Low heart sound

Introduction Low heart bluntness means low heart rate. Low heart bluntness is not necessarily morbid. In the case of obesity, etc., because the chest wall is thick, auscultation heart sounds can be low and blunt. In some cases, heart sounds may be blunt, such as myocarditis, cardiomyopathy, myocardial infarction, heart failure due to weakened myocardial contractility, and the first heart sound is low and blunt. Pericardial effusion, emphysema, pleural effusion, gas accumulation, and thickening of the chest wall due to edema, the first heart sound is low and blunt. For the low-blunt heart sound caused by obesity, there is no need for treatment, pay attention to the adjustment of diet and living habits. Other pathologically induced low heart sounds should be actively treated for the primary disease.

Cause

When the chest wall is thick, obese, etc., auscultation heart sounds can be low and blunt. In some cases, it can also occur, such as pericardial effusion (pericardial effusion is a common clinical manifestation, especially after echocardiography is the routine examination of cardiovascular disease, the detection of pericardial effusion in patients The rate has risen significantly, up to 8.4%), heart failure, shock and so on.

an examination

Related inspection

ECG heart sound map check

Heart sound is the mechanical vibration caused by factors such as myocardial contraction and relaxation, valve opening and closing, blood flow impacting the ventricular wall and aorta, etc., passing through the surrounding tissue to the chest wall, holding the ear against the chest wall or placing the stethoscope on the chest wall. Part, the sound heard. It is often easy to hear the first and second heart sounds, and sometimes in some cases the third or fourth heart sounds.

First heart sound: occurs at the beginning of the systole, with a low pitch and a long duration (about 0.15 seconds). Causes include ventricular muscle contraction, sudden closure of the atrioventricular valve, and subsequent ejection of blood into the aorta. The best auscultation site for the first heart sound is in the fifth intercostal space of the midline of the clavicle or on the right rim of the sternum.

The first heart sound enhancement: There are four factors that affect the strength of the first heart sound. 1, the anatomical lesion nature of the atrioventricular valve; 2, the rate of rise of ventricular pressure in the systolic phase; 3, the filling of the ventricular diastolic; 4, the location of the atrioventricular valve when the ventricle contracts. The first heart sound hyperthyroidism is common in mitral stenosis, because the blood flow through the stenotic mitral valve into the left atrium is obstructed, the left ventricular filling is less in the diastolic period, and the mitral valve is still in the maximum open state before the ventricular contraction. The free edge of the cuspidate leaves away from the valve orifice, and the free edge of the ventricular contraction moves to a greater extent, resulting in greater vibration, so the first heart sound of the apex is hyperthyroidism. The sound of the second heart sound of the mitral stenosis is hyperthyroidism and open, and the sound is the first heart sound of complete atrioventricular block.

The first heart sound is weakened: common and mitral regurgitation, due to mitral regurgitation, left ventricular blood flow, large amount of blood flowing into the left ventricle, left ventricular diastolic overfilling, so before contraction The free edge of the cusp is close to the mouth of the chamber, the fibrosis or calcification of the valve leaf is incomplete, the vibration of the mitral valve is small, and the first heart sound of the apex is relieved.

Second heart sound: occurs at the beginning of the diastolic phase, with a higher frequency and a shorter duration (about 0.08 seconds). The cause is the half moon valvular closure, the collision of the valves with each other, and the vibrations caused by deceleration of blood in the aorta and rapid decrease in pressure in the chamber. The best auscultation site for the second heart sound is in the aortic valve region on the right side of the second intercostal space and the pulmonary valve region on the left side.

The second heart sound enhancement: the intensity affecting the second heart sound is the size of the circulation resistance, the level of the blood pressure and the anatomical lesion of the semilunar valve. When the pulmonary circulation resistance is increased and the pulmonary blood flow is increased, the second heart sound pulmonary valve component is enhanced, and the second sound of the pulmonary valve region is hyperthyroidized, and generally does not pass to the apex. When the circulation resistance increases, the aortic pressure is high, the aortic valve is closed, and the aortic valve area is second, and can be transmitted to the apex. Therefore, the second heart sound of the apex is mainly the aortic valve component.

The third heart sound and the fourth heart sound: the third heart sound occurs 0.1 to 0.2 seconds after the second heart sound, the frequency is low, and its production is related to the rapid flow of blood into the ventricle to cause vibration of the ventricle and the valve, which is usually only heard in children because More easily transmitted to the body surface. The fourth heart sound is caused by atrial contraction, also known as atrial sound.

Differential diagnosis

1, : If the contents of the abdominal cavity less into the chest, and just stay in front of the heart, then can cause low heart blunt.

2, pericardial effusion: pericardial effusion can also cause heart sounds low blunt.

3, myocardial damage: myocarditis or asphyxia causes myocardial damage (there may be a doctor's acceptance of the standard of A's score is not accurate).

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