Cardiac arrest is usually caused by premature contractions of the heart, or premature beats, which may be caused by atrial premature beats, ventricular premature beats, junctional premature beats, or arrhythmias such as atrial fibrillation. If the episodes of cardiac arrest sensation are frequent, it is recommended that an electrocardiogram be performed when the cardiac arrest sensation appears to clarify the presence and type of arrhythmia. If the episodes are infrequent and it is not possible to reach the hospital in time for a general ECG, an ambulatory ECG is recommended to monitor the heart rhythm continuously for more than 24 hours to clarify the type of arrhythmia. In addition, ancillary tests such as cardiac ultrasound should be completed to clarify the cause and guide the next step of treatment according to the specific situation.