Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Familial atrial fibrillation ?
    ### Response:
    Familial atrial fibrillation is an inherited heart condition that disrupts the heart's rhythm. It is characterized by erratic electrical activity in the heart's upper chambers (the atria), causing an irregular response in the heart's lower chambers (the ventricles).
    