AURICULAR fibrillation is generally considered to be a less efficient cardiac mechanism than sinus rhythm. Support for this concept is offered by reports of improvement in the clinical conditions of patients * on conversion from auricular fibrillation to sinus rhythm. Furthermore, as much as a twofold increase in the cardiac output may occur.f In nearly all reports accounts can be found of patients who did not improve. Occasionally conversion to sinus rhythm heralds the general deterioration of the patient's condition. This event is usually explained as being due to emboli or the toxic effects of quinidine. Sometimes no explanation is attempted. The following case report again calls attention to the problem.
A 49-year-old white man with mitral stenosis was admitted to University Hospitals on Oct. 2, 1953, for evaluation for mitral valvuloplasty. He was known to have had a heart murmur for many years. For one year he had noted dyspnea