Atrial fibrillation is a common disease affecting millions of Americans. A century ago, it was a less regularly recognized phenomenon. With the advent of the electrocardiogram (ECG), this arrhythmia could be more readily identified. Frederick Willius, the first specialist in cardiology at the Mayo Clinic Rochester, became interested in the survival of patients with this condition. Using the tools at hand, he studied the outcome of 500 patients found to have ECG changes consistent with auricular fibrillation, as the condition was known at that time.