Phonocardiography is a special technique for graphically recognizing heart sounds and sounds using a device called a phonocardiograph. You can go through this study at any medical center where this device is available, and in the absence of the opportunity to come to the hospital, the procedure can be completed even at home.
Methods for checking the state of the heart
There are five main methods for examining the heart - auscultation, phonocardiography, echocardiography, electrocardiography and radiological techniques. Each of them is widely used in our area, so first of all you need to understand what their difference from each other is.
- Auscultation allows you to listen to all sounds that occur during the work of the heart, by applying a stethoscope to the chest.
- Phonocardiography allows you to record all heart murmurs and tones in the range of 15-1000 Hz, that is, it is an addition to the previous method.
- Echocardiography examines large vessels and the heart, based on the reflection of an ultrasound signal using a special transducer containing a crystal.
- Electrocardiography makes it possible to calculate the frequency and nature of heart rhythms, as well as to find out the features of the electrical processes that occur in it, thereby allowing timely diagnosis of heart rhythm disturbance.
- X-ray methods accurately determine the size and shape of the whole heart and its departments, indicate the presence of fluid in the pericardium and the state of blood circulation in the lungs, and also note the pulsation of the heart.
What is the procedure for?
As we have already found out, phonocardiography is an addition to auscultation that allows you to hear even those noises and tones that occur during the work of the heart and are not heard with a stethoscope. The phonocardiograph, with the help of which this study is carried out, allows you to catch the most poorly distinguishable sounds that are heard when the heart rhythmically pumps blood, heart valves work alternately and myocardial rhythmic contraction occurs. And in accordance with the duration of the recorded sounds, the intervals between them, the presence of changes in tones and additional clicks, one can judge the presence of certain heart pathologies.
Sound capture
Having learned that auscultation and phonocardiography allow you to hear various sounds that occur during the work of the heart, let's look at exactly what they are and what characteristics they have in order to accurately understand the whole necessity of the procedures:
- Sound power is calculated in decibels and represents the sound energy carried over 1 second per 1 cm 2 . It is proportional to the amplitude of sound vibrations, so the higher it is, the stronger the volume of heartbeats is stronger.
- The frequency of sound is calculated in hertz and represents the number of sound vibrations that occur in one second. A person can hear an average frequency of sound in the range of 20-20000 Hz.
- Pure heart sounds on phonocardiography are very rare and represent sound vibrations with a single sound frequency.
- Complex tones are obtained when a certain amount of pure tones are mixed, which happens much more often.
- Noises are multiple sound vibrations that are not related to each other by the correct ratio, so their presence most often indicates the presence of pathologies.
Who is assigned the study
Now let's find out who is prescribed phonocardiography (FCG) and with what symptoms the patient is sent for such a study. So, this procedure is necessarily prescribed for those who suffer from any defects of the valvular apparatus, congenital heart abnormalities and rheumatism, which is accompanied by inflammation of the organ.
In addition, patients who come to a cardiologist or therapist with complaints of shortness of breath during exercise or chest and heart pain, as well as those who have previously had myocardial infarction, have an enlarged organ, and those who has had an abnormal sound during examination with a stethoscope.
Advantages of the FCG
Some people think that if there is an opportunity to undergo auscultation, then the phonocardiography of the heart is no longer needed. However, this is not at all true, because this procedure has a number of advantages. And the most important of them is that such a study eliminates all subjective factors that may arise as a result of an auscultation technique of sound fixation. Indeed, in such a case, the doctor’s hearing, various extraneous noise, device malfunction may affect him, and during phonocardiography all the sounds are recorded by the machine, so here the result will be completely true and will allow you to give an accurate assessment of the strength and frequency of sound, duration of noise and tones, as well as intervals that occur between them. And if to conduct simultaneously FKG and ECG, then the result of the study will help the doctor see the clearest picture of the patient’s heart condition and prescribe him the appropriate treatment.
Disadvantages of FCG
However, all is not so good, because the phonocardiography method has not only advantages, but also significant disadvantages. And the main one is that the phonocardiograph has a very weak sensitivity of the device compared to the human ear, which is why weak sounds that a well-hearing doctor can distinguish during auscultation will not be visible on the phonocardiogram.
