title: Stroke with intermittent atrial fibrillation: incidence and predictors during aspirin therapy. Stroke Prevention in Atrial Fibrillation Investigators. Factors associated with ischemic stroke during aspirin therapy in atrial fibrillation: analysis of 2012 participants in the SPAF I-III clinical trials. The Stroke Prevention in Atrial Fibrillation (SPAF) Investigators. Risk factors for new thromboembolic stroke in patients > or = 62 years of age with chronic atrial fibrillation. Predictors of thromboembolism in atrial fibrillation: II. Echocardiographic features of patients at risk. The Stroke Prevention in Atrial Fibrillation Investigators. Risk factors for thromboembolic stroke in elderly patients with chronic atrial fibrillation. Predictors of major vascular events in patients with a transient ischemic attack or minor ischemic stroke and with nonrheumatic atrial fibrillation. European Atrial Fibrillation Trial (EAFT) Study Group. Patients with nonvalvular atrial fibrillation at low risk of stroke during treatment with aspirin: Stroke Prevention in Atrial Fibrillation III Study. The SPAF III Writing Committee for the Stroke Prevention in Atrial Fibrillation Investigators. Risk factors for stroke in patients with nonrheumatic atrial fibrillation: a case-control study. Predictors of thromboembolism in atrial fibrillation: I. Clinical features of patients at risk. The Stroke Prevention in Atrial Fibrillation Investigators. Warfarin versus aspirin for stroke prevention in an elderly community population with atrial fibrillation (the Birmingham Atrial Fibrillation Treatment of the Aged Study, BAFTA): a randomised controlled trial Cost-effectiveness of warfarin and aspirin for prophylaxis of stroke in patients with nonvalvular atrial fibrillation. Echocardiographic predictors of stroke in patients with atrial fibrillation: a prospective study of 1066 patients from 3 clinical trials. Anticoagulation therapy for stroke prevention in atrial fibrillation: how well do randomized trials translate into clinical practice? Asymptomatic atrial fibrillation: demographic features and prognostic information from the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study. Risk factors for thromboembolic complications in chronic atrial fibrillation. The Copenhagen AFASAK study. Assessment of three schemes for stratifying stroke risk in patients with nonvalvular atrial fibrillation.
abstract: OBJECTIVE This study was performed to characterize the risk of stroke in elderly patients with recurrent intermittent atrial fibrillation ( AF ) . BACKGROUND Although intermittent AF is common , relatively little is known about the attendant risk of stroke . METHODS A longitudinal cohort study was performed comparing 460 participants with intermittent AF with 1,552 with sustained AF treated with aspirin in the Stroke Prevention in Atrial Fibrillation studies and followed for a mean of two years . Independent risk factors for ischemic stroke were identified by multivariate analysis . RESULTS Patients with intermittent AF were , on average , younger ( 66 vs. 70 years , p < 0.001 ) , were more often women ( 37 % vs. 26 % p < 0.001 ) and less often had heart failure ( 11 % vs. 21 % , p < 0.001 ) than those with sustained AF . The annualized rate of ischemic stroke was similar for those with intermittent ( 3.2 % ) and sustained AF ( 3.3 % ) . In patients with intermittent AF , independent predictors of ischemic stroke were advancing age ( relative risk [ RR ] = 2.1 per decade , p < 0.001 ) , hypertension ( RR = 3.4 , p = 0.003 ) and prior stroke ( RR = 4.1 , p = 0.01 ) . Of those with intermittent AF predicted to be high risk ( 24 % ) , the observed stroke rate was 7.8 % per year ( 95 % confidence interval 4.5 to 14 ) . CONCLUSIONS In this large cohort of AF patients given aspirin , those with intermittent AF had stroke rates similar to patients with sustained AF and similar stroke risk factors . Many elderly patients with recurrent intermittent AF have substantial rates of stroke and likely benefit from anticoagulation . High-risk patients with intermittent AF can be identified using the same clinical criteria that apply to patients with sustained AF BACKGROUND AND PURPOSE Nonvalvular atrial fibrillation ( AF ) is a strong , independent risk factor for stroke , but the absolute rate of stroke varies widely among AF patients , importantly influencing the potential benefit of antithrombotic prophylaxis . We explore factors associated with ischemic stroke in AF patients taking aspirin .  