Phonography

PHONOGRAPHY, the recording of heart sound phenomena, has developed over the last few decades. The sound phenomena occurring in the heart (tones, murmurs) cause chest wall vibrations of high frequency, which are detected and recorded by a special apparatus - the cardiophonograph. The main task in cardiophonography is to record only those vibrations caused by sound phenomena in the heart and to exclude all other chest wall vibrations occurring during heart contraction and caused mainly by the cardiac thrust. To eliminate these coarser and significantly slower chest wall vibrations, the receiving part of the cardiophonograph is constructed on the stethoscope principle. Heart tones can be recorded mechanically or electrically. Of the mechanical methods, the most common at present is the Ohm method. Heart sound phenomena detected by the stethoscope are transmitted through a rubber tube to a thin gelatin membrane with a small mirror attached to it. Receiving a beam of light from a source, the mirror reflects it, and the mirror's vibrations are recorded on light-sensitive paper. In electrical recording, sound phenomena are transformed into electrical signals and recorded by an electrocardiograph or an oscillograph. The first tone consists of two parts: atrial and ventricular, which in physiological conditions partially overlap. In pathological conditions (such as atrioventricular block), each of these parts is recorded separately. The recording of the first tone (Fig. 1) shows that it consists of initial vibrations caused by the muscular tone of atrial contraction, giving 2-3 small spikes, followed by main vibrations with 3-5 high spikes. The amplitude of these spikes, recorded on an electrocardiogram, is maximal, coincides with the closure of the atrioventricular valves, and characterizes the mechanism of this closure. After the main vibrations, there are variable final vibrations. The duration of the first tone, recorded by Ohm's method, is 0.22-0.25 seconds. The second tone consists of 2-3 spikes. Its duration is 0.06-0.1 seconds. The third tone is very rarely recorded. If present, according to Einthoven, it appears 0.13 seconds after the beginning of the second tone and 0.32 seconds before the beginning of the subsequent first tone. Its intensity is 200 times weaker than the first tone, with a duration of 0.02-0.03 seconds. Splitting of tones is easily discernible on the phonogram. In splitting of the first tone, the gallop rhythm is observed with two maxima of vibrations separated by vibrations of small amplitude (Fig. 2). The same is observed in splitting of the second tone.

In extrasystoles, the amplitude of vibrations corresponding to the first tone of the extrasystole, as well as the intensity of this tone, are variable. In ventricular extrasystoles, the amplitude of vibrations is always reduced. The phonogram is characteristic in atrioventricular block. On the phonogram, the atrial part of the first tone consists of two phases. The first phase, with smaller vibrations, is due to the muscular tone of atrial contraction. The second phase, with somewhat larger vibrations, is due to sound phenomena arising from the closure of atrioventricular valves when blood flow from the atria to the ventricles ceases. The duration of the isolated atrial part of the first tone is 0.20-0.22 seconds. Ventricular contractions are drawn on the phonogram without initial atrial vibrations. The duration of the ventricular part of the first tone is 0.18-0.20 seconds. The amplitude of the first tone's vibrations in atrioventricular block varies sharply. Sometimes, when atrial contraction closely follows ventricular contraction, there is a sharp increase in the amplitude of the main vibrations of the first tone, corresponding to the so-called 'pistol' tone (Fig. 4). In atrial fibrillation, the atrial vibrations of the first tone are absent on the phonogram. The amplitude of the first tone's vibrations varies (see Atrial fibrillation). Changes in sound phenomena in heart diseases are reflected on the phonogram. The most characteristic is the phonogram in stenosis of the left atrioventricular orifice. Atrial vibrations increase. This increase has a crescendo character due to the presystolic murmur. The main vibrations of the ventricular part of the first tone are also increased, especially the initial ones, which is caused by accentuation of the first tone. Splitting of the second tone is clearly visible on the phonogram. In mitral insufficiency, atrial vibrations are also somewhat increased. To the usual vibrations of the ventricular part of the first tone, two or three additional vibrations of gradually decreasing magnitude are added, caused by the systolic murmur. In congenital defects, the phonogram clearly shows the uniformity of the accompanying murmur: the vibrations recording the murmur have equal amplitude (see Heart diseases, congenital heart diseases). The phonogram is an objective record of heart sound phenomena. Despite the insufficient technical perfection of modern recording methods, phonography has made it possible to analyze the constituent parts of heart sound phenomena. By measuring the interval between the first and second tones on the phonogram, the duration of systole can be determined. Thanks to phonography, it has been possible to approach a more detailed study of the pathogenesis of various types of changes in heart sound phenomena (splitting, accentuations, murmurs, etc.).

Fig. 4. Phonogram, electrocardiogram in the first and third leads, and sphygmogram in complete atrioventricular block, recorded by Ohm's apparatus.

On the phonogram, the isolated atrial part of the first tone and the unevenness of the ventricular part of the first tone are clearly visible. In the case of the *pistol* tone, the vibrations have equal amplitude (see Heart diseases, congenital heart diseases). The phonogram is an objective record of heart sound phenomena. Despite the insufficient technical perfection of modern recording methods, phonography has made it possible to analyze the constituent parts of heart sound phenomena. By measuring the interval between the first and second tones on the phonogram, the duration of systole can be determined. Thanks to phonography, it has been possible to approach a more detailed study of the pathogenesis of various types of changes in heart sound phenomena (splitting, accentuations, murmurs, etc.).

L. Vogelson.