Heart assistance or replacement device

Abstract

The invention relates to a device for temporary circulatory support or replacement of the heart (13) of a patient (12), comprising: a linear actuator (10) configured to move a membrane (70) within a chamber (11) so as to induce a pulsatile fluid flow capable of supporting the activity of the patient's heart, which flow is characterized by a succession of aspiration and ejection phases of the fluid; a control unit (40) configured to drive the actuator (10) and control the movement of the membrane (70), which control is achieved by taking into account input data from an ECG signal of the patient (12); the control unit (40) is configured to determine a time lag ∆T between the time TR when the QRS complex of the ECG signal is detected and the time when an ejection phase is initiated. Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: Heart assistance or replacement device. Technical field.

[0001] The present invention relates to a device for assisting or supplementing the heart.

[0002] The term assistance is used when a portion of the blood arriving at the heart is taken away, while the term replacement is used when all, or almost all (> 90%), of the blood arriving at the heart is taken away by the heart replacement device.

[0003] It relates to the technical field of devices used by extracorporeal circulatory assistance / supplementation which maintain a hemodynamics compatible with life, in the context of cardiac muscle failure 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.

[0004] The heart's function is to distribute blood throughout the body, transporting oxygen and nutrients necessary for the functioning of the various organs, and to transport metabolic waste products to the lungs, the organs for CO2 elimination, and urea and creatinine to the kidneys. It is divided into two parts: the right side of the heart, which receives deoxygenated blood (depleted of oxygen) via the venae cavae and pumps it through the right ventricle to the pulmonary artery and the respiratory system (where it is oxygenated and CO2 released); and the left side of the heart, which receives oxygenated blood via the pulmonary veins and pumps it through the aorta to the various organs. The contractions of the cardiac muscle (pump) generate a pulsating blood flow throughout the body. This allows for the continuous regulation of blood flow to meet the physiological needs of the body and each organ.

[0005] In the presence of cardiac muscle failure (in the case of myocardial infarction for example), it is necessary to temporarily replace the pumping function of said cardiac muscle with a mechanical circulatory assistance system, the objective being to gain time for the heart to recover.

[0006] Among the circulatory support systems currently in use, extracorporeal circulation (ECC) devices are known, which bypass the failing heart by using a servo-controlled pump placed outside the body, which receives blood at the level of the vena cava and injects it at the level of the aorta (thoracic), to To mechanically generate a continuous blood flow compatible with the body's vital needs. The main objective of circulatory support is to regulate the pumped flow rate in complete accordance with the patient's physiological needs, which vary continuously.

[0007] As a power source, a console or central processing unit incorporates a mathematical model based on physical laws governing the movement of a fluid in a closed circuit. This circuit typically consists of a pump, a heat exchanger, a flow meter, a blood gas and electrolyte analyzer, a pressure sensor, and biocompatible components such as tubing, arterial and venous cannulas, a venous reservoir, an oxygenator, and an 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 standard cardiopulmonary bypass (CPB) and are portable, with a usage time of several days, unlike conventional CPB. Indeed, unlike conventional CPB, ECMO and ECLS are maintained until the patient's cardiopulmonary recovery or as a bridge before transplantation.

[0008] Although these systems have demonstrated their effectiveness in their conventional circulatory support functions, they are not entirely satisfactory insofar as the control of the generated blood flow is not optimal with regard to the patient's physiology. The current survival rate for some of the pathologies addressed does not exceed 30%. Blood circulation may be imperfectly synchronized, leading to an increase in left ventricular afterload, which opposes the contraction (ejection) of the heart muscle during systole. A fatigued or failing heart will become even more fatigued if aortic pressure is high during systole: the aortic valves do not open properly, afterload increases, and so does left ventricular end-diastolic pressure, with a lack of ejection. Mitral valve regurgitation may also occur, potentially causing irreversible pulmonary edema.This is one of the main limitations of prior art systems.

