Heart assistance or back-up device

Abstract

The invention relates to a device for the temporary circulatory assistance or back-up of the heart (13) of a patient (12), comprising: - a linear actuator (10) configured to move a membrane (70) in a chamber (11) in such a way as to cause a pulsatile fluid flow able to support the activity of the heart of said patient, which flow is characterized by a succession of phases of aspiration and phases of ejection of the fluid, - a control unit (40) configured to control the actuator (10) and to control the movement of the membrane (70), which control is carried out taking into account the input data from an ECG signal of the patient (12), - the control unit (40) is configured to determine a time offset AT between the instant TR at which the QRS complex of the ECG signal is detected and the instant at which an ejection phase is initiated.

Description

Description Title: Device for assisting or supplementing the heart. [Technical field. [1] The present invention relates to a device for assisting or supplementing the heart. [2] The term assistance is used when a portion of the blood arriving at the heart is withdrawn while the term replacement is used when all, or almost all (> 90%), of the blood arriving at the heart is withdrawn by the heart's replacement device. [3] It concerns the technical field of devices used for extracorporeal circulatory assistance / supplementation which maintain haemodynamics compatible with life, in the context of a failure of the cardiac muscle threatening the patient's life prognosis, following acute or chronic heart failure (coronary insufficiency and / or cardiovascular disease, or other associated pathology). State of the art. [4] The heart's function is to distribute blood throughout the body to transport oxygen and nutrients necessary for the functioning of the various organs and to transport metabolic waste to its CO elimination organ. 2 the lungs, urea and creatinine to the kidneys. It is divided into two parts, the right heart which receives venous blood (depleted in oxygen) through the vena cavae and which sends it through the right ventricle to the pulmonary artery to the respiratory system (where it is recharged with oxygen and discharged with CO 2 ), and the left heart, which receives oxygenated blood through the pulmonary veins and ejects it through the aorta to the various organs. Contractions of the heart muscle (pump) generate a pulsating blood flow in the body. They allow continuous control of blood flow to the physiological needs of the body and each organ. [5] In the presence of cardiac muscle failure (in the case of myocardial infarction for example), it is necessary to temporarily supplement the pumping function of said heart muscle by a mechanical circulatory assistance system, the objective being to gain time for the heart to recover. [6] Among the circulatory assistance systems currently in use, extracorporeal circulation devices (abbreviated as CEC) are known, which allow bypassing the failing heart by using a servo-controlled pump placed outside the body, which receives blood at the level of the vena cavae and injects it at the level of the aorta (thoracic), to mechanically generate a continuous blood flow compatible with the vital needs of the body. The main objective sought during circulatory assistance is to regulate the pumped flow in complete adequacy with the physiological needs of the patient, the latter varying continuously. [7] As a power source, a console or central unit includes a mathematical model designed from physical laws governing the movement of a fluid in a closed circuit. This circuit is generally composed of a pump, a heat exchanger, a flow meter, a blood gas and electrolyte analyzer, a pressure sensor as well as biocompatible materials such as tubing, arterial and venous cannulae, venous reservoir, oxygenator, arterial filter. Usually a centrifugal or peristaltic pump is used as the arterial head pump and four other peristaltic pumps are used for cardiotomy suction, cardiac chamber circulation, cardioplegia administration and a backup pump. If a failure persists, ECMO (Extracorporeal Membrane Oxygenation) or ECLS (Extracorporeal Life Support) is indicated.These systems are simpler than a standard CEP and are transportable, with a usage time of several days, unlike conventional CEP. Indeed, unlike conventional CEP, both ECMO and ECLS are maintained until the patient's cardiopulmonary recovery or as a bridge before a transplant. [8] Although these systems have demonstrated their effectiveness in their conventional circulatory assistance functions, they are not perfectly satisfactory insofar as the control of the blood flow generated is not not optimal in view of the patient's physiology. The current survival rate for certain addressed pathologies does not exceed 30%. Blood circulation may be imperfectly synchronized, which leads to an increase in left ventricular afterload which opposes the "contraction" (ejection) of the cardiac muscle in systole. A tired or failing heart will tire even more if the aortic pressure is high during systole: the aortic valves open poorly, the afterload increases and the end-diastolic pressure of the left ventricle also increases with a lack of ejection. There is also a leakage of the mitral valve which can cause irreversible pulmonary edema. This is one of the main limitations of prior art systems. [9] Patent document EP3818996A1 describes an assistance device comprising a linear actuator whose piston is movable in translation in a chamber. The translation of the piston ensures the displacement of a membrane and the aspiration and ejection of blood. A controller synchronizes the control of the actuator according to the patient's cardiac cycle. In particular, the blood ejection phase is delayed from the detection of the QRS complex of the ECG signal. The time shift is however determined in a particularly complex manner and does not make it possible to avoid an increase in the left ventricular afterload.

