Because atrial fibrillation is a major risk factor for ischemic stroke, there is a need for strategies to identify people at risk for stroke and prevent it at all ages. The American Academy of Neurology (AAN) has helped fill this gap with the release of new evidence-based guidelines (Culebras A, et al. Neurology. 2014;82:716-724).
The Guideline Development Subcommittee of the AAN reviewed evidence published since 1998 with regard to the detection of nonvalvular atrial fibrillation (NVAF) in patients with a history of stroke, as well as new therapies for preventing stroke in this patient population. The new guidelines are focused on these 2 questions:
- For patients with cryptogenic stroke (ie, no cause can be identified—How often can current technologies identify undiagnosed NVAF?
- For patients with NVAF, which therapies reduce the risk for ischemic stroke with the least risk of hemorrhage?
The main recommendation is to use cardiac rhythm monitoring in patients with cryptogenic stroke to identify those with occult NVAF, to routinely offer anticoagulation to patients with NVAF and a history of transient ischemic attack (TIA) or stroke, and to carefully counsel patients with NVAF (and no previous stroke) about the potential benefits of antithrombotic medications, as well as their potential risks.
Lead author Antonio Culebras, MD, of SUNY Upstate Medical University in Syracuse, NY, told Value-Based Care in Neurology that this recommendation differs in some ways from previous guidelines.
“The new guidelines encourage the use of monitoring devices to identify atrial fibrillation in patients with cryptogenic stroke. The new guidelines also encourage physicians to consider anticoagulation in patients who are old, who sustain a moderate number of falls and who have mild dementia. These were traditional areas of exemption in the past,” Dr Culebras said.
NVAF and Stroke Frequency
In the studies evaluated, the proportion of patients identified with NVAF ranged from 0% to 23%, averaging a detection rate of 10.7%. Longer monitoring was significantly more likely to detect NVAF; therefore, the expert panel suggests that clinicians consider monitoring patients for at least 1 week, instead of the standard 24 hours, to increase the diagnostic yield.
The analysis showed that within the population of patients with NVAF, the absolute risk for ischemic stroke varies widely, based on the presence of other stroke risk factors. The absolute stroke risk is highest among patients with NVAF who have a history of stroke and TIA, with an aggregated risk of approximately 10% annually. The panel recommends that clinicians consider not offering anticoagulation therapy to patients with NVAF who do not have additional risk factors, or consider prescribing aspirin.
The panel further notes that although multiple risk stratification tools are available for estimating the absolute stroke risk in patients with NVAF, the results of these tools vary widely.
“Because it is difficult to determine with precision the absolute stroke risk in patients with NVAF, determining when the benefit from reduced stroke risk outweighs the harm of increased bleeding is likewise difficult,” the panel wrote. “In these circumstances, patient preferences and physician judgment become especially important.”
Anticoagulants: What Are the Relative Efficacies and Risks?
Specific patient considerations should inform the selection of the specific anticoagulant therapy in patients with NVAF who are judged to need anticoagulation therapy, the panel notes; they also offer information that should guide this decision-making. The effects of the antithrombotic regimens are being compared with dose-adjusted warfarin for the outcomes of stroke or systemic embolism, ischemic stroke, major bleeding, intracranial bleeding, and gastrointestinal bleeding from the best published studies.
The panel concludes, based on their review of the evidence, that several anticoagulant medications decrease the risk for ischemic stroke in patients with NVAF, and these agents are “noninferior or superior” to warfarin, they note. “In most patients, the reduction in ischemic stroke risk outweighs the risk of bleeding complications,” the authors state.
Specific Anticoagulant Therapies
Regarding the individual agents, the panel provides the following conclusions:
- In patients with NVAF, the anticoagulants dabigatran, rivaroxaban, and apixaban are probably at least as effective as warfarin in preventing stroke and have a lower risk of intracranial hemorrhage
- The combination of triflusal plus acenocoumarol is likely more effective than acenocoumarol alone in reducing stroke risk
- Clopidogrel plus aspirin is probably less effective than warfarin in preventing stroke and has a lower risk of intracranial bleeding
- Clopidogrel plus aspirin compared with aspirin alone probably reduces stroke risk but increases the risk of major hemorrhage
- Apixaban is likely more effective than aspirin for decreasing stroke risk and has a bleeding risk similar to that of aspirin.
When asked whether any of the recommendations may be considered value-based—that is, consider cost versus benefit as part of the recommendations—Dr Culebras acknowledged, “The new oral anticoagulants are more costly in the pharmacy than warfarin. However, there could be long-term cost-saving in the improved safety inherent to a better bleeding profile.”
“The combination of triflusal (a generic antiplatelet agent) and low-intensity acenocoumarol (a warfarin-like agent) for moderate-risk NVAF patients is safer than acenocoumarol [alone] and definitely less costly than the new oral anticoagulants,” he noted. “This combination could have great added value in developing countries, where triflusal is available but new oral anticoagulants are unavailable or unreachable,” Dr Culebras commented.