Factor analysis of the electrocardiogram. Test of electrocardiographic theory: normal hearts.

EAELIER electrocardiographic recording procedures utilized the limb leads described by Waller and standardized by Einthoven. In 1913, Einthoven, Fahr, and de Waart made the first vectorial approach to the study of electrocardiographic potentials, using the standard limb leads to estimate the mean direction and magnitude of the electromotive forces produced by the heart in the plane denned by these leads. Their assumptions, and the inherent limitations, are well known. In 1932, the recording of the unipolar leads was developed by Wilson and his coworkers, and in 1938, Wilson and Johnston described a technic for recording a planar vectorcardiogram on a cathode ray oscilloscope. In this procedure, 2 voltages recorded from '' perpendicular co-planar'' leads are fed into the vertical and horizontal deflection plates of an oscilloscope and a continuous vector loop is described. Procedures for stereovectorcardiography (3-dimensional veetorcardiography) have been described by Schmitt, but generally vector loops are recorded sequentially in 2 perpendicular planes.