Modeling of hydraulic shock as one of the main risk factors of main arteries atherosclerosis in arrhythmias

Olga A. Germanova; Германова Ольга Андреевна; Vladimir A. Germanov; Германов Владимир Андреевич; Yuriy V. Shchukin; Щукин Юрий Владимирович; Andrey V. Germanov; Германов Андрей Владимирович; Maxim V. Piskunov; Пискунов Максим Владимирович; Andrey E. Burmistrov; Бурмистров Андрей Евгеньевич; Rinat Yu. Yusupov; Юсупов Ринат Юнусович; G. Galati; Галати Дж.

doi:10.17816/2072-2354.2020.20.3.43-48

Modeling of hydraulic shock as one of the main risk factors of main arteries atherosclerosis in arrhythmias

Authors: Germanova O.A.¹, Germanov V.A.¹, Shchukin Y.V.¹, Germanov A.V.¹, Piskunov M.V.¹, Burmistrov A.E.², Yusupov R.Y.², Galati G.³
Affiliations:
1. Samara State Medical University
2. Samara National Research University named after S.P. Korolev
3. Ospedale San Raffaele
Issue: Vol 20, No 5-6 (2020)
Pages: 43-48
Section: Clinical Medicine
URL: https://aspvestnik.ru/2410-3764/article/view/84463
DOI: https://doi.org/10.17816/2072-2354.2020.20.3.43-48
ID: 84463

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Abstract

Introduction. Atherosclerosis is the main reason of cardiocerebral events, its mechanisms and reasons are still being studied. Hydraulic shock in arrhythmias has not been studied before.

Aim. To perform the modeling of hydraulic shock as a risk factor of the main arteries in arrhythmias with original experimental model created by the authors.

Materials and methods. We created the original experimental model, it was used to imitate hydraulic shock in arrhythmias. It imitated the real arterial vessel and it allowed to make intra-vessel circulation of liquid in the regular rhythm and in arrhythmias (extrasystole).

Results. In extrasystolic arrhythmia imitation in the first post-extrasystolic contraction the speed of liquid flow was revealed to rise in mean value 158% in comparison with the regular rhythm.

Conclusion. In extrasystolic arrhythmia during the spread of the wave of the first post-extrasystolic contraction, blood flow accelerates and reflected waves and standing waves form. These hemodynamic changes are characterized by the term “hydraulic shock”. The use of our original experimental model helps to make the wide range of investigations and studies connected with intra-arterial hemodynamics in different conditions of functioning of cardiovascular system.

Keywords

hydraulic shock, extrasystole, intra-arterial blood flow modeling

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Introduction

Atherosclerosis is a multifactorial disease that predominantly affects large and medium-sized arteries. The causes and mechanisms of atherosclerosis are well understood [1–5]. However, among the generally recognized risk factors, indications of the possible onset of atherogenesis and its progression due to the mechanical effect of intravascular hemodynamic factors (hydraulic shock) on the inner arterial wall in rhythm disorders are unavailable [6–8]. For the first time earlier in our works, the possibility was indicated on the influence of the hydraulic shock wave of the first post-extrasystolic contraction and the pulse wave after a long pause between ventricular contractions in atrial fibrillation [9–14]. Thus, an increase was revealed in all the analyzed parameters of the kinetics of the arterial vascular wall in arrhythmias and a more severe course of the atherosclerotic process was indicated in the category of patients with certain cardiac arrhythmias [9–14].

In possible thromboembolic complications, a type IIIB plaque is morphologically the most unfavorable variant of an atherosclerotic plaque [4]. Is it possible to damage such a plaque by the impact of a hydraulic shock during the pulse wave passage in case of rhythm disorders?

Until now, no experimental studies are conducted on the simulation of a hydraulic shock leading to atherosclerosis of the main arteries in cardiac arrhythmias.

This study aimed to model the hydraulic shock as a risk factor for atherosclerosis of the main arteries in cardiac arrhythmias using an original device that we developed.

Materials and methods

The hydraulic shock was simulated for arrhythmias using an original device that we developed. The useful model was designed in such a way that imitated an arterial vessel and allowed for the intravascular circulation of fluid at the regular rhythm, as well as in cardiac arrhythmias (extrasystoles).