[0010] The present invention aims to overcome the aforementioned drawbacks. In particular, one objective of the invention is to propose an assistance device whose operation avoids, at each cardiac cycle, an increase in the left ventricular afterload. Another objective of the invention is to optimize the real-time synchronization of the ejection phases with regard to the physiology of the patient in order to maintain hemodynamics compatible with the life of said patient. Yet another objective of the invention is to propose an assistance device whose control is simple to implement and particularly reliable. The invention also aims to enable better performance and increased precision of the pumping cycles. Presentation of the invention.

[0011] The solution proposed by the invention is a device for temporary circulatory assistance or replacement of a patient's heart, comprising: - a linear actuator configured to move a membrane in a chamber so as to cause a pulsating flow of fluid capable of supporting the activity of the heart of said patient, which flow is characterized by a succession of suction phases and ejection phases of the fluid, - a control unit configured to drive the actuator and control the movement of the membrane, which control is carried out by taking into account input data from an ECG signal of the patient, - the control unit is configured to determine a time shift AT between the instant TR where the QRS complex of the ECG signal is detected and the instant where an ejection phase is initiated,

[0012] Furthermore, the control unit is configured to determine, at each cardiac cycle identified in the ECG signal, the AT time offset by the following formula: AT= E + K. (Freal - Fret) where: • E is a time value; • K is a coefficient such that K>0; • Frei corresponds to the patient's measured heart rate; • F re corresponds to a reference heart rate.

[0013] The time shift AT (corresponding to the triggering of the artificial systole) as defined by the formula according to the invention, makes it possible to simply and reliably ensure that at each cardiac cycle the fluid (blood) is not ejected during the natural systole, but once it is finished and the aortic valve is closed. The ventricle is thus protected from any overload. In addition, taking into account the patient's heart rate as a triggering parameter for the artificial systole makes it possible to optimize the real-time synchronization of the ejection phases with regard to the patient's physiology. The applicant has found that this device is particularly efficient and makes it possible to achieve a very precise pulsating flow, in perfect harmony with the patient's physiological needs.The observed performances concern all or part of the following improvements: improvement of the patient's condition generally reducing the patient's stay in hospital, improvement of the circulatory situation and organ perfusion. thanks to the characteristics of pulsating fluid flow which induces better microcirculation of vital organs, better vascular compliance, a reduction of inotropic drug support where necessary, an increase in cerebral oxygen saturation.

[0014] Other advantageous features of the apparatus that is the subject of the invention are listed below. Each of these additional features can be considered alone or in combination with the remarkable features defined above. Each of these additional features contributes, where appropriate, to the resolution of specific technical problems defined further in the description and in which the remarkable features defined above do not necessarily contribute. These additional features may be the subject, where appropriate, of one or more divisional patent applications:

[0015] Device according to claim 1, wherein the control unit (40) is configured to drive the actuator (10) by taking into account input data further coming from an aortic pressure signal, the value of E differing depending on whether a dicrotic wave is detected or not in said aortic pressure signal.

[0016] According to one embodiment, the control unit is configured such that if a dicrotic wave is detected in the aortic pressure signal, then E = (TD-TR), where TR is the time at which the R wave of the QRS complex is detected and TD is the time at which the dicrotic wave is detected.

[0017] According to one embodiment, the control unit is configured such that if no dicrotic wave is detected in the aortic pressure signal, then E takes a fixed value.

[0018] According to one embodiment, the value of E is fixed.

[0019] According to one embodiment, the value of E is set between 0.22 seconds and 0.27 seconds.

