Heart pump with cardiac resynchronization functions.

Abstract

The invention relates to a cardiac assistance system comprising: - an intraventricular implantable heart pump, - a processing unit, - at least one probe intended to be placed on an external wall of the heart. The processing unit comprises a heart pump management function, a pacing function and / or a defibrillation function. The processing unit is configured to: - carry out cardiography impedance measurements between said at least one probe and a metal part of the heart pump so as to determine the following hemodynamic parameters: - a cardiac electromechanical delay from the cardiography impedance measurements, - a blood filling time in the heart from the cardiography impedance measurements, - a blood ejection time from the heart from the cardiography impedance measurements and - a variation in volume of the right ventricle and / or the left ventricle over time.Figure for abstract: Fig. 1.

Description

Title of the invention: Heart pump with cardiac resynchronization functions. Technical field

[0001] The present invention relates to a system comprising a heart pump and at least one implantable probe.

[0002] It finds a particularly interesting application in the field of cardiac assistance devices. State of the prior art

[0003] A heart needs to be electrically assisted, especially in cases of heart failure. This heart failure is a pathology in which the heart muscles no longer have the capacity to properly and sufficiently propel blood. The heart rhythm is thus disrupted.

[0004] To treat this pathology, we can consider:

[0005] - the implantation of a cardiac device, such as a heart pump capable of propelling blood from a ventricle to the aorta,

[0006] - the implantation of a pacemaker, which monitors in continuously monitors cardiac activity and generates electrical impulses in the right ventricle and left ventricle (several probes per ventricle are possible) in order to synchronize the contraction of all the remaining viable left ventricular walls over time (concept of cardiac resynchronization developed in 1994 by doctors Philippe Ritter and Serge Cazeau).

[0007] A pacemaker is a small cardiac device implanted under the skin and consisting of a pacemaker and one or more stimulation leads whose ends are connected to the heart.

[0008] Probes are flexible, insulated electrical wires capable of picking up signals from the heart and transmitting electrical impulses to the heart. The signals picked up correspond to the heart's natural electrical activity.

[0009] Implanted automatic defibrillation devices are also known that can deliver life-saving shocks to terminate dangerous arrhythmias and prevent sudden cardiac death.

[0010] However, the natural rhythm of the heart can vary over time depending in particular on age or any other consideration.

[0011] During installation, a pacemaker is set to match the patient's natural rhythm. Thus, when the natural rhythm changes over time, the pacemaker is able to adapt to these changes and stimulate the heart when necessary.

[0012] However, the hemodynamic variations caused by the action of the pacemaker can, until now, only be identified and monitored by summoning the patient to the Cardiology department so that the patient can benefit from non-invasive (echocardiography) or even invasive (arterial puncture with measurement of intra-cardiac pressures, which is rarer) explorations. In the prior art, to resolve such a problem, the patient is encouraged to go to the hospital regularly for periodic monitoring.

[0013] The present invention aims at a non-invasive monitoring method.

[0014] Another object of the invention is an automatic tracking method.

[0015] Another object of the invention is an integrated cardiac assistance system. Statement of the invention

[0016] At least one of the objectives is achieved with a cardiac assistance system comprising:

[0017] - an implantable heart pump, intraventricular or extraventricular,

[0018] - a processing unit, and

[0019] - at least one probe intended to be placed on an external wall of the heart or in a branch of the coronary sinus.

[0020] According to the invention, the processing unit comprises a heart pump management function and a cardiac resynchronization function, this cardiac resynchronization function comprising a stimulation function (infra-threshold or not) and / or a defibrillation function; the processing unit being configured to:

[0021] - carrying out cardiographic impedance measurements between said at least one probe and a metal part of the heart pump in order to determine the following hemodynamic parameters:

[0022] - an electromechanical cardiac delay from impedance measurements because diography,

[0023] - a duration of blood filling in the heart from impedance measurements cardiography, and

[0024] - a duration of blood ejection from the heart from the impedance measurements because diography.

[0025] Said probe can be placed opposite the left ventricle either by epicardial and / or transmyocardial route, or by coronary sinus route in a branch leading opposite the left ventricle, or by endocavitary route with probe placed in the apical region or opposite the septal wall of the right ventricle.