METHODS We performed multivariate logistic regression analysis of 2012 participants given aspirin alone or in combination with low , inefficacious doses of warfarin in the Stroke Prevention in Atrial Fibrillation I-III trials followed for a mean of 2.0 years , during which 130 ischemic strokes were observed . RESULTS Age ( relative risk [RR]=1.8 per decade , P<0.001 ) , female sex ( RR=1.6 , P=0.01 ) , history of hypertension ( RR=2.0 , P<0.001 ) , systolic blood pressure > 160 mm Hg ( RR=2.3 , P<0.001 ) , and prior stroke or transient ischemic attack ( RR=2.9 , P<0.001 ) were independently associated with increased stroke risk . Regular consumption of > /=14 alcohol-containing drinks per week was associated with reduced stroke risk ( adjusted RR=0.4 , P=0.04 ) . Among SPAF III participants , estrogen hormone replacement therapy was associated with a higher risk of ischemic stroke ( adjusted RR=3.2 , P=0.007 ) . With the use of these variables , a risk stratification scheme for primary prevention separated participants into those with high ( 7.1%/y , 22 % of the cohort ) , moderate ( 2.6%/y , 37 % of the cohort ) , and low ( 0.9%/y , 41 % of the cohort ) rates of stroke . Ischemic strokes in low-risk participants were less often disabling ( P<0.001 ) . CONCLUSIONS Patients with AF who have high and low rates of stroke during treatment with  aspirin can be identified . However , validation of our risk stratification scheme is necessary before it can be applied with confidence to clinical management . Postmenopausal estrogen replacement therapy and moderate alcohol consumption may additionally modify the risk of stroke in AF , but these findings require confirmation In a prospect i ve study of 312 older patients with chronic atrial fibrillation , at 36-month follow-up evaluation , new thromboembolic stroke developed in 162 of 312 patients ( 52 % ) . Significant independent risk factors for new thromboembolic stroke were prior stroke ( risk ratio = 1.6 ) , rheumatic mitral stenosis ( risk ratio = 2.0 ) , left ventricular ( LV ) hypertrophy ( risk ratio = 2.8 ) , abnormal LV ejection fraction ( risk ratio = 1.8 ) , serum total cholesterol ( risk ratio = 1.005 ) , and serum high-density lipoprotein cholesterol ( risk ratio = 0.96 ) OBJECTIVE To identify echocardiographic predictors of arterial thromboembolism in patients with nonrheumatic atrial fibrillation and to determine whether these add to clinical variables for risk stratification . DESIGN Cohort study of patients assigned to placebo in a r and omized clinical trial . SETTING Five hundred sixty-eight in patients and out patients with nonrheumatic atrial fibrillation assigned to placebo therapy at 15 U.S. medical centers from 1987 to 1989 in the Stroke Prevention in Atrial Fibrillation study . Patients were followed for a mean of 1.3 years . MEASUREMENTS M-mode and two-dimensional ( 2-D ) echocardiograms performed at study entry and interpreted by local cardiologists . The predictive value of 14 echocardiographic variables for later ischemic stroke or systemic embolism was assessed by multivariate analysis . MAIN RESULTS Left ventricular dysfunction from 2-D echocardiograms ( P = 0.003 ) and the size of the left atrium from M-mode echocardiograms ( P = 0.02 ) were the strongest independent predictors of later thromboembolism . Multivariate analysis of these two independent echocardiographic predictors with the three independent clinical predictors of thromboembolism ( history of hypertension , recent congestive heart failure , previous thromboembolism ) identified 26 % of the cohort with a low risk for thromboembolism ( 1.0 % per year ; 95 % Cl , 0.2 % to 4.0 % ) . Compared with risk stratification using clinical variables alone , echocardiographic results altered thromboembolic risk stratification in 18 % of the entire cohort and in 38 % of those without clinical risk factors . CONCLUSIONS Both left ventricular and left atrial variables are significant predictors of thromboembolism in patients with nonvalvular atrial fibrillation . Our results challenge traditional views of the pathogenesis of ischemic stroke in patients with atrial fibrillation and suggest that st and ard echocardiography contributes to risk stratification , differentiating the one third of patients without clinical risk factors who are at increased risk for stroke from the remainder who may not need antithrombotic prophylaxis Abstract Chronic atrial fibrillation ( AF ) in the presence or absence of rheumatic valvular heart disease is associated with an increased incidence of stroke . 