Heart sounds are brief, clearly audible vibrations of a certain intensity and frequency that are produced by the beating of the heart and the flow of blood. The mechanism of its formation is the sudden acceleration and deceleration of blood flow in the heart chambers during ventricular contraction, resulting in vibrations of the heart valves, the left ventricular wall and its surrounding tissues, the aortic wall and the pulmonary artery wall. There are four heart sounds that can be recorded on a cardiogram, namely the first, second, third and fourth heart sounds. The third heart sound is sometimes heard in some healthy children and young adults. The fourth heart sound is usually not heard, and can occasionally be heard in healthy individuals over the age of 40.
Common clinical abnormalities of heart sounds
I. Change in heart sound intensity
The heart sounds can be enhanced or diminished due to heart disease or extracardiac factors. The change may occur simultaneously or separately for both heart sounds. A significant change in the intensity of one heart sound is mostly due to heart disease.
1.Enhancement of the first heart sound
The patient is seated or supine, and when the patient is auscultated in the apical and precordial regions, if the first heart sound is heard with elevated loudness and tone, it is “La (La)-de (De) La-de” like with clapping. This is called first heart sound augmentation. The first heart sound enhancement can be pathological or physiological.
2.First heart sound is diminished
When the patient is seated or supine, if the first heart sound is low and vague during auscultation in the apical and precordial regions, it is called diminished first heart sound.
3.The first heart sound is not equal in strength and weakness
If the patient is seated or supine, and the first heart sound is heard in the apical region, if the intensity of the first heart sound varies, sometimes strong, sometimes weak, and not regular, the first heart sound is unequal. Most of the first heart sounds are due to arrhythmias, so the changes in heart rate and rhythm should be noted at the same time when auscultating. Commonly seen in.
4.Large cannon sound
Also known as cannonade sound. If the patient is supine and auscultated in the apical region, if the heart rate is extremely slow at 20-40 beats per minute, the rhythm is regular and the first heart sound varies in intensity, with occasional extremely loud first heart sounds, this is the “cannon sound”. This sound is unique to complete atrioventricular conduction. In complete atrioventricular block, all atrial excitation is blocked in the atrioventricular junctional area, while the part below the block has a slow self-rhythm. When the atrial and ventricular contractions are coupled, i.e., the atrial sound and the first heart sound are produced simultaneously, resulting in an extremely loud first heart sound.
5. Enhanced second heart sound
If the second heart sound in the aortic valve area is stronger than the second heart sound in the pulmonary valve area, with a “le(le)-da(answer)le-da” sound or a metallic tone, which can be transmitted to the pulmonary valve area and the apical part of the heart, it is called augmented second heart sound in the aortic valve area. If the second heart sound in the pulmonary valve area is soft and the second heart sound in the aortic valve area is strong, with a “le (le) – da (answer) le – da” sound, which is more limited and conducts to the aortic valve area and the third intercostal area at the left edge of the sternum, it is called the enhanced second heart sound in the pulmonary valve area. In determining the enhancement of the second heart sound in the pulmonary valve area or aortic valve area, factors such as age should be taken into consideration. The second heart sound of the pulmonary artery is louder than the second heart sound of the aorta in youth, while the opposite is true in old age.
6.Diminished second heart sound
The patient is placed in the supine position and auscultated in the aortic valve and pulmonary valve area respectively. If the second heart sound in the aortic valve area and the second heart sound in the pulmonary artery area is less loud, dull and loses its crispness, it is called a diminished second heart sound. The former is called the second heart sound of the aortic valve area, and the latter is the second heart sound of the pulmonary valve area.
Second, the nature of the heart sound changes
Pendulum rhythm: also known as fetal heart rhythm, fetal heart-like heart sounds. If the first heart sound loses its inherent low obtuse tone and is similar to the second heart sound, and the tachycardia occurs continuously, with a “ticking” sound like a pendulum, it is called pendulum rhythm. If the tachycardia is accompanied by a heart rate of 120 beats per minute or more and resembles a fetal heart sound, it is called a fetal heart rhythm.
The pendulum rhythm is an important clinical sign, if it appears, it often indicates serious illness, and is seen in acute myocarditis, acute myocardial infarction, heart failure, peripheral circulation failure, and also in paroxysmal tachycardia or hyperthyroidism and other tachycardias.
