Mrs. Lin is a 45 years old woman who hospitalized of "rheumatic heart disease" and "atrial fibrillation", she complained of palpitation, dizziness, chest tightness and weakness in the limbs. The nurses found her pulse was light and quick and irregular when they diagnosed her pulse. The heart rate of the same time was greater than the pulse rate, the rhythm of heart was irregular, and the heart sound was different. This pulse is called ( )