Sinus tachycardia is generally not dangerous. When the body’s blood and oxygen requirements increase, the body self-regulates, the heart contraction increases, and the heart rate increases as a result of self-regulation. However, sometimes self-regulation of sustained sinus tachycardia can be harmful, such as fever, anemia, or hyperthyroidism can cause sinus tachycardia. However, hyperthyroidism or anemia, prolonged sinus tachycardia, and a state of failure will gradually occur after the heart keeps beating rapidly. Hyperthyroid heart disease and anemia causing heart failure are dangerous. Generally, sinus tachycardia caused by factors such as sinus tachycardia after exercise or self-regulation of the body such as fever is not dangerous. Prolonged tachycardia caused by hyperthyroidism and anemia can lead to heart failure. In addition to treating the primary hyperthyroidism and finding the cause of anemia to treat the anemia, the heart also needs to be treated. It is necessary to suppress the increase of rapid heart rate and reduce the ventricular rate. Furthermore, if symptoms of heart failure appear, it is also necessary to reduce the anterior and posterior load on the heart, such as vasodilator therapy, using ACEI drugs or nitrates to reduce the burden on the heart, allowing the heart to rest and gradually relieve.