The definition of atrial fibrillation is not defined by how much the heart rate is, but by the rhythmic characteristics of the electrocardiogram. Electrocardiographic manifestations of atrial fibrillation include absolute irregularity of the cardiac rhythm, loss of the p-wave, but normal QRS wave morphology. Patients with atrial fibrillation with fast ventricular rate (ventricular rate more than 150 beats/min) may have angina symptoms, chest tightness, dyspnea, and other symptoms of insufficient cardiac output. When the ventricular rate is not fast, there may be no obvious symptoms. Atrial fibrillation can also be determined by cardiac auscultation. In a heart with atrial fibrillation, the first heart sound is not equal in strength and the heart rhythm is extremely irregular. In addition, when the ventricular rate is fast, while listening to the number of heart beats and touching the number of pulses, the pulse rate is smaller than the heart rate. In case of atrial fibrillation it is recommended to visit the hospital and be treated under the supervision of a doctor.