Patients with atrial fibrillation, even lone atrial fibrillation without other evidence of heart disease, are at increased risk of stroke during long term follow up. A systematic review of risk factors for stroke in patients with nonvalvular atrial fibrillation concluded that a prior history of stroke or TIA is the most powerful risk factor for future stroke, followed by advancing age, hypertension, diabetes. The risk of stroke increases whether the lone atrial fibrillation was an isolated episode, recurrent, or chronic. 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 antiplatelet agents like 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.

The CHADS2 score is the best validated clinical prediction rule for determining the risk of stroke (and therefore who should be anticoagulated); it assigns points (totaling 0-6) depending on the presence or absence of co-morbidities such as hypertension and diabetes. To compensate for the increased risk of stroke, anticoagulants may be required. However, in the case of warfarin, if a patient 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. Atrial fibrillation in the context of mitral stenosis is associated with a seventeen-fold increase in stroke risk.

Acute anticoagulation: If anticoagulation is required urgently (e.g. for cardioversion), heparin, enoxaparin (lovenox) or similar drugs achieve the required level of protection much quicker than warfarin, which will take several days to reach adequate levels.In cases of chronic stable atrial fibrillation without any other risk factors for thromboembolism, warfarin can be started without bridging heparin or lovenox. While there is a theoretical concern of causing a transient prothombotic state with the initiation of warfarin, a study comparing the initiation of warfarin alone with warfarin and low molecular weight heparin shows no significant difference in the concentrations of endogenous anticoagulants or in markers of active clot formation. Chronic anticoagulation: Among patients with "non-valvular" atrial fibrillation, anticoagulation with warfarin can reduce stroke by 60% while antiplatelet agents can reduce stroke by 20%. There is evidence that aspirin and clopidogrel are effective when used together, but the combination is still inferior to warfarin.

Warfarin treatment requires frequent monitoring with a blood test called the international normalized ratio (INR); this determines whether the correct dose is being used. In atrial fibrillation, the usual target INR is between 2.0 and 3.0 (higher targets are used in patients with mechanical artificial heart valves, many of whom may also have atrial fibrillation). A high INR may indicate increased bleeding risk, while a low INR would indicate that there is insufficient protection from stroke.

An attempt was made to find a better method of implementing warfarin therapy without the inconvenience of regular monitoring and risk of intracranial hemorrhage. Unfortunately in a study of AF patients with additional risk factors for thromboembolism, it was shown that the combination of aspirin and fixed-dose warfarin (initial INR 1.2-1.5) is significantly inferior to adjusted-dose warfarin (INR 2.0-3.0), and has a similar risk of intracranial hemorrhage.

Anticoagulation in Elderly patients: This is a difficult scenario to deal with. Elderly patients are the once with the highest risk of stroke from AFib but are also very high risk for falls and possible bleeding complications. The very elderly (patients aged 75 years or more) may benefit from anticoagulation provided that their anticoagulation does not increase hemorrhagic complications, which is a difficult goal.

Elderly require less Warfarin, more likely to have INRs outside the therapeutic range and more difficult to get therapeutic from subtherapeutic levelsThe weekly maintenance Warfarin dose was 0.4 mg lower for every additional year of age, and the average maintenance dose of warfarin for patients older than 70 was < 5 mg. A patient would have to fall nearly300 times per year for warfarin to no longer be the preferred therapy. Pts with AF & high fall risk had higher subsequent rates of intracranial hemorrhage. Pts with high fall risk but low stroke risk, anticoagulation was not likely to be beneficial. Conversely, pt with high fall risk at moderate or high risk for stroke still appeared to benefit from warfarin.

Warfarin decreases bone mineral density in experimental studies. One retrospective analysis found that long-term warfarin use increased the risk of osteoporotic fractures by 25%. High fall risk and neuropsychiatric disease were risk factors for fractures. It is important to closely monitor INRs in cognitively and functionally impaired older adults taking warfarin.

AF can cause disabling and annoying symptoms. Palpitations, angina, lassitude (weariness), and decreased exercise tolerance are related to rapid heart rate and inefficient cardiac output caused by AF. Furthermore, AF with a persistent rapid rate can cause a form of heart failure called tachycardia induced cardiomyopathy. This can significantly increase mortality and morbidity, which can be prevented by early and adequate treatment of the AF.

There are two ways to approach these symptoms: rate control and rhythm control. Rate control treatments seek to reduce the heart rate to normal, usually 60 to 100 beats per minute. Rhythm control seeks to restore the normal heart rhythm, called normal sinus rhythm. Studies suggest that rhythm control is mainly a concern in newly diagnosed AFib, while rate control is more important in the chronic phase. Rate control with anticoagulation is as effective a treatment as rhythm control in long term mortality studies, the AFFIRM Trial. The AFFIRM study showed no difference in risk of stroke in patients who have converted to a normal rhythm with anti-arrhythmic treatment, compared to those who have only rate control. AFib is associated with a reduced quality of life, and while some studies indicate that rhythm control leads to a higher quality of life, the AFFIRM study did not find a difference. In patients with a fast ventricular response, intravenous magnesium significantly increases the chances of successful rate and rhythm control in the urgent setting without significant side-effects.