Hypothyroidism is also known as hypothyroidism. The effects of hypothyroidism on the heart include causing coronary artery disease, pericardial effusion, and hypothyroid heart disease. 1. Patients with hypothyroidism may have a slowed heart rate, decreased per-beat volume, decreased cardiac output at rest, increased peripheral vascular resistance, and decreased pulse pressure. Patients may be accompanied by increased blood pressure, and those who have been ill for a long time are prone to complications of atherosclerosis and coronary heart disease. 2. Due to the decrease of myocardial oxygen consumption, angina pectoris and heart failure rarely occur. Angina pectoris can be induced or aggravated during the application of thyroid hormone therapy. Patients with hypothyroidism may have symptoms of bradycardia, diminished heart sounds, and enlarged heart boundaries. 3. Primary hypothyroidism is characterized by enlargement of the heart and pericardial effusion, which is called hypothyroid heart disease. Pericardial effusion is manifested by the enlargement of the heart border bilaterally, which changes with the body position, the heart turbid tone border is flask-like in sitting position, and the turbid tone border at the bottom of the heart is enlarged in lying position. Patients with hypothyroidism should follow the doctor’s instructions for treatment to avoid adverse consequences.