During the late 1950s and most of the 1960s, Dr John Ross and I led the busy clinical cardiology program then existing at the Clinical Center of the National Institutes of Health. During this period, the assessment and surgical treatment of severe aortic stenosis (AS) in adults, predominantly rheumatic in origin, were both undergoing rapid changes. In the 1950s, before open heart surgery and left-sided heart catheterization were available, after thoracotomy dilators were inserted through a ventriculotomy, and severely obstructed aortic valves were "blindly" opened. 1 The selection of patients for this operation was difficult. Dr Paul Wood, Director of the National Heart Institute in London, who was considered by many to be the world9s leading clinical cardiologist of the era, wrote: "At the present time aortic valvotomy is too hazardous and too crude an operation to advise when it is most desirable (just before the onset of symptoms) and frequently too late when impending disaster makes it imperative." 2