The first phonendoscopes were sheets of paper folded into a tube or hollow bamboo sticks, and many doctors used only their own hearing organ. But they all wanted to hear what was happening inside the human body, especially when it comes to such an important organ as the heart.
Heart sounds are sounds that are formed during the contraction of the walls of the myocardium. Normally, a he althy person has two tones, which may be accompanied by additional sounds, depending on which pathological process develops. A doctor of any speci alty must be able to listen to these sounds and interpret them.
Cardiac cycle
The heart beats at a rate of sixty to eighty beats per minute. This, of course, is an average value, but ninety percent of the people on the planet fall under it, which means that you can take it as the norm. Each beat consists of two alternating components: systole and diastole. The systolic heart sound, in turn, is divided into atrial and ventricular. In time, it takes 0.8 seconds, however, the hearthas time to contract and relax.
Systole
As mentioned above, there are two components involved. First, there is atrial systole: their walls contract, blood enters the ventricles under pressure, and the valve flaps slam shut. It is the sound of closing valves that is heard through the phonendoscope. This entire process lasts 0.1 seconds.
Then comes ventricular systole, which is much more complex work than the atria. First, note that the process lasts three times longer - 0.33 seconds.
The first period is the tension of the ventricles. It includes phases of asynchronous and isometric contractions. It all starts with the fact that the eclectic impulse spreads through the myocardium, It excites individual muscle fibers and causes them to spontaneously contract. Because of this, the shape of the heart changes. Due to this, the atrioventricular valves close tightly, increasing the pressure. Then there is a powerful contraction of the ventricles, and the blood enters the aorta or pulmonary artery. These two phases take 0.08 seconds, and in the remaining 0.25 seconds, blood enters the great vessels.
Diastole
Here, too, everything is not as simple as it might seem at first glance. The relaxation of the ventricles lasts 0.37 seconds and occurs in three stages:
- Proto-diastolic: after the blood has left the heart, the pressure in its cavities decreases, and the valves leading to large vessels close.
- Isometric relaxation: muscles continue to relax,the pressure drops even more and levels off with the atrial pressure. This opens the atrioventricular valves, and blood from the atria enters the ventricles.
- Ventricular filling: Fluid fills the lower chambers of the heart along a pressure gradient. When the pressure equalizes, the flow of blood gradually slows down, and then stops.
Then the cycle repeats again, starting from systole. Its duration is always the same, but diastole can be shortened or lengthened depending on the speed of the heartbeat.
Mechanism of formation of the I tone
No matter how strange it may sound, but 1 heart sound consists of four components:
- Valve - he is the leader in the formation of sound. In fact, these are fluctuations of the leaflets of the atrioventricular valves at the end of ventricular systole.
- Muscular - oscillatory movements of the walls of the ventricles during contraction.
- Vascular - stretching the walls of the main vessels at the moment when blood enters them under pressure.
- Atrial - atrial systole. This is the immediate beginning of the first tone.
Mechanism of formation of II tone and additional tones
So, the 2nd heart sound includes only two components: valvular and vascular. The first is the sound that arises from the blows of blood on the valves of the artia and the pulmonary trunk at the moment when they are still closed. The second, that is, the vascular component, is the movement of the walls of large vessels when the valves finally open.
In addition to the two main ones, there are also 3rd and 4th tones.
The third tone is myocardial fluctuationsventricles during diastole, when blood passively drains into an area of lower pressure.
The fourth tone appears at the end of systole and is associated with the end of the expulsion of blood from the atria.
I tone characteristics
Heart sounds depend on many causes, both intra- and extracardiac. The sonority of 1 tone depends on the objective state of the myocardium. So, first of all, the volume is provided by the tight closure of the heart valves and the speed with which the ventricles contract. Such features as the density of the cusps of the atrioventricular valves, as well as their position in the cavity of the heart, are considered secondary.
It is best to listen to the first heart sound at its top - in the 4-5th intercostal space to the left of the sternum. For more accurate coordinates, it is necessary to percussion the chest in this area and clearly define the boundaries of cardiac dullness.
2 tone characteristics
To listen to him, you need to put the bell of the phonendoscope over the base of the heart. This point is slightly to the right of the xiphoid process of the sternum.
The volume and clarity of the second tone also depends on how tightly the valves close, only now semi-lunar. In addition, the speed of their work, that is, the closing and oscillation of the risers, affects the reproduced sound. And additional qualities are the density of all structures involved in the formation of tone, as well as the position of the valves during the expulsion of blood from the heart.
Rules for listening to heart sounds
The sound of the heart is probably the mostsoothing in the world, after white noise. Scientists have a hypothesis that it is he who hears the child in the prenatal period. But just listening to the heart beat is not enough to detect damage to the heart.
First of all, you need to do auscultation in a quiet and warm room. The posture of the examined person depends on which valve needs to be listened to more carefully. This can be lying on the left side, upright, but with the body tilted forward, on the right side, etc.
The patient should breathe rarely and shallowly, and at the request of the doctor, hold his breath. In order to clearly understand where the systole is and where the diastole is, the doctor must, in parallel with listening, palpate the carotid artery, the pulse on which completely coincides with the systolic phase.
