Cardiac ultrasound examinations cannot directly diagnose hyperthyroid heart disease, which often leads to an enlargement of the heart and a reduction in cardiac pumping function. Cardiac ultrasound can detect these structural changes in the heart caused by hyperthyroidism and can assess heart function, but it cannot determine if these are caused by an overactive thyroid. A combination of blood tests for thyroid function or a thyroid ultrasound is needed for a comprehensive diagnosis. If the thyroid ultrasound shows a rich blood flow in the thyroid region, appearing flame-like, or if the blood tests show a significant decrease in thyroid-stimulating hormone, in conjunction with cardiac ultrasound, it can confirm the presence of hyperthyroid heart disease.