[0009] Patent document EP3818996A1 describes an assistance device comprising a linear actuator whose piston moves in translation within a chamber. The translation of the piston causes the movement of a membrane and the aspiration and ejection of blood. A controller synchronizes the actuator's operation 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 delay is, however determined in a particularly complex way and does not prevent an increase in left ventricular afterload.

[0010] The present invention aims to overcome the aforementioned drawbacks. In particular, one objective of the invention is to provide an assistance device whose operation prevents, with each cardiac cycle, an increase in left ventricular afterload. Another objective of the invention is to optimize the real-time synchronization of ejection phases with respect to the patient's physiology in order to maintain hemodynamics compatible with the patient's life. Yet another objective of the invention is to provide an assistance device whose control is simple to implement and particularly reliable. The invention also aims to enable improved 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 supplementation of a patient's heart, comprising: - a linear actuator configured to move a membrane within a chamber so as to cause a pulsating fluid flow capable of supporting the activity of the patient's heart, which flow is characterized by a succession of aspiration and ejection phases of the fluid, - a control unit configured to drive the actuator and control the movement of the membrane, which control is achieved by taking into account input data from an ECG signal from the patient, - the control unit is configured to determine a time offset AT between the time TR when the QRS complex of the ECG signal is detected and the time when 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 shift by the following formula: AT = E + K.(Fréel - Fref)

[0013] where: • E is a time value; • K is a coefficient such that K>0; • Freei corresponds to the patient's measured heart rate; • Fre corresponds to a reference heart rate.

[0014] The AT time shift (corresponding to the triggering of artificial systole), as defined by the formula according to the invention, makes it possible to ensure simply and reliably that, at each cardiac cycle, the fluid (blood) is not ejected during natural systole, but only after it has ended and the aortic valve has closed. The ventricle is thus protected from any overload. Furthermore, taking into account Using the patient's heart rate as a trigger parameter for artificial systole allows for real-time synchronization of ejection phases with the patient's physiology. The applicant observed that this device was particularly effective and enabled a highly precise pulsatile flow, perfectly aligned with the patient's physiological needs. The observed performance benefits include some or all of the following improvements: improved patient condition, generally reducing hospital stays; improved circulatory status and organ perfusion thanks to the characteristics of the pulsatile fluid flow, which induces better microcirculation of vital organs, improved vascular compliance, a reduction in the need for inotropic drug support where applicable, and an increase in cerebral oxygen saturation.

[0015] Other advantageous features of the apparatus of the invention are listed below. Each of these additional features may be considered alone or in combination with the notable features defined above. Each of these additional features contributes, where appropriate, to solving specific technical problems defined further in the description and in which the notable features defined above do not necessarily participate. These additional features may, where appropriate, be the subject of one or more divisional patent applications:

[0016] Device according to claim 1, wherein the control unit (40) is configured to drive the actuator (10) taking into account input data further 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.

[0017] According to one embodiment, the control unit is configured so that if a dicrotic wave is detected in the aortic pressure signal, then E = (TD-TR), where TR is the time when Fonde R of the QRS complex is detected and TD is the time when the dicrotic wave is detected.

[0018] According to one embodiment, the control unit is configured so that if no dicrotic wave is detected in the aortic pressure signal, then E takes a fixed value.

[0019] According to one embodiment, the value of E is fixed.

[0020] According to one embodiment, the value of E is fixed between 0.22 seconds and 0.27 second.

[0021] According to one embodiment, the reference heart rate Fref is between 50 bpm and 90 bpm.

[0022] According to one embodiment, the reference heart rate value Fref is pre-parameterized and fixed.

[0023] According to one embodiment, the value of the reference heart rate Fref is variable and / or adjustable.

[0024] According to one embodiment, the value of the coefficient K is between 0.01 and 0.05 and whose unit is a time squared.

[0025] According to one embodiment, the value of the coefficient K is pre-parameterized and fixed.

