[The P wave, P-R interval, and Q-T ratio of the normal orthogonal electrocardiogram].

E LECTRIC signals generated from the heart are more properly defined in mag. n-itude and direction by an orthogomial 3 lead system with constancy iii lead direction and strenogth.l1The spatial heart veetors are projected on the 3 perpendicular axes of such a Cartesiani coordiiiate system, and are readily available for analysis. With the advent of corrected orthogonal lead systems1-4 it appeared appropriate to reevaluate the time-phase relationships of the electrocardiograin ini siimulltanieously recorded tracings of the 3 orthogonal leads. Such ani analysis should come very close to the determination of the true b)eginniinig and enid of electric events as they take place ini the heart, as far as these cani be ascertained from the body surface. I previous studies by Blackburn and Simonsoit'; and fronm this laboratory7 it was found that the QRS duration differs markedly fromii conmmonily accepted, normal standards wx-hen simnultanieotislyrecorded tracings of orthogonal leads are anialz-ed. It seemed appIarent, therefore, that ot.her intervals used inl electrocardiographic interpretations should also be reiinvestigated in the same fashion. W~hite and associates aid(l Lepeschkin and