Premature beats are one of the most common arrhythmias, and many normal people can have premature beats, but they are not very dangerous. However, there are some specific types of premature contractions that can be fatal and can lead to sudden death. Today we will talk about atrial and ventricular preterm contractions. In atrial premature contractions, patients may experience chest tightness, weakness, and a self-conscious feeling of cardiac arrest, but there are some patients who do not experience any uncomfortable symptoms. Most atrial preterm contractions do not require treatment unless there are significant symptoms, or if they are triggered by supraventricular tachycardia, which is relatively dangerous and may result in syncope, myocardial ischemia, or pulmonary edema. With ventricular premature contractions, patients may present with dizziness, weakness, and chest tightness. In some patients, prolonged and frequent ventricular asystole may aggravate angina pectoris and cause hypotension and heart failure. For occasional ventricular premature without organic lesions, drug therapy is often not required. In patients with acute myocardial ischemia or infarction combined with ventricular premature, aggressive reperfusion therapy is always necessary to reduce the risk of sudden death. Multi-source ventricular premature or paired, continuous occurrence of premature is relatively a certain risk of sudden death, especially for R-on-T phenomenon, which can easily induce ventricular tachycardia or ventricular fibrillation, leading to sudden death of patients in cardiac arrest. When patients have precordial discomfort, panic and palpitations, it is recommended that they should actively go to the hospital for further examination to clarify the nature of the disease, whether it is a functional lesion or an organic lesion, combined with the application of drugs to avoid adverse events.