RU2725083C1 - Device and method for blood flow control of rotary pumps - Google Patents

Abstract

FIELD: medicine.SUBSTANCE: group of inventions refers to medical equipment, namely to extracorporal and implantable devices of mechanical circulatory support (MCS). MCS system includes a rotary pump with a pump control unit, an inlet main line of the pump for connection to the left ventricle of the heart and an outlet line of the pump for connection to the aorta through a vascular prosthesis. Pump inlet line comprises hydraulic resistance providing complete opening of inlet line lumen in systolic phase of cardiac cycle and reduced lumen of inlet main line into diastolic phase of cardiac cycle. In the passive version of the system the hydraulic resistance is made in the form of a mechanical valve of direct action. Active version of system uses hydraulic resistance with drive. Actuator drive may be connected to the drive control unit containing the cardiosynchronization unit connected to the ECG registration unit. Disclosed is a method of MCS, in which the disclosed MCS system is used extracorporally or intracorporally, in a mode of pulsation with a patient's heart.EFFECT: technical result consists in creation of physiological pulsating flow and pressure in aorta at constant preset pump speed, improvement of intra-pump hydrodynamics, minimization of blood injury due to reduction of area of blood contact with foreign surface of MCS system.8 cl, 1 tbl, 5 dwg

Description

FIELD OF TECHNOLOGY

This invention relates to medical equipment, namely to extracorporeal and implantable devices for mechanical support of blood circulation (MPC), based on the use of rotary pumps or non-pulsating flow pumps (NNP), can be used during auxiliary blood circulation.

BACKGROUND

The IPC method using NNP, built on the principle of centrifugal and axial devices, has taken a leading direction (94%) in world clinical practice for the treatment of patients with terminal heart failure. This is due to the significant advantages of these pumps compared to pulsating pumps, due primarily to their small size, high energy efficiency, greater reliability and resource.

At the same time, with rather optimistic forecasts for the use of this technology, the extensive clinical practice of using NNP has revealed a number of shortcomings that need to be revised in their management strategies.

In almost all clinical IPC systems built on the basis of implantable NNP, the main control strategy is based on maintaining the speed of the pump rotor as specified by the operator. At the same time, a flow with a small ripple is formed at the output of the pumps.

As shown by numerous clinical studies, an increase in pump speed is accompanied by non-surgical bleeding, pathologies of the heart valves and a decrease in myocardial unloading in comparison with the results of pulsating pumps. It is known that sufficient, adequate myocardial unloading is the main factor in restoring the contractility of one’s own myocardium.

The use of NNP in the mode of increased revolutions of the pump rotor is necessary to maintain systemic circulation, but often leads to a rarefaction at the pump inlet, which can cause tissue damage in the area of the inlet cannula, displacement of the interventricular septum, impaired right ventricular function, arrhythmia, cardiac ischemia and hemolysis.

On the other hand, when the lower limit of the NNP rotor speed is reached, a regime is established in which conditions arise in the diastolic phase to regurgitate blood flow from the aorta to the left ventricle. This mode creates unfavorable conditions for filling the right ventricle and, ultimately, leads to right ventricular failure. Another negative phenomenon associated with the use of NNP is the likelihood of developing aortic valve insufficiency. The work of HHP establishes a high transvalvular gradient, which affects the structure of cells and leads to the formation of an adhesion process, incomplete opening and thrombosis of AK.

To solve this complex of problems, a concept was proposed for converting the mode of predetermined constant revolutions of NNP into the mode of generating pulsating pulses synchronized with the work of one’s own heart (Pirbodaghi T, Asgari S. Cotter C. Physiologic and hematologic concerns of rotary blood pumps: what needs to be improved? // Heart Fail Rev 2014; 19: 259-266; Rotary pumps and diminished pulsatility: do we need a pulse? ASAIO J. 2013 Jul-Aug; 59 (4): 355-66; Kishimoto S, Date K, Arakawa M , Takewa Y, Nishimura T, Tsukiya T et al. Influence of a novel electrocardiogram-synchronized rotational-speed-change system of an implantable continuous-flow left ventricular assist device (EVAHEART) on hemolytic performance. J Artif Organs. 2014; 17 ( 4): 373-3770).

