Inclusion Criteria:  Adult (≥18y) KPNC members presenting to the ED with a primary ED diagnosis of atrial fibrillation/flutter (AF/FL). Subjects who meet criteria will be identified electronically within the CDSS tool in the electronic health record.  Exclusion Criteria:  Children (<18y). Non-members of KPNC. Patients who were prisoners, pregnant, receiving hospice or palliative care, or who left against medical advice at the index encounter for AF/FL.