The occurrence of tachycardia during naps considers the patient to have a tachyarrhythmia. Tachyarrhythmias are common in many people and there are many causes of the disease, which has many subtypes and can be classified as supraventricular and ventricular. There are many causes, such as fever, infection, hyperthyroidism, anemia, and other diseases that can lead to the development of tachyarrhythmias. If a patient develops tachycardia during a nap, it is important to consider whether the patient has other symptoms in combination. If the patient is also experiencing sweating and hunger, consider whether the patient is hypoglycemic; if the patient is also experiencing dizziness, headache, nausea, or vomiting, consider whether the patient is having a cerebrovascular accident. Tachycardia can also occur in these patients. If the patient has a fever, the patient may have an infection because the patient’s body temperature rises after a fever and his or her heart rate also increases. If a patient has tachycardia during sleep, after ruling out the above diseases, it is important to consider whether the patient has a nightmare during sleep and the patient will have tachycardia after waking up. If the patient has frequent tachycardia during sleep, he or she should visit a hospital to improve the electrocardiogram examination to clarify the cause.