The implementation of this concept in known systems is based on the provision of a pulsating mode due to modulation of the NNP speed.

A device is known (US 7850594, B2), which contains an NNP with a drive providing a pulsating pump mode synchronously with the work of the heart. Moreover, the cardiac cycle is determined from the ripple index of the back EMF of the drive non-contact DC motor.

A device is known (WO 2009150893, A1), which consists of a detector of the reference signals of the cardiac cycle and an NNP control unit that controls the speed of the pump, synchronously with the cardiac cycle.

An implanted NNP is described that is connected to the body according to the “left ventricle – aorta” scheme (US 2017080138, A1). The device includes a pump drive and a sensor for electrophysiological signals, such as an electrocardiogram. At the same time, the sensor is connected to the pump drive for cardiosynchronized control of it in the mode of pulsation and counter-pulsation. Obtaining the parameters of the cardiac cycle in this case is based on averaging of two or more cardiac cycles.

Other MPC systems using NNP with cardiosynchronized modulation of the impeller rotation speed are described (US 9579435, B2, US 9345824, B2, US 8864644, B2). These systems contain auxiliary NNP connected according to the "ventricle - artery" scheme. The device includes a drive that periodically changes the rotation speed of the pump rotor according to the signals received from the electrocardiogram sensor, for synchronization with the heart cycle.

The main disadvantage of the devices described above is the periodic change in the speed of rotation of the impeller of the pump, synchronized with the frequency of the heart cycle, which can lead to an increase in shear stresses in the blood stream and, accordingly, to blood injury.

Another disadvantage of these devices is the inertia of the engine-pump system, which limits the obtaining of a given amplitude of flow and pressure in the systolic phase and leads to a phase shift of the pump ejection relative to the cardiac cycle, which significantly reduces the pulsating flow generation effect (S Bozkurt, van de Vosse FN, Rutten MCM Enhancement of Arterial Pressure Pulsatility by Controlling Continuous-Flow Left Ventricular Assist Device Flow Rate in Mock Circulatory System. J. Med. Biol. Eng. (2016) 36: 308-31). In addition, these devices require significant material and technical costs for the improvement of pumps and control units of existing MPC systems using NNP (axial and centrifugal pumps).

As a prototype, we have chosen a device and method for generating a pulsating blood flow of rotary pumps, presented in patent RU 2665178 C1.

The proposed IPC system includes at least one pump NNP with a control unit that maintains a constant speed of rotation of the impeller of the pump, as well as a channel for adjustable blood recirculation, connected in parallel to the input and output lines of the pump with a controlled valve. The valve is connected to its own control unit, receiving signals from the cardiosynchronization unit. The valve performs the function of regulating the blood flow, which consists in partial or complete closure, as well as opening the lumen of the blood recirculation channel in accordance with the phases of the cardiac cycle both in the mode of pulsation and in the mode of counterpulsation with the patient's heart.

Despite the efficiency of this system in terms of generating a pulsating flow, its main drawback is the need to introduce a recirculation loop, which further increases the area of contact of blood with a foreign surface. A controlled valve installed in the recirculation channel, when closed, requires relatively high power to operate and maintain a given gap at a relatively high blood pressure in the systole phase of the ventricle, which makes it limited to use this system in implantable pumps for long-term use.

SUMMARY OF THE INVENTION

An IPC system is proposed, including a rotary pump with a pump control unit that maintains a constant speed of rotation of the pump impeller, an input pump line for connecting to the left ventricle of the heart, and an output pump line for connecting to the aorta via a vascular prosthesis. The input line of the pump contains hydraulic resistance, providing full opening of the lumen of the input line in the systolic phase of the heart cycle and reducing the clearance of the input line in the diastolic phase of the cardiac cycle at a given constant speed of rotation of the impeller of the pump.

In the passive version of the system, the hydraulic resistance is made in the form of a direct-acting mechanical valve.

In the active version of the system used hydraulic resistance with a drive (or actuator).

The actuator can be used electromechanical or electro-pneumatic, or electro-hydraulic drive.

The actuator drive may be connected to a drive control unit comprising a cardiosynchronization unit connected to an ECG recording unit.

The cardiosynchronization unit can be connected to the pump control unit with the possibility of receiving signals of the reverse electromotive force of the pump control unit.

