Patients with atrial fibrillation and low risk of stroke: do they really need anticoagulation?

Atrial fibrillation (AF) significantly increases the risk of thromboembolic events, in particular the risk of stroke. Anticoagulation therapy has been shown to reduce this risk; therefore, the treatment should be lifelong. However, the risk in patients with nonvalvular AF is not equally distributed, and there is a population of patients at low risk. According to the current guidelines, the decision on the need of anticoagulation is primarily dependent on whether the patient is at low risk. The CHA2DS2-VASc is currently the most commonly recommended scheme for assessing thromboembolic risk in patients with nonvalvular AF. In a large group of nontreated patients with a CHA2DS2-VASc of 0 (1 in women), the annual risk of stroke was 0.49%; ischemic stroke, 0.43%; bleeding, 1.08%; intracranial bleeding, 0.15%; and death, 3.87%. In patients on warfarin, the frequency of ischemic stroke was similar. Patients with a CHA2DS2-VASc of 0 (1 in women) are low-risk patients who do not benefit from anticoagulation. The low-risk group is also defined as patients younger than 65 years of age without structural cardiovascular disease, regardless of sex. They represent from 6% to 10% of patients with nonvalvular AF. Thromboembolic risk in patients with a score of 1 (2 in women) is much more controversial, as reflected by several recently published cohort studies. In a Swedish study, the risk was found to be low, while in Danish and Taiwanese studies—as significantly higher. Another analysis has shown that the use of vitamin K antagonists is appropriate when the risk of stroke is higher than 1.7%/year. Owing to a lower risk of intracranial bleeding, anticoagulation with nonvitamin K antagonist oral anticoagulants may be considered already at an annual risk of stroke exceeding 0.9%. Patients at low risk do not require chronic anticoagulation.