Heart auscultation order
After a preliminary determination of the absolute and relative cardiac dullness, the doctor listens to the heart sounds. It starts, as a rule, from the top of the organ. The mitral valve is clearly audible. Then they move on to the valves of the main arteries. First to the aortic - in the second intercostal space to the right of the sternum, then to the pulmonary artery - at the same level, only on the left.
The fourth point to listen to is the base of the heart. It is located at the base of the xiphoid process, but can move to the sides. So the doctor must check what the shape of the heart is, and the electrical axis to accurately listen to the tricuspid valve.
Complete auscultation at the Botkin-Erb point. Here you can hear the aorticvalve. It is located in the fourth intercostal space on the left side of the sternum.
Additional tones
The sound of the heart does not always resemble rhythmic clicks. Sometimes, more often than we would like, it takes bizarre forms. Doctors have learned to identify some of them only by listening. These include:
- Mitral valve click. It can be heard near the apex of the heart, it is associated with organic changes in the valve leaflets and appears only with acquired heart disease.
- Systolic click. Another type of mitral valve disease. In this case, its valves do not close tightly and, as it were, turn outward during systole.
- Perekardton. Found in adhesive pericarditis. Associated with excessive stretching of the ventricles due to internal moorings.
- Quail Rhythm. Occurs with mitral stenosis, manifested by an increase in the first tone, an accent of the second tone on the pulmonary artery and a click of the mitral valve.
- Gallop rhythm. The reason for its appearance is a decrease in myocardial tone, appears against the background of tachycardia.
Extracardiac causes of amplification and weakening of tones
The heart beats in the body all my life, without breaks and rest. So, when it wears out, outsiders appear in the measured sounds of its work. The reasons for this may or may not be directly related to heart damage.
Tones are enhanced by:
- cachexia, anorexia, thin chest wall;
- atelectasislung or part thereof;
- tumor in the posterior mediastinum, moving the lung;
- infiltration of the lower lobes of the lungs;
- bullae in lungs.
Weaken heart sounds:
- overweight;
- chest wall muscle development;
- subcutaneous emphysema;
- the presence of fluid in the chest cavity;
- effusion pericarditis.
Intracardiac causes of increased and decreased heart sounds
Heart sounds are clear and rhythmic when a person is at rest or in a dream. If he began to move, for example, climbed the stairs to the doctor's office, then this can cause an increase in heart sound. Also, an acceleration of the pulse can be caused by anemia, diseases of the endocrine system, etc.
A muffled heart sound is heard in acquired heart defects such as mitral or aortic stenosis, valve insufficiency. The aortic stenosis in the departments close to the heart brings its contribution: the ascending part, the arch, the descending part. Muffled heart sounds are associated with an increase in myocardial mass, as well as with inflammatory diseases of the heart muscle, leading to dystrophy or sclerosis.
Heart Murmurs
In addition to tones, the doctor can hear other sounds, the so-called noises. They are formed from the turbulence of the flow of blood that passes through the cavities of the heart. Normally, they shouldn't be. All noises can be divided into organic and functional.
- Organic appear when anatomical, irreversible changes in the valvularsystem.
- Functional noises are associated with impaired innervation or nutrition of the papillary muscles, an increase in heart rate and blood flow velocity, and a decrease in its viscosity.
Music may accompany heart sounds or may be independent of them. Sometimes the pleural friction noise in inflammatory diseases is superimposed on the heartbeat, and then you need to ask the patient to hold his breath or lean forward and auscultate again. This simple trick will help you avoid mistakes. As a rule, when listening to pathological noises, they try to determine in which phase of the cardiac cycle they occur, to find the place of the best listening and to collect the characteristics of the noise: strength, duration and direction.
Noise properties
Several types of noise are distinguished by timbre:
- soft or blowing (usually not associated with pathology, often in children);
- rough, scraping or sawing;
- musical.
Distinguished by duration:
- short;
- long;
Volume:
- quiet;
- loud;
- decreasing;
- increasing (especially with narrowing of the left atrioventricular orifice);
- increasing-decreasing.
Change in volume is recorded during one of the phases of cardiac activity.
Height:
- high-frequency (with aortic stenosis);
- low-frequency (with mitral stenosis).
There are some general patterns in auscultation of murmurs. First, they are well heard in placesthe location of the valves, due to the pathology of which they were formed. Secondly, the noise radiates in the direction of blood flow, and not against it. And thirdly, like heart sounds, pathological murmurs are best heard where the heart is not covered by the lungs and is tightly attached to the chest.
Systolic murmurs are best heard in the supine position, because the blood flow from the ventricles becomes easier and faster, and diastolic murmurs are best heard while sitting, because under the force of gravity, fluid from the atria enters the ventricles faster.
It is possible to differentiate noises by their localization and the phase of the cardiac cycle. If the noise in the same place appears both in systole and in diastole, then this indicates a combined lesion of one valve. If in systole the noise appears at one point, and in diastole at another point, then this is already a combined lesion of two valves.