1,2 We reported in a prospect i ve study that at 27-month follow-up , echocardiographic left ventricular ( LV ) hypertrophy in elderly patients with systolic or diastolic hypertension was associated with an increased incidence of new atherothrombotic brain infa rct ion . 3 We also demonstrated in a prospect i ve study that at 3-year follow-up , risk factors for atherothrombotic brain infa rct ion were cigarette smoking , systolic or diastolic hypertension and diabetes mellitus in elderly men and systolic or diastolic hypertension , diabetes mellitus and obesity in elderly women . 4 This report correlates in elderly patients with chronic AF the prevalence of thromboembolic ( TE ) stroke with the presence or absence of rheumatic mitral stenosis , mitral anular calcium , valvular aortic stenosis , systolic or diastolic hypertension , prior myocardial infa rct ion , left atrial enlargement and LV hypertrophy BACKGROUND AND PURPOSE The risk of major vascular events after an initial episode of cerebral ischemia in patients with nonrheumatic atrial fibrillation ( NRAF ) varies from 2 % to 15 % in the first year and is approximately 5 % yearly thereafter . Few studies have reported on risk factors that can be used to identify high-risk subgroups within this patient population . METHODS We studied the predictive value of several easily obtainable clinical characteristics in a group of 375 placebo-treated patients with NRAF and a recent episode of transient or nondisabling cerebral ischemia who were entered in a multicenter clinical trial . The mean follow-up was 1.6 years . RESULTS By means of multivariate modeling , six independent variables were identified : history of previous thromboembolism , ischemic heart disease , enlarged cardiothoracic ratio on chest roentgenogram , systolic blood pressure greater than 160 mm Hg at study entry , NRAF for more than 1 year , and presence of an ischemic lesion on CT scan . These variables could also be used to stratify patients in low- , medium- , and high-risk subgroups for the other two arms of the trial , those treated with anticoagulation and aspirin .  Patients older than 75 years with three or more risk factors seemingly benefited less from both aspirin and anticoagulant treatment . CONCLUSIONS Easily obtainable patient characteristics are helpful in estimating the potential effect of adequate secondary prevention in patients with NRAF who recently suffered a transient ischemic attack or minor ischemic stroke CONTEXT Nonvalvular atrial fibrillation ( AF ) carries an increased risk for stroke , but absolute rates of stroke vary widely within the broad spectrum of AF patients . OBJECTIVE To prospect ively vali date a risk stratification scheme identifying patients with AF with low rates of stroke when given aspirin .  DESIGN Prospect i ve cohort study with mean duration of follow-up of 2.0 years , conducted between 1993 and 1997 . SETTING Outpatient clinics affiliated with academic medical centers . PATIENTS Patients with AF categorized as " low risk " based on the absence of 4 prespecified thromboembolic risk factors : recent congestive heart failure or left ventricular fractional shortening of 25 % or less , previous thromboembolism , systolic blood pressure greater than 160 mm Hg , or female sex at age older than 75 years . INTERVENTION All participants given aspirin , 325 mg/d . MAIN OUTCOME MEASURES Ischemic stroke ( considered disabling when Rankin score was II or worse 1 - 3 months later ) and systemic embolism ( primary events ) . RESULTS Among 892 participants , the mean ( SD ) age was 67 ( 10 ) years , 78 % were men , and histories of hypertension , diabetes , and ischemic heart disease were present in 46 % , 13 % , and 16 % , respectively . The rate of primary events was 2.2 % per year ( 95 % confidence interval [ CI ] , 1.6%-3.0 % ) , of ischemic stroke was 2.0 % per year ( 95 % CI , 1.5%-2.8 % ) , and of disabling ischemic strokes was 0.8 % per year ( 95 % CI , 0.5%-1.3 % ) . Those with a history of hypertension had a higher rate of primary events ( 3.6 % per year ) than those with no history of hypertension ( 1.1 % per year ) ( P<.001 ) . The rate of disabling ischemic stroke was low in those with and without a history of hypertension ( 1.4 % per year and 0.5 % per year , respectively ) . The rate of major bleeding during aspirin therapy was 0.5 % per year . CONCLUSION Patients with AF who have relatively low rates of ischemic