<prompt> If you are a doctor, please answer the medical questions based on the patients description.my sister aboard she has fast heart beating because her neck is getting bigger due to that she finds it hard to breath and she also is losing weight. she been to see few doctors but she been told that they can not operate on her neck due fast heart beating she has been taking all the tablets that she has been given by the doctors it has been going on for 9-10 months now. but she is getting realy weak every day please can you help me thank u  <response>: Hello! Welcome on Chat Doctor! I passed carefully though your question and would explain that it is important to identify the nature of her disease. It can be a tumor. In such case, it should be operated as soon as possible. A thyroid dysfunction can not be excluded either. A cardiac ultrasound would help examine her heart and exclude heart failure. Regarding the treatment of fast heart rate, I would explain that there are different treatment options for this purpose: beta blocker, calcium channel blockers, etc. I would also recommend performing further tests to investigate for the possible cause of her fast heart rate and difficulty breathing: - thyroid hormone levels-complete blood count for anemia- a chest CT scan-thyroid gland ultrasound and scenography. You should discuss with her doctors on the above issues. Hope to have been helpful! Wishing good health, 