Q: My dad fainted and they told him needed a pacemaker. I would like to understand more about pacemakers.A: To understand pacemakers, the first step is to understand the normal electrical activity of the heart. Each of the half billion cells in the heart plays a role in its mechanical contraction (of the atria, which ‘passively fill’ with blood and then squeeze blood out to load the ventricles, and of the ventricles, with the right [...]