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The management of atrial fibrillation (AF), is focused on preventing temporary circulatory instability and to prevent stroke and other ischemic events. Control of heart rate and rhythm are principally used to achieve the former, while anticoagulation may be employed to decrease the risk of stroke. Within the context of stroke, the discipline may be referred to as stroke prevention in atrial fibrillation (SPAF). In emergencies, when circulatory collapse is imminent due to uncontrolled rapid heart rate, immediate cardioversion may be indicated. The primary factors determining AF treatment are duration and evidence of circulatory instability. Cardioversion is indicated with new onset AF (for less than 48 hours) and with circulatory instability. If rate and rhythm control cannot be maintained by medication or cardioversion, it may be necessary to perform electrophysiological studies with ablation of abnormal electrical pathways.〔 ==Anticoagulation== Most patients with AF are at increased risk of stroke. The possible exceptions are those with lone AF (LAF), characterized by absence of clinical or echocardiographic findings of other cardiovascular disease (including hypertension), related pulmonary disease, or cardiac abnormalities such as enlargement of the left atrium, and age under 60 years . The incidence of stroke associated with AF is 3 to 5 percent per year in the absence of anticoagulation, which is significantly higher compared to the general population without AF (relative risk 2.4 in men and 3.0 in women). A systematic review of risk factors for stroke in patients with nonvalvular AF concluded that a prior history of stroke or TIA is the most powerful risk factor for future stroke, followed by advancing age, hypertension, and diabetes. For patients with LAF, the risk of stroke is very low and is independent of whether the LAF was an isolated episode, paroxysmal, persistent, or permanent. The risk of systemic embolization (atrial clots migrating to other organs) depends strongly on whether there is an underlying structural problem with the heart (e.g. mitral stenosis) and on the presence of other risk factors, such as diabetes and high blood pressure. Finally, patients under 65 are much less likely to develop embolization compared with patients over 75. In young patients with few risk factors and no structural heart defect, the benefits of anticoagulation may be outweighed by the risks of hemorrhage (bleeding). Those at a low risk may benefit from mild (and low-risk) anticoagulation with aspirin (or clopidogrel in those who are allergic to aspirin). In contrast, those with a high risk of stroke derive most benefit from anticoagulant treatment with warfarin or similar drugs. A new class of anticoagulant drugs, the direct thrombin inhibitors (Dabigatran), has recently arrived on the scene and shown efficacy in treating complications of nonvalvular chronic AF. In the United Kingdom, the NICE guidelines recommend using a clinical prediction rule for this purpose. The ''CHADS2'' score is a well-validated simple clinical prediction rule for determining the risk of stroke (and therefore who should and should not be anticoagulated with warfarin); it assigns points (totaling 0-6) depending on the presence or absence of co-morbidities such as hypertension and diabetes. In a comparison of seven prediction rules, the best was CHADS2 which performed similarly to the SPAF and Framingham prediction rules. The following treatment strategy is based on the CHADS2 score: More recently, the 2010 European Society of Cardiology (ESC) guidelines have recommended a risk factor based approach to stroke prevention, and de-emphasised the artificial stratification into low/moderate/high risk, given the poor predictive value of these 3 categories. To complement the ''CHADS2'' score, the (ESC guidelines on atrial fibrillation management ) recommend using the new (CHA2DS2-VASc score ) (Congestive heart failure, Hypertension, Age ≥75 years (doubled), Diabetes mellitus, Stroke (doubled), Vascular disease, Age 65–74 years, Sex category], which is more inclusive of 'stroke risk modifier' risk factors. The new (CHA2DS2-VASc score ) (Congestive heart failure, Hypertension, Age ≥75 years (doubled), Diabetes mellitus, Stroke (doubled), Vascular disease, Age 65–74 years, Sex category] has also been validated in other large independent cohorts.〔Van Staa TP, Setakis E, Di Tanna GL, Lane DA, Lip GY. "A comparison of risk stratification schema for stroke in 79884 atrial fibrillation patients in general practice. J Thromb Haemost. 2010 Oct 1. PMID 21029359.〕 The most recent validation study used nationwide data on 73,538 hospitalized non-anticoagulated patients with AF in Denmark, whereby in ‘low risk’ subjects (score=0), the rate of thromboembolism per 100 person-years was 1.67 (95% confidence interval 1.47 to 1.89) with CHADS2 and 0.78 (0.58 to 1.04) with (CHA2DS2-VASc score ), at 1 year follow-up.〔Olesen JB, Lip GY, Hansen ML, Hansen PR, Tolstrup JS, Lindhardsen J, Selmer C, Ahlehoff O, Olsen AM, Gislason GH, Torp-Pedersen C. Validation of risk stratification schemes for predicting stroke and thromboembolism in patients with atrial fibrillation: nationwide cohort study. BMJ. 2011 Jan 31;342:d124. 〕 Thus, those categorised as ‘low risk’ using (CHA2DS2-VASc score ) were ‘truly low risk’ for thromboembolism, and consistent with other cohorts,〔 (CHA2DS2-VASc score ) performed better than CHADS2 in identifying these 'low risk' patients. The c-statistics at 10 years follow-up were 0.812 (0.796 to 0.827) with CHADS2 and 0.888 (0.875 to 0.900) with CHA2DS2-VASc, respectively - and suggests that (CHA2DS2-VASc score ) also performed better than CHADS2 in predicting ‘high risk’ patients. To compensate for the increased risk of stroke, anticoagulants may be required. However, in the case of warfarin, if someone with AF has a yearly risk of stroke that is less than 2%, then the risks associated with taking warfarin outweigh the risk of getting a stroke from AF. However, since these older data, there is now greater recognition of the importance of good anticoagulation control (as reflected by time in therapeutic range) as well as greater awareness of bleeding risk factors as well as data from recent trials that aspirin carries a similar rate of major bleeding to warfarin, especially in the elderly. The new (ESC guidelines on atrial fibrillation ) recommend assessment of bleeding risk in AF using the HAS-BLED (Hypertension, Abnormal renal/liver function, Stroke, Bleeding history or predisposition, Labile International Normalized Ratio, Elderly, Drugs/alcohol concomitantly) bleeding risk schema as a simple, easy calculation, whereby a score of ≥3 indicates "high risk" and some caution and regular review of the patient is needed. The (HAS-BLED ) score has also been validated in an anticoagulated trial cohort of 7329 patients with AF - in this study, the HAS-BLED score offered some improvement in predictive capability for bleeding risk over previously published bleeding risk assessment schemas and was simpler to apply.〔Lip GYH, Frison L, Halperin J, Lane D. Comparative Validation of a Novel Risk Score for Predicting Bleeding Risk in Anticoagulated Patients With Atrial Fibrillation: The HAS-BLED (Hypertension, Abnormal Renal/Liver Function, Stroke, Bleeding History or Predisposition, Labile INR, Elderly, Drugs/Alcohol Concomitantly) Score" ''J Am Coll Cardiol'' 2010; 〕 With the likely availability of new oral anticoagulants that avoid the limitations of warfarin (and may even be safer), more widespread use of oral anticoagulation therapy for stroke prevention in AF is likely. AF in the context of mitral stenosis is associated with a seventeenfold increase in stroke risk. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Management of atrial fibrillation」の詳細全文を読む スポンサード リンク
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