Recent years have brought increasing interest in the use of the electrocardiogram as a means of understanding the damage to the heart muscle wrought by disease. Since Einthoven's discovery of the string galvanometer, this instrument has been used in the study of the direction, amplitude and time relations of the electrical currents produced by the contraction of the heart muscle. For over sixty years this was done only as a scientific procedure, with little clinical application. In recent years, however, more and more interest has been focused on the clinical value of such a study, until its merit has become definitely established. Three standard leads have been used, and these have yielded a great deal of information. However, it was thought that still more information could be gained if the technic was modified. Wolferth and Wood1 in 1932 reintroduced and made popular a fourth lead, or so-called chest lead.
DWAN PF, SHAPIRO MJ. THE FOUR LEAD ELECTROCARDIOGRAM OF CHILDREN. Am J Dis Child. 1937;54(2):265-276. doi:10.1001/archpedi.1937.01980020059005