An IPC method is also proposed, in which the proposed IPC system is used extracorporeally or intracorporeally, in a mode of pulsation with the patient’s heart, connecting the pump inlet to the left ventricle of the heart, and the pump outlet through a vascular prosthesis to the aorta.

In the IPC method, a periodic resistance reduction mode can be used for a period of at least five cardiac cycles and with a duration of 0.5 to 1 minute.

The technical result achieved for the implementation of this group of inventions is:

- creating a physiological pulsating flow and pressure in the aorta at a constant given speed of the impeller of the pump while bypassing the left ventricle of the heart;

- improving the internal pump hydrodynamics, minimizing blood trauma and blood recirculation and stagnation zones that are potentially dangerous for thrombosis, by generating a pulsating flow in the pump without changing the pump speed, and also by reducing the area of blood contact with the foreign surface of the IPC system;

- the universality of the proposed IPC, in which a pump of any design can be used as a basic NNP.

- the possibility of implementing this invention for both extracorporeal and implantable IPCs, including implantable IPCs of long-term use.

A feature of these schemes for including passive or active hydraulic resistance in the pump input line is that the main energy is expended on the operation of this resistance at the time of low diastolic pressure in the ventricles of the heart. Therefore, the energy intensity of the active controlled resistance is quite low, which can significantly reduce its weight, size and energy characteristics, as well as implement the implantable version of the controlled resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the figures, where

in FIG. 1 shows a diagram of the generation of a pulsating flow in IPC systems in the bypass mode of the left ventricle of the heart when a variable hydraulic resistance is installed in the input line of the NNP in the form of a mechanical valve, which is a passive element of direct action with the complete opening of the input line to the systole of the heart and incomplete overlap of the input line, providing decrease in the amplitude of blood flow through the pump into the diastole of the heart;

in FIG. 2. shows a diagram of the generation of a pulsating flow in IPC systems in the bypass mode of the left ventricle of the heart when an actuator containing variable hydraulic resistance and a drive is installed in the input line of the NNP;

in FIG. 3 shows an experimental hydrodynamic bench;

in FIG. Figure 4 shows the pressure and flow chart obtained on a hydrodynamic bench when simulating heart failure and operating a pump without a pulsator, where P _ao is the pressure in the aorta, P _lp is the pressure in the left atrium, P _lp is the pressure in the left atrium, P _l is the pressure in the left ventricle, R _false - pressure in the left ventricle. Q _n - flow rate in the pump, Q _ao - flow rate in the aorta.

in FIG. Figure 5 shows the pressure and flow chart obtained on a hydrodynamic bench when simulating heart failure and operating a pump with a pneumatic pulsator, where P _ao is the pressure in the aorta, P _lp is the pressure in the left atrium, P _LV is the pressure in the left ventricle, Q _n is flow rate in the pump, Q _ao - flow rate in the aorta.

The following positions are indicated in the figures: 1 - pump (NNP), 2 - hydraulic resistance - direct acting mechanical valve, 3 - aorta, 4 - left ventricle of the heart, 5 - pump inlet pipe, 6 - pump outlet pipe with vascular prosthesis, 7 - actuator actuator, 8 - actuator, 9 - pump control unit, 10 - actuator control unit, 11 - cardiac synchronization unit, 12 - ECG registration unit, 13 - pneumatic actuator, 14 - aortic reservoir, 15 - atrium, 16 - peripheral resistance, 17 - flowmeter, 18 - pressure sensors.

SUMMARY OF THE INVENTION

The patented device is designed in two versions.

On the example of the “left ventricle – aorta” connection diagram shown in FIG. 1 and 2, we consider the principle of generating pulsed auxiliary circulation.

The circuit contains NNP 1 (axial or centrifugal) with drive 9, the left ventricle 4 of the heart and the aorta 3. In the first embodiment, FIG. 1 when connected to the left ventricle 4 of the heart of the NNP 1 in the input line 5 is installed variable hydraulic resistance, made in the form of a mechanical valve 2 direct action.

