Abnormal heart sounds

It is confirmed by heart sound examination that there are four normal heart sounds, which are called first, second, third, and fourth heart sounds in the order of their appearance. The first and second heart sounds are usually heard, and some children and young people sometimes hear the third heart sound. The fourth heart sound is generally inaudible, and healthy puppets over the age of 40 may show the fourth heart sound. The mechanism and characteristics of normal heart sounds: The first heart sound: It is mainly caused by the sudden closing of the mitral and tricuspid valves at the beginning of ventricular contraction. In addition, the ventricular muscle contraction, the terminal part of the atrial muscle contraction, the opening of the semilunar valve, and the vibration generated by the blood flow impacting the large blood vessels all participate in the formation of the first heart sound. The appearance of the first heart sound marks the beginning of heart contraction. The tone of the first heart sound is low and blunt. It sounds like a "Le" sound and is louder. It is 50% higher than the second heart sound at the apex of the heart and is equal to or lower than the second heart sound at the bottom of the heart. The duration is longer, generally 0.10-0.16 s, and the auscultation is loudest in the apical region and between the apical region and the left margin of the sternum. Second heart sound: It is mainly caused by the vibration of pulmonary valve and aortic valve closing at the beginning of ventricular diastole. In addition, the relaxation of ventricular muscles, blood flow in large blood vessels, and the opening of mitral and tricuspid valves also contribute to the formation of second heart sounds. The presence of a second heart sound marks the beginning of ventricular diastole. The second heart sound has a higher and clearer tone and sounds like a "De (得)" sound. Its intensity is not as good as the first heart sound, and the time is shorter than the first heart sound, generally 0.08-0.12 s. In the aortic valve area and the pulmonary valve area, the loudest, straight auscultation. In children and young people, the pulmonary valve area is second heart sound than the aortic valve area. The middle-aged people are the same, while the elderly are the opposite. Third heart sound: Sometimes a short and weak sound can be heard 0.12-0.20s after the start of the second heart sound, which is called the third heart sound. This sound is due to the vibration of the ventricular wall during rapid filling of the ventricle. The third heart sound is low, weak, blunt and heavy. It sounds "Le (Le) -De (得) -He (合) Le-De-He") on auscultation, which seems to be the echo of the second heart sound. The duration is very short, generally 0.03-0.8s, and appears 0.12-0.18 s after the second heart sound. Fourth heart sound: Occurs in the late diastole, 0.07-0.10s before the beginning of the first heart sound. It is caused by the vibration of the atrial muscles that constricted against the end-diastolic pressure of the ventricle. This tone is very weak, and is normally not heard under normal circumstances. The difference between the first and second heart sounds: Correctly distinguishing the first and second heart sounds is the most important part of auscultation. Because only the first heart sound is distinguished from the second heart sound, can the ventricular systole and diastole be accurately determined, and then whether the abnormal heart sound or murmur is in the systole or diastole and its relationship with the first heart sound or Time relationship between second heart sounds. The difference between the two: ① the first heart sound is lower and the time is longer, the apex of the heart is the loudest; the second heart sound is higher, the time is shorter, and the bottom of the heart is the loudest. ② The interval between the first heart sound and the second heart sound is short, and the interval between the second heart sound and the first heart sound in the next cardiac cycle is longer. ③ The first heart sound appears simultaneously with the apical pulse, while the carotid pulses appear almost simultaneously, and the second heart sound appears after the apical pulse. ④Movement method. When the first and second heart sounds cannot be judged by the apex, you can first auscultate at the bottom of the heart to determine the first and second heart sounds, and then gradually move the stethoscope body toward the apex, according to this law. Put the apex of the heart first. The heart sound is distinguished from the second heart sound.

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