Idiopathic hyperkinetic state: a new clinical syndrome.

A number of new or hitherto inadequately defined diseases of the heart have been described in recent years. Among these have been subendocardial fibrosis (Thomas et al., 1954), localized outflow tract hypertrophy (Brock, 1957), and viral myocardiopathy (Silber, 1958) as causes of heart failure, and rheumatoid spondylitis (Clark and Bauer, 1948), Marfan's syndrome (McKusick, 1955), and, the carcinoid syndrome (Mattingly and Sjoerdsma, 1956) as precursors of valvular disease. In addition, the introduction of accurate diagnostic techniques has indicated that a certain percentage of so-called functional heart murmurs are related to definite, although mild, anatomical cardiac defects (unpublished data). In the past three years, we have had the opportunity to study and observe a group of eight patients who have in common certain clinical and physiological abnormalities described in the following case histories. We believe they comprise a hitherto undescribed form of heart disease, possibly related to chronic elevation of the cardiac output.