RU2127544C1 - Method of determining pressure systolic gradient between right ventricle and pulmonary artery - Google Patents

Abstract

FIELD: medicine; cardiology. SUBSTANCE: method includes the following operations. During contrast echocardiography in single-dimensional mode trajectories of systolic movement of echocontrast gas microbubbles through pulmonary artery opening, along ultrasonic beam are recorded. Ultrasonic beam is set in compliance with single axis of right ventricle efferent tract and initial section of pulmonary artery so that difference between marked axis and direction of ultrasonic beam does not exceed 15 deg. Average value of speed of microbubble systolic ejection (V m/s) is determined by trajectories on basis of values of microbubbles systolic ejection speed measured in five cardiac cycles with good quality of visualization of trajectory systolic fragment. Trajectories are analyzed, and microbubble speed is measured within time interval equal to 0.43-0.7 of interval QT from origin of tooth Q of corresponding complex QRST of simultaneously recorded electrocardiogram. Gradient of systolic pressure between right ventricle and pulmonary artery (ΔP mm Hg) is calculated by formula: ΔP (mm Hg) = 4.8 x V² (m/s). EFFECT: simplified determination procedure, enhanced efficiency of cardiac pathology diagnostics. 1 dwg

Description

 The invention relates to medicine, in particular to cardiology.

 In clinical practice, for the accurate diagnosis of cardiovascular and pulmonary pathology, it is extremely important to determine the systolic pressure gradient between the right ventricle of the heart and the pulmonary artery (ΔP). Currently, there are two main ways of measuring ΔP, namely: heart sounding and Doppler echocardiography.

 Cardiac sounding is the direct and most accurate way to record pressure in the cardiac cavities and vessels. However, it refers to highly invasive, relatively life-threatening methods for patients. In this regard, its use is limited [2].

 Much more often, the Doppler echocardiography technique is used, which is absolutely safe and quite accurate, but requires the use of complex special equipment.

A known method for determining ΔP during Doppler echocardiography is that in the continuous or pulsed Doppler signal mode, the maximum direction of the ultrasound beam corresponds to the orientation of the axis of the initial part of the pulmonary artery and the outflow tract of the right ventricle. Then register the Doppler spectrum of systolic ejection through the mouth of the pulmonary artery. Taking into account the angle of divergence of the axes of the ultrasound beam and the pulmonary artery (usually in the range from 0 ^o to 20 ^o ), the maximum rate of systolic ejection (V "Doppler") is determined from this spectrum. Based on it, the desired ΔP is calculated by the simplified Bernoulli equation: ΔP "doppler" (mm Hg) = 4 • V "doppler" ² (m / s) [].

 However, the use of well-known techniques requires the use of expensive ultrasound equipment having a Doppler unit and a fairly wide range of computer processing of the received signals. This leads to a noticeable complication and a significant increase in the cost of the examination procedure.

 The technical result consists in simplifying the determination of ΔP, cheapening the cost of the examination and the equipment used, as well as increasing the efficiency of the diagnosis of cardiac pathology.

 The result is achieved by the fact that a method has been developed for determining the systolic pressure gradient between the right ventricle and the pulmonary artery during echocardiography, based on recording in one-dimensional mode the velocity of the echo-contrast microbubbles of gas through the mouth of the pulmonary artery, taking into account the duration of the QT interval of the electrocardiogram, recorded simultaneously with the echocardiogram.

 The method is as follows.

An echocardiographic examination of the heart is performed. In the one-dimensional mode of echocardiography, the M-strobe (axis of the ultrasound beam) is set in accordance with the direction of the single axis of the outflow tract of the right ventricle and the initial section of the trunk of the pulmonary artery so that the angle between the axis of the ultrasound beam and the single axis does not exceed 15 ^o .

 The necessary orientation of the M-strobe is ensured by monitoring its position with a two-dimensional echocardiographic mode in the transverse parasternal section of the heart at the level of the outflow tract of the right ventricle.

 Then, with the introduction of an echo contrast medium containing gas microbubbles, their movement is recorded during the cardiac cycle (Fig. 1).

