ECG MNEMONIC. THE DIAGONAL RULE.

      A diagonal line is drawn from lead III through aVL, to V1,. All of these leads can have upright, inverted, or diphasic P or T waves in a normal tracing. Similarly, significant Q waves ( > 0.04 second in duration or  > 25% of the R wave) can be seen in the leads transected by the diagonal line. The box around aVR, causes one to recognize the fact that the P and T waves are inverted and a significant Q wave is always present in this lead on a normal ECG record. All other leads should have upright P and T waves, as well as the absence of a significant Q wave. (It must be realized that rarely a significant Q wave or inverted P or T waves may be present in lead V2 on a normal tracing.)

Wilmer L. Sibbitt Jr., M.D. Department of Medicine University of New Mexico School of Medicine Albuquerque, NM 87131