[0020] According to one embodiment, the reference heart rate F re f is between 50 bpm and 90 bpm.

[0021] According to one embodiment, the value of the reference heart rate Fret is pre-parameterized and fixed.

[0022] According to one embodiment, the value of the reference heart rate Fret is variable and / or adjustable.

[0023] According to one embodiment, the value of the coefficient K is between 0.01 and 0.05 and the unit of which is a unit of time squared (in particular the second or one of these fractions and / or multiples).

[0024] According to one embodiment, the value of the coefficient K is pre-parameterized and fixed.

[0025] According to one embodiment, the value of the coefficient K is variable and / or adjustable. Brief description of the figures.

[0026] Other advantages and characteristics of the invention will appear more clearly on reading the description of a preferred embodiment which follows, with reference to the appended drawings, produced as indicative and non-limiting examples and in which: [Fig. 1] is a schematic view of the device for temporary circulatory assistance or replacement of a patient's heart according to the invention. [Fig. 2] illustrates a QRS complex in an ECG signal. [Fig. 3] illustrates the variation of aortic pressure P as a function of time. [Fig. 4] illustrates the determination of AT in the case where a dicrotic wave is detected in the aortic pressure signal. [Fig. 5] illustrates the determination of AT in the case where a dicrotic wave is not detected in the aortic pressure signal. Description of the embodiments.

[0027] The device which is the subject of the invention is intended to be used during a degraded hemodynamic situation directly threatening the vital prognosis of a patient 12 (for example with a tissue perfusion pressure - PF - less than 50 mm Hg). It makes it possible to assist or supplement the heart 13 of the patient 12.

[0028] Referring to Figure 1, the device which is the subject of the invention comprises a pumping system making it possible to partially or totally supplement the cardiac muscle by admitting a sufficient quantity of blood during the diastole phase of the cardiac cycle and by reinjecting it during the systole phase of said cycle.

[0029] The operator introduces an inlet cannula 15 (21 or 23 French or “Fr”, the FRENCH representing 1 / 3 of a millimeter) capable of drawing blood from the venous system of the patient 12 and an ejection cannula 16 capable (17 or 19 French) of injecting the blood into the arterial system of said patient 12. The inlet 15 and ejection 16 cannulas that are commonly used on the extracorporeal circulation market (CEC, ECMO, ECLS) are compatible with the invention. Reinforced cannulas are preferably used in order to avoid a collapse of suction of the piston, and / or a kinking of said cannulas which would cause a reduction in the flow.

[0030] The operator can perform: - a left heart / left heart setup for partial assistance in the event of left heart failure, by positioning the admission cannula 15 at the level of the right atrium (if the septum is pierced, the left atrium is discharged) and the ejection cannula 16 at the level of the abdominal aorta; - a right heart / right heart setup for partial assistance in the event of right heart failure, by positioning the inlet cannula 15 at the level of a vena cava and the ejection cannula 16 at the level of the pulmonary artery; - a right heart / left heart setup in the event of failure of the right heart and the left heart, by positioning the inlet cannula 15 at the level of a vena cava and the ejection cannula 16 at the level of the aorta. In the latter case, the lungs are also bypassed and an oxygenation system 17 (preferably comprising a heat exchanger), is placed in the bypass circuit to remove CO2 from the blood and charge it with O2 before reinjecting it into the body. This oxygenation system 17 is advantageously arranged after the reservoir 11, i.e. on the ejection portion 18 of the bypass circuit.

[0031] The cannulas 15, 16 can be inserted percutaneously, in a cardiac and / or vascular catheterization room or in a resuscitation unit or by an IIMAC SAMU unit (Mobile Circulatory Assistance Unit for UMAC and Emergency Medical Aid Service for SAMU), by introducing them through a peripheral blood vessel and bringing them close to the heart 13, at the level of the targeted veins or arteries. They can also be inserted surgically in a surgical block, mixed implantation percutaneous puncture and surgical opening of the vessels.

[0032] These cannulas 15, 16 are connected to the pumping system by catheter-type tubes, also compatible with those usually used for a CEC (for example 3 / 8th gauge) to form on the one hand the inlet portion 19 and the ejection portion 18 of the bypass circuit.

