Some myocardial ischemia can be detected by 24-hour monitoring. 24-hour monitoring, clinically known as a 24-hour ambulatory electrocardiogram (ECG), monitors the electrical activity of the heart in real time over a 24-hour period, and can detect occult myocardial ischemia, as well as being valuable in the diagnosis of arrhythmias. 24-hour ambulatory monitoring does not detect all myocardial ischemia, and in some patients, if there is no myocardial ischemia attack during the testing process, the ambulatory monitoring will not record abnormal manifestations, and if the patient has an attack of myocardial ischemia during the monitoring process, it will usually be accompanied by an abnormal manifestation of the ECG, and the diagnosis can be made. Some patients do not necessarily have ECG changes during an episode of myocardial ischemia, and dynamic monitoring has certain limitations, so patients also need to undergo coronary artery CT or coronary angiography to check for myocardial ischemia.