The heart, just like a house, has an electrical system and a plumbing system. The electrical system and “wiring” in the heart cause it to beat and circulate blood throughout the body. An ECG is a test looking at the electrical activity of the heart. A normal ECG shows the heart beating in the proper order and at the correct rate. This is identified by P-waves, which show the activity of the atria (upper chambers of the heart), QRS complexes, which demonstrate the activity of the ventricles (lower chambers of the heart), and the T-waves, which exhibit the resetting of the electrical system of the ventricles. There are established norms for the size and shapes of all of these ECG complexes as well as the cadence, rates and intervals between complexes and individual beats. A normal ECG illustrates a rhythm between 60 and 100 beats per minute.