The most common cause of a sudden rapid heartbeat may be a premature beat, which is an arrhythmia in itself, but may also be seen in cardiomyopathy, heart failure, myocardial ischemia and other heart diseases. 1. Arrhythmia: premature beats, i.e. intermittent, such as atrial premature beats, ventricular premature beats, etc., is a kind of arrhythmia, in the normal sinus rhythm, the heart beats regularly, the heart may suddenly happen to beat early, commonly seen in the case of fatigue, anxiety and so on. 2. Cardiomyopathy: When the heart muscle is diseased and the electrical activity of the heart is disturbed, premature beating of the heart muscle may occur, i.e. premature beats. 3. Heart failure: heart failure patients have enlarged heart, unstable electrical activity, and often complicated by electrolyte disorders, such as potassium deficiency, which is prone to arrhythmias, such as premature ventricular contractions. 4. Myocardial ischemia: When myocardial ischemia occurs, the electrocardiographic vector is affected, and the electrocardiographic activity is unstable, which makes it easy for arrhythmias, such as premature beats, to occur. If your heart suddenly skips a beat, which happens more frequently, you should go to the cardiology department in time to have the cause of your heartbeat treated.