Hospitalization for acute heart failure syndromes (AHFS) results in substantial in-hospital and postdischarge morbidity and mortality. Management of AHFS presents significant challenges, given the heterogeneity of the patient population and the differing etiologies underlying why patients present with acute decompensation. Arrhythmias in the setting of AHFS, such as atrial fibrillation and wide complex tachycardia, present additional challenges. Compounding this challenge is the paucity of evidence on which to base early management. General principles for the management of atrial fibrillation and wide complex tachycardia in the setting of emergency department AHFS are discussed.