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May 22, 1967

Cardiac Vectors in The Frontal Plane

Author Affiliations


JAMA. 1967;200(8):728-729. doi:10.1001/jama.1967.03120210114030

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To the Editor:—  The brief essay, "Determining the Direction of the Cardiac Vectors in the Frontal Plane" (199:665, 1967), offers presumably a simplification of an established method of determining by inspection the mean frontal-plane vector of the QRS, T, or other elements of the curve.The authors' principle, that a mean or instantaneous vector force is the center of a 180° arc of positivity, is only a corollary to the principle that the establishment of a null line or zone, or the determination of a scalar lead which is algebraically near zero, puts the mean vector force for the complex 90° away from the null line.It would have been much simpler for them to examine their curve, with lead III having a negative QRS potential and lead aVF a positive potential, and assume that an algebraically zero force or netisoelectric line would fall between the two leads.