The use of isoproterenol (Isuprel) in the evaluation of congenital cardiac defects.

CARDIAC catheterization continues to be the principal means for definitive study of a wide variety of cardiac lesions. Information essential for the selection of surgical candidates and for their postoperative evaluation is provided by this type of investigation. However, the continued search for additional laboratory studies is evidence that current methods frequently do not provide the necessary or desired data. One of the pitfalls of the past has been a failure to consider that physiologic material gathered under resting conditions does not necessarily reflect circulatory response to the activities of everyday life. In recent years this shortcoming has been partially overcome by studying the circulatory dynamics during physical exercise as well as during rest.1-8 Active physical exercise can usually be accomplished in the adult but in the infant or child, a number of obstacles are frequently encountered. Chief among these are inability to comprehend or to carry out instructions and an unwillingness to cooperate. Even when successfully accomplished, the fear, apprehension, and anxiety that prevail in the conscious child may profoundly affect cardiac output, and this may in turn give rise to significant errors in the interpretation of the data obtained.9 Since most of the catheterization studies now performed are in this younger age group, the problem is one of major proportions. The purpose of this investigation was to attempt to produce the physiologic alterations of exercise by the intravenous infusion of a synthetic catecholamine, isoproterenol.* Iso-