A missed beat, clinically known as a premature beat, is a heart beat that occurs prematurely by an ectopic pacing point issuing an impulse on top of a regular heart rhythm. 1. Premature beats are the most common ectopic rhythm and can occur on top of sinus or ectopic rhythms. Premature beats can occur in almost all patients with heart disease and in 90% of the healthy population. 2. Premature beats can be occasional or frequent, and most patients have no obvious symptoms. Common symptoms include palpitations, chest tightness, a sense of weightlessness, and a sense of cardiac arrest. Patients with pre-existing heart disease can be induced or aggravated angina pectoris and heart failure. There is even a risk of sudden death. 3. Premature beats can be divided into atrial premature beats, atrioventricular junctional premature beats, and ventricular premature beats. They are usually due to physiologic or pathologic factors. Physiological factors mean that premature beats can be induced in normal people by factors such as mental tension, anxiety, and overwork. Pathological factors are common in organic heart, such as coronary heart disease, cardiomyopathy, heart failure and other diseases. Patients with premature beats should go to professional hospitals for examination in a timely manner, clarify the cause of the disease under the guidance of doctors and actively cooperate with the treatment.