The decision to anticoagulate: assessing whether benefits outweigh the risks for patients with atrial fibrillation

Abstract

In a review of relevant articles from the Medline database on stroke risk in atrial fibrillation (AF) and adverse events related to anticoagulation treatment, we found that research to date shows a major potential benefit of warfarin therapy (International Normalized Ratio [INR] 2.0-3.0) for patients with AF (68% risk reduction in primary stroke prevention with warfarin vs. placebo). Despite this highly significant reduction in stroke risk, fewer than 50% of eligible patients are treated, in many cases because of fears of intracranial hemorrhage (ICH). The decision to implement anticoagulant therapy to improve outcome requires balancing the decreased risk for stroke against the increased risk for ICH. Various methods have been developed to define patient-specific stroke risk. In contrast, risk for ICH strongly correlates with the intensity of anticoagulation, which is an unpredictable but controllable variable requiring frequent dose adjustments. Recent studies have also identified subgroups of patients with neurologic pathologies who are at increased risk for ICH. However, when the INR is properly controlled, the benefit from anticoagulation therapy for patients with AF and other risk factors for stroke exceeds the risk for ICH. Careful monitoring of anticoagulation and warfarin dose titration to maintain the INR between 2.0 and 3.0 is critical for reducing the risk for ICH, as is excluding patients with neurologic conditions that increase the likelihood of ICH. Future developments, such as the introduction of oral direct thrombin inhibitors with more predictable pharmacokinetics than warfarin, may further improve the benefit-to-risk ratio of anticoagulation therapy for patients with AF.