DURING recent years, considerable interest in the management of patients with chronic auricular fibrillation has developed. Previously, it was believed that this arrhythmia was merely a manifestation of the unfavorable progress of severe heart disease, and that in itself it did not materially affect the health of the patient or interfere with his cardiac efficiency.1Now, however, abundant evidence, both clinical and experimental, supports the view that auricular fibrillation does have deleterious effects upon the circulation. In experimental animals, several groups of investigators2have demonstrated a decrease in cardiac output during auricular fibrillation. Blumgart and Weiss,3as well as Stewart and his associates,4have reported that the rate of blood flow is reduced by as much as 20 to 68%. After the restoration of sinus rhythm, the blood flow returned to normal. Blood gas studies during and after auricular fibrillation indicate that cardiorespiratory efficiency is greater with a normal sinus rhythm,