The basis of the device is a glass transparent tube of a rotameter with a length of 365 mm and a wall thickness of 2.5 mm, with an inlet and outlet with diameters of 20 and 16.5 mm, respectively. Thus, the tube design follows the natural course of the artery when the distal part is narrower than the proximal one (Fig. 1).

Fig. 1. The main tube of the device / Рис. 1. Основная трубка устройства

A fitting on the side of the proximal opening enabled the injection of dye using a syringe with a needle and installation of a metal holder with a silk thread attached to it and a piezoelectric crystal pressure sensor connected to an oscilloscope.

A closed system was created using flexible elastic tubes sealed through silicone gaskets to the inlet and outlet of the rotameter. The free ends of the elastic tubes were connected to an electric pump, which was powered by a 12 W battery.

The closed system of the rotameter was filled with a solution of glycerol with water corresponding to the viscosity of human blood to maximally stimulate the intra-arterial blood flow (Fig. 2).

Fig. 2. The main view of the device / Рис. 2. Общий вид устройства

This device was filed for a patent by the Russian Federation and a certificate of acceptance was obtained.

By regulating the pump operation, pulse waves were created in a closed-loop, which corresponded to hemodynamics during extrasystole, with different times of occurrence of the extrasystole ventricular systole in the cardiac cycle.

Various diaphragms with an outer diameter of 18 mm and a length of 20 mm with variable lumen were used to simulate the tube narrowing (i.e., to simulate an atherosclerotic plaque) (Fig. 3). The diaphragms are made of hard light plastic with a smooth surface. When installing, the diaphragms fully corresponded to the inner diameter of the rotameter tube.

Fig. 3. Diaphragms. a: stenosis 50%; b: stenosis 70% (the hole is located in the center of the diaphragm); c: stenosis 90%; d: stenosis 70% (the hole is located asymmetrically) / Рис. 3. Диафрагмы: a — стеноз 50 %; b — стеноз 70 % (отверстие расположено по центру диафрагмы); c — стеноз 90 %; d — стеноз 70 % (отверстие расположено асимметрично)

Figure 4 presents drawings of the two diaphragms with 70% stenosis with asymmetrical and asymmetric holes.

Fig. 4. Drawings of two diaphragms. a: stenosis 70% (the hole is located in the center of the diaphragm); b: stenosis 70% (the hole is located asymmetrically) / Рис. 4. Чертежи двух диафрагм: а — стеноз 70 % (отверстие расположено по центру диафрагмы); b — стеноз 70 % (отверстие расположено асимметрично)

Thus, the use of these diaphragms created a prototype of atherosclerotic plaques, namely hemodynamically significant ones with 70% stenosis (with a symmetric and asymmetric arrangement of atheromas), with 90% stenosis, and hemodynamically insignificant ones with 50% stenosis.

Results

The diaphragms were alternately installed with varying degrees of stenosis of the internal opening inside the rotameter tube. A metal holder with a 5 cm long silk thread was inserted through the fitting.

Then the operating mode of the electric pump was set, which corresponded to the passage of pulse waves in extrasystolic arrhythmia. Pressure waves, propagating through a closed system, transferred the energy of fluid movement to the oscillation of a silk thread. The movement of the silk thread was visually monitored. The occurrence of reflected waves from the rotameter wall, as well as standing waves, were recorded, and a significant decrease was visualized in the velocity of the fluid flow in the place directly behind the diaphragm, up to the reverse current (Fig. 5).

Fig. 5. The occurrence of reflected and standing waves during extrasystole in the first post-extrasystolic contraction (silk thread is the indicator) / Рис. 5. Возникновение отраженных и стоячих волн при экстрасистолии в первом постэкстрасистолическом сокращении (индикатор — шелковая нить)

At stage 2 of the experiment, a dye (blue ink) was injected into the tube of the rotameter using a syringe with a needle and the appearance of a turbulent fluid flow was monitored during the passage of the wave of the first post-extrasystolic contraction (Fig. 6).

