"Cardiac muscle is like the pistons in a car's engine; it is the mechanical source that powers the
engine. However, without spark plugs, a battery, generator, alternator, and the other components
of the automobile's electrical system, the car would not function properly, even if its pistons and
cylinders were totally normal. Likewise, although cardiac muscle is specialized to contract and
pump blood, it can do so only when triggered by the heart's electrical system. Therefore, if
abnormal electrical circuits in the heart become operative, they can profoundly affect the
mechanical activity of the heart "