Spatial Magnitude, Orientation, and Velocity of the Normal and Abnormal QRS Complex

SPATIAL characteristics of the electro-cardiogram have been increasingly em-phasized since the advent of vectorcardiogra-phy. Progress in this field was hampered originally, however, through introduction of numerous lead systems with discrepancies in lead performance. ' Only the more recently developed, corrected orthogonal leads result-ed in relatively close agreement among sys-tems, thus enhancing the comparability of results.2 Commonly, spatial electrocardiographic data are displayed in the form of vector loops projected on three mutually perpendicular planes. The oscilloscope beam is interrupted at regular intervals for timing. It was realized soon, however, that part of the time informa-tion cannot be recovered from such records. Beginning and end of QRS loops are frequent-ly hidden by superimposed P or T loops. Parts of loops may be perpendicular to a given plane and not be represented at all. Further-more, time intervals between P, QRS, and T loops cannot be measured. This becomes feas-ible when loops are recorded on running film. Such a display, however, leads to severe dis-tortions in vector directions. A new type of spatial electrocardiographic display on a continuous time basis was devel-oped more recently.3-7 Curves of spatial mag-nitude and orientation have been recorded on a time basis by means of analog computers. The spatial orientation is usually expressed in terms of azimuth and elevation angles. This type of data display provides complete spatial information without loss of time information