Phonocardiography belongs to the category of diagnostics of the functioning of the heart muscle. It has been used in official medicine for far from the first ten years, for which advanced scientists called the method obsolete. Today he is rarely attracted, but only in those cases when it comes to using phonocardiography in itself. If the patient was sent to do the classic electrocardiogram, then the technique often goes as a set to the main analysis, which can significantly expand the information content of the results.
During its activities, the heart makes many sounds that in ordinary life a person rarely notices. Good sensors help to hear them well, which pick up sounds during contraction of the myocardium, movement of the valves, blood flow. The technique for recording all internal sounds in medical terminology is briefly called FCG.
Initially, only a phonendoscope was used to evaluate the sound effects emanating from heart contractions. This way of listening is correctly called auscultation. But far from always by such a simple means it was possible to catch all the waves, which prompted experts to create more advanced equipment aimed at capturing the sounds produced.
After sound research methods were recognized, the authors of medical devices tried to adjust their ability to capture sounds under a common denominator. So there was percussion and some other branches of the diagnosis. But all of them could not absolutely guarantee the correctness of the suspicion of the attending doctor. The problem was that with classical auscultation, each doctor hears his patient in different ways due to the characteristics of personal hearing and perception.
Also, the human ear is unlikely to be able to catch a clear amplitude without amplifying devices, the intervals between weak sound vibrations and their exact duration. So the idea came up to make an independent unit that would take measurements completely objectively, relying only on science.
The basis for the improvements was the involvement of the device, where a special microphone was previously installed. All incoming information was almost instantly converted into a diagnostic value, which is a completely understandable graphic record. An experienced diagnostician or a narrow specialist working in the field of cardiology can decrypt it.
Initially, the methodology for assessing the health of the cardiovascular system was aimed at tracking down the location of a certain noise. A little later, experts learned how to directly relate it to the reduction of certain cardiac departments, which made it possible to diagnose various specialized ailments with increased accuracy.
One of the most important advantages of the survey is the ability to apply it with the same productivity in both adults and children. There are also models of devices that are tailored to the standards of the body structure of animals. They are installed in veterinary clinics.
Despite all the efforts of the technicians, the FKG did not become the main and only research option, after which the diagnosis could be accurately determined. Even experienced physicians still insist on undergoing auxiliary tests such as clinical tests or studying the structure of large vessels through computed tomography with contrast.
Also, problems are added by the fact that only the master who is well versed in auscultatory signs should deal with decryption. Be sure to ensure that the sensors are stacked in accordance with a strict prescription. And for this, you can not do without the skills of handling a phonendoscope.
The essence of the methodology
Human physiology provides for the formation of various sound waves, which have their own distinctive features. Sometimes it’s difficult to distinguish them even from a professional. But to deal with the power of sound characteristics and frequency is an order of magnitude easier.
Force is a value that is proportional to the amplitude of the generated wave. It is measured in decibels. The louder the resulting sound, the greater the force with amplitude displayed in the graphic result.
The frequency of the studied impulses is measured in Hertz. The value is the number of sound vibrations for a particular unit of time. The human ear can only capture a modest range at a level of 20 Hz to 20 thousand Hz. Everything that is outside the acceptable range can be covered, converted into graphic information only with special equipment.
A healthy heart muscle, along with all the accompanying actions, can make noise at about 150 Hz to 200 Hz, which is enough to hear it with a phonendoscope. The parameters of the noise product are altogether 1000 Hz.
But since most people who are sick come to see a cardiologist, they will not be able to recognize pathologies that respond with low-frequency vibrations without special equipment. Difficulties are added by the fact that from the main tone lines the doctor will hear on his own unless the first two are in the most successful scenario.
Against the background of other sound options, it is difficult to recognize the third and fourth heart sounds. They are most often the basis for confirming the suspicions of various diseases.
Schematically, all sounds recorded by the main "blood pump" are divided into two equal camps:
The first paragraph is a fairly loud, distinct and clear sound. With pathologies, in addition to tone, different noises are heard. They are not interconnected, and also have different strengths, frequencies.