On a one-dimensional contrast echocardiogram (K-EchoCG), the average value of the rate of systolic ejection of echo-contrast microbubbles through the mouth of the pulmonary artery (V "contrast", m / s) is determined based on the rate of their systolic ejection, measured by the usual method of estimating the speed of a moving object in M-mode with the construction of a tangent line (CD) to the studied area of the object (in this case, to the trajectories of the microbubbles) [1] in 5 cardiac cycles with good visualization of systolic fragments of the trajectories. Trajectory analysis and measurement of systolic velocity of microbubbles are made taking into account the electrocardiographic interval QT in the time interval AB, starting at a distance of 0.43 • QT seconds (point A) and ending at a distance of 0.7 • QT seconds (point B) from the Q wave of the corresponding complex QRST recorded simultaneously with K-EchoCG electrocardiogram (ECG). Systolic pressure gradient is calculated by the formula:
ΔP "contrast" (mmHg) = 4.8 • V "contrast" ² (m / s).

 The change in the coefficient "4.8" (instead of "4", as in the prototype) is due to the fact that the hydrodynamics of a phase-inhomogeneous gas-liquid (in this case, gas-blood) suspension, which is a mixture of ultrasonic contrast medium with blood, can significantly differ from hydrodynamics with respect to phase-uniform blood. Gas-liquid suspensions are phase-inhomogeneous non-Newtonian liquids containing gas and liquid components (phases), which can lead to significant differences in the laws of the speed of movement of the suspension from significantly more phase-homogeneous blood.

 Calculations of the pressure gradient performed using the old formula in the case of using contrast echocardiography in the mode indicated in this method do not coincide with the results of direct measurement of this gradient when cardiac sounding and its Doppler echocardiographic index are calculated. Such a mismatch is very significant and does not allow us to navigate in the real level of the discussed gradient to solve issues of clinical practice.

 It is also important that there is a fundamental difference between the methods for recording blood movement (by Doppler echocardiography in the prototype) and gas-blood suspension (by one-dimensional echocardiography in this method). These circumstances determined the need to change the conversion factor in the above formula.

 The absolute value of the correction coefficient equal to "4.8" was obtained by comparing the data of cardiac sounding and / or Doppler echocardiography with the parameters of contrast echocardiography obtained during examination of 81 patients.

 Studies have shown that the proposed value of the correction gradient provides the calculation of ΔP values closest to the level of the pressure gradient, measured directly by cardiac sounding and / or calculated by Doppler echocardiography.

 Example 1

Patient M., 7 years old, weighing 28 kg, height 122 cm, with complaints of shortness of breath during physical exertion, the presence of systolic noise detected along the left edge of the sternum, was determined by the systolic pressure gradient between the right ventricle and the pulmonary artery (ΔP).
Initially, during continuous wave Doppler echocardiography under the control of a two-dimensional image of the heart cross section at the level of the right ventricular outflow tract and the pulmonary artery mouth, the average value of the maximum systolic ejection rate (V "Doppler") was determined based on the maximum systolic ejection rate in 5 cardiac cycles , which amounted to 1.24 m / s.

Taking it into account, according to the simplified Bernoulli equation (ΔP "Doppler" mm Hg. = 4 • V "Doppler" ² m / s), the pressure gradient is calculated - ΔP "Doppler" = 4 • 1.24 ² m / s = 6, 15 mmHg Art.

 Then the patient underwent echoconstraining of the right heart cavities by introducing into the ulnar vein a 0.2% solution of hydrogen peroxide in sterile physiological solution in a total amount of 3 ml at a rate of 1 ml per second.

At this time, the axis of the M-mode ultrasound beam was set in accordance with the direction of the single axis of the right ventricular outflow tract and the initial section of the pulmonary artery so that the angle between the axis of the ultrasound beam and the single axis was 10 ^o .

 In the one-dimensional mode, the trajectories of gas microbubbles were recorded. The mean value of their systolic speed of movement (V "contrast") at the mouth of the pulmonary artery was determined, calculated on the basis of measurements of this speed in 5 cardiac cycles with good visualization of the systolic fragment of the motion paths of echo-contrast microbubbles.

