What are the mechanisms of the third heart sound, the fourth heart sound and the extra heart sound?

Hello! The third heart sound (S3). It is caused by the sudden deceleration of blood flow from atrium to ventricle during rapid filling in early diastole, which causes the vibration of blood column and then the vibration of ventricular wall. Physiological S3 is more common in young people and children, but rare in people over 40 years old. The fourth heart sound (S4). Also known as atrial sound, it occurs in the late diastole of the ventricle, because after atrial contraction, blood quickly flows into the ventricle and then slows down, which makes the ventricular muscles suddenly vibrate-extra heart sounds or extra heart sounds. Heart sounds other than S 1S2 can be divided into diastolic extra sounds and systolic extra sounds according to their appearance phases. Diastolic extra sounds Diastolic heart sounds can be normal heart sounds, such as S3 and S4, or abnormal heart sounds. Pathological S3 is also called ventricular galloping sound, so it is called diastolic ventricular galloping sound because it is a trisyllabic sound combined with S 1S2, and auscultation is like the hoofbeat of a galloping horse. The occurrence of pathological S3 is similar to physiological S3, but the amplitude and frequency are higher than S3, and sometimes it can be touched. It is caused by the decrease of ventricular muscle tension (decreased compliance) and the overload of ventricular diastolic or systolic period. The enlarged ventricular cavity is filled with rapid blood flow, which makes the ventricular wall with decreased compliance vibrate and bulge, and the blood flow can hit the surrounding tissues and chest wall, so the amplitude is large and the sound is loud and palpable. Ventricular galloping rhythm, commonly known as heart calling for help, often leads to myocardial damage, such as heart failure, myocardial infarction or atrioventricular valve insufficiency, ventricular septal defect with a large number of left-to-right shunt, etc. Pathological S4 is also called atrial galloping sound. The trisyllabic rhythm composed of this sound and S 1 and S2 is called late diastolic atrial galloping rhythm. Pathological S4 is similar to physiological S4, but with larger amplitude and higher frequency, and can record and hear phonocardiogram. Left pathological S4 is common in left ventricular systolic overload, such as acute myocardial infarction, angina pectoris, hypertension and aortic stenosis. Pathological right S4 is common in pulmonary valve stenosis and pulmonary hypertension. If the P-R interval is prolonged or tachycardia occurs, pathological S3 and S4 will recombine the overlapping galloping rhythm, which is seen in rheumatic fever with ventricular failure and tachycardia, and P-R prolongation and tachycardia. The vibration caused by normal atrioventricular valve opening is the fourth part of S2 which is inaudible on the phonocardiogram. 70 ~ 85% of mitral stenosis, severe tricuspid stenosis, strong opening of atrioventricular valve or excessive blood flowing through atrioventricular valve, resulting in relatively narrow valve orifice, can all cause sharp flapping sound, which is called flapping sound or opening snapping sound (OS). The mitral valve orifice is most easily heard in the fourth intercostal space of the left sternum or at the apex of the heart. OS has high frequency and short duration, including 1 ~ 2 rapid vibrations lasting 0.02 ~ 0.05 seconds. Pericardial tapping (PK) is a vibration caused by the sudden stop of diastolic process due to the restriction of contractile pericardium during the rapid filling of ventricle in the early diastolic period. It is found in 70% patients with constrictive pericarditis. Extra sounds during systole can be roughly divided into two categories. First of all, it is the ejection sound in the systole, also known as the ticking sound and the ejection sound in the semilunar valve, while the extra sound or popping sound in the early systole is called the ejection sound (ES). Jet sounds can be divided into valve sounds and vascular sounds. Valve ejection occurs when the aortic valve or pulmonary valve is fully opened, and the dome valve suddenly stops and vibrates due to valve stenosis. When the systemic circulation or pulmonary circulation is high, the blood vessel jet sound will appear, which is caused by the vasodilation and the vibration of the turbulent vortex of blood flow. The aortic ejection sound (AES) is most obvious in the aortic valve area and can spread to the apex of the heart. Pulmonary artery jet sound (PES) is confined to the pulmonary valve area, and it is clear when exhaling, but weakened or disappeared when inhaling. Secondly, it is the click sound (SC) in the middle and late period of uterine contraction, which is also a high-frequency and short-lasting sound. It is often heard or recorded in the lower sternum and precordial area, which is mostly caused by the activities of extra-cardiac organs or tissues (such as the vibration of cartilage sternum and xiphoid sternum), and often changes with the change of breathing posture, without delayed contraction noise. Generally speaking, it doesn't make any sense. The other is the click sound in the middle and late contraction, which has high frequency and short time limit, and is often accompanied by noise in the middle and late contraction. This is the so-called systolic tick. Murmur syndrome or mitral valve prolapse syndrome. This is because the mitral leaflet is too long for various reasons. When the ventricle contracts, the mitral valve is prolapsed (inverted) to the left atrium. Due to the increase of left ventricular pressure, the leaflets or chordae tendineae suddenly tighten, resulting in clicking sound and systolic noise caused by mitral regurgitation. Production. Usually not, but occasionally in normal infants, children and the elderly.