If a patient wakes up with a rapid heartbeat after a nap, several factors are usually taken into consideration. Firstly, it should be considered that it is caused by sympathetic overexcitation, and secondly, it should be considered whether the patient has cardiac neurosis due to plant nerve dysfunction. In addition, if the patient suffers from endocrine metabolic diseases, such as hyperthyroidism or hyperadrenocorticism, he or she may also feel tachycardia when waking up after a nap. In addition, diabetic patients with hypoglycemic reactions may also wake up with rapid heartbeat and sweating. In addition, for some organic heart diseases, such as coronary atherosclerotic heart disease, myocarditis, pericarditis, and heart valve disease, tachycardia may occur due to ischemic stenosis and spasm of the coronary arteries. Finally, if the patient develops an increased body temperature, it may also cause secondary tachycardia due to high body temperature.