Your patient is a 60-year-old hypertensive, alcoholic woman whose symptomless atrial fibrillation was first documented 3 months ago. An echocardiogram shows an enlarged left atrium, rendering successful cardioversion unlikely. She tells you that both of her parents had severe strokes that made the last years of their lives horrible, and she is terrified of having a stroke. You know that a meta-analysis of 5 randomized trials of warfarin in nonvalvular atrial fibrillation demonstrated a 68% relative risk reduction (RRR) in stroke (1). You consider prescribing warfarin for this patient but know that she would not have qualified for the study because alcoholism increases her risk for major hemorrhage (2).