CARDIAC SOUNDS — the sound manifestation of mechanical action of the heart determined at auscultation by the alternating short (percussions) sounds in a certain communication with phases of a systole and a diastole of heart. Graphic registration of T. page by means of a phonocardiography (see) showed that on physical. entities of T. pages are noise since consist of aperiodic fluctuations; their perception as tones is caused by short duration and a bystry deadening of swings. T. pages are formed in connection with oscillatory dvi-
of Riye. The diagrammatic representation synchronously registered phonocardiograms (below) and electrocardiograms (above) is normal: and — an initial component I of tone; — the central segment of 1 tone; in — a final component of 1 tone; And — an aortal component II of tone; R — a pulmonary component II of tone.
zheniye of valves of heart, chords, cardiac muscle and vascular wall. As well as any fluctuation, T. pages are characterized by intensity (size of amplitude), frequency (the number of fluctuations in 1 sec.) I duration. The listened loudness of tones is defined not only their amplitude, but also frequency (see Auscultation). Now most of researchers distinguish 4 normal (physiological) T. pages, from to-rykh I and II tones are listened always, III and IV tones are defined not always, is more often graphically, than at auscultation (r not.).
Origin of each of T. the page continues to be studied. The greatest recognition was gained by the ideas of an origin of tones which found confirmation in wide the clip, practice.
The I tone is listened as rather intensive sound over all surface of heart. As much as possible it is expressed in the field of a top of heart and in a projection of the mitral valve. The main fluctuations of the I tone are connected with closing of atrioventricular valves that was established still by A. A. Ostroumov in the thesis «About an origin of the first cardiac sound» (1873). As a part of the I tone allocate the following components for FKG: the initial low-amplitude low-frequency fluctuations connected with reduction of muscles of ventricles. Main — the central segment I of tone consisting of the fluctuations of big amplitude and more high frequency arising owing to closing of mitral and three-leaved valves. A final part — the low-amplitude fluctuations connected with opening of semi-lunar valves of an aorta and pulmonary artery and fluctuation of their walls. The general duration of the I tone fluctuates ranging from 0,07 to 0,25 sec. Assessment of intensity of the I tone can be made at its graphic registration, however precision measurement of amplitude is not performed in connection with impossibility of exact standardization of amplitude characteristics at a phonocardiography. On a top of heart amplitude is I tone 1,5 — 2 times more amlituda of the II tone. Easing of the I tone can be connected with decrease in sokratitelny function of a muscle of heart at a myocardial infarction (see), myocarditis (see), a rheumatic carditis (see Rheumatism) and with insufficiency of the mitral valve (see the Heart diseases acquired). The clapping nature of the I tone (increase and amplitudes and frequencies of fluctuations) is caused by consolidation of shutters of the mitral valve and shortening of their free edge at preservation of mobility at a mitral stenosis (see the Heart diseases acquired). Very loud («gun») I tone arises at a total atrioventricular block (see the Heart block).
The II tone is also listened over all area of heart, as much as possible — on the basis of heart: in the second mezhreberye on the right and to the left of a breast where its intensity is more, than the I tone. The origin of the II tone is connected generally with closing of valves of an aorta and a pulmonary trunk. Also low-amplitude low-frequency fluctuations resulting from opening mitral and a three-alignment
chaty valves are its part. In structure And tone allocate the first for FKG (aortal) and the second (pulmonary) components. Amplitude of the first is 1,5 — 2 times more than the second. The interval between them can reach 0,06 sec. what is perceived at auscultation as splitting of the II tone. It is connected with fiziol. asynchronism of the left and right heart; most often occurs at children. Important characteristic fiziol. splittings of the II tone its variability depending on breath («unstable splitting») is. At the heart of pathological, «fixed», splittings of the II tone with change of a ratio of aortal and pulmonary components increase in duration of a sphygmic phase and delay of intra ventricular conductivity lies. The loudness of the II tone at its auscultation over an aorta and a pulmonary trunk is approximately identical; if it prevails over any of these vessels, speak about accent of the II tone. Easing of the II tone is connected most often with destruction of shutters of the aortal valve at its insufficiency or with sharp restriction of their mobility at the expressed aortal stenosis (see the Heart diseases acquired). Strengthening, and also accent of the II tone over an aorta arises at arterial hypertension in a big circle (see arterial hypertension); strengthening, and also its accent over a pulmonary trunk — at pulmonary hypertensia (see Hypertensia of a small circle of blood circulation).
The III tone — low-frequency — is perceived at auscultation as a weak, deaf sound. Is defined on FKG on the low-frequency channel, a thicket at children and athletes. In most cases it is registered on a top of heart, and its origin is connected with fluctuations of a muscular wall of ventricles owing to their stretching at the time of bystry diastolic filling. This genesis of the III tone was for the first time described by V.P. Obraztsov (1900). Fonokardiograficheski in some cases distinguish left-and right ventricular III tone. The interval between II and III left ventricular tone makes 0,12 — 0,15 sec. Pathological III tone causes proto-or a mesodiastolic cantering rhythm (see Gallop a rhythm).
The IV tone — atrial — is connected with reduction of auricles. At synchronous record with an ECG the weak, low-frequency, seldom listened tone which is registered on the FKG low-frequency channel at children and athletes is registered at the termination of a tooth of R. Eto. Patol. The IV tone causes a presystolic cantering rhythm at auscultation. Merge
of III and IV patol. tones at tachycardia define as «summatsionny gallop».
A number of additional systolic and second sounds (clicks) is defined at a pericardis (see), ilevroperikardialny unions, a prolapse of the mitral valve.
Bibliography: Kassirsky G. I. A phonocardiography at the inborn and acquired heart diseases, Tashkent,
1972, bibliogr.; Nightingales V. V. and Kassirsky G. I. Atlas of a clinical phonocardiography, M., 1983;
Fitileva JI. M. Clinical phonocardiography, M., 1968; The hall -
d and to To. and In about l f. The atlas and the guide to a phonocardiography and adjacent mechanocardiographical methods of a research, the lane with it., M., 1964; L 1 and n C. Phonocardiographie, R., 1961; Schmidt-Voigt J. Atlas der klinischen Phonokar-diographie, Miinchen — B., 1955;
Z u-ckermann R. Herzauskultation, Lpz., 1965. G. I. Kassirsky.