 Velocity indices were determined by constructing a tangent CD to the most qualitatively recorded trajectories of microbubbles in the indicated analyzed zone of the heart, taking into account the QT interval of the electrocardiogram, taken simultaneously with the echocardiogram, in the time interval AB, starting at a distance of 0.43 • QT seconds (point A) and ending at a distance of 0.7 • QT seconds (point B) from the beginning of the Q wave of the corresponding QRST complex.

 In this case, the QT interval was 0.36 s.

 The time interval AB, during which the analysis of the motion paths of echo-contrast microbubbles and the determination of their velocity, began from point A, located at a distance of 0.15 s (0.43 • 0.36 s = 0.15 s), and ended at B, located at a distance of 0.25 s (0.7 • 0.36 s = 0.25 s) from the beginning of the Q wave of the corresponding QRST complex of simultaneously recorded ECG.

 V "contrast" in a given period of time was determined by constructing a tangent C-D to the most qualitatively recorded trajectories of microbubbles and corresponded to 1.05 m / s.

The systolic pressure gradient between the right ventricle and the pulmonary artery was calculated on the basis of V "contrast" according to the formula: ΔP "contrast" (mmHg) = 4.8 • V "contrast" ² (m / s) and amounted to 4, 8 • 1.05 ² m / s = 5.29 mmHg. Art.

 When cardiac sounding, ΔP corresponded to 5.5 mm RT. Art.

 The difference between the measured and calculated pressure gradients was: when using the known Doppler echocardiographic technique - 11.8%; when applying the proposed method - 3.8%.

 Thus, when using this method, the degree of deviation of the calculated indicator ΔP from the measured was less than in the case of using the known Doppler echocardiographic technique.

 In addition, its use did not require equipping with complex and expensive Doppler equipment.

 Example 2

Patient P., 7 years old, 124 cm tall, with systolic murmur heard at the left edge of the sternum, was determined systolic pressure gradient between the right ventricle and pulmonary artery (ΔP).
First, with pulsed Doppler echocardiography under the control of a two-dimensional image of the cross section of the heart at the level of the outflow tract of the right ventricle and the mouth of the pulmonary artery, taking into account the correction for the difference in the direction of the axis of the ultrasound beam and the axis of the pulmonary artery, equal to 17 ^o , when the control volume is located immediately above the disclosure level cusps of the pulmonary valve based on indicators of the maximum rate of systolic ejection in 5 cardiac cycles, the average value of the maximum speed of the syst emissions (V "Doppler"), which amounted to 0.648 m / s.

Based on it, using the simplified Bernoulli equation (ΔP "Doppler" mm Hg = 4 • V "Doppler" ² m / s), the pressure gradient was calculated: ΔP "Doppler" = 4 • 0.648 ² m / s = 1.68 mm Hg. Art.

 Then, the patient was echo-contrasted three times in the right cavities of the heart by introducing within 3 seconds 10 ml of a 0.9% sterile sodium chloride solution through a catheter installed in the right subclavian vein.

At this time, the axis of the ultrasound beam in the M-mode was set in accordance with the direction of the single axis of the right ventricular outflow tract and the initial section of the pulmonary artery so that the angle between the axis of the ultrasound beam and the single axis corresponded to 10 ^o .

 In the one-dimensional mode, the trajectories of gas microbubbles were recorded. The mean value of their systolic speed of movement (V "contrast") at the mouth of the pulmonary artery was determined, calculated on the basis of measurements of this speed in 5 cardiac cycles with good visualization of the systolic fragment of the motion paths of echo-contrast microbubbles.

 Velocity indices were determined by constructing a tangent CD to the most qualitatively recorded trajectories of microbubbles in the indicated analyzed zone of the heart, taking into account the QT interval of the simultaneously recorded echocardiogram, in the time interval AB, starting at a distance of 0.43 • QY seconds (point A) and ending at a distance of 0 , 7 • QT seconds (point B) from the beginning of the Q wave of the corresponding QRST complex.

 In this case, the QT interval was 0.31 s.

