What Are the Common Causes of Abnormal Heart Sounds?

Basic Information

Chinese name

Abnormal heart sounds

Abnormal heart sounds

1. The first heart sound (S1)

The first heart sound occurs during ventricular systole, marking the beginning of ventricular contraction. The first heart sound has a low tone and a relatively long duration, which lasts 0.12 to 0.14 seconds. The auscultation is most clear in the apical region and between the apical region and the left margin of the sternum. Causes include contractions of the ventricular muscles, sudden closure of the atrioventricular valve, and subsequent vibrations into the arteries.

2. The second heart sound (S2)

The second heart sound occurs at the beginning of the isovolumic diastole, marking the beginning of the ventricular diastole. The second heart rate is higher and the duration is shorter, which is mainly related to the vibration caused by the closing of the aortic and pulmonary valves.

3. The third heart sound (S3)

The third heart sound appears in the early stage of ventricular diastole and is a low-frequency, low-amplitude vibration. It can be heard in some healthy young people, especially children with thin chest walls and patients with left heart failure. The third heart sound is related to the sudden filling of blood from the atrium into the ventricle, causing the ventricular wall and papillary muscles to vibrate.

4. The fourth heart sound (S4)

The fourth heart sound appears in the late stage of ventricular diastole and is related to atrial contraction, also known as atrial sound. In a normal heart, no sound is generally heard during atrial contraction, but the fourth ventricular sound can be heard when the compliance of the left ventricle wall decreases and the atrial contraction is abnormally strong.

Abnormal heart sounds

1. Heart sound intensity changes

In addition to cardiac factors such as chest wall thickness and lung air volume, the main factors affecting the intensity of heart sounds are ventricular contractility, cardiac output, valve position and activity, etc., which can increase or decrease heart sounds.

(1) The first heart sound

Enhancement: During auscultation in the apical and anterior regions, if the sound and pitch of the first heart are heard to increase, and those with a slap sample, the first heart sound is enhanced. Common in mitral stenosis. In addition, increased myocardial contractility and tachycardia, such as anemia, high fever, hyperthyroidism, and complete atrioventricular block can also lead to enhanced first heart sounds.

Weakening: When auscultating in the apical and anterior regions, if the first heart sound is dull and vague, the first heart sound is weakened. It is common in mitral regurgitation, prolonged PR interval of ECG, pericardial effusion, myocarditis, cardiomyopathy, myocardial infarction, heart failure and aortic insufficiency.

Variations in strength: When auscultating in the apical area, if the first heart sound is strong and weak when there is no regularity, it means that the first heart sound is strong or weak. Common in atrial fibrillation, atrial flutter, ventricular tachycardia, complete atrioventricular block and so on.

(2) Second heart sound

Systemic and pulmonary circulation resistance and pathological changes of the semilunar valve are the main factors affecting the second heart sound change. The second heart sound has two main parts, the aortic valve (A2) and the pulmonary valve (P2).

Enhancement: Auscultation is performed in the aortic valve area and the pulmonary valve area respectively. If the second heart sound in the aortic valve area is stronger than the second heart sound in the pulmonary valve area, the tone is metallic and can be transmitted to the pulmonary valve and the apex of the heart, that is, the aortic valve. The second heart sound of the pulmonary valve area is enhanced; if the second heart sound of the pulmonary valve area is stronger than the second heart sound of the aortic valve area, it is more localized and conducts to the aortic valve and the third rib space of the left margin of the sternum, which is the second heart sound enhancement of the pulmonary valve area . Enhancement of the second heart sound in the aortic valve area: due to the increased pressure in the aorta and the strong closing of the aortic valve. It is clinically common in diseases such as hypertension, aortic sclerosis, and aortic insufficiency. The second heart sound in the pulmonary valve area is enhanced: it is caused by the increased pressure in the pulmonary artery and the strong closure of the pulmonary valve. It is clinically seen in diseases such as pulmonary hypertension, mitral valve stenosis, emphysema, atrial septal defect, ventricular septal defect, and open ducts. .

Weakening: Auscultation is performed in the aortic valve area and the pulmonary valve area respectively. If the second heart sound is weakened, the tone is dull, and the crispness is lost, the second heart sound is weakened. The second heart sound in the aortic valve area is weakened: it is caused by the reduced pressure in the aortic valve area. It is clinically common in arrhythmia, aortic valve insufficiency, aortic valve stenosis, hypotension, and severe anemia. The second heart sound of the aortic valve and pulmonary valve area is weakened at the same time: seen in pleural effusion, emphysema, pericardial effusion, myocardial infarction, heart failure, etc.

2. Change in heart sound properties

In severe myocardial disease, the first heart sound loses its original nature and weakens significantly, and the second heart sound also weakens. Both properties are similar and can form a monophonic rhythm; if the heart rate increases, auscultation looks like a pendulum sound, also known as a pendulum rhythm Found in large-scale acute myocardial infarction and severe myocarditis, but also in paroxysmal tachycardia or hyperthyroidism, etc., often suggesting a serious condition.

3. Heart sound split

Splitting of the heart sound means that the distance between the two main components of the first heart sound or the second heart sound is extended, and it can be heard at auscultation and split into two sounds.

(1) First heart sound split

Auscultation at the 4th and 5th intercostal space of the left margin of the sternum or the lower end of the sternum. If the first heart sound is heard for a long time and is vague, it sounds like a "sound-to" sound, which is the first heart sound split, often by the mitral valve And tricuspid valve closing time are not synchronized. It is common in mitral stenosis, pulmonary hypertension, atrial septal defect, and complete right bundle branch block.

(2) Second heart sound split

Auscultation was performed in the aortic valve area and the pulmonary valve area, respectively. If you hear the - -like sound, it is the second heart sound split, often caused by the aortic valve and the pulmonary valve closing time are not synchronized. Clinically common in pulmonary stenosis, pulmonary hypertension, mitral regurgitation, ventricular septal defect, complete left bundle branch block and so on.