Atrial fibrillation is the most common tachyarrhythmia and is an abnormality in the electrical generation and transmission within the atria. In atrial fibrillation, intra-atrial excitation is rapid and irregular, up to 300-600 beats/min, which deprives the atria of effective mechanical contraction. Although the atrial rate is more than 300 beats/min, the protective effect of the atrioventricular node prevents all of these electrical excitations from being transmitted to the ventricles, and the ventricular rate (heart rate, i.e., the number of beats per minute) can still reach 100-160 beats/min, which is much faster than normal sinus rhythm, and the rhythm is definitely not uniform. At this time, if the pulse is detected, it will be unequal in strength and slower than the heart rate (pulse dystocia).