Background: Atrial fibrillation is the most common cardiac arrhythmia. An estimated 2.2 million American adults have atrial fibrillation, but many cases remain undiagnosed. Approximately one third of hospital admissions for cardiac rhythm problems are attributed to atrial fibrillation. The number of hospital admissions for atrial fibrillation has risen by 66 percent over the past two decades, and the number of patients with atrial fibrillation is expected to increase because of the aging population and increasing diagnosis of the condition. Patients with atrial fibrillation have increased risk of stroke, heart failure, and all-cause mortality. An expert consortium conducted an evidence-based review to update quality-of-care performance measures.

The Study: The recommendations were developed by a writing committee that was supported exclusively by the American College of Cardiology, the American Heart Association, and the Physician Consortium for Performance Improvement. The committee reviewed the four most widely used clinical guidelines on atrial fibrillation and their supporting evidence to develop updated performance measures. For approval, a performance measure had to demonstrate utility in improving patient outcomes; use precise definitions; have validity and reliability; and be feasible to implement at reasonable cost. The final document underwent peer review and public comment before being submitted to the governing bodies of the sponsoring organizations for approval in late 2007. The clinical performance measures will be reviewed annually and updated, as needed.

Key Recommendations: The recommendations focused on stroke risk stratification and anticoagulation therapy. Several independent risk factors for ischemic stroke have been identified for patients with atrial fibrillation. Based on five randomized trials, the strongest risk factor is history of stroke or transient ischemic attack (TIA; relative risk [RR] = 2.5), followed by diabetes (RR = 1.7), hypertension (RR = 1.6), coronary artery disease (RR = 1.5), heart failure or impaired left ventricular systolic function (RR = 1.4), and advancing age (RR = 1.4 per decade).

Anticoagulation is required for all patients with prior stroke or TIA unless contraindications exist. The necessity of anticoagulation for other risk factors and combinations of risk factors is more controversial. Good evidence supports the use of the CHADS₂ (cardiac failure, hypertension, age, diabetes, stroke [doubled]) stroke risk stratification scheme (see accompanying table). Some experts recommend anticoagulation for patients with atrial fibrillation at intermediate or higher risk (estimated stroke rate 3 to 5 percent per year or greater). Others advocate greater individualization of benefit and relative risk, with special attention given to bleeding risks, availability of organized anticoagulation management programs, and patient preferences.

Current guidelines recommend aspirin (81 to 325 mg daily) for patients with atrial fibrillation with no risk factors for stroke; aspirin in the same dosage or warfarin (Coumadin) to a target International Normalized Ratio (INR) of 2.5 for patients with one moderate risk factor; and warfarin to a target INR of 2.5 for patients with any high risk factor or more than one moderate risk factor.