 The time interval AB, in the framework of which the analysis of the trajectories of the echo-contrast microbubbles was carried out and the determination of their velocity, began from point A, located at a distance of 0.13 s (0.43 • 0.31 s = 0.13 s), and ended at An ECG is simultaneously recorded at a distance of 0.22 s (0.7 • 0.31 s = 0.22 s) from the beginning of the Q wave of the corresponding QRST complex.

 V "contrast" in a given period of time was determined by constructing the tangent C-D to the most qualitatively recorded trajectories of microbubbles and corresponded to 0.694 m / s.

ΔP "contrast" was calculated based on V "contrast" according to the formula
ΔP "contrast" (mm Hg) = 4.8 • V "contrast" ² (m / s) and amounted to 4.8 • 0.694 ² m / s = 2.31 mm Hg. Art.

 Later, the patient underwent cardiac sounding with pressure measurement in his cavities. ΔP turned out to be equal to 2.0 mm RT. Art.

 The difference between the measured and calculated pressure gradients was: when using the known Doppler echocardiographic technique - 16.0%, when using this method - 15.0%.

 Therefore, the calculated ΔP indices when applying the known Doppler echocardiographic technique and when using the proposed method differed from the measured pressure gradient almost equally.

 However, the application of the proposed method did not require complicated expensive Doppler equipment.

 Example 3

Patient K., 14 years old, weighing 48 kg, height 166 cm, with systolic murmur recorded along the left edge of the sternum with a maximum of 3 intercostal space, determined systolic pressure gradient between the right ventricle and pulmonary artery (ΔP).
Initially, with continuous wave Doppler echocardiography under the control of a two-dimensional image of the heart cross section at the level of the right ventricular outflow tract and the pulmonary artery orifice, taking into account the correction for the difference in directions of the axis of the ultrasound beam and the axis of the pulmonary artery, equal to 12 ^o , based on the maximum systolic velocity ejection in 5 cardiac cycles was determined by the average value of the maximum speed of systolic ejection (V "Doppler"), which amounted to 0.656 m / s.

Based on it, according to the simplified Bernoulli equation (ΔP "Doppler" mm Hg = 4 • V "Doppler" ² m / s), the pressure gradient was calculated: ΔP "Doppler" = 4 • 0.656 ² m / s = 1.72 mmHg Art.

 Further, the patient underwent echoconstraining of the right chambers of the heart by dropwise injection of a 0.3% hydrogen peroxide solution in sterile physiological saline at a rate of 90 drops per minute in a total amount of 95 ml into the ulnar vein.

Under the control of a sectoral (two-dimensional) image, the axis of the ultrasound beam (M-strobe of the one-dimensional echocardiography mode) was set in accordance with the direction of the single axis of the outflow tract of the right ventricle and the initial section of the pulmonary artery so that the angle between the axis of the ultrasound beam and the single axis was 14 ^o .

 In the one-dimensional mode, the trajectories of gas microbubbles were recorded. The mean value of their systolic speed of movement (V "contrast") at the mouth of the pulmonary artery was determined, calculated on the basis of measurements of this speed in 5 cardiac cycles with good visualization of the systolic fragment of the motion paths of echo-contrast microbubbles.

 Velocity indices were determined by constructing a tangent CD to the most qualitatively recorded trajectories of microbubbles in the indicated analyzed zone of the heart, taking into account the QT interval of the electrocardiogram, taken simultaneously with the echocardiogram, in the time interval AB, starting at a distance of 0.43 • QT seconds (point A) and ending at a distance of 0.7 • QT seconds (point B) from the beginning of the Q wave of the corresponding QRST complex.

 In this case, the QT interval was 0.39 s.

 The time interval AB, during which the analysis of the motion paths of echo-contrast microbubbles and the determination of their velocity, began from point A, located at a distance of 0.17 s (0.43 • 0.39 s = 0.17 s), and ended at B, located at a distance of 0.27 s (0.7 • 0.39 s = 0.27 s) from the beginning of the Q wave of the corresponding QRST complex of simultaneously recorded ECG.

 V "contrast" in a given period of time was determined by constructing a tangent C-D to the highest quality recorded trajectories of microbubbles and corresponded to 0.688 m / s.

