The vertical component of the heart vector
American heart journal
Aged; Genetic Vectors; Heart; Humans; Vectorcardiography
When a dipole is immersed in a homogeneous right cylinder of arbitrary cross section, the vertical component is equal to kAVy, where k is the conductivity, A is the cross-sectional area, and Vy is the mean potential difference between bottom and top surfaces. By means of experiments in an accurate, life-size, Plexiglas thorax model, it was shown that this equation is valid when using the left-leg-to-head lead for Vy, provided that a certain fraction of the sagittal component of the dipole moment is added to VF - VH. For 11 representative dipole locations in the heart volume, this ratio, K, is 0.15, on the average.
A new system of measuring the mean vertical voltage was tested, but was found to have no advantage over the simple foot-head lead. Changes in dipole location in a mediumsized heart can cause changes in the observed value of the vertical component of up to 16 per cent. Changes of location in the sagittal direction have much more effect than shifts parallel to the frontal plane. A generalized Burger equation for the foot-head lead was derived, with the factor resistivity divided by area common to all three vector components. A vector lead for the vertical component is proposed. Absolute magnitudes and directions of the spatial vector for one indicidual are given, on the assumption of a homogeneous thorax of mean resistivity equal to 500 ohm-cm. The peak value of the depolarization moment was 3.2 ma.-cm.
NELSON CV, MATSUOKA S. The vertical component of the heart vector. Am Heart J. 1963;65:774-788. doi:10.1016/0002-8703(63)90243-6