The axostat. An improved form of the instrument, and its application to the establishment of spatial. Electrocardiographic indices in 102 normal subjects

Document Type

Article

Publication Date

1-1-1955

Publication Title

American Heart Journal

Volume

50

Issue

4

Abstract

An electrocardiographic instrument, known as the axostat, is described which provides a simple method for rapid and accurate determination of the directions of mean QRS and T vectors in their frontal and sagittal projections without the need for planimetric evaluation of areas under electrocardiographic deflections. Such determinations were made in a group of 102 normal, youthful adults, and the orientation of the mean spatial QRS and T vectors was calculated from these data. The validity of several types of spatial electrocardiographic connections is discussed. Probably none of the associated frames of reference are accurate from the standpoint of strict geometric interpretation, but undoubtedly some of them will prove useful for the interpretation of electrocardiographic data. Other frames of reference should be discarded because they introduce certain incompatibilities. The Wilson tetrahedron is employed in this study because it introduces no such incompatibilities, the associated lead connections are simple and easily reproduced, and the frontal plane components of our spatial data are directly applicable to conventional extremity lead electrocardiography. The directions of mean QRS and T vectors in our group of normals display as much variability in the sagittal plane as they do in the frontal plane. However, the two sets of data are interrelated in a highly significant manner. Analysis of these relationships strongly suggests that three spatial electrocardiographic indices be firmly established and further investigated: (a) the locus of the mean spatial QRS vector, (b) the locus of the mean spatial T vector, and (c) the angle between the mean spatial QRS and T vectors. The primary virtue of these spatial indices appears to be reduced variability in the range of normal values. According to the standard deviations in our group of normals the scatter of the spatial electrocardiographic indices about their average values is reduced to almost one-half the scatter in the case of the corresponding planar indices. It is anticipated that this reduction in scatter will result in more precise criteria of normality and abnormality. © 1955.

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