To the Editor.
—Right and left arm electrocardiograph lead reversal (such as displayed so embarrassingly on page 809 of the June 1966 Archives) is obvious to one who tries to "think vector."A big help to vectorial thinking is an electrocardiogram mounting format which puts vectorially related leads close together on the page. For several years now, instead of mounting electrocardiograms in the arbitrary historical order in which the leads were developed, I have been mounting leads I, V5, V6, and II—leads "facing" the left side of the heart—on the right side of the page; AVR, V1, and III on the left side; and III, AVF, and II on the bottom. Then the directions of vectors of atrial and ventricular activation and repolarization stand out at a glance. Null zones are immediately apparent and can be indicated by lines drawn on a simple lead diagram, as shown on the enclosed