Most of the noise along with tones can be detected even simply when using auscultation. The fact that their volume will vary at different points will help. But if the patient hears from the medical staff in the diagnostic room something like: "Prepare FKG," this indicates a doctor's suspicion regarding rare or complex anomalies. They can be both congenital and acquired in nature.
Thanks to the phonocardiograph it is possible to detect even minor effects, which are then converted into electrical signals in order to appear on paper in the form of specific graphs. The principle of operation is extremely similar to that characteristic of a traditional ECG.
The advantage of the phonocardiograph is the presence of many filters that are aimed at eliminating secondary noise, which are of no practical use for diagnosis. So it turns out to collect in the result only the most accurate basic data.
Due to the fact that the manipulation is non-invasive, it does not cause significant discomfort, excluding soreness. For this, she is loved by cardiologists who work with young children and even newborn babies.
For the procedure, special preparation of the patient, such as a special long-term diet, is not required.
Advantages and disadvantages
In addition to the absence of pain during the manipulation, it has several significant advantages. We are talking about objectivity, especially in situations where you need to correctly measure the intervals between the tone and the noise following it.
To do this, during the preparation, you just need to fix the sensors correctly by choosing the optimal point of contact.
But against the background of the numerous advantages of the method, it has several disadvantages. We are talking about the fact that the device does not always capture absolutely all vibrations. This is explained by the fact that in some cases a person’s ear is more susceptible to a certain number of sounds that the device simply does not perceive. Because of this, the unit sometimes misses important low-frequency vibrations that are not within its hearing range. This means that they can’t be found on the final schedule, but a specialist with a phonendoscope can perfectly catch them.
To avoid such an imbalance, the nurse must write in conclusion not only the results of the FCG itself, but also the initial examination by the doctor. Confusion is possible here, so doctors have established an unspoken rule for themselves. If the vibrations are not heard through the phonendoscope, but are visible on the phonocardiography, then preference is given to what the doctor heard himself. The only exception is a record of low frequencies. It follows that without prior auscultation, analysis is pointless.
Another clue is the definition of timbre, which is also not included in the competence of the machine. Instead, the specialist on duty deals with the issue. At the same time, the timbre still remains a subjective characteristic, which does not protect the patient from medical error. But without timbral miscalculations, it will not be possible to detect a number of valve defects.
To make the final presentation as true as possible, you must first listen to the chest to identify individual best points for listening. A preliminary assessment of audibility is an important preparatory measure due to the fact that with the development of diseases, the heart tends to change:
If you rely on standards without being tied to a specific victim, improper microphone position ensures reduced sound power.
Due to its safety, as well as the lack of radioactive load, FCG has recently been used to confirm or refute fetal hypoxia.
Phonocardiography is not a preventive diagnosis like an ECG. She is prescribed only strictly on the basis of concomitant indications, and the final decision is made by the attending doctor. The main reasons for issuing directions for testing are:
- rhythm disturbances;
The ability to dynamically monitor reproducible effects is highly regarded by both cardiologists and therapists. Sometimes the author of the direction is even a rheumatologist.
It is believed that an apparatus for conducting research is available in every public hospital or almost every medical center. But in practice, it turns out that not all private clinics are ready to purchase equipment, which is increasingly called obsolete. And in the clinics, the devices are written off, not receiving new ones in return.
In order to obtain more reliable data, it is better to arrange FCG in the morning after a person has slept well. No need to refuse breakfast, but drinking tea, coffee, alcohol is not recommended. The reason for this is the high chance of provoking tachycardia or other rhythm disturbances.
At the very beginning of the procedure, the victim is laid on the couch, and then periodically asked:
- hold your breath
- take a deep breath.
During the manipulation, the microphone will have to be moved to different parts of the chest, using the information obtained from the auscultation picture for the canvas. In rare cases, additional pharmacological preparations are called in to:
- dilate blood vessels;
- change heart activity.
If the prescription drug load is not provided, then you will have to spend about ten minutes on the reception. But if you need to attract drugs, you have to wait about half an hour. It is also worth considering the factor of whether phonocardiography is a pure procedure or whether it is connected to an ECG for increased clarity of results.
