Hyperthyroidism occurs when an excessive amount of T3 and T4 is released by the thyroid gland, leading to hyperactive metabolism throughout the body. This can cause disturbances in autonomic nervous function or receptor hyperactivity, resulting in a series of conditions related to excessive cardiac load and insufficient blood supply. Therefore, the majority of hyperthyroidism-related heart diseases improve after controlling the hyperthyroidism and are relatively easy to treat. However, if the thyroid function is not controlled repeatedly, or if the treatment is not effective, it may lead to severe enlargement of the heart and recurrent arrhythmias, making hyperthyroid heart disease difficult to cure. Nonetheless, such cases are relatively rare, with an incidence of less than 10%.