Mechanical inscription of the vectorcardiogram.

A modification of the vectorcardiographic method of studying electrical events is presented. Simultaneous scalar leads, taken by any vector lead system, are first recorded. The important time intervals, difficult or impossible to read from the loop itself, are measured from these tracings. Proper pairs of the scalar leads can then be rapidly integrated into vector loops by an easily constructed drawing board based on the pulley system. This instrument is described in detail. It is demonstrated that loops so derived do not appear to differ in their important characteristics from electronically integrated loops. THE CLINICAL usefulness of the vec-torcardiogram is most obviously limited by its inability to record satisfactorily temporal relationships such as P-R and Q-T intervals, heart rate, and types of irregularity. Practical considerations, such as a heavy investment in expensive electronic equipment, processing time, and the need of trained personnel also restrict its use. It is believed that the method to be described will adequately answer these objections until the higher frequency deflections, not recordable on direct-writing apparatus or in mechanically inscribed loops are proven to be of diagnostic importance. The first requirement is a two-channel recording electrocardiograph with a paper speed of at least 50 mm. per second. The scalar electrocardiograms so recorded may be used for determining the important time relationships referred to above. The choice of a vector-cardiographic lead system may be left to the discretion or bias of the investigator. All such systems currently in vogue have electrodes so placed that the scalar components in any plane allegedly record along axes at right angles to each other. The magnetic plates which deflect the beam of electrons in the cathode ray tube are, therefore, at right angles. This same geometric principle has been utilized in designing a drawing board by means of which a vector loop can be derived from a From the Departments of Physiology and Medicine ,