stroke , particularly disabling stroke , during treatment with aspirin can be reliably identified PURPOSE R and omized controlled trials have demonstrated that anticoagulant therapy is very effective at preventing stroke among patients with nonrheumatic atrial fibrillation . However , these trials have reported too few strokes for powerful risk factor analysis . Observational studies may provide additional information . The purpose of this study was to identify risk factors in a larger number of patients with stroke and nonrheumatic atrial fibrillation , using case-control methodology . PATIENTS AND METHODS We identified all patients discharged from one hospital over an 8-year period who met our case definition of nonrheumatic atrial fibrillation and ischemic stroke ( n = 134 ) , and compared them with contemporaneous control subjects who were discharged with nonrheumatic atrial fibrillation without stroke ( n = 131 ) . RESULTS Cases and controls were similar in terms of duration of atrial fibrillation ; proportion with paroxysmal atrial fibrillation ; percentage with a past medical history of angina , myocardial infa rct ion , congestive heart failure , diabetes , or smoking ; and mean left atrial size . In contrast , cases were significantly older than controls ( 78.5 versus 74.8 years , p = 0.002 ) and more likely to have a history of hypertension ( 55 % versus 38 % , p = 0.0093 ) . The relative odds for stroke was 1.91 for patients with hypertension , 1.73 for patients older than 75 years , and 3.26 for patients with both factors . CONCLUSIONS Our analysis suggests that age and hypertension should be considered when deciding upon long-term anticoagulant therapy to prevent stroke in patients with nonrheumatic atrial fibrillation OBJECTIVE To identify those patients with nonrheumatic atrial fibrillation who are at high risk and those at low risk for arterial thromboembolism .  DESIGN Cohort study of patients assigned to placebo in a r and omized clinical trial . SETTING Five hundred sixty-eight in patients and out patients with nonrheumatic atrial fibrillation assigned to placebo therapy at 15 U.S. medical centers from 1987 to 1989 in the Stroke Prevention in Atrial Fibrillation study . Patients were followed for a mean of 1.3 years . MEASUREMENTS Clinical variables were assessed at study entry and correlated with subsequent ischemic stroke and systemic embolism by multivariate analysis . MAIN RESULTS Recent ( within 3 months ) congestive heart failure , a history of hypertension , and previous arterial thromboembolism were each significantly and independently associated with a substantial risk for thromboembolism ( greater than 7 % per year ; P less than or equal to 0.05 ) . The presence of these three independent clinical predictors ( recent congestive heart failure , history of hypertension , previous thromboembolism of 2.5 % per year ( no risk factors ) , 7.2 % per year ( one risk factor ) , and 17.6 % per year ( two or three risk factors ) . Nondiabetic patients without these risk factors , comprising 38 % of the cohort , had a low risk for thromboembolism ( 1.4 % per year ; 95 % Cl , 0.05 % to 3.7 % ) . Patients without clinical risk factors who were under 60 years of age had no thromboembolic events . CONCLUSION Patients with atrial fibrillation at high risk ( greater than 7 % per year ) and low risk ( less than 3 % per year ) for thromboembolism can be identified by readily available clinical variables BACKGROUND Anticoagulants are more effective than antiplatelet agents at reducing stroke risk in patients with atrial fibrillation , but whether this benefit outweighs the increased risk of bleeding in elderly patients is unknown . We assessed whether warfarin reduced risk of major stroke , arterial embolism , or other intracranial haemorrhage compared with aspirin in elderly patients . METHODS 973 patients aged 75 years or over ( mean age 81.5 years , SD 4.2 ) with atrial fibrillation were recruited from primary care and r and omly assigned to warfarin ( target international normalised ratio 2 - 3 ) or aspirin ( 75 mg per day ) . Follow-up was for a mean of 2.7 years ( SD 1.2 ) . The primary endpoint was fatal or disabling stroke ( ischaemic or haemorrhagic ) , intracranial haemorrhage , or clinical ly significant arterial embolism . Analysis was by intention to treat . This study is registered as an International St and ard R and omised Controlled Trial , number IS RCT N89345269 . FINDINGS There were 24 primary events ( 21 strokes , two other intracranial haemorrhages , and one systemic embolus ) in people assigned to warfarin and 48 primary events ( 44 strokes , one other intracranial haemorrhage , and three systemic emboli ) in people assigned to aspirin ( yearly risk 1.8%vs 3.8 % , relative risk 0.48 , 95 % CI 0.28 - 0.80 , p=0.003 ; absolute yearly risk reduction 2 % , 95 % CI 0.7 - 3.2 ) . Yearly risk of extracranial haemorrhage was 1.4 % ( warfarin ) versus 1.6 % ( aspirin ) ( relative risk 0.87 , 0.43 - 1.73 ; absolute risk reduction 0.2 % , -0.7 to 1.2 ) . INTERPRETATION These data support the use of anticoagulation therapy for people aged over 75 who have atrial fibrillation , unless there are contraindications or the patient decides that the benefits are not worth the inconvenience OBJECTIVE To examine the cost-effectiveness of prescribing warfarin sodium in patients who have nonvalvular atrial fibrillation ( NVAF ) with or without additional stroke risk factors ( a prior stroke or transient ischemic attack , diabetes , hypertension , or heart disease ) . DESIGN Decision and cost-effectiveness analyses . The probabilities for stroke , hemorrhage , and death were obtained from published r and omized controlled trials . The quality -of-life estimates were obtained by interviewing 74 patients with atrial fibrillation .  Costs were estimated from literature review , phone survey , and Medicare reimbursement . PATIENTS In the base case , the patients were 65 years of age and good c and i date s for warfarin therapy . INTERVENTIONS Treatment with warfarin , aspirin , or no therapy in the decision analytic model . MAIN OUTCOME MEASURES Quality -adjusted survival and marginal cost-effectiveness of warfarin  as compared with  aspirin  or no therapy . RESULTS For patients with NVAF and additional risk factors for stroke , warfarin therapy led to a greater quality -adjusted survival and to cost savings . For patients with NVAF and one additional risk factor , warfarin therapy cost $ 8000 per quality -adjusted life-year saved . For 65-year-old patients with NVAF alone , warfarin cost about $ 370,000 per quality -adjusted life-year saved , as compared with aspirin therapy . However , for 75-year-old patients with NVAF alone , prescribing warfarin cost $ 110,000 per quality -adjusted life-year saved . For patients who were not prescribed warfarin , aspirin was preferred to no therapy on the basis of both quality -adjusted survival and cost in all patients , regardless of the number of risk factors present . CONCLUSIONS Treatment with warfarin is cost-effective in patients with NVAF and one or more additional risk factors for stroke . In 65-year-old patients with NVAF but no other risk factors for stroke , prescribing warfarin instead of aspirin would affect quality -adjusted survival minimally but increase costs significantly BACKGROUND Clinical features that consistently predict ischemic stroke in patients with nonvalvular atrial fibrillation have been identified , while echocardiographic risk factors are less well defined . OBJECTIVE To determine whether the results of transthoracic echocardiography add independent information to the clinical risk factors for stroke in patients with atrial fibrillation . METHODS Transthoracic echocardiographic findings and clinical features from 1066 patients with atrial fibrillation assigned to placebo or control in 3 r and omized trials ( Boston Area Anticoagulation Trial for Atrial Fibrillation , Stroke Prevention in Atrial Fibrillation I Study , and Veterans Affairs Prevention in Atrial Fibrillation Study ) were correlated with subsequent ischemic stroke by multivariate analysis . RESULTS The mean + SD age of patients was 67 + /- 10 years , 78 % were men , 55 % had a history of hypertension , 19 % had a history of diabetes , 7 % had a previous transient ischemic attack or stroke , and 27 % had a history of heart failure . During a mean follow-up of 1.6 years , 78 ischemic strokes occurred ( annual rate , 4.7 % ) . Moderate to severe left ventricular systolic dysfunction shown via 2-dimensional echocardiography was a strong independent predictor of stroke ( relative risk , 2.5 ; P<.001 ) in the 1010 patients in whom echocardiographic values for left ventricular function were available . Left atrial diameter by M-mode echocardiography did not predict stroke ( relative risk , 1.02/mm ; P = .10 ) . Of 163 patients categorized as low risk based on clinical features ( annual stroke rate , 0.8 % ; 95 % confidence interval , 0.2%-3.0 % ) , 10 