ΔP "contrast" was calculated by the formula:
ΔP "contrast" (mm Hg) = 4.8 • V "contrast" ² (m / s) and amounted to 4.8 • 0.688 ² m / s = 2.27 mm Hg. Art.

 Then the patient underwent cardiac sounding and measured the pressure in his cavities. ΔP turned out to be equal to 2.0 mm RT. Art.

 The difference between the measured and calculated indicators was: when applying the known Doppler echocardiographic technique - 14%, when using the proposed method - 13.5%.

 Therefore, the calculated ΔP indices when applying the known Doppler echocardiographic technique and when using the proposed method differed from the measured pressure gradient by almost a degree.

 However, the application of this method did not require equipping with complex and expensive Doppler equipment.

 Example 4

 Patient Z., 21 years old, weighing 72 kg, height 169 cm, with suspected atrial septal defect was determined systolic pressure gradient (ΔP) between the right ventricle and pulmonary artery.

Initially, with pulsed Doppler echocardiography under the control of a two-dimensional image of the cross section of the heart at the level of the outflow tract of the right ventricle and the mouth of the pulmonary artery, taking into account the correction for the difference in the directions of the axis of the ultrasound beam and the axis of the pulmonary artery, equal to 16 ^o , when the control volume is immediately above the level of opening of the valves of the pulmonary valve on the basis of indicators of the maximum rate of systolic ejection in 5 cardiac cycles, the average value of the maximum soon ti cardiac output (V "Doppler"), which amounted to 1.21 m / s.

Based on it, according to the simplified Bernoulli equation (ΔP "Doppler" mm Hg = 4 • V "Doppler" m / s), the pressure gradient is calculated - ΔP "Doppler" = 4 • 1.21 ² m / s = 5.86 mmHg Art.

 Next, the patient underwent echoconstraining of the right heart chambers by intravenous drip of a 0.3% hydrogen peroxide solution in sterile physiological saline at a rate of 120 drops per minute, in total 100 ml.

The axis of the ultrasound beam was set in accordance with the direction of the single axis of the outflow tract of the right ventricle and the initial section of the trunk of the pulmonary artery so that the angle between the axis of the ultrasound beam and the single axis was 15 ^o .

 In the one-dimensional mode, the trajectories of gas microbubbles were recorded. The mean value of their systolic speed of movement (V "contrast") at the mouth of the pulmonary artery was determined, calculated on the basis of measurements of this speed in 5 cardiac cycles with good visualization of the systolic fragment of the motion paths of echo-contrast microbubbles.

 Velocity indices were determined by constructing a tangent CD to the most qualitatively recorded trajectories of microbubbles in the indicated analyzed zone of the heart, taking into account the QT interval of the electrocardiogram, taken simultaneously with the echocardiogram, in the time interval AB, starting at a distance of 0.43 • QT seconds (point A) and ending at a distance of 0.7 • QT seconds (point B) from the beginning of the Q wave of the corresponding QRST complex.

 In this case, the QT interval was 0.45 s.

 The time interval AB, during which the analysis of the motion paths of echo-contrast microbubbles and determination of their speed, began from point A, located at a distance of 0.19 s (0.43 • 0.45 s = 0.19 s), and ended at the point B, located at a distance of 0.31 s (0.7 • 0.45 s = 0.31 s) from the beginning of the Q wave of the corresponding QRST complex of simultaneously recorded ECG.

 V “contrast” in a given period of time was determined by constructing the tangent C-D to the most qualitatively recorded trajectories of microbubbles and corresponded to 1.15 m / s.

ΔP "contrast" was calculated based on V "contrast" according to the formula:
ΔP "contrast" (mm Hg) = 4.8 • V "contrast" ² (m / s) and amounted to 4.8 • 1.15 ² m / s = 6.35 mm Hg. Art.

 Later, the patient underwent heart sounding and measured ΔP, which turned out to be equal to 7.0 mm RT. Art.

 The difference between the measured and calculated indicator reached: when using the known Doppler echocardiographic technique - 16.3%, when using the proposed method - 9.3%.

 Therefore, when using the proposed method, the difference between the calculated ΔP and the measured one turned out to be less than when using the known Doppler echocardiographic technique.

