The first phonendoscopes were sheets of paper folded in a tube or hollow bamboo sticks, and many doctors used only their own hearing organs. 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 healthy person has two tones, which can be accompanied by additional sounds, depending on which pathological process develops. A doctor of any specialty must be able to listen to these sounds and interpret them.
Heart cycle
The heart beats with a frequency of sixty to eighty beats per minute. This, of course, is an average value, but ninety percent of people on the planet fall under it, which means that you can take it as the norm. Each stroke consists of two successive components: systole and diastole. Systolic heart tone, in turn, is divided into atrial and ventricular. In time it takes 0.8 seconds, but the heart manages to contract and relax.
Systole
As mentioned above, two components are involved here. Initially, there is atrial systole: their walls contract, blood under pressure falls into the ventricles, and valve flaps slam shut. It is the sound of the closing valves that is heard in the phonendoscope. This whole process lasts 0.1 seconds.
Then comes ventricular systole, which is a much more complex job than what happens with the atria. To begin with, we note that the process lasts three times longer - 0.33 seconds.
The first period is ventricular tension. It includes the phases of asynchronous and isometric contractions. It all starts with the fact that an eclectic impulse spreads across 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 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 main vessels.
Diastole
Here, too, is not so simple as it might seem at first glance. The ventricular relaxation lasts 0.37 seconds and occurs in three stages:
- Protodiastolic: after the blood leaves the heart, the pressure in its cavities decreases, and the valves leading to the large vessels close.
- Isometric relaxation: muscles continue to relax, pressure drops even more and aligns with the atrial. From this, the atrioventricular valves open, and blood from the atria enters the ventricles.
- Ventricular filling: according to the pressure gradient, the fluid fills the lower chambers of the heart. When the pressure is equalized, the blood flow gradually slows down, and then stops.
Then the cycle repeats again, starting with systole. Its duration is always the same, but diastole can be reduced or lengthened depending on the heart rate.
The mechanism of formation of I tone
No matter how strange it may sound, but 1 heart tone consists of four components:
- Valve - it is leading in the formation of sound. In fact, these are oscillations of the valves of the atrioventricular valves at the end of ventricular systole.
- Muscular - oscillatory movements of the walls of the ventricles during contraction.
- Vascular - stretching of the walls of the great vessels at the moment when blood enters them under pressure.
- Atrial - atrial systole. This is the immediate beginning of the first tone.
The mechanism of formation of II tone and additional tones
So, the 2 heart tone includes only two components: valvular and vascular. The first is the sound that arises from blood strokes on the valves of the artifact and pulmonary trunk at a time when they are still closed. The second, that is, the vascular component, is the movement of the walls of large vessels, when the cusps finally open.
In addition to the two main, distinguish between 3 and 4 tones.
The third tone is the fluctuations of the ventricular myocardium during diastole, when blood passively flows to the lower pressure area.
A fourth tone appears at the end of systole and is associated with the end of the expulsion of blood from the atria.
I tone characteristic
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 closing of the heart valves and the speed with which the ventricles contract. Such features as the density of the valves 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 tone at its apex - in the 4-5 intercostal space to the left of the sternum. For more accurate coordinates, it is necessary to percussion of the chest in this area and clearly define the boundaries of cardiac dullness.
II tone characteristic
To listen to him, you need to put a bell phonendoscope above the base of the heart. This point is located 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 they are half-moon. In addition, the speed of their work, that is, the closure and vibrations of the free ends, 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 cusps during the expulsion of blood from the heart.
Rules for listening to heart sounds
The sound of the heart is probably the most pacifying in the world, after white noise. Scientists have a hypothesis that it is he who is heard by the child in the prenatal period. But in order to detect damage to the heart, just listening to how it beats is not enough.
First of all, auscultation should be done in a quiet and warm room. The pose of the person being examined depends on which valve needs to be listened more carefully. This may be a lying position on the left side, vertically, but with the body leaning forward, on the right side, etc.