Decoding of the norm
A healthy muscle allows you to clearly hear the first and second tones without unnecessary devices. But not all ordinary people understand that it allows you to evaluate each of these parameters.
The first tone is formed when the valves are closed, which are localized between the ventricles with the atria. Closing the wings produces a fairly loud sound, which has the following distinctive features:
- medium frequency;
- amplitude - 25 mm;
- duration - 0.15 seconds.
It is not possible to capture the effect of each individual valve because of the speed of physiological response. Therefore, it is much more productive to try to catch immediately all the vibrations inherent in the closing of the valves, which overlap each other, creating a single whole - the first tone.
The second tone covers the parameters for closing the aortic valves along with the pulmonary artery. It will turn out better to hear if you move the microphone to the second intercostal space. We are talking about the right and left side, respectively, because it is these points that are most closely in contact with the heart base.
In contrast to the predecessor tone, in this case there is immediately a duet of components that come from each valve. Distinguish sounds will turn out just as the ear, and the device. The easiest way to listen to the following persons:
The first item fixes the closure of the aortic valve. It is much louder than the analogue, and its amplitude sometimes exceeds the sound of the valve from the pulmonary artery by about two times. The anatomically similar phenomenon is explained by the fact that the pressure in the aorta is an order of magnitude higher.
Difficulties arise at the stage of need to cover with the help of FCG the third and fourth tone. But if suddenly they made themselves felt, then this is not a reason to hang the patient’s label.
The third tone is sometimes heard in people of thin physique, as well as babies. It is collected on the basis of fluctuations in the walls of the ventricles. It is also closely associated with physical activity, manifesting itself after activity. Just listening to it is problematic, so recording is recommended in the low frequency range.
The fourth tone makes itself felt even less often than the third. But if it already appeared, then this is more likely to indicate a threatening anomaly.
Starting to study the results of tests handed out to hands, people are lost from medicine. They are not told anything by the configuration of the systolic discharge noise, and any comments regarding the change in the size of the amplitude lead to panic.
The last aspect really says that the victim has the likelihood of developing pathology, but here you need to consider each parameter in detail. If sound attenuation has occurred, which is recorded in the column "decrease in the intensity of the first tone", then usually the deviation indicates:
- mitral valve insufficiency;
- decreased contractile function of the left ventricle.
During the development of the first scenario, the victim will face the destruction of the valve cusps, which is the result of an extensive inflammatory process, or atherosclerosis. The desired sound wave is not fixed due to incomplete slamming of the valve “doors”.
Specific stenosis, which is characterized by an additional deposition of calcium salts, is capable of blocking the complete closure of the hole. Such development becomes the key to shortening the cusps of the mitral valve.
A decrease in contractile capabilities traditionally signals:
- chronic ischemia;
- myocarditis of a rheumatic type.
An experienced expert also necessarily adopts auxiliary factors, which also lead to an identical sound result, but have a mediocre attitude to cardiac activity. This is about:
- some types of pleurisy;
It rarely happens that the tone is even amplified. Classical primary sources of changes for the worse are called thyrotoxicosis, anemia, mitral stenosis. But with stenosis of both valves, the first tone splits into a pair of subtones. The same can be seen with the blockade of the legs of the bundle of His.
The second tone is also able to modify. So, an increase in amplitude can be seen in arterial or pulmonary hypertension. A similar clinical picture describes the compaction of aortic valve valves during the development of syphilis.
But sometimes this is quite normal if other tests do not confirm anything, and the patient himself is thin. But even in such people, a weakening of the second tone is found, which indicates aortic valve insufficiency and a decrease in pulmonary blood flow.
Things are a little more confusing with the third and fourth tones. Their deviations will tell about a much larger list of possible pathologies, among which hypertension, myocardial infarction, cardiosclerosis with concomitant heart failure are distinguished.
When the third and fourth tones are out of balance, they create a gallop rhythm. This is the first alarm bell that tells about the impending heart attack, myocarditis, pronounced hypertension.
But no matter how comprehensive the diagnostic result is, it is imperative to take note of the results of other examinations. Based on the material collected, together with the current complaints of the patient, the doctor will be able to more accurately determine the diagnosis.