For example, we can see a pulse waveform in this slide. The ECG pulse is initiated by the body’s natural pacemaker, the sinoatrial (SA) node. This initiates a wave of depolarization starting with the atrial muscle to the AV node, then to the common bundle and to the bundle branches, on to fibers and finally to the ventricles. Because each portion of the heart has a unique contribution to the wave form that is displayed, doctors are able to pick out certain conditions that are targeted to a specific part of the heart by just looking at the waveform itself. In the slide, it can be seen that the P, Q, R, S, and T intervals or segments of the heart wave have been defined. A specific portion of the heart is being depolarized at each point of this waveform. If an irregular event is happening at one of those points, the cardiologist is able to pinpoint it.