Fig. 6. Turbulent fluid flow during the passage of the wave of the first post-extrasystolic contraction / Рис. 6. Турбулентный поток жидкости при прохождении волны первого постэкстрасистолического сокращения

The flow velocities were measured with each of the diaphragms installed when simulating the regular heart rate, with extrasystole and with extrasystole of the wave of the first post-extrasystolic contraction. Extrasystole was early, 0.20 s after the previously generated wave (Table).

Table. Basic device parameters / Таблица. Основные параметры устройства

Diaphragm type	D_tube, mm	d_d, mm	S_tube, mm²	S_d, mm²	(S_d/S_tube) · 100%	Constriction, %	V_{flow reg}, m/s	V_{flow ES}, m/s	V_{flow PES}, m/s
1	17.96	6	253.21	28.26	11.16	88.84	8.96	0.10	12.36
	18.01	10	254.62	78.50	30.83	69.17	3.24	0.04	5.26
	18.09	12.5	256.89	122.66	47.75	52.25	2.09	0.03	3.83
2	18.19	10	259.74	78.5	30.22	69.78	3.31	0.04	5.32

Note. D_tu_be: inside diameter of the tube in the section corresponding to the middle part of the diaphragm (in length); d_d: diameter of the diaphragm opening; S_tube: section area of the tube corresponding to the middle part of the diaphragm (in length); S_d: section area of the diaphragm opening; V_{flow reg} = D²_tube/d²_d: flow rate of the ideal fluid in the diaphragm opening when the flow rate in the uncovered section 1 m/s in case of regular heart rate; V_{flow ES}: flow rate of the ideal fluid in the diaphragm opening at the rate of flow in uncovered section 1 m/s in extrasystole; V_{flow PES}: flow rate in the diaphragm opening at the rate flow in uncovered section 1 m/s in extrasystole in the first post-extrasystolic wave; type 1 of the diaphragm: diaphragm with a symmetrical inner opening; type 2 of the diaphragm: diaphragm with an asymmetrical inner opening.

Примечание. D_тр — внутренний диаметр трубки в сечении, соответствующем середине (по длине) установленной диафрагмы; d_д — диаметр отверстия диафрагмы; S_тр — площадь сечения трубки, соответствующая середине (по длине) установленной диафрагмы; S_д — площадь сечения отверстия диафрагмы; V_{потока прав} = D²_тр / d²_д — скорость потока для идеальной жидкости в отверстии диафрагмы при скорости потока в неперекрытом сечении 1 м/с при правильном сердечном ритме; V_{потока ЭС} — скорость потока для идеальной жидкости в отверстии диафрагмы при скорости потока в неперекрытом сечении 1 м/с при экстрасистолии; V_{потока ПЭС} — скорость потока для идеальной жидкости в отверстии диафрагмы при скорости потока в неперекрытом сечении 1 м/с при экстрасистолии в первой постэкстрасистолической волне; 1-й тип диафрагмы — с симметричным внутренним отверстием; 2-й тип диафрагмы — с асимметричным внутренним отверстием.

When simulating extrasystolic arrhythmia in the first post-extrasystolic contraction, the velocity of fluid flow through the diaphragms increased by an average of 158% compared to the regular rhythm.

Conclusions

With extrasystolic arrhythmia during the passage of the pulse wave of the first post-extrasystolic contraction, the blood flow velocity increases, and the waves are reflected from the vessel walls, as well as standing waves are formed. These changes in hemodynamics are characterized by the concept of “hydraulic shock.” In our opinion, it can become a provoking factor of mechanical action with further damage to the atherosclerotic plaque, which has signs of instability (uneven heterogeneous surface with the inclusion of calcium, with hemorrhages in its structure, as well as hypoechoic or shielding areas), even if the stenosis is hemodynamically insignificant.

The experimental device that we developed enables implementation of a wide range of monitoring and studies related to intra-arterial hemodynamics under various conditions of the cardiovascular system functioning. Its use is advisable in the practice of a cardiologist and a cardiovascular surgeon when performing fundamental research, as well as scientific work in the field of normal, pathological physiology, and medical biophysics.

The authors declare no conflict of interest.