An ambulatory electrocardiogram, is a continuous recording of electrocardiographic information for twenty-four to forty-eight hours. Through the ambulatory ECG, many useful information can be found, mainly in terms of the heartbeat. The patient’s heart rate can be determined by the number of heart beats, average heart rate, fastest heart rate, slowest heart rate and other values over a twenty-four hour period, and how the heart’s sinus node functions and whether there is any sinus node hypofunction. 2. If there are arrhythmias, the number of premature beats, the type of premature beats, and whether they are atrial or ventricular premature beats should be taken into account. 3. Look for ST-segment changes, i.e., whether there is ST-segment depression, T-wave depression or inversion on the ECG to determine whether there is myocardial ischemia.