[0033] The device comprises a chamber 11 forming a reservoir (equivalent to an artificial external ventricle) and making it possible to temporarily store a volume of fluid (e.g. blood, blood substitute, blood + blood substitute). A linear actuator 10 is configured to move a membrane 70 in the chamber 11 so as to cause a pulsating flow of fluid capable of supporting the activity of the heart 13. This flow is characterized by a succession of suction phases and ejection phases of the fluid.

[0034] As an example and to give an order of magnitude, for a heart beating at 70 bpm (beats per minute), the duration of the suction phase is approximately 0.56 seconds so that a normal suction flow rate is approximately 90 ml / s or 5 l / min (liters per minute). The duration of the ejection phase is approximately 0.25 seconds so that a normal ejection flow rate is approximately 40 ml / s, or 2 l / min. Thanks to the device according to the invention, it is possible to increase (or possibly reduce) the quantities of blood aspirated / ejected to correspond as closely as possible to the actual functioning of a heart and the needs of the body.

[0035] According to one embodiment, the actuator 10 is of the linear motor type or any other equivalent means (for example a jack) making it possible to move the membrane 70. According to one embodiment, this membrane 70 is fixed, on its periphery, to the internal wall of the chamber 11. It is advantageously made of a flexible and elastic material, elastomer or other. membrane 70 houses a central insert, not visible in the attached figures, provided with an actuating arm forming a piston 31, this piston being fixed to the actuator 10 by means of a mechanical means of engagement, fixing or connection. According to one embodiment, the actuator 10 is configured to execute the high velocity movement commands in order to adjust the actual movement of the fluid to said commands. For this purpose, a linear motor with a low time constant (advantageously less than or equal to 10 ms) and capable of generating a significant force (advantageously greater than or equal to 500 N) can be used, to which a lever arm system can be added to accelerate it further. The fluid can then be suddenly set in motion and stopped at the chosen moment.

[0036] A control unit 40 is provided to automatically control the actuator 10 and control the movement of the membrane 70. This unit 40 may be in the form of a processor, microprocessor, CPU (for Central Processing Unit) integrated into a computer, a calculator or similar means.

[0037] Each displacement step of the actuator 10 corresponds to an internal volume of the chamber 11. This correspondence between the step of the actuator 10 and the internal volume of the chamber 11 is stored or recorded in a memory area of ​​the unit 40. By controlling the displacement of the actuator 10, it is therefore possible to very precisely control the volume of fluid sucked and ejected by the device during the successive suction and ejection phases.

[0038] According to one embodiment, one or more sensors 2 are installed to acquire an electrocardiographic signal (ECG signal) which corresponds to an electrical activity of the heart 13. The control unit 40 is configured to control the movement of the actuator 10 by taking into account input data coming from this ECG signal. According to a preferred embodiment, the acquisition of the data is carried out in real time, at a fast frequency of 200 Hz. Fast processing (real time 200 Hz) of the measurements with embedded behavioral models, making it possible to send the signal to the actuation system

[0039] The control unit 40 is notably configured to recognize a QRS complex (or QRS wave) as a component of the ECG signal. The unit 40 integrates for example a QRS complex detection algorithm. Referring to Figure 2, the QRS complex corresponds to the depolarization (and contraction) of the right and left ventricles. In other words, the QRS complex corresponds to the beginning of natural systole. The Q wave is the first negative wave of the complex. The R wave is the first positive component of the complex. The S wave is the second negative component. The shape and amplitude of the QRS vary according to the leads and according to any pathology of the underlying cardiac muscle. The QRS complex has a normal duration of less than 0.1 seconds, most often less than 0.08 seconds and its variable amplitude is between 5 mV and 20 mV.

[0040] The time at which the QRS complex is detected advantageously coincides with the time of detection of the R wave since this wave is the most characteristic of the complex and therefore the easiest to detect. However, the time of detection of the QRS complex can coincide with the time of detection of the Q wave or the S wave.

[0041] According to a characteristic of the invention, the artificial systole (the phase of ejection of the fluid from the chamber 11), is not triggered at the same time as the natural systole: a time shift AT is induced between the instant TR where the QRS complex of the ECG signal is detected and the instant when the ejection phase is initiated. This time shift AT makes it possible to ensure that the aortic valve is perfectly closed when the artificial systole is initiated, so that the ventricle is protected from any overload.

