The normal human heartbeat is very regular. Each time the heart contracts or diastolic, the blood flow hits the valves and blood vessels to produce a regular sound. If you use a stethoscope to listen to the heart, you can hear two regular and clear heart sounds (i.e., the first and second heart sounds). The heart murmur is an additional sound other than the two normal heart sounds. The common causes of this pathological heart murmur are: narrowing of blood flow channels, blood countercurrent, abnormal channels between the large blood vessels of the heart and other factors. So is it true that the louder the heart murmur, the more serious the heart disease? In fact, the loudness of the heart murmur is not directly proportional to the severity of the disease. The strength of the murmur is related to the location of the murmur, the ratio of the caliber of the heart’s vascular chambers, the speed of blood flow, and the pressure difference between the two chambers of the heart. For example, in a patient suffering from pulmonary stenosis, the greater the pressure difference between the cardiac vascular chambers in front of and behind the valve, and the greater the blood flow velocity, the higher the murmur’s pitch. In this case, it can be said that the louder the heart murmur, the more severe the surface valve stenosis. In the case of a patient with a ventricular septal defect, blood from the left ventricle with high pressure flows through the defect site to the right ventricle with low pressure. As the condition develops, the pressure in the right ventricle and pulmonary artery gradually increases, and the pressure difference between the left and right ventricles gradually decreases, at which point the heart murmur sounds lower instead, but the condition becomes more severe. At this point, if one mistakenly believes that active treatment is not necessary, the condition will develop further and lead to heart failure. Therefore, the strength of the heart murmur does not really indicate the severity of heart disease.