The determination of heart size is essential for ' evaluating prognosis and the need for physical limitations after an acute attack of rheumatic fever. Of the available simple techniques for measuring cardiac size, radiography is more sensitive than physical examination and is, in rheumatic heart disease, more generally useful than electrocardiography. However, radiologic examination of the heart has certain major disadvantages: (1) Measurements of the cardiac silhouette may often be affected by physiologic factors and do not provide a sharp demarcation between normal and abnormal; (2) quantitation of chamber size is done subjectively, and (3) fluoroscopy, which is usually considered better than films for assessing the effects of respiration or of cardiac contraction, is undesirable because of the need for increased radiation1,2 and the lack of a permanent record.
Despite these disadvantages, radiography continues to be the major clinical technique for appraisal of heart size. The present work was done