Conversation: The conversation between human and AI assistant.
[|Human|] What can you tell me about bifasicular heart block in a healthy 50 year old man, no symptoms, has run 2 marathons in last 2 months. Heart rate is 40-45 with an abnormal 12 lead EKG...only other circulatory complaint is possible raynauds syndrome...never dx but cold sensitive in fingertips...
[|AI|]  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.