: 3 - 8 Ini Ai I Irl

T IS undisputed that the administration of digitalis to patients with many forms of congestive heart failure results in an improvement in both the clinical state and in the abnormal circulatory dynamics that are characteristic of heart failure.'-6 The effects of digitalis in subjects without heart failure are less well defined. Although some glycosides augment the contractile force of nonfailing hearts of patients with heart disease,7 and increase the rate of intraventricular pressure development in intact normal subjects,8 these drugs have not been shown to elevate the cardiac output at rest and during exercise in normal subjects or in patients with heart disease without failure.9-15 When administered acutely to patients with "latent" heart failure, an improvement of circulatory dynamics occurs in some individuals, but not in all.16 In view of the conflicting interpretations of these observations, the role of digitalis in the treatment of patients with heart disease but without heart failure is not clear. Accordingly, the present investigation was designed to assess the effects of digitalis on the response of the cardiovascular system to the stress of muscular exercise in patients with heart disease and cardiac enlargement without clinical evidence of congestive heart failure. One of the fundamental functions of the cardiovascular system is delivery of oxygen for metabolism in tissues at rest and during activity. The inability of the cardiovascular system to perform this function adequately results in the accumulation of excess lactate,17 and the development of an abnormally high