Electrical Axis of the Human Heart. 



67 



lateral spike is to be admitted as affording per se proof of the existence of 

 right or left hypertrophy or dilatation. 



Considering, further, that a negative left lateral spike is of frequent 

 occurrence in the normal as well as in the diseased heart, it cannot be 

 admitted as affording per se proof or even evidence of an interruption of the 

 right branch of the auriculo-ventricular bundle. The facility with which in 

 certain hearts a positive left lateral spike can be rendered negative is such as 

 to forbid us from admitting a temporary reversal as an indication of 

 temporary interruption of conduction to the right ventricle. 



[Note added May 23, 1914. — By courtesy of Dr. Part of the National 

 Hospital for Diseases of the Heart, I am able to complete the account of the 

 cases of A. D. W. and of J. C. W. by the reduced skiagraphic outlines 

 (tig. 10) of their hearts in the positions of deep inspiration and expiration. 

 The outlines of the heart and diaphragm indicate approximately the anatomical 

 alterations corresponding with the electrical alterations given in figs. 7 and 8. 

 There is, however, in these cases no absolute correspondence of axial angles 

 to be made out between the anatomical and the electrical estimates. The 

 skiagrams required the breath to be held for several seconds in inspiration 

 and in expiration respectively. In general, the correspondence between the 

 anatomical and the electrical axial angle is not very close. As a rule the 



Insp. 



A.D.W. J.C.W 



Fig. 10. 



right and left electrical effects of the infantile heart which is mesial may 

 be expected to be about equal, while in the senile heart which tends to 

 become horizontal the left hand inferior spike is more usually negative. 

 But cases occur of apparently normal as well as of diseased hearts (e.g. 

 mitral diseases) where the left inferior is larger than the right inferior spike 

 (implying an electrical axis directed to the right and a reversed transverse 

 spike), but where the anatomical axis is distinctly directed to the left. Cases 

 also occur of reversed left inferior spike where the electrical axis comes out 



F 2 



