It records the heart's return to the resting state. By studying the shape and size of the waves, the time between waves, and the rate and regularity of beating, a doctor can learn a lot about the heart and its rhythm. Many different kinds of abnormal rhythms can occur. If an abnormal rhythm occurs, it's important to find out its type. Treatment recommendations depend on what kind of arrhythmia it is.
Tachycardias fall into two major categories.
Those that involve only the ventricles are called ventricular tachycardia. Those that involve both the atria and the ventricles are called supraventricular tachycardia. Irregular heart rhythms are most often caused by premature beats or extra beats. In reality, the heart doesn't skip a beat. Instead an extra beat comes sooner than normal.