[0026] According to one embodiment, the value of the coefficient K is variable and / or adjustable. Brief description of the figures.

[0027] Other advantages and features of the invention will become more apparent upon reading the description of a preferred embodiment which follows, with reference to the accompanying drawings, which are provided by way of illustrative and non-limiting examples and on which:

[0028] [Fig-1] is a schematic view of the circular assistance or supplementary device temporary culation of the heart of a patient according to the invention.

[0029] [Fig.2] illustrates a QRS complex in an ECG signal.

[0030] [Fig.3] illustrates the variation of aortic pressure P as a function of time.

[0031] [Fig.4] illustrates the determination of AT in the case where a dicrotic wave is detected in the aortic pressure signal.

[0032] [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 implementation methods.

[0033] The device of the invention is intended for use in a degraded hemodynamic situation directly threatening the life of a patient 12 (for example, with a tissue perfusion pressure - PF - of less than 50 mm Hg). It allows for the assistance or replacement of the heart 13 of patient 12.

[0034] With reference to [Fig.1], the device of the invention comprises a pumping system enabling partial or total supplementation of the cardiac muscle by admitting a sufficient quantity of blood during the diastole phase of the cardiac cycle and reinjecting it during the systole phase of said cycle.

[0035] The operator introduces an inlet cannula 15 (21 or 23 French or "Fr," the FRENCH representing 1 / 3 of a millimeter) adapted to draw blood from the venous system of patient 12 and an ejection cannula 16 adapted (17 or 19 French) to inject the blood into the arterial system of said patient 12. The inlet cannulas 15 and ejection cannulas 16 commonly used in the extracorporeal circulation (ECC, ECMO, ECLS) market are compatible with the invention. Reinforced cannulas are preferably used to prevent suction collapse of the piston and / or kinking of said cannulas, which would result in a reduction of flow.

[0036] The operator can perform:

[0037] - a left heart / left heart placement for partial assistance in case of left heart failure, by positioning the inlet 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;

[0038] - a right heart / right heart placement for partial assistance in case of de right heart failure, by positioning the inlet cannula 15 at the level of a vena cava and the outlet cannula 16 at the level of the pulmonary artery;

[0039] - a right heart / left heart placement in case of right heart failure and of the left heart, by positioning the inlet cannula 15 at the level of a vena cava and the outlet cannula 16 at the level of the aorta. In this latter case, the lungs are also bypassed, and an oxygenation system 17 (preferably including a heat exchanger) is placed in the bypass circuit to remove CO2 from the blood and oxygenate it before reinjecting it into the body. This oxygenation system 17 is advantageously located after the reservoir 11, i.e., on the outlet portion 18 of the bypass circuit.

[0040] The cannulas 15, 16 can be inserted percutaneously in a cardiac and / or vascular catheterization lab, in an intensive care unit, or by a SAMU (Mobile Circulatory Assistance Unit for UMAC and Emergency Medical Assistance Service for SAMU) team, by introducing them through a peripheral blood vessel and guiding them close to the heart 13, at the level of the targeted veins or arteries. They can also be inserted surgically in a surgical suite, using a combination of percutaneous puncture and surgical opening of the vessels.

[0041] These cannulas 15, 16 are connected to the pumping system by catheter-type tubes, also compatible with those usually used for CEC (for example 3 / 8 gauge) to form on the one hand the intake portion 19 and the ejection portion 18 of the bypass circuit.

[0042] The device comprises a chamber 11 forming a reservoir (equivalent to an artificial external ventricle) and allowing the temporary storage of a volume of fluid (e.g., blood, blood substitute, blood + blood substitute). A linear actuator 10 is configured to move a membrane 70 within the chamber 11 so as to induce a pulsating fluid flow capable of supporting the activity of the heart 13. This flow is characterized by a succession of aspiration and ejection phases of the fluid.

[0043] By way of example and to give an order of magnitude, for a heart beating at 70 bpm (beats per minute), the duration of the aspiration phase is approximately 0.56 seconds, so that a normal aspiration 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 The invention allows us 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.