[0042] The unit 40 is notably configured to determine, at each cardiac cycle identified in the ECG signal, the time offset AT by the formula: AT = E + K.(Fréei - Fref). In this formula, E is a time value whose value is determined further in the description; K is a coefficient; Fréei corresponds to the heart rate of the patient 12; F re f corresponds to a reference heart rate.

[0043] The frequency Fréei is expressed in number of beats per minute (bpm). For the sake of simplification, it is advantageously measured from the signal ECG, but can be measured using another device connected to the unit 40, such as a blood pressure monitor or a pulse oximeter. Taking into account the variability of the frequency Fréei in the calculation of the AT time shift, makes it possible to adapt in real time the triggering of the artificial systole to the physiological needs of the patient.

[0044] The best results in terms of device performance are obtained when the reference heart rate Fret is between 50 bpm and 90 bpm, preferably equal to 70 bpm. According to one embodiment, the value of Fref is pre-parameterized and fixed. According to another embodiment, the value of Fref is variable and / or adjustable for example according to the age and / or the weight and / or the general condition of the patient 12. According to another embodiment, the value of F re f is determined according to behavioral models embedded in unit 40.

[0045] The difference (Fréei - Fref) is equivalent to a correction parameter which is a function of the actual activity of the heart 13: the faster the heart, the more the value of AT decreases (i.e. the more quickly the artificial systole is triggered). And vice versa.

[0046] K is a coefficient such that K>0 and whose unit is a time squared (in particular the second or one of these fractions and / or multiples). The best results in terms of performance of the device are obtained when the value of K is between 0.01 and 0.05, preferably equal to 0.02. According to one embodiment, the value of K is pre-parameterized and fixed. According to another embodiment, the value of K is variable and / or adjustable for example according to the variation of the frequency Fréei and / or according to the evolution of the venous pressure and / or the aortic pressure.

[0047] According to one embodiment, the value of E is fixed. The best results in terms of performance of the device are obtained when the value of E is between 0.22 seconds and 0.27 seconds, preferably equal to 0.23 seconds. The value of E can also be variable and / or adjustable, for example according to the age and / or the weight and / or the general condition of the patient 12 and / or the behavioral models embedded in the unit 40.

[0048] According to an advantageous characteristic of the invention, the unit 40 is configured to control the actuator by taking into account as input data not only those coming from the ECG signal, but also those coming from an aortic pressure signal. According to an embodiment illustrated in FIG. 1, this pressure signal comes from a pressure sensor 50 advantageously positioned in the ejection portion 18 of the bypass circuit, which sensor is connected to the unit 40.

[0049] A typical example of aortic pressure variation P is illustrated in Figure 3. The characteristic points and / or phases of such a curve are as follows: - phase 1: increase in systolic pressure; point 2: pressure peak; phase 3: decrease in systolic pressure; point 4: dicrotic wave (this "hook" rebound corresponds to the closure of the aortic valve); phase 5: decrease in diastolic pressure; point 6: end-diastolic pressure.

[0050] The detection of the dicrotic wave is in fact important information to ensure that the aortic valve is properly closed. The unit 40 therefore advantageously integrates a dicrotic wave detection algorithm into the aortic pressure signal. However, depending on the patient's condition and / or the arterial stiffness, this dicrotic wave may not be detected.

[0051] Also, according to an advantageous characteristic of the invention, the value of E differs depending on whether a dicrotic wave is detected or not in the aortic pressure signal.

[0052] Referring to Figure 4, if the unit 40 detects a dicrotic wave then E = (TD-TR), where TR is the instant when the R wave of the QRS complex is detected and TD is the instant when the dicrotic wave is detected. Since the R wave is the most characteristic of the complex, it is the easiest to detect. The invention can also be implemented by detecting the Q wave or the S wave of the QRS complex. This first scenario makes it possible to obtain optimized operation where the triggering of the artificial systole is perfectly synchronized with the closure of the aortic valve and the patient's heart rate.

