In this tracing, note the initial small, positive deflection, or R wave, in leads aVR and V1, the right-sided, anterior leads, and the initial small, negative deflection, or Q wave, in leads I, aVL and V6, the left-sided, posterior leads. Thiese deflections reflect the left to right and posterior to anterior direction of septal depolarization and are the most common electrocardiographic expression of this event. The duration of these initial deflections is about 1/2 of one small box, i.e., about 0.02 seconds (20 msec) when recorded at the usual paper speed of 25mm/second. Because of their small amplitudes, they are often sometimes labeled "r" and "q" waves