[0044] In one embodiment, the actuator 10 is a linear motor or any other equivalent means (for example, a cylinder) for moving the diaphragm 70. In one embodiment, this diaphragm 70 is fixed, on its periphery, to the inner wall of the chamber 11. It is advantageously made of a flexible and elastic material, such as an elastomer. The diaphragm 70 houses a central insert, not visible in the accompanying figures, equipped with an actuating arm forming a piston 31, this piston being fixed to the actuator 10 by means of a mechanical engagement, fastening, or connection. In one embodiment, the actuator 10 is configured to execute high-velocity displacement commands in order to adjust the actual fluid movement to said commands.A linear motor with a short 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 for this purpose, to which a lever arm system can be added to accelerate it further. The fluid can then be abruptly set in motion and stopped at the desired moment.

[0045] 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, microprocessors, CPU (for Central Processing Unit) integrated into a computer, a calculator or similar means.

[0046] Each step of the actuator 10's movement 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 movement of the actuator 10, it is therefore possible to control very precisely the volume of fluid aspirated and ejected by the device during the successive phases of aspiration and ejection.

[0047] According to one embodiment, one or more sensors 2 are used to acquire an electrocardiographic signal (ECG signal) corresponding to the electrical activity of the heart 13. The control unit 40 is configured to drive the movement of the actuator 10 based on input data from this ECG signal. In a preferred embodiment, data acquisition is performed in real time at a high frequency of 200 Hz. Rapid processing (real-time, 200 Hz) of the measurements using embedded behavioral models allows the signal to be sent to the actuation system.

[0048] The control unit 40 is configured, in particular, to recognize a QRS complex (or QRS wave) as a component of the ECG signal. The unit 40 incorporates, for example, a QRS complex detection algorithm. Referring to [Fig. 2], the The QRS complex corresponds to the depolarization (and contraction) of the right and left ventricles. In other words, the QRS complex marks 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 complex vary depending on the leads and any underlying cardiac muscle pathology. The QRS complex normally has a duration of less than 0.1 seconds, most often less than 0.08 seconds, and its variable amplitude ranges from 5 mV to 20 mV.

[0049] The instant of detection of the QRS complex advantageously coincides with the instant of detection of Fonde R, since this wave is the most characteristic of the complex and therefore the simplest to detect. However, the instant of detection of the QRS complex may coincide with the instant of detection of Fonde Q or Fonde S.

[0050] According to one feature of the invention, artificial systole (the ejection phase of fluid from chamber 11) is not triggered simultaneously with natural systole: a time lag AT is induced between the TR time at which the QRS complex of the ECG signal is detected and the time at which the ejection phase is initiated. This time lag AT ensures that the aortic valve is fully closed when artificial systole is initiated, thus protecting the ventricle from any overload.

[0051] Unit 40 is specifically configured to determine, for each cardiac cycle identified in the ECG signal, the time shift AT using 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 patient's heart rate 12; Fref corresponds to a reference heart rate.

[0052] The heart rate (Fréei) is expressed in beats per minute (bpm). For simplicity, it is advantageously measured from the ECG signal, but can also be measured using another device connected to unit 40, such as a blood pressure monitor or pulse oximeter. Taking into account the variability of the Fréei in the calculation of the AT time shift allows for real-time adaptation of the artificial systole triggering to the patient's physiological needs.

[0053] The best results in terms of device performance are obtained when the reference heart rate Fref is between 50 bpm and 90 bpm, preferably equal to 70 bpm. In one embodiment, the Fref value is pre-set and fixed. In another embodiment, the Fref value is variable and / or adjustable, for example, according to the patient's age and / or weight and / or general condition. In yet another embodiment, the Fref value is determined according to behavioral models embedded in the unit.

[0054] 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 lower the AT value (i.e., the more quickly the artificial systole is triggered). And vice versa.