[0053] Referring to Figure 5, if the unit 40 does not detect a dicrotic wave, then E takes a fixed value, in particular the one mentioned previously (between 0.22 seconds and 0.27 seconds, preferably equal to 0.23 seconds). The operation is slightly degraded compared to the first case, but still allows artificial systole to be triggered with certainty that the aortic valve is closed. If the dicrotic wave is detected in the next cycle or in a later cycle, the determination of E according to the first case applies.

[0054] The dual tracking of the QRS complex in the ECG signal and the dicrotic wave in the aortic pressure signal allows unit 40 to decide in real time on the triggering of artificial systole in order to obtain optimized operation at each cardiac cycle, and particularly robust to changes in the patient's physiological parameters.

[0055] The best results for achieving optimal synchronization between artificial circulation and the natural heart (whether beating or not) are obtained by mastering the following three elements: The combined measurement of the ECG signal (QRS complex) and the dicrotic waveform allows for an accurate assessment of the heart's condition. These two measurements, depending on their availability and quality, provide an optimal synchronization signal, ensuring in particular the preservation of echocardiography and sinus rhythm. Fast processing of measurements (preferably with a fast acquisition frequency of 200 Hz or of this frequency order) to send commands to the actuator 10 in real time. High velocity command execution to match actual fluid motion to commands.

[0056] The arrangement of the various elements and / or means and / or steps of the invention, in the embodiments described above, should not be understood as requiring such an arrangement in all implementations. In any event, it will be understood that various modifications may be made to these elements and / or means and / or steps, without departing from the spirit and scope of the invention.

[0057] Further, one or more features exhibited only in one embodiment may be combined with one or more others features disclosed only in another embodiment. Similarly, one or more features disclosed only in one embodiment may be generalized to other embodiments, even if that or those features are described only in combination with other features.

[0058] In any event, in the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

Claims

1. [Device for temporary circulatory assistance or replacement of the heart (13) of a patient (12), comprising: a linear actuator (10) configured to move a membrane (70) in a chamber (11) so as to cause a pulsating fluid flow capable of supporting the activity of the heart of said patient, which flow is characterized by a succession of suction phases and ejection phases of the fluid, a control unit (40) configured to control the actuator (10) and control the movement of the membrane (70), which control is carried out by taking into account input data coming from an ECG signal of the patient (12), the control unit (40) is configured to determine a time shift AT between the instant TR at which the QRS complex of the ECG signal is detected and the instant at which an ejection phase is initiated, characterized in that the control unit (40) is configured to determine, at each cardiac cycle identified in the ECG signal,the time shift AT by the following formula: AT— E + K. (F real, > F ref) where: • E is a time value; • K is a coefficient such that K>0; • Frei corresponds to the patient's measured heart rate (12); • Fref corresponds to a reference heart rate.

2. Device according to claim 1, wherein the control unit (40) is configured to drive the actuator (10) by taking into account input data further coming from an aortic pressure signal, the value of E differing depending on whether a dicrotic wave is detected or not in said aortic pressure signal.

3. The device of claim 2, wherein the control unit (40) is configured such that if a dicrotic wave is detected in the aortic pressure signal, then E = (TD-TR), WHERE TR is the instant when the R wave of the QRS complex is detected and TD is the instant when the dicrotic wave is detected.

4. Device according to one of claims 2 or 3, wherein the control unit is configured so that if no dicrotic wave is detected in the aortic pressure signal, then E takes a fixed value.

5. Device according to claim 1, in which the value of E is fixed.

6. Device according to one of claims 4 or 5, in which the value of E is fixed between 0.22 seconds and 0.27 seconds.

7. Device according to one of the preceding claims, in which the reference heart rate F re f is between 50 bpm and 90 bpm.

8. Device according to one of claims 1 to 7, in which the value of the reference heart rate F re f is pre-parameterized and fixed.

9. Device according to one of claims 1 to 7, in which the value of the reference heart rate F re f is variable and / or adjustable.

10. Device according to one of the preceding claims, in which the value of the coefficient K is between 0.01 and 0.05 and the unit of which is a time squared.

11. Device according to one of claims 1 to 10, in which the value of the coefficient K is pre-parameterized and fixed.

12. Device according to one of claims 1 to 10, in which the value of the coefficient K is variable and / or adjustable.

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