Management of atrial fibrillation: Out-of-hospital approach

Atrial fibrillation is increasingly common with advancing age and is responsible for 10% of the half-million strokes that occur annually in the United States. When a patient presents with atrial fibrillation, the physician's first task is to use the history, physical examination, and electrocardiogram to determine whether hospitalization is necessary. Factors indicating a need for hospital care include evidence of infarction or ischemia, congestive heart failure, hypotension or hypoperfusion, excessive rate, or pre-excitation. In addition, if the episode began within 18 hours, consider early cardioversion, which also requires hospitalization. Next, the need for control of the ventricular rate should be assessed. A heart rate under 90 beats/min at rest and under 120 beats/min after 1 minute of step exercise is a reasonable goal. Digoxin usually controls the resting rate, but sometimes beta-blockers or calcium channel blockers are needed to control the exercise rate. The need for anticoagulation is determined by the presence of clinical risk factors such as valvular heart disease, previous thromboembolism, hypertension, age over 65 years, congestive heart failure, and left atrial enlargement, An echocardiogram is necessary to complete this assessment. Patients having one or more of these risk factors are most effectively treated with warfarin, as evident from several clinical trials. Although patients over age 65 demonstrate reduced thromboembolism with warfarin therapy, they also are more prone to cerebral hemorrhage, thus, their international normalized ratio (INR) should be kept at the lower end of the therapeutic range [2-3]. Other patients can be treated with aspirin, although stroke reduction in these patients may be more related to reduction of arterial thrombosis than thromboembolism. Patients under age 65 with no risk factors have a very low annual risk of stroke without therapy (approximately 1%). If symptoms persist or if this is a first episode in someone without left atrial enlargement, cardioversion can be considered after 3 weeks of warfarin therapy with INR in the therapeutic range. Otherwise, warfarin should be continued indefinitely, Prevention of recurrence with antiarrhythmic drugs is somewhat problematic because of incomplete efficacy (30% recurrence at 1 year) and the potential for inducing other, life-threatening arrhythmias.