There are three cable-like networks to the lower chambers that carry the message to beat. They are called fascicles. When they fail in the setting of other heart disease, that is sometimes a concern. They may decline in function for no particular reason as we age. For reasons that aren't really clear, if their decline is not due to some underlying illness, it is rare for the third to become dysfunctional. Therefore, aside from warning the next doctor who is doing an EKG, it rarely matters.