The patient should rarely and shallowly breathe, and at the request of the doctor to hold his breath. In order to clearly understand where the systole is and where the diastole is, the doctor must palpate the carotid artery in parallel with listening, the pulse on which completely coincides with the systolic phase.
The procedure for auscultation of the heart
After preliminary determination of absolute and relative cardiac dullness, the doctor listens to heart sounds. It starts, as a rule, from the top of the organ. The mitral valve is clearly audible there. Then go 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 to 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 be shifted to the sides. So the doctor should check what shape of the heart, and the electric axis, in order to accurately listen to the tricuspid valve.
Auscultation is completed at the point of Botkin-Erba. Here you can hear the aortic valve. It is located in the fourth intercostal space on the left at the sternum.
Extra tones
The sound of the heart does not always resemble rhythmic clicks. Sometimes, more often than we would like, it takes bizarre forms. Doctors learned to detect some of them only by listening. These include:
- The click of the mitral valve. It can be heard near the apex of the heart, it is associated with organic changes in the valve cusps and appears only with acquired heart disease.
- Systolic click. Another type of mitral valve disease. In this case, its wings are not tightly closed and, as it were, are turned outward during systole.
- Perekardton. It is detected with adhesive pericarditis. It is associated with excessive ventricular distension due to the formation of a mooring inside.
- The rhythm of the quail. It occurs with mitral stenosis, manifested by an increase in the first tone, an emphasis on the second tone on the pulmonary artery and a click of the mitral valve.
- The rhythm of the gallop. The reason for its appearance is a decrease in myocardial tone, appears against a background of tachycardia.
Extracardial causes of amplification and attenuation of tones
The heart beats in the body all my life, without interruptions and rest. So, when it wears out, then strangers appear in the measured sounds of his work. The reasons for this can be either directly related to heart damage, or not depend on it.
Tone enhancement is facilitated by:
- cachexia, anorexia, thin chest wall;
- atelectasis of the lung or part thereof;
- a tumor in the posterior mediastinum, moving the lung;
- infiltration of the lower lobes of the lungs;
- bullae in the lungs.
Attenuation of heart sounds:
- overweight;
- development of the muscles of the chest wall;
- subcutaneous emphysema;
- the presence of fluid in the chest cavity;
- effusion pericarditis.
Intracardial causes of amplification and weakening of heart sounds
Heart sounds are clear and rhythmic when a person is at rest or in a dream. If he set in motion, for example, climbed the stairs to the doctor’s office, this could cause an increase in heart sound. Also, the acceleration of the pulse can be caused by anemia, diseases of the endocrine system, etc.
A dull heart tone is heard with acquired heart defects, such as mitral or aortic stenosis, valve insufficiency. 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 murmur
In addition to tones, the doctor can hear other sounds, the so-called noises. They are formed from the turbulence of blood flow that passes through the cavity of the heart. Normally, they should not be. All noise can be divided into organic and functional.
- Organic appear when anatomical, irreversible changes in the valve system occur in the organ.
- Functional noise is 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.
Noises can accompany heart sounds, and can 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 perform auscultation again. This simple technique will help to avoid mistakes. As a rule, when listening to pathological noises, they try to determine what phase of the cardiac cycle they occur, find the place for the best listening and collect the characteristic of noise: strength, duration and direction.
Noise Properties
According to the timbre, several types of noise are distinguished:
- soft or blowing (usually not associated with pathology, often in children);
- rough, scraping or sawing;
- musical.
According to the duration, they distinguish:
- short;
- long;
By volume:
- quiet;
- loud;
- decreasing;
- increasing (especially with narrowing of the left atrioventricular foramen);
- increasing and decreasing.
The 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 noise auscultation. Firstly, they are well heard at the locations of the valves, due to the pathology of which they were formed. Secondly, 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 lies closely to the chest.
Systolic murmurs are best heard when lying down, because the flow of blood from the ventricles becomes easier and faster, and diastolic murmurs are sitting, because under gravity, fluid from the atria gets into the ventricles faster.
Noise can be differentiated by their location and 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, noise appears at one point, and in diastole - at another - then this is a combined defeat of two valves.