 However, the application of this method did not require equipping with complex and expensive Doppler equipment.

Clinical trials of the proposed method were performed during the examination of 81 people, comprising three groups of individuals:
1st - 12 people without heart disease;
2nd - 27 patients with non-closure of the oval window;
3rd - 6 patients with open ductus arteriosus,
4 patients with Ebstein's anomaly, 21 patients with atrial septal defect, 4 patients with interventricular septal defect, 7 patients with pulmonary stenosis.

 The state of the cardiovascular system in the examined was established during a comprehensive clinical and instrumental study using echocardiography, cardiac sounding, and radiopaque ventriculography.

 Echocardiographic examination was performed using Sonolayer SSH-40A (Toshiba, Japan), Sonoline CD (Siemens, Germany), Vingmed CFM-725 (Diasonics Sonotron, Germany).

 Indicators of a systolic pressure gradient between the right ventricle and pulmonary artery, obtained using the well-known Doppler echocardiographic technique, had a Pearson linear correlation coefficient (r) with a gradient measured by heart probing: for the 1st group - 0.85; for the 2nd group - 0.90; for the 3rd group - 0.91. The same coefficient for the indices of the marked gradient obtained by the proposed method, in comparison with the indices measured during cardiac sounding, corresponded to: for the 1st group - 0.79; for the 2nd group - 0.89; for the 3rd group - 0.88.

 Therefore, the linear correlation coefficient of the proposed method with respect to the direct measurement of ΔP during heart sounding is almost very close to the r known Doppler echocardiographic technique in the group of healthy individuals and in groups of patients with cardiovascular pathology of varying severity.

 There was no statistically significant difference (p> 0.05) between the average results of ΔP "Doppler" and ΔP "contrast" indicators, as well as each of them in comparison with the average result ΔP obtained by sounding of cardiac cavities in all three groups of patients persons.

 Also, in the indicated groups, when comparing the reproducibility of obtaining the ΔP indicator by two methods (using the known Doppler echocardiographic technique and using the proposed method) with the standard deviation variance estimation by the Fisher criterion with a confidence probability of 99%, there was no difference in data reproducibility.

 All of the above indicates good adequacy and high reliability of the proposed method. It is not inferior in accuracy to the well-known Doppler echocardiographic method for determining ΔP and, at the same time, it is carried out using less complex and cheaper equipment.

 When using this method, there were no serious and life-threatening complications, which is a significant advantage compared to a much more invasive technique for sensing heart cavities.

 The method can be recommended for widespread use in medical practice both in a hospital and in an outpatient setting.

Sources of information
1. Schiller N., Osipov M.A. Clinical echocardiography. M., 1993, S. 45 - 59 (prototype).

 2. Sidelnikov V. M., Krivchenya D. Yu., Babko S. A. Assessment of the state of the cardiovascular system according to instrumental research methods. // Cardiology of childhood / Ed. P.S. Moshicha, V.M. Sidelnikova, D. Yu. Krivcheni. Kiev, "Health", 1986, 42-50.

Claims (1)

A method for determining the systolic pressure gradient between the right ventricle and the pulmonary artery (ΔP mm Hg) during echocardiography, characterized in that the right chambers of the heart are echoed by gas microbubbles and the trajectories of their systolic movement through the mouth of the pulmonary artery are monitored in one-dimensional mode when the ultrasound axis is installed beam in accordance with the direction of the single axis of the right ventricular outflow tract and the initial section of the pulmonary artery trunk so that the angle between the ultrasound axis the pit ray and a single axis did not exceed 15 ^o , the average value of the speed of their systolic ejection through the mouth of the pulmonary artery (V m / s), determined on the basis of the speed of their systolic ejection, measured in 5 heart cycles with high-quality visualization of systolic a fragment of the trajectories of the movement of microbubbles, while the analysis of the trajectories and the measurement of the velocity of the microbubbles is carried out within a time interval equal to 0.43 - 0.7 of the QT interval from the beginning of the Q wave, respectively of the existing QRST complex of simultaneously recorded electrocardiograms, and the systolic pressure gradient is calculated by the formula ΔP (mmHg) = 4.8 • V ² (m / s).