![]() ![]() Note that the first vector in Figure 7 is not discussed here as it belongs to atrial activity. Inspired by MacFarlane et al (Springer, Comprehensive Electrocardiology, 2010). V1 and V5 are exploring electrodes and the reference is composed of the average of the electrodes placed on the limbs (this reference is called Wilson’s central terminal). The heart’s main electrical vectors seen from the horizontal plane. Study Figure 7 carefully, as it illustrates how the P-wave and QRS complex are generated by the electrical vectors. Figure 7 illustrates the vectors in the horizontal plane. It is fundamental to understand the genesis of these waves and although it has been discussed previously a brief rehearsal is warranted. Electrical vectors that engender the QRS complexĭepolarization of the ventricles generate three large vectors, which explains why the QRS complex is composed of three waves. The positive areas are yellow and the negative areas are green. Approximations of the net direction of the QRS-complex. Panel B in Figure 6 shows a net negative QRS complex, because the negative areas are greater than the positive area. These calculations are approximated simply by eyeballing. The QRS complex is net positive if the sum of the positive areas (above baseline) exceeds that of the negative areas (below baseline). The QRS complex can be classified as net positive or net negative, referring to its net direction. Large waves are referred to by their capital letters (Q, R, S), and small waves are referred to by their lower-case letters (q, r, s).įigure 5 shows examples of naming of the QRS-complex.Any negative wave occurring after a positive wave is an S-wave.If a third positive wave occurs (rare) it is referred to as “R-bis wave” (R”). The second positive wave is called “R-prime wave” (R’). The first positive wave is simply an “R-wave” (R). All positive waves are referred to as R-waves.If the first wave is not negative, then the QRS complex does not possess a Q-wave, regardless of the appearance of the QRS complex. If the first wave is negative then it is referred to as Q-wave.A deflection is only referred to as a wave if it passes the baseline.The following rules apply when naming the waves: Naming of the waves in the QRS complex is easy but frequently misunderstood. Regardless of which waves are visible, the wave(s) that reflect ventricular depolarization is always referred to as the QRS complex. Some leads may display all waves, whereas others might only display one of the waves. However, all three waves may not be visible and there is always variation between the leads. ![]() The QRS complex (ventricular complex): normal and abnormal configurations and intervalsĪ complete QRS complex consists of a Q-, R- and S-wave. ![]()
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