Review
The Increasing Need for Anticoagulant Therapy to Prevent Stroke in Patients With Atrial Fibrillation

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Ischemic stroke, a major complication of atrial fibrillation (AF), is believed to result from atrial thrombus formation caused by ineffective atrial contraction. Oral anticoagulant therapy effectively reduces the risk of ischemic stroke in patients with AF; this therapy is recommended for patients with any frequency or duration of AF and other risk factors for stroke, such as increased age (>75 years), hypertension, prior stroke, left ventricular dysfunction, diabetes, or heart failure. Recently published data comparing rate-control and rhythm-control strategies in AF emphasized the importance of maintaining an international normalized ratio higher than 2.0 during warfarin therapy and the need for continuing anticoagulant therapy to prevent stroke in high-risk patients, even if the strategy is rhythm control. Hemorrhagic complications can be minimized by stringent control of the international normalized ratio (particularly in elderly patients) and appropriate therapy for comorbidities such as hypertension, gastric ulcer, and early-stage cancers. Undertreatment of patients with AF is a continuing problem, particularly in the elderly population. Patients perceived as likely to be noncompliant, such as the functionally impaired, are less likely to receive warfarin therapy. However, stroke prevention with anticoagulants is cost-effective and improves quality of life, despite the challenges of maintaining appropriate anticoagulation with monitoring and warfarin dose titration. New medications in development with more predictable dosing and fewer drug-drug interactions may reduce the complexities of achieving optimal anticoagulation and increase the practicality of long-term anticoagulant therapy for patients with AF at risk of stroke.

Section snippets

Current Guidelines

Multiple clinical guidelines recommend warfarin as the treatment of choice in patients with AF15, 16, 17, 18, 19 (Table 115, 16, 18, 20, 21). Although the need for rate-control or rhythmcontrol medication is stratified by the duration and frequency of AF, anticoagulant medication is indicated for patients with any frequency or duration of AF and other risk factors for stroke (ie, increased age, hypertension, diabetes, left ventricular dysfunction, coronary artery disease). After adjustment for

Importance of INR Control

The major complication of warfarin therapy with consequences approaching the severity of thromboembolic stroke is hemorrhage. Although INR values less than 2.0 decrease the effectiveness of warfarin treatment, INR values greater than 3.0 increase the risk of bleeding complications15 (Figure 3). Indeed, elevated INR is the leading risk factor for bleeding during warfarin therapy,28, 29, 30 although improved control of anticoagulation has markedly reduced the incidence of bleeding complications.31

BARRIERS TO ANTICOAGULANT THERAPY

Barriers to appropriate anticoagulant therapy in AF can be classified into 4 major areas: physician perceptions, patient knowledge, health care systems, and pharmacotherapeutic options.55

CONCLUSIONS

The number of adults in the United States with AF will more than double in the next 50 years, with the greatest increases expected in elderly patients. Therefore, although stroke in patients with AF represents a major health problem now, it may be an even larger problem in the future. Anticoagulant therapy with warfarin is recommended for patients with AF of any intensity and duration if other risk factors for stroke (including age and comorbidities) are present.

The RACE and AFFIRM trials

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      Citation Excerpt :

      The need for anticoagulation can be determined by 3 schemas. These schemas include the Atrial Fibrillation Investigators (AFI) scheme that has pooled data from 5 randomized stroke prevention trials in patients with nonvalvular or nonrheumatic AF, including the Boston Area Anticoagulation Trial for Atrial Fibrillation (BAATAF),5 Veteran Affairs Stroke Prevention in Nonrheumatic Atrial Fibrillation (SPINAF),9 Atrial Fibrillation, Aspirin, and Anticoagulation Study (AFASAK),10 Canadian Atrial Fibrillation Anticoagulation Study,11 and Stroke Prevention in Atrial Fibrillation Study (SPAF),6 the SPAF III trial scheme, and the most accurate predictor of stroke, the CHADS2 scoring. The pooled data of the AFI, which was the first risk stratification system developed, identified 4 independent risk factors: history of stroke or transient ischemic attack (TIA), age greater than 65 years (Fig. 1), diabetes mellitus, and history of systemic hypertension (Box 1).12

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    1

    Drs Ezekowitz and Falk have been consultants for AstraZeneca, manufacturer of Exanta (ximelagatran).

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    Copyright © 2004 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.