MECHANOCARDIOGRAPHY (grech, mechanikos mechanical + kardia heart + grapho to write, represent) — a method of registration of the low-frequency fluctuations connected with mechanical action of the heart. Includes pulse recording of large veins and arteries (see. Sfigmografiya ), and also apekskardiogramma (see. Cardiography ).
In domestic medical literature the term «mechanocardiography» is used usually for designation of a physical method of definition of a number of parameters of the central hemodynamics on the basis of studying of ratios between the systolic (percussions) volume of heart, pulse pressure in arteries, the elastic resistance of vascular system and resistance to a blood-groove in capillaries. Such value of the term is connected with the name of the offered
H. N. Savitsky of the device — the mechanocardiograph, with the help to-rogo carries out registration of sphygmograms and essentially new (takhoostsillografichesky) technique of registration of the ABP parameters — minimum (diastolic), average, side systolic and final (see. Arterial pressure ). Pulse pressure necessary for calculation of a stroke output of heart for Bremzer's technique and Wound (Ph. Broemser, K. E. Ranke, 1933), is determined by Savitsky's technique as a difference between side systolic and minimal pressure that significantly specified result of calculation. Since the average of the ABP defined by M. across Savitsky, almost equally average hemodynamic pressure (see. Blood pressure ), the technique allows to determine as well the general peripheric resistance to a blood-groove — one of the major hemodynamic indicators (see. Hemodynamics , Blood circulation ).
The method matters both for diagnostic, and for scientific research, especially for studying of relative changes of indicators of the central hemodynamics at same inspected in dynamics. The method is not suitable for studying of the central hemodynamics at persons with a ciliary arrhythmia, large arteriovenous shunts and in the presence of valve heart diseases.
M.'s technique across Savitsky usually includes simultaneous registration of a takhoostsillogramma of arteries of a shoulder and the sphygmogram of a beam artery on the same hand for determination of all ABP parameters (fig. 1), and also definition of rate of propagation of pulse wave in arterial system for the purpose of calculation of a stroke output of heart and for assessment of elastoviscous properties of arterial walls.
A basis of manometrical system of the mechanocardiograph of Savitsky is the highly sensitive differential manometer, to-ry registers not absolute changes of pressure in a cuff, and dependence of change of pressure on time, during to-rogo there are these changes. The curve registered at the same time received the name «takhoostsillogramm».
For registration of a takhoostsillogramma for a shoulder of inspected impose the standard cuff for measurement of the ABP attached to the mechanocardiograph, in Krom it is reported with a compression chamber and with the manometrical part of the device having an exit to the chart recorder. Pressure in a cuff moves in the mode of a compression smoothly, with constant speed, at the same time compensation (counter-pressure) of pressure in vessels of a shoulder and their gradual compression is provided. At overpressure in a cuff, equal to end systolic pressure in a humeral artery, the last is pressed completely, and pulse on a beam artery disappears that serves as a signal to the termination of a compression. According to changes of transmural pressure in arteries of a shoulder in the period of a smooth compression there are changes of a gain of pulse volume of fabrics under a cuff for a cardial cycle that is shown by cyclic changes of pressure in a cuff, to-rye are perceived by the manometer and are registered.
