Because anticoagulants significantly increase the risk of bleeding, including gastrointestinal bleeding and intracranial hemorrhage, current AF guidelines recommend an individualized approach when balancing the benefits of anticoagulants and risks of bleeding.2 The HAS-BLED (Table 3) bleeding score is effective for quantifying bleeding risk.15 Patients with a HAS-BLED score of 3 or greater are at increased bleeding risk; therefore, those on anticoagulants should be closely observed for bleeding, or therapy should be avoided if risks outweigh potential benefits.
No matter which type of AF patients have, their risk of stroke is substantially increased because blood flow in the left atrial appendage is reduced even in paroxysmal AF.2,16 Therefore, the decision for anticoagulant therapy should not be based on a patient's AF classification but on overall stroke risk. Once the need for anticoagulant therapy is determined, selection of agents depends on patient characteristics and preferences.
The two types of oral anticoagulants, vitamin K antagonists and target-specific anticoagulants, reduce the risk of AF-related stroke by two-thirds.17
Warfarin, a vitamin K antagonist, is the standard therapy for stroke prophylaxis in patients with AF. Effective and inexpensive, warfarin has few contraindications, and reversal agents are available if the patient develops serious bleeding. Unfortunately, warfarin's narrow therapeutic index means that patients need routine blood monitoring, and the drug is affected by drug and dietary interactions.
Target-specific anticoagulants approved for stroke prevention in patients with nonvalvular AF include the direct thrombin inhibitor dabigatran, and factor Xa inhibitors rivaroxaban, apixaban, and edoxaban.2 A meta-analysis demonstrated decreased risk of stroke and systemic embolism, all-cause mortality, and intracranial hemorrhage with target-specific anticoagulants compared with warfarin.18 Target-specific anticoagulants require a dose adjustment in patients with moderate-to-severe chronic kidney disease, although they are an alternative to vitamin K antagonists. Target-specific anticoagulants are contraindicated in patients with bioprosthetic and mechanical heart valves, previous mitral valve repair, or end-stage renal disease.18 Although more expensive than generic warfarin, target-specific anticoagulants are associated with lower medical costs due to indirect savings through reduced laboratory costs and reduced iatrogenic complications.19
These drugs inhibit platelet aggregation and have a limited role in AF-related thromboprophylaxis.
Aspirin and adenosine diphosphate receptor inhibitors are inferior to anticoagulants at reducing stroke when used as monotherapy or in combination with anticoagulants or cyclooxygenase inhibitors, such as clopidogrel, prasugrel, and ticagrelor.2 Although antiplatelets are associated with a decreased risk of intracranial hemorrhage, several studies showed no significant difference in the overall risk of major bleeding between oral anticoagulants and antiplatelets.2 For most patients, antiplatelets are not the preferred therapy for prevention of AF-related stroke.
An emerging strategy in thromboprophylactic prevention is left atrial appendage exclusion. Because the left atrial appendage is a common source of thrombus in patients with AF, removal or occlusion of the appendage reduces the risk of embolism.20 Methods of excluding the appendage include excision at time of cardiac surgery, thorascopic left atrial appendectomy, minimally invasive ligation, and percutaneous transcatheter occlusion with a closure device. Exclusion of the left atrial appendage is indicated only in patients who are not candidates for anticoagulation.20 Complications include risk of incomplete appendage occlusion causing thromboembolic events, and occlusion-device dislodgement.
AF is a common condition that is increasing in frequency. Although the dysrhythmia is associated with significant morbidity and mortality, evidence-based AF management improves patient outcomes. In particular, anticoagulation in high-risk patients, as determined by the CHA2DS2-VASc score, reduces the risk of AF-related stroke. Clinicians must select appropriate rate control and rhythm control therapies to minimize patient symptoms and adverse reactions. Knowing current AF management strategies helps primary care providers manage AF and minimize its sequelae.
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