The significance of 24-hour ambulatory cardiac monitoring, or 24-hour ECG, is twofold: the first is to diagnose the presence of arrhythmias, that is, problems with the heart rhythm. For example, if a patient has premature beats, the ECG can show the type of beats and the total number of beats in 24 hours, which can help determine whether treatment is needed. In some patients with paroxysmal tachyarrhythmias, the type of arrhythmia can be determined by the ECG. For chronic arrhythmias, such as sinus syndrome, the ECG can show whether there is a long interval between heartbeats during the slowest heart rate in the sleep state, which can be used to diagnose the need for treatment. Another aspect is that the ECG can diagnose the presence of myocardial ischemia. For example, if a patient has recurrent chest pain, the ECG can be worn to induce symptoms, and if the pain is caused by the heart, i.e. angina pectoris, there will be ST segment changes on the ECG, and then the diagnosis of pain caused by myocardial ischemia can be confirmed.