On a takhoostsillogramma amplitude of the oscillations directed up characterizes the speed of a volumetric gain of fabrics under a cuff in the period of a systole. At a gradual compression of a shoulder amplitude of these positive waves increases in the beginning, then decreases, as well as on usual oscillograms (see. Oscillography , arterial). Unlike the last the takhoostsillogramma during a compression undergoes the most characteristic changes on diastolic pieces of a curve. At a small compression of a shoulder (it is lower than the level of the diastolic ABP) with the termination of systolic rush of blood the membrane of the differential manometer holds zero position therefore a diastolic part of a takhoostsillogramma practically does not deviate the horizontal line. At achievement in a cuff of pressure above the diastolic ABP the volume of the compressed artery in a phase of a diastole decreases, and the speed of its emptying increases that is reflected in a takhoostsillogramma emergence of negative waves, of to-rykh is considered to be the first corresponding to the diastolic ABP (a wave of M in fig. 1). Further build-up of pressure in a cuff leads to reduction of a diastolic gleam, and then and to full fall of walls of an artery at the end of a diastole that on a takhoostsillogramma is reflected emergence of «a wave of closing» — a knotty thickening in the ascending part of a negative wave, a cut usually corresponds also to the moment of achievement of the maximum amplitude of positive waves on a curve. This deformation of a negative wave (site C in fig. 1) corresponds to achievement of counter-pressure in a cuff, equal to the average ABP. Continuation of a compression is followed by gradual reduction positive and growth of negative waves of a takhoostsillogramma. Pressure, at Krom the negative wave reaches the maximum amplitude (a wave of B in fig. 1), corresponds to the side systolic ABP, exceeding to-rogo further a compression leads already to absorption of energy of hemodynamic blow owing to what intake of blood in an artery in the period of a systole and the speed of outflow of blood in the period of a diastole decreases, and amplitude of a takhoostsillogramma decreases both in systolic, and in diastolic phases. End systolic pressure is determined by disappearance of pulse on a beam artery (a point To on fig. 1); on a takhoostsillogramma its achievement accurately is not registered since, despite complete cessation of inflow of blood to the compressed artery, pulse fluctuations on a takhoostsillogramma continue to come to light (apparently, due to transfer fluctuations of volume of the fabrics located proksimalny cuffs).
For definition of rate of propagation of pulse wave on an aorta receptors of the sfigmografichesky sensors of the mechanocardiograph (presented in the device by highly sensitive manometers on certain canals of registration) have over sleepy and femoral arteries that allows to measure length of a vascular way between receptors taking into account the different directions of a blood-groove in vessels. Register synchronously both sphygmograms and measure a time lag of pulse on a femoral artery — time Δt (fig. 2). Rate of propagation of pulse wave is estimated as private from division of a way of a run of a wave on a vessel on a time lag. The research of this indicator is made for arteries of muscular type by the corresponding rearrangement of sfigmografichesky receptors. Determine time of a cardial cycle and its systolic and diastolic phases (fig. 2) by carotid sphygmograms.
Calculation of systolic (shock) volume of heart (V) is made on a formula:
where 0,6 correction factor; 1333 — coefficient of transfer of the values of pressure expressed in mm of mercury., in other dimension — in / sm*sek 2 ; 1,06 — density of blood in g/cm 3 ; Q — the cross-sectional area of an aorta in cm 2 ; Rb — side systolic pressure in mm of mercury.; Rd — diastolic pressure in mm of mercury.; and — rate of propagation of pulse wave in cm/sec.; S, D and S — respectively time of a systole, diastole and complete cardial cycle in sec.
As well as all other known methods of studying of the central hemodynamics, a method M. has the merits and demerits. The technical simplicity and not injury of the procedure allowing to make any necessary number of repeated researches, and also lack of influence of the procedure on a hemodynamics belongs to advantages. Shortcomings of a method consist in impossibility to precisely define absolute values of a stroke output of heart, calculation to-rogo is connected with approximate data on the cross-sectional area of an aorta and usually with a margin error, the defined rate of propagation of pulse wave since speed depends not only on the elastic tension of walls of arteries, but also on their consolidation (e.g., at atherosclerosis). The specified errors increase at elderly people. On a nek-eye to data (Y. N. Vasilev, 1978), the accuracy of calculation of a stroke output of heart increases during the definition of average rate of propagation of pulse wave for arteries of elastic and muscular types.
Bibliography: Bayevsky R. M. Physiological measurements in space and a problem of their automation, M., 1970, bibliogr.; Savitsky H. H. Biophysical bases of blood circulation and clinical methods of studying of a hemodynamics, L., 1974, bibliogr.
Yu. T. Gunner; V. I. Belkevich (tekhn.).