Split heart sound
Under normal conditions, the closure of the mitral and tricuspid valves (the two main components of the first heart sound) is not synchronized during ventricular systole, and the tricuspid valve closes slightly later than the mitral valve: the closure of the aortic and pulmonary valves (the two main components of the second heart sound) is also not synchronized during ventricular diastole, and the pulmonary valve closes slightly later than the aortic valve. Although the two main components of the first and second heart sounds are not synchronized, they are so close that they cannot be distinguished during auscultation and each becomes a single heart sound. If the time spacing between the left and right ventricular activity is increased compared to the normal asynchronous time spacing, the time spacing between the first and second heart sounds and the two main components is prolonged, then the phenomenon of one heart sound splitting into two parts during auscultation is called heart sound splitting.
Fourth, the third and fourth heart sounds and heart sound distant
1.Third heart sound
It is also called early diastolic and rapid filling sound. The patient is placed in the supine or left lateral position, and the patient is auscultated with a bell-type stethoscope in the apical region or slightly medial to it (the stethoscope is pressed lightly against the chest wall during auscultation), and a low-pitched, weak and dull, short sound called the third heart sound can be heard 0.12-0.20s after the start of the second heart sound. This sound is produced by the vibration of the ventricular wall during rapid filling of the ventricle.
If the sound is clearest at the end of expiration and disappears after deep inspiration and breath-holding, it is the third heart sound originating from the left ventricle. If the sound is clearer between the 3rd and 4th ribs at the left edge of the sternum and intensifies during inspiration, it suggests that the third heart sound is from the right ventricle.
The third heart sound is present only in the prone position and disappears when standing. It is not palpable on palpation. It is not palpable on palpation, but can be enhanced by exercise, abdominal pressure, or lifting of the legs. This sound can be enhanced by exercise, abdominal pressure, or lifting of the legs. Because the third heart sound is heavy, low and short, it is easy to produce auditory adaptation during auscultation, and can be heard at first, but gradually decreases or even cannot be heard. Therefore, when the third heart sound is heard, it must be repeatedly intermittently auscultated.
2.Fourth heart sound
Also known as atrial systolic sound, atrial sound. The patient is in supine or lateral position, and a bell-type stethoscope is used to auscultate in the apical region or tricuspid region as well as between the above two, and the stethoscope should be pressed lightly against the chest wall during auscultation. This sound is produced by the vibration of the atrial muscle in overcoming the end-diastolic pressure of the ventricle. It is also thought that in late ventricular diastole, after atrial contraction, blood rapidly enters the ventricle, causing a sudden increase in ventricular filling, resulting in vibration of the ventricular muscle or due to the sudden filling and expansion of the ventricle with incomplete compensation.
The fourth heart sound originating from the left atrium is apparent during exhalation and left lateral recumbency, while the fourth heart sound originating from the right atrium is apparent during inspiration. Because this sound is weak, it cannot normally be heard under normal circumstances unless the fourth heart sound is very loud and can only be recorded on a cardiogram. Care should also be taken not to mishear the first heart sound split or the post-first heart sound ejective karate as the fourth heart sound.
In the past, it was once thought that as long as the fourth heart sound could be heard, it was pathologic. In recent years, it has been found that the fourth heart sound can be present in healthy people of all age groups. However, the fourth heart sound is an extremely valuable sign for the diagnosis of coronary artery disease and left ventricular hypertrophy. Therefore, it is important to clarify the nature of the fourth heart sound when it is detected clinically. Clinically it can be seen as.
3. Distant heart sounds
When a physician performs cardiac auscultation with a stethoscope, if both the first and second heart sounds are weak, heavy, faint, and distant, the heart sound is considered distant. Patients are often forced to take a semi-recumbent position with their seats tilted forward, and if they can lie flat, the distant heart sound is more obvious. This sound is a characteristic sign of pericardial effusion and is seen in pericardial effusion due to various etiologies (tuberculosis, cancer, septic, rheumatic, and certain connective tissue diseases).
V. Additional heart sounds (tritone rhythm)
The presence of an additional heart sound in addition to the original two heart sounds. This is called an additional heart sound. This sound is important for the diagnosis of heart disease and the estimation of the condition. Among them, the systolic extra heart sound is also called systolic triplet rhythm and systolic ticking sound. Diastolic extra heart sounds include gallop rhythm, mitral valve opening beat sound, pericardial percussion sound, etc.
1, systolic extra heart sounds.
2.Diastolic extra heart sounds.