The characteristics of the first heart sound include

Auscultation features of the first heart sound: ① low pitch; 2 loud voice; ③ Dull in nature; ④ It takes a long time (lasting about 0.1s); ⑤ It appears at the same time as apical pulsation; ⑥ Apex auscultation is the clearest.

The first heart sound is mainly caused by the closure of mitral and tricuspid valves and the sudden tension of valve leaflets. Others, such as the opening of the semilunar valve, the contraction of ventricular muscle, the vibration caused by the impact of blood flow on the ventricular wall and the wall of large blood vessels, and the terminal part of atrial contraction also participate in the formation of the first heart sound.

Extended data:

Precautions:

Due to the contraction and relaxation of myocardium, the opening and closing of valves, the vibration of ventricular wall and the impulse and form of arterial blood shock, it spreads to the chest wall and passes through surrounding tissues. If the ear is close to the proper position of the chest wall or a stethoscope is used in some parts of the chest wall, "Tongta" claims to be heart sound.

First, it occurs at the beginning of systole and lasts for a long and deep time (about 0. 15 seconds). Causes include ventricular contraction, sudden closure of atrioventricular valve and subsequent aortic ejection. The best position for the first heart sound auscultation is the middle of the fifth intercostal clavicle or the right edge of the sternum.

Second, it appears in the early diastole with high frequency and short duration (about 0.08 seconds). The reasons for this situation are the closing of crescent valves, the mutual impact between valves, the deceleration of blood in aorta and the vibration caused by the rapid drop of indoor pressure. The best auscultation sites of the third heart sound are the left pulmonary valve area and the right aortic valve area of the second intercostal space.