Welcome to HCM. I had gone through your question and understand your concerns.
(Thyroid stimulating Hormone
) will be elevated when thyroid hormones in your body is low. This is our body's response to low thyroid hormones in blood. That may be the reason for low heart rate
and EKG changes in your mother.
Don't worry, This can be easily corrected by the thyroid hormone replacement
Hope I have answered your question. If you have any further questions I will be happy to help.
Dr Ajish TP