Silhouette measurements of the heart were made in 119 cases of effort syndrome by the teleroentgen method. The same technic was followed throughout the work. All exposures were taken with the subject in the standing position, with the target 6½ feet from the plate. When in position, facing the plate, the subject was told to take a deep breath and then empty his lungs as completely as possible. Following this, he took a half breath and held it for the exposure, which was from 1½2 to 4 seconds' duration, varying with the weight of the individual and the thickness of the chest wall. This method was adopted because the directions were easily carried out, and it gave satisfactorily uniform results.
From the plates thus obtained the following measurements were made:
Ml.: Maximum left border.
Mr.: Maximum right border. From the sum of these was obtained the maximum transverse diameter T.D.
SMITH B. TELEROENTGEN ESTIMATIONS OF HEART SIZE IN CASES OF EFFORT SYNDROME. Arch Intern Med (Chic). 1920;25(5):532-536. doi:10.1001/archinte.1920.00090340083005