had moderate to severe left ventricular dysfunction shown via 2-dimensional echocardiography and a 9.3 % per year risk of stroke ( 95 % confidence interval , 1.3%-66 % ) . Conversely , 728 of the 847 patients at high risk for stroke based on clinical criteria had normal or mildly abnormal left ventricular function ; their stroke rate was 4.4 % ( 95 % confidence interval , 3.4%-5.8 % ) . CONCLUSIONS Left ventricular systolic dysfunction shown via 2-dimensional transthoracic echocardiography independently predicts risk of stroke in patients with atrial fibrillation . Echocardiography may prove most useful in a small group of patients who have a low risk of stroke according to clinical factors CONTEXT Warfarin has been shown to be highly efficacious for preventing  thromboembolism in atrial fibrillation in r and omized trials , but its effectiveness and safety in clinical practice is less clear . OBJECTIVE To evaluate the effect of warfarin on risk of thromboembolism , hemorrhage , and death in atrial fibrillation within a usual care setting . DESIGN Cohort study assembled between July 1 , 1996 , and December 31 , 1997 , and followed up through August 31 , 1999 . SETTING Large integrated health care system in Northern California . PATIENTS Of 13,559 adults with nonvalvular atrial fibrillation , 11,526 were studied , 43 % of whom were women , mean age 71 years , with no known contraindications to anticoagulation at baseline . MAIN OUTCOMES Ischemic stroke , peripheral embolism , hemorrhage , and death according to warfarin use and comorbidity status , as determined by automated data bases , review of medical records , and state mortality files . RESULTS Among 11,526 patients , 397 incident thromboembolic events ( 372 ischemic strokes , 25 peripheral embolism ) occurred during 25,341 person-years of follow-up , and warfarin therapy was associated with a 51 % ( 95 % confidence interval [ CI ] , 39%-60 % ) lower risk of thromboembolism compared with no warfarin therapy ( either no antithrombotic therapy or aspirin ) after adjusting for potential confounders and likelihood of receiving warfarin . Warfarin was effective in reducing thromboembolic risk in the presence or absence of risk factors for stroke . A nested case-control analysis estimated a 64 % reduction in odds of thromboembolism with warfarin compared with no antithrombotic therapy . Warfarin was also associated with a reduced risk of all-cause mortality ( adjusted hazard ratio , 0.69 ; 95 % CI , 0.61 - 0.77 ) . Intracranial hemorrhage was uncommon , but the rate was moderately higher among those taking vs those not taking warfarin ( 0.46 vs 0.23 per 100 person-years , respectively ; P = .003 , adjusted hazard ratio , 1.97 ; 95 % CI , 1.24 - 3.13 ) . However , warfarin therapy was not associated with an increased adjusted risk of nonintracranial major hemorrhage . The effects of warfarin were similar when patients with contraindications at baseline were analyzed separately or combined with those without contraindications ( total cohort of 13,559 ) . CONCLUSIONS Warfarin is very effective for preventing ischemic stroke in patients with atrial fibrillation in clinical practice while the absolute increase in the risk of intracranial hemorrhage is small . Results of r and omized trials of anticoagulation translate well into clinical care for patients with atrial fibrillation BACKGROUND Atrial fibrillation  ( AF ) may occur without symptoms . Little is known about demographic features and prognostic information in patients with asymptomatic AF . METHODS In the AFFIRM study , 4060 patients were r and omized to either rhythm or rate control . At baseline , patients were identified as asymptomatic if they answered " no " to a 15-item question naire related to cardiac symptoms during AF in the 6 months before study entry . RESULTS There were 481 ( 12 % ) asymptomatic patients at baseline . Compared with symptomatic patients , asymptomatic patients were more often men and had a lower incidence of coronary artery disease and congestive heart failure , but had more cerebrovascular events . Asymptomatic patients had a longer duration of AF , a lower maximum heart rate , and better left ventricular function . They received fewer cardiac medications and fewer therapies to maintain sinus rhythm . At 5 years , there was a trend for better survival in asymptomatic patients ( 81 % vs 77 % , P = .058 ) , and they were more likely to be free from disabling stroke or anoxic encephalopathy , major bleeding , and