What Is a Phonocardiogram?

A phonocardiogram (PCG) is a graph that records the vibration of a heart sound into a time series vibration wave record. The echocardiograph records heart sounds and heart murmurs for clinical analysis, which helps to diagnose the etiology of heart disease and understand the mechanism of heart murmurs. Each cardiac cycle produces 4 heart sounds, but generally only the first heart sound and the second heart sound can be heard with a stethoscope. In some healthy children and young people, sometimes the third heart sound can be heard. Generally, it is difficult to hear the first heart sound with a stethoscope. Four heart sounds, and most normal people can record a low fourth heart sound on the heart sound map, so the heart sound map examination can make up for the lack of clinical auscultation.

Basic Information

Chinese name

Heart sound graph

Foreign name

phonocardiogram, PCG

Principle

Different frequency vibration waves are transmitted to the chest wall

Clinical significance

Helps diagnose the cause of heart disease

Heart sound diagram principle

The heart sound map is a graph obtained by recording the heart sound, that is, different vibration waves generated by the cardiac contraction and diastolic cycles with different frequencies transmitted to the chest wall. The electrocardiograph is mainly composed of four parts: a microphone, a frequency filter, an amplifier and a recorder. The microphone first converts the sound wave into electrical energy according to the pressure of the sound wave, and then the frequency filter attenuates some frequencies and prevents certain frequencies from passing. When the output frequency passes through the amplifier to increase the amplitude, it finally passes through the recorder. Record it as a graphic.

Heart sound examination method

1. Set the standard voltage and correct the height of the heart sound calibration curve to 1 cm by the calibration device.
2. Place the pickup on the traced part according to the heart sound or abnormal heart sound.
3. Frequency band: Select the appropriate frequency band according to the nature of the heart sounds to be recorded.
4. Decibel: If there is interference in the meeting, the noise will be missed if it is too small, so 4X6 decibel is appropriate.
5. Recording paper speed: Generally, 50mm / s is used to continuously record 5 to 10 cardiac cycles.
6. Choice of body position: The supine position is generally used, and sometimes special positions are required. For example, when the mitral valve prolapses, the left lateral position and the sitting position should be used.

Clinical Significance of Heart Sound Map

1. Record heart sounds and murmurs, which can be used as one of the basis of diagnosis. Compare or observe before and after treatment to understand the evolution of the disease.
2. Provide time stamps for cardiac function tests. Judge the occurrence time of the heart sound and the additional heart sound, provide time stamps for calculating the systolic time interval and the cardiac impedance blood flow chart, etc., so that the cardiac function status can be correctly analyzed.
3. Make up for the lack of auscultation, and help to solve the following problems: understand whether the normal heart sounds are hyperthyroid, splitting or other mutations; understand whether there are additional sounds and the time and nature of the occurrence of additional sounds; understand the shape and frequency of cardiac noise , Sound, time limit and the relationship with normal heart sounds, help to judge the nature of the murmur, and have an auxiliary diagnostic significance for the pathological changes of heart disease.
4. Heart sound maps have unique significance for cardiac function measurement and diagnosis of certain cardiovascular diseases, and cannot be replaced by other tests.

Heart sound map notes

1. Keep the environment quiet to reduce noise interference outside the body; stay away from electrical equipment and large power sources to avoid electrical interference.
2. The temperature should be appropriate to prevent over-cooling, so as not to cause muscle tremor due to cold and interfere with heart sound recording.
3. Calibrate the standard voltage so that the amplitude of the heart sound and the additional sound can be compared.
4. Perform cardiac auscultation before heart sound examination, place the pickup on the abnormal heart sound or the clearest part of abnormal heart sound, and then perform heart sound examination.