Systolic tremor is a small vibration sensation felt in the palm of the hand during palpation, similar to the respiratory tremor felt in the larynx of cats, also known as feline wheezing. The mechanism of tremor is the same as that of interstitial tremor. It is caused by the flow of blood through a narrow caliber or in an abnormal direction to form a vortex that causes vibration of the valve, vessel wall, or heart chamber wall to the chest wall. When a tremor is detected, the location and source (valve, large vessel, or septal defect) should be determined first, followed by the phase of the cardiac cycle (systolic, diastolic, or continuous), and finally, its clinical significance should be analyzed. The systolic murmur is the most common clinical murmur and can be functional or organic, with functional being the most common type of cardiac murmur. A cardiac murmur is an abnormal sound produced by the vibration of the ventricular wall, valves, or vessel walls at the point where the heart sounds with additional heart sounds, due to the turbulence of blood in the heart or vessels during systole or diastole. In mitral valve insufficiency, blood returns from the left ventricle to the left atrium during left ventricular systole and produces a murmur, and the resulting systolic murmur is transmitted to the left axilla. Any factor that increases the pressure step difference between the left ventricle and left atrium during systole can enhance the murmur. During inspiration, the intrathoracic pressure decreases (less than atmospheric pressure), the right ventricle pumps less blood into the pulmonary circulation, and the left ventricular filling volume decreases; at the same time, influenced by the thoracic pressure, the pressure step difference between the left ventricle and the left atrium during systole decreases, and the blood flow in the regurgitation decreases, and the murmur is weakened. During expiration, the thoracic pressure rises (greater than atmospheric pressure), the right ventricle pumps more blood into the pulmonary circulation, the left ventricular filling volume also increases, and at the same time, influenced by the thoracic pressure, the pressure step difference between the left ventricle and the left interventricular pressure during systole relatively rises, the volume of regurgitant blood relatively increases, and the murmur increases.