cardiac arrest ( 79 % vs 67 % , P = .024 ) . However , mortality and major events were similar after correction for baseline differences . CONCLUSIONS Patients with asymptomatic AF have less serious heart disease but more cerebrovascular disease . Asymptomatic patients receive different therapies than symptomatic patients . However , the absence of symptoms and the differences in treatment does not confer a more favorable prognosis when differences in baseline clinical parameters are considered . Anticoagulation should be considered in these patients As previously reported , 1007 patients with chronic atrial fibrillation participated in the Copenhagen AFASAK study . Before inclusion to trial , they all had a physical examination , chest roentgenogram , and echocardiogram with determination of left atrial size . This study evaluated the importance of cardiovascular risk factors for development of thromboembolic complications . To exclude any treatment effects on occurrence of thromboembolic complications , we included only the 336 patients from the placebo group . Using Cox 's regression model , previous myocardial infa rct ion was a significant risk factor for development of thromboembolic complications . Age , gender , heart failure , chest pain , hypertensive heart disease , diabetes , systolic and diastolic blood pressure , smoking , relative heart volume , and left atrial size were all without statistical importance PURPOSE The risk of ischemic stroke varies widely among patients with nonvalvular atrial fibrillation , influencing the choice of prophylactic antithrombotic therapy . We assessed three schemes for stroke risk stratification in these patients who were treated with aspirin and who did not have prior cerebral ischemia . SUBJECTS AND METHODS Criteria from three schemes of risk stratification were applied to a longitudinally observed cohort of patients with atrial fibrillation who did not have prior cerebral ischemia and who were treated with aspirin alone or aspirin combined with low , ineffective doses of warfarin in a multicenter clinical trial . The ability of the schemes to identify patients at high ( > /=6 % ) , low ( < /=2 % ) , and intermediate annual risks of ischemic stroke was assessed . RESULTS During a mean follow-up of 1.8 years , 48 ischemic strokes occurred among 1,073 patients with atrial fibrillation who were taking aspirin ( rate = 2.5 per 100 person-years ) . Each of the three schemes predicted stroke and disabling stroke , and successfully identified patients at low risk ( observed stroke rates of 0.3 to 1.1 per 100 person-years ) , although the fractions of the cohort that were categorized as low risk varied from 14 % to 45 % . The observed rates of ischemic stroke among patients categorized as high risk ranged from 3.5 to 7.2 per 100 person-years among the stratification schemes . Two schemes considered all patients > 75 years old as high risk ( observed stroke rate 4.2 per 100 person-years ) , while the remaining scheme classified one third of patients in this age group as low risk ( observed stroke rate 0.6 per 100 person-years ) . CONCLUSIONS When tested in a large cohort of patients with atrial fibrillation who were treated with aspirin  , available risk-stratification schemes successfully identified patients with low rates of ischemic stroke , but less consistently identified high-risk patients
target: Few models had addressed the cumulative nature of risk factors where a combination of risk factors would confer a greater risk than either factor alone .
  In patients at high risk of stroke , anticoagulation is cost effective , but not for those with a low risk of stroke .
background: The risk of stroke in atrial fibrillation ( AF ) needs to be assessed in each patient to determine the clinical and cost-effectiveness of thromboprophylaxis , with the aim of appropriate use of antithrombotic therapy .
  To achieve this , stroke risk factors in AF population s need to be identified and stroke risk stratification models have been devised on the basis of these risk factors .
  In this article , we firstly provide a systematic review of studies examining the attributable stroke risk of various clinical , demographic and echocardiographic patient characteristics in AF population s. Secondly , we performed a systematic review of published stroke risk stratification models , in terms of the results of the review of stroke risk factors and their ability to accurately discriminate between different levels of stroke risk .