Dynamic electrocardiography V. The "imaginary cardiac vector" hypothesis: experimental evaluation.

This paper experimentally evaluates the "imaginary cardiac vector" hypothesis, that the cardiac vector is not a real vector. We have previously shown on theoretical grounds that the basis of the cardiac vector is invalid in that Einthoven used scalar, not vector, procedures. Attempts by subsequent workers to compensate for the theoretical flaws have not succeeded. The concept of the "cardiac vector" which they have invented has the dimensions of an imaginary entity. Experimental measurement of isopotential maps derived from dipoles in a volume conductor demonstrates that these dipoles do not summate vectorially. Isopotential maps of the thoracic surface confirm that this applies to the human ECG. An imaginary "man-frog" cardiac vector loop is demonstrated using a lead from a man and a lead from a frog. This illustrates that the "imaginary cardiac vector" is a tenable concept. Finally, a crucial test of the hypothesis is reported which demonstrates that exercise causes deviations of the so-called cardiac vector in opposite directions, simultaneously, in different VCG lead systems. Since a physical entity can only be in one place and more in one direction at a particular instant, this experiment invalidates the "real cardiac vector" hypothesis. This strongly suggests that the cardiac vector is a brilliant, but imaginary, construction with immense clinical value, especially in the interpretation of the sequence of depolarization. Nevertheless, it obstructs analysis of the real basis of the electricity of the heart.