Every cell in your heart
have pacemaking abilities, and can fire impulses before your sinus node (the natural <span style = 'background-color: #dae8f4'>pacemaker</span>
) does. Though it can be annoying, this is actually a possible life saving ability. If your sinus node for some reason fails, or the heart
develops a blocking due to heart
disease that makes ordinary impulses not conduct - PVCs will keep you alive until you've got a pacemaker
However, those cells can fire impulses though it's not needed.