Normally the SA node in your right atrium is the natural pacemaker
, but any spot in the heart can take over for the SA node just in case it goes bad. Think of it like an extensive back-up generator
system. It's a good thing. However, if one of the back-up generator
s gets antsy it will fire off a beat before it should happen. If the antsy spot was in one of the ventricles it is a PVC and if it was in the atriums it's a PAC. One is not worse than the other. They just are what they are.