The relation of precordial and orthogonal leads.

IT has become evident that much of the diagnostic information now obtained from precordial leads may be furnished by an adequate orthogonal lead system.' 3 This is innportant to the further development of diagInostic electrocardiography, since quantitative (lescription of only three variables has obvious advantages over the description of larger riunmbers of body surface leads. At present the optimum methods of recordilagf and analyzing orthogonal leads have not been established. Conventional electrocardiograns, vectoreardiograms, polar co-ordinate displays, the '"normalized" eleetrocardiogramn and digital computer analvsis are all under investigation.1-10 Whatever miethods of display and analysis of orthogonial leads prove to be most useful, it is desirable that thev utilize the extensive diagnostic experience that has been accumulated with precordial leads. T'hiis requires definition of the spatial relation letween precordial and orthogonal leads. In the present study, a systematic searchl wvas made for the effective lead axes derived from an orthogonal system that corresponded most closely to aetual precordial leads V, through V6. This differed from caneellationi studies in that clinically significant details of configuration were the basis for selectioni of effective orthogonal lead axes corresponiding to precordial leads. The results will be presented as the effec.tive position of orthogonal axes that corre