[0026] With the system according to the invention, hemodynamic parameters such as the electromechanical delay, the filling time and the ejection time are determined. These parameters are obtained automatically from impedance measurements because diography or cardio-impedance performed using the probe as the first electrode and a metal part of the heart pump as the second electrode. These parameters allow monitoring of cardiac activity by performing measurements and calculations at each cardiac cycle for example. Comparison between several successive or non-successive measurements makes it possible to identify changes in the heart rate.

[0027] Thus, the solution according to the invention avoids the use of an additional probe as may be the case in the prior art. Indeed, in the prior art, the gold standard is to perform an echocardiography in order to calculate the electromechanical delays and reprogram the pacemaker accordingly, if necessary. Invasive arterial exploration of the Millar® type introduced into the left ventricle remains little used today (too invasive except in exceptional cases).

[0028] The present invention therefore proposes a non-invasive solution using permanently implanted probes to carry out measurements and determine hemodynamic parameters.

[0029] Two modes of use of these parameters are possible:

[0030] -the data is retrieved by the device and a clinician analyzes and re program the device parameters if necessary according to the data collected

[0031] - either an automatic mode embedded in the device allowing the parameters of the device to be automatically modified with positive and negative feedbacks (retrocontrols) on the rotational speeds of the device and monitoring functions via the internet using a server available to doctors and engineers so that the programming modifications are verified by the doctor taking care of the patient.

[0032] Thus, these parameters can be stored in a memory of the processing unit and / or transferred wirelessly to the outside.

[0033] Using a programmer, the physician can interrogate the implanted device and at the same time retrieve the impedance-graphy information stored in a cardiac assistance system according to the invention.

[0034] This information can also be transmitted electronically via the Internet to a website to which the doctor can connect and obtain the information collected in the device implanted in the patient.

[0035] With the system according to the invention, cardiographic impedance measurements are carried out by advantageously using a metal part of a heart pump as a reference electrode.

[0036] Preferably, a heart pump according to the invention is intended to be arranged totally or partially inside a ventricle. The metal part is preferably located inside the ventricle of the heart.

[0037] In operation, we thus take advantage of the presence of the cardiac pump in intra- ventricular to obtain high-precision measurements.

[0038] The end of said at least one probe may be in the form of a ring intended to be screwed or sutured onto a wall of the heart, in particular onto the wall of a ventricle in which the heart pump is installed. But other arrangements are possible, such as for example a probe placed on a wall of a first ventricle and a heart pump placed inside the other ventricle.

[0039] In operation, the impedance measurements effectively take into account the distance between the ventricle wall and a reference disposed inside the ventricle. The measurements are accurate and sensitive to wall movements due to the specific positioning of the electrodes.

[0040] According to an advantageous characteristic of the invention, the cardiac electromechanical delay can be the duration, in a cardiac cycle, between an instant of electrical activation measured by means of said at least one probe placed outside the wall of the heart and a following instant for which the cardiographic impedance is the lowest.

[0041] The instant when the cardiographic impedance value is the lowest corresponds to an instant at which the aortic valve of the heart begins to open.

[0042] The instant when the cardiographic impedance value is highest corresponds to an instant at which the aortic valve of the heart begins to close.

[0043] By “next instant” is meant here the first opening following an instant of electrical activation.

[0044] The electrical activation moment corresponds to the moment when the heart in operation generates an electrical excitation signal which will result in the opening of the aortic valve. But this opening is not immediate. There is a time lag between this signal and the mechanical opening of the aortic valve; this is the electromechanical delay. This is a hemodynamic parameter which can be monitored. Advantageously, the excitation signal is measured by means of said at least one probe, and the opening of the aortic valve is determined from the cardiographic impedance curve.

[0045] According to an additional characteristic of the invention, the duration of blood filling in the heart can be the duration, in a cardiac cycle, between an instant for which the cardiographic impedance is the highest and a following instant for which the cardiographic impedance is the lowest.

[0046] This filling time is obtained from two times determined on the cardiography impedance curve, i.e. the measurement of the mapped impedance as a function of time.

[0047] The filling time is a hemodynamic parameter which also deserves to be monitored over successive or non-successive cardiac cycles.

[0048] Preferably, the next instant for which the cardiographic impedance is the lowest is determined as being the instant of the next change of sign of the derivative of a cardiographic impedance curve.

