Following the R wave. The QRS duration is measured from the beginning of the Q wave to the end of the S wave. The normal QRS duration measures less than 0.12 seconds or greater indicates a delay in conduction through the ventricle. It should be noted that you may not always observe all three waveforms; there may be a Q wave (no R or S), or a R waves (no Q or S), or a combination of Q and R, or R and S waves (see Figure 1) (Huff,2006).