A normal electrocardiogram is known as sinus rhythm, which is characterized by a neat rhythm of the heartbeat. The obvious difference between atrial fibrillation and sinus rhythm is that in patients with atrial fibrillation, the heartbeat is definitely irregular and varies in speed, and the P waves of the heartbeat disappear and are replaced by f waves of varying size and amplitude. Patients with AF have a faster heart rate, usually >100 beats/min. Because of the absolute irregularity of the heartbeat in AF patients, it is clinically important to note the number of heartbeats in these patients and to time them to be greater than 1 minute in order to clarify the patient’s heart rate.