The vectorcardiogram in 100 healthy subjects using a new drawing instrument.

The development of electrocardiography has led to the recording of the potentials produced by the heart at an increasing number of sites on the body surface by various combinations of leads. This trend has focussed attention on greater numbers of patterns, with emphasis on more and more detail. Pari passu with these developments, many investigators have endeavoured to record and interpret the central electrical field of the heart as a whole. Mann (1920) showed that a single continuous curve could be obtained by the fusion of three leads into a monocardiogram. He constructed the curve from direct voltage measurements at equal and successive time intervals from standard leads; simultaneous QRS complexes were not measured, but Mann considered that this did not introduce a serious error. Eighteen years later, Mann (1938) described a moving-coil galvanometer that could respond in two planes to the potentials from two leads, and the resulting loop was recorded photographically. This technique has not been generally accepted. Schellong (1936) and Wilson and Johnston (1938) independently showed that the cathode-ray tube could be used to produce a continuous curve from the amplified voltage of extremity leads; they preferred to call this loop a vectorcardiogram. Wilson and Johnston and others employed leads based on the Einthoven triangle to record the vectorcardiogram in the frontal plane, and more recently a central terminal placed at the back has been used to provide reference in depth to form a tetrahedral system. Duchosal and Sulzer (1949) have made extensive contributions to this subject using cathode-ray apparatus with a split electron beam, thus enabling simultaneous loops from the frontal and saggital planes to be recorded. They have used a parallelepiped reference system. The slow development of vectorcardiography has been in some measure due to the elaborate and time-consuming nature of these methods. Grant (1950) has recently sought to overcome this difficulty by drawing or envisaging the curve from an inspection of standard and pracordial leads; his method is an approximation and no integrating apparatus is used. As the principal application of vectorcardiography is likely to be in the field of myocardial disease where conventional electro-cardiography already shows a high degree of correlation with pathological findings, it would seem desirable to retain at least the degree of accuracy obtained in recording the scalar electrocardiograms. The mathematical and physical approach that has been used by some authors to treat the fundamental problems of this subject is …