In a second embodiment of the circuit of FIG. 2, when connecting to the left ventricle 4 of the heart of the NNR 1, an actuator 8 is installed in the input line 5 containing variable hydraulic resistance 2 and a drive 7. The control unit 10 of the actuator 8 should ensure the complete opening of the input line 5 in the systolic phase of the left ventricle of the heart with increasing amplitude of the systolic blood flow in the aorta, in comparison with the non-pulsating operation of the pump, and the specified hydraulic resistance in the diastolic phase of the heart, which ensures a decrease in the amplitude of the diastolic volumetric blood flow at the output of the NNP. The actuator control unit 10 is connected to the cardiosynchronization unit 11, which receives signals from the ECG recording unit 12 or cardioverter pulses.

The cardiosynchronization unit 11 can be connected to the NNP control unit 9 to receive back emf signals.

The output line 6 of the NNP through the vascular prosthesis is connected to the aorta 3.

The work of this IPC scheme is as follows.

The input line 5 of the NNP 1 with actuator 8 is connected to the left ventricle 4 of the heart, and the output cannula 6 is connected through the vascular prosthesis to the aorta 3. Accordingly, at the output of the NNP 1 in the aorta 3, due to a change in the variable hydraulic resistance created by the actuator 8, a physiological pulsating flow and pressure. At the same time, due to an increase in the blood flow in the systolic phase of NNP 1, it is more effective to reduce the afterload of the ventricle of the heart as compared to the NNP operation in the standard non-pulsating mode, which is one of the main factors in the restoration of the myocardium during secondary circulation.

In addition, the operating mode of the NNP 1 - actuator 8 with a minimum blood flow into the diastole helps to eliminate dangerous conditions associated with the occurrence of rarefaction at the entrance of the NNP 1 and reverse regurgitation of the blood from the artery into the ventricle. An additional advantage of this invention is to increase the internal pump pulsation of blood, which is one of the most important factors in reducing the likelihood of thrombosis in the cavities of the pump.

The control unit 10 provides a mode of periodically reducing the hydraulic resistance with a frequency of from 30 seconds to 1 minute with a duration of at least a period of 5 cardiac cycles. This mode is introduced to create conditions conducive to the periodic functioning of the aortic valve, in order to exclude the likelihood of its insufficiency. Thus, when using the activator system, the mode of periodic opening of the input line can be implemented with an interval from 30 seconds to 1 minute, at least for five cardiac cycles.

The actuator can be used electromechanical, electro-pneumatic or electro-hydraulic drive. The drive should provide a card synchronization mode in accordance with the phases of the cardiac cycle (systole / diastole). To implement cardiosynchronization, both an electrocardiogram and cardioverter pulses or reverse emf signals of a rotary pump drive system can be used.

In FIG. 3 shows the hydrodynamic stand of the circulatory system, on which studies were carried out confirming the achievement of the specified technical result, the possibility of implementing the claimed purpose using the proposed system and method of the IPC.

The input line 5 of the NNP system 1 - actuator 8 is connected to the simulator of the left ventricle of the heart (IHL) 4, and the output line 6 is connected to the aorta and the aortic reservoir 14, and then, sequentially, to the peripheral resistance 16 and the left atrium 15, the output of which is connected to input IZHS 4. The actuator is an adjustable pneumatic resistance 2 and is controlled by synchronized with the operation of IZHS 4 pneumatic actuator 13.

Thus, during the systole IZHS 4, the actuator 2 completely opens the input line 5, reducing its hydraulic resistance and ensuring the complete passage through it of the fluid flow due to the systolic pressure of IZHS 4 and the operation of the NNP 1 at high speeds. In the diastolic phase of IZHS with a decrease in pressure in IZHS in the range of 0-3 mm Hg, actuator 2 partially blocks the input line 5, reducing the volumetric blood flow from NNP1 to the aorta 3.

Thus, systolic blood flow to the aortic reservoir (Q _ao ) is determined by the operation of IZHS 4 and the operation of the NNP1 - actuator 2 system, providing an increase in the amplitude of the aortic systolic flow at an increased speed of the NNP1 impeller. In the diastolic phase, due to the partial overlap of the input line 5, the amplitude of the aortic diastolic flow is reduced. As a result, due to an increase in the amplitude of the systolic flow and a decrease in the amplitude of the diastolic flow, under the conditions of modeling heart failure, the general blood flow in aorta 3 is restored to normal with a significant increase in pulse flow and pressure compared to the operation of NNP1 in the standard non-pulsating mode. The additional effect of increased systolic blood flow through the NNP1 system - actuator 8 contributes to a relatively greater decrease in afterload of IZhS 4.