[0055] K is a coefficient such that K > 0 and whose unit is time squared. The best results in terms of device performance are obtained when the value of K is between 0.01 and 0.05, preferably equal to 0.02. In one embodiment, the value of K is pre-parameterized and fixed. In another embodiment, the value of K is variable and / or adjustable, for example, according to the variation of the heart rate Freei and / or according to the evolution of venous pressure and / or aortic pressure.

[0056] According to one embodiment, the value of E is fixed. The best results in terms of device performance 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 weight and / or general condition of the patient 12 and / or behavioral models embedded in the unit 40.

[0057] According to an advantageous feature of the invention, the unit 40 is configured to drive the actuator by taking into account as input data not only those from the ECG signal, but also those 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.

[0058] A typical example of aortic pressure variation P is illustrated in [Fig.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.

[0059] The detection of the dicrot wave is indeed important information for ensuring that the aortic valve is properly closed. Unit 40 therefore advantageously incorporates a dicrot wave detection algorithm within the aortic pressure signal. However, depending on the patient's condition and / or arterial stiffness, this dicrot wave may not be detected.

[0060] Also, according to an advantageous feature of the invention, the value of E differs depending on whether a dicrotic wave is detected or not in the aortic pressure signal.

[0061] Referring to [Fig. 4], if unit 40 detects a dicrotic wave, then E = (TD - TR), where Tr is the time when the R wave of the QRS complex is detected and TD is the time 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 allows for optimized functioning where the triggering of artificial systole is perfectly synchronized with the closure of the aortic valve and the patient's heart rhythm.

[0062] Referring to [Fig. 5], if unit 40 does not detect a dicrotate 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 dicrotate wave is detected in the next cycle or a subsequent cycle, the determination of E according to the first case applies.

[0063] The dual tracking of the QRS complex in the ECG signal and of 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.

[0064] The best results for achieving optimal synchronization between artificial circulation and the natural heart (beating or not) are obtained by controlling the following three elements: • The combined measurement of the ECG signal (QRS complex) and the dicrotic wave allows for a precise 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 the echocardiogram and a sinus rhythm. • Rapid processing of measurements (preferably with a fast acquisition frequency of 200 Hz or of this order of frequency) to send commands in real time to the actuator 10. • High-velocity command execution to adjust the actual fluid motion to the commands.

[0065] 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.

[0066] Furthermore, one or more features exhibited only in one embodiment can be combined with one or more other features exhibited only in another embodiment. Similarly, one or more features exhibited only in one embodiment can be generalized to other embodiments, even if that feature or those features are described only in combination with other features.

[0067] In any event, in the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. A device for temporary circulatory support 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 induce a pulsating fluid flow capable of supporting the activity of the patient's heart, which flow is characterized by a succession of aspiration and ejection phases of the fluid, • a control unit (40) configured to drive the actuator (10) and control the movement of the membrane (70), which driving is performed by taking into account input data from an ECG signal of the patient (12), • the control unit (40) is configured to determine a time lag AT between the time TR when the QRS complex of the ECG signal is detected and the time when 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 is given by the following formula: AT = E + K.(Freel - Fref) where: • E is a time value; • K is a coefficient such that K > 0; • Freel corresponds to the measured heart rate of the patient (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) taking into account input data further 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. Device according to 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 time when the R wave of the QRS complex is detected and TD is the time when the dicrotic wave is detected.

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

5.

6. A device according to claim 1, wherein the value of E is fixed. A device according to claim 4 or 5, wherein the value of E is fixed between 0.22 seconds and 0.27 seconds.

7. Device according to any one of the preceding claims, wherein the reference heart rate Fref is between 50 bpm and 90 bpm.

8. Device according to any one of claims 1 to 7, wherein the reference heart rate value Fref is pre-set and fixed.

9. Device according to any one of claims 1 to 7, wherein the reference heart rate value Fref is variable and / or adjustable.

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

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

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

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