prior examination , but not on the current examination .  Before matching , the 47 subjects with prevalent AF had higher levels of fibrinogen , von Willebr and factor , and tPA antigen than those without AF , all p < or = 0.03 . Compared with 167 referent subjects matched for age , sex , and other risk factors , those with AF had higher tPA antigen levels than those without AF , 1 1.8 + /- 4.0 ng/ml versus 10.5 + /- 3.9 ng/ml ( p = 0.04 ) . However , when further stratified according to their cardiovascular disease status , the differences in hemostatic factors were no longer significant . We conclude that the prothrombotic profile associated with AF was explained by the risk factors of the subjects and the presence of cardiovascular disease . Nonetheless , the hemostatic changes may contribute toward the propensity for thromboembolic complications in AF . Further prospect i ve studies are needed to evaluate whether measurement of these and other hemostatic factors will identify patients with AF who are at increased risk for thromboembolic complications , and who may therefore benefit from more intensive therapy BACKGROUND A prothrombotic or hypercoagulable state in atrial fibrillation may contribute to stroke and thromboembolism . Results of longitudinal population -based studies in elderly people with atrial fibrillation are not yet available . METHODS In the Rotterdam Study , a population -based prospect i ve cohort study , 162 participants with atrial fibrillation at baseline , aged 55 years and over , were matched for age and gender with 324 people in sinus rhythm . Associations were examined between three coagulation factors and the risk of total and cardiac mortality and stroke . Hazard rate ratios were calculated with 95 % confidence intervals using Cox 's proportional hazards model , adjusted for potential confounders . RESULTS Plasma von Willebr and factor was , age- and gender-adjusted , associated with cardiac mortality in the total population ( relative risk 1.16 ; 1.06 - 1.27 , per 10 IU dL(-1 ) increase ) , 
    Output:
    
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