The obtained effect of the pump 1 - actuator 8 system is shown in the diagrams of pressures (R _ao , R _ls , R _lp ) and flow _rates (Q _ao , Q _n ), in FIG. 4 and 5, measured using flow meters 17 and pressure sensors 18. As can be seen from the diagrams, the pulse pressure in the aorta R _ao during the operation of the NNP1 - actuator 8 system is significantly higher than the pulse pressure in the aorta 3 than when the NNP without the actuator 8 is used.

In addition, as can be seen from the obtained diagrams, the fluid flow in NNP1 Q _n during the operation of the NNP1 - actuator 8 system, the internal pump pulsation of the liquid flow is significantly higher compared to the NNP operation in non-pulsating mode, due to which the conditions for minimizing stagnation and recirculation zones are created dangerous for blood clots.

In this work, on the hydrodynamic bench, the operating conditions of the MPC systems were reproduced in modeling heart failure for adult patients with a decrease in the systemic release of IHD from 5 l / min (normal) to 2.5 l / min. Six tests were carried out using a ROTAFLOW pump (Maquet, Germany). The results of comparing the operation of NNP in the non-pulsating mode and in the operating mode of the NNP1 - actuator system (8) for modeling heart failure, obtained on a hydrodynamic stand, are summarized in the table, where P _ao is the pressure in the aortic reservoir 14, ΔР _ao is the aortic pressure pulsation, R _{false (} sys ₎ -systolic pressure in IZhS 2, P _{lp (sr)} - average pressure in the atrium 15, Q _ao - average blood flow in the aorta.

As can be seen from the table, the pulsation pressure ΔP _ao during the operation of NNP1 with actuator 8 in the aortic reservoir 2 increases compared to the operation of NNP1 when operating in non-pulsating mode almost 3 times during restoration of systemic blood flow. In this case, the pressure in the systolic phase, the pressure in IZhS 4 decreases by 1.4 times compared with the operation of NNP1 in non-pulsating mode, which indicates the effective unloading of the LV.

In another experiment, a hydrodynamic test bench reproduced the operating conditions of MPC systems when simulating heart failure when a mechanical valve 2 was installed in the input line 6 during NNP1 operation with a given increased rotor speed, a physiological aortic pressure pulsation was obtained within 25-30 mmHg with an internal pump flow pulsations - 6-8 l / min.

Claims (8)

1. The system of mechanical support of blood circulation, including a rotary pump with a pump control unit that maintains a constant speed of rotation of the impeller of the pump, the input line of the pump to connect to the left ventricle of the heart and the output line of the pump to connect to the aorta through a vascular prosthesis; however, the input line of the pump contains hydraulic resistance, providing full opening of the lumen of the input line in the systolic phase of the cardiac cycle and reducing the clearance of the input line in the diastolic phase of the cardiac cycle. 2. The system of claim 1, wherein the hydraulic resistance is in the form of a direct-acting mechanical valve. 3. The system according to claim 1, in which the hydraulic resistance with the drive is used. 4. The system of claim 3, wherein an electromechanical, or electro-pneumatic, or electro-hydraulic drive is used. 5. The system of claim 3, wherein the hydraulic resistance drive is coupled to a drive control unit comprising a cardiosynchronization unit connected to an ECG recording unit. 6. The system according to claim 5, in which the cardiosynchronization unit is connected to the pump control unit with the possibility of receiving signals of the reverse electromotive force of the pump control unit. 7. The method of mechanical support of blood circulation, in which the system according to any one of paragraphs. 1-6 are used extracorporeally or intracorporeally, in a mode of pulsation with the patient’s heart, connecting the pump inlet to the left ventricle of the heart, and the pump outlet through the vascular prosthesis to the aorta. 8. The method of mechanical support of blood circulation according to claim 7, in which the regime of periodic decrease in resistance is set for at least five cardiac cycles and with a duration of from 0.5 to 1 minute.

Images