In addition, it will not be possible to determine the nature of the noise, even subjective, which is completely unique in some cases of heart valve pathologies. And finally, in the case of a displacement of the heart or dilatation and hypertrophy of its chambers, it is very difficult to find a place where you should place the microphone of the phonocardiograph.
Contraindications
According to cardiologists and therapists, phonocardiography is a procedure that has virtually no contraindications. In addition, this research method is completely safe and painless, so that it is prescribed even to those patients who are in serious condition. However, there are still several factors due to which the microphone of the phonocardiograph cannot be attached close to the chest, and they can become contraindications for this procedure.
These factors include severe obesity, as well as a violation of the integrity of the skin of the chest such as injuries, burns or wounds. In addition, FCG is not recommended for patients who drank coffee in the morning, as it increases pressure, which means that the result of the study will be unreliable.
Research process
A study on phonocardiography technique is a procedure that is carried out using a phonocardiograph consisting of a microphone and an amplifier that helps to hear all the sounds of the heart, a frequency filter that eliminates noise and makes the sound clearer, and a recording device, thanks to which we receive a phonocardiogram with a detailed description of the strength and frequency of sound, as well as all the noise and heart sounds.
To get the right result, before attaching six microphones to the chest, the doctor listens to the patient, and then puts him horizontally, installs the elements of the device on the chest and for ten minutes examines the work of the heart.
If necessary, the patient during the procedure may be asked to roll over on his side, hold his breath or take a deep breath. In parallel with the FKG, the patient is additionally given an ECG, which allows you to compare all the sounds recorded by the phonocardiograph with the electrical activity of the heart. The whole procedure in this case takes a maximum of 10 minutes.
Study of the work of the fetal heart
Also, using phonocardiography, the physiology of sound waves emitted by the child’s working heart in the mother’s womb can be examined to find out how the fetus develops and if there are any complications. In this case, the microphone is attached to that part of the abdomen of the pregnant woman where the fetal heart tones are best heard.
And when mom begins to give birth, the microphone is moved even lower, to the pubic symphysis. And in this case, the FCG is already being done from the very contractions to the birth, in order to know that they pass normally, focusing on the phonocardiogram indices, where it should be seen that the heart sounds are even and heard at regular intervals. The only thing when a woman is pushing and her contractions begin, the amplitude of the second tone increases, but then the height is again leveled.
But, if the fetal phonocardiography shows a heart murmur, an increase or decrease in the rhythm frequency, a change in the tone or strength of the sound or its splitting, this may indicate peritoneal asphyxiation, and then the gynecologist must do something to ensure that the birth continues normally.
Amplitude of sounds
The main factor that phonocardiography examines is the amplitude of sounds, the increase or decrease of which indicates the presence of various diseases in the patient.
- The appearance on the phonocardiogram of tones III and IV may indicate myocardial infarction or hypertension, while the former often signals heart failure, and the latter indicates an increased reduction of atria or ventricular hypertrophy.
- An increase in II tone may indicate pulmonary or arterial hypertension, and a decrease in it may indicate a deterioration in blood flow through the pulmonary artery or aortic valve insufficiency.
- Strengthening of the I tone can be observed with hyperthyroidism, anemia or stenosis of the bicuspid valve, and its weakening is about the expansion of the bronchioles, inflammation of the pericardium or exudative pleurisy of the lung on the left side, in addition, a weak first tone is in overweight people.
- An increase in the amplitude of the first tone may indicate mitral stenosis, and a decrease in it may indicate pathology of the heart muscle, decompensation of the heart, or a slowdown in atrioventricular conduction.
- Reducing the intensity of the I tone on the phonocardiogram can be caused by problems with the contractile function of the left ventricle. This phenomenon can often be observed in diseases such as chronic cardiac ischemia, myocardial dystrophy, rheumatic heart disease or cardiomyopathy.
Heart murmur
When decoding a phonocardiogram, recorded noise in the heart plays an important role, which can also be used to judge whether this human organ functions well.
- Presystolic murmur may indicate the development of mitral stenosis.
- Oval or diamond-shaped forms of noise on the phonocardiogram indicate the development of aortic stenosis.
- Diastolic murmur may portend the development of aortic insufficiency.
- Ribbon-like systolic murmur, which occurs at a low frequency, may indicate tricuspid valve insufficiency.
- Functional noises occur only in children and can indicate both the development of various pathologies and the health of the child, therefore, they should be judged only in conjunction with all other factors of FCG and ECG.