The measurement of heart size in the antero-posterior chest radiograph.

A computed tomography model was used in eight patients to show how the heart diameter and cardiothoracic ratio might change between antero-posterior and postero-anterior positions. Results were compared with measurements made on erect antero-posterior chest radiographs taken on 103 patients without cardiac failure (controls) and 106 with cardiac failure. An upper limit of cardiothoracic ratio of 55% and of heart diameter of 165 mm in males and 150 mm in females was shown to provide useful discrimination between normal and abnormal heart size.