[0049] Thus, the electromechanical delay or the filling time involves two instants, a first instant and a second instant, the second instant being the instant when the derivative of the cardiographic impedance curve changes sign for the first time since the first instant.

[0050] According to an advantageous characteristic of the invention, the duration of blood ejection from the heart can be the duration, in a cardiac cycle, between an instant for which the cardiographic impedance is the lowest and a following instant for which the cardiographic impedance is the highest.

[0051] By "next instant" is meant here the next closure of the aortic valve.

[0052] This ejection duration is obtained from two times determined on the curve impedance cardiography. Ejection time is a hemodynamic parameter that also deserves to be monitored over successive or non-successive cardiac cycles.

[0053] According to the invention, the processing unit can further be configured to determine a volume and / or a variation of blood filling in the heart from the cardiography impedance measurements.

[0054] The filling volume corresponds to diastole, a phase during which the left ventricle fills in two stages: a first stage of filling with a passive blood flow and a second stage of filling with an active blood flow induced by an atrial contraction (of the right atrium for the right ventricle, and respectively the left atrium for the left ventricle).

[0055] According to the invention, the hemodynamic parameters may comprise a variation in volume of the right ventricle and / or the left ventricle over time.

[0056] According to an advantageous characteristic of the invention, the processing unit can further be configured to determine an ejection volume and / or a variation in blood volume from the heart from the cardiography impedance measurements.

[0057] The ejection volume corresponds to systole, the phase during which the left ventricle empties, the QRS complex generating an ejection of blood.

[0058] Filling volume and ejection volume are also hemodynamic parameters that can be monitored and compared to successive or non-successive measurements.

[0059] Preferably, the blood filling volume in the heart or the blood ejection volume from the heart is determined from a calculated area under or above the cardiography impedance curve respectively during the blood filling time in the heart or the blood ejection time from the heart.

[0060] This area calculation can be a time-velocity integral (TVI) calculation of the cardiography impedance curve over the defined duration. This value is directly linked to the stroke volume. This value also allows cardiac output to be deduced.

[0061] Advantageously, said at least one probe may be a unipolar, bipolar, tripolar or quadripolar probe. Depending on the probe used, numerous measurement configurations are possible.

[0062] According to an advantageous embodiment, said at least one probe can be a single probe:

[0063] - suitable for use as an electrode for cardiographic impedance measurements,

[0064] - capable of transmitting electrical impulses to the heart in response to a control of the stimulation function (infra-threshold or not), and

[0065] - comprising a coil for generating electric shocks in response to a defibrillation function control.

[0066] With this configuration, the single probe is used to perform all three functions.

[0067] Said at least one probe may comprise at least two probes; a first probe capable of being used as an electrode for cardiographic impedance measurements, and a second probe:

[0068] - capable of transmitting electrical impulses to the heart in response to a control of the stimulation function, or

[0069] - comprising a coil for generating electric shocks in response to a defibrillation function control.

[0070] The first probe can notably play two roles: cardiography and stimulation impedance measurements, or cardiography and defibrillation impedance measurements.

[0071] Said at least one probe may also comprise three separate probes, each intended for one of the following functions:

[0072] - suitable for use as an electrode for cardiographic impedance measurements,

[0073] - capable of transmitting electrical impulses to the heart in response to a control of the stimulation function, and

[0074] - comprising a coil for generating electric shocks in response to a defibrillation function control.

[0075] When using multiple probes, at least two probes may be intended to be placed on two different ventricles.

[0076] It is also possible to provide for the use of an atrial probe intended to be connected to an atrium of the heart. This probe will have the function of transmitting the detected cardiac rhythm of the heart to the processing unit.

[0077] According to an advantageous characteristic of the invention, the processing unit can further be configured to determine at least the cardiac electromechanical delay, the duration of blood filling in the heart and the duration of blood ejection from the heart, periodically and to emit an alert signal when a predetermined duration threshold is exceeded.

[0078] Advantageously, the processing unit can further be configured to determine hemodynamic parameters during a cardiac cycle N and to deduce therefrom an operating mode of the cardiac pump during a cardiac cycle N+1.

[0079] It is possible to consider calculating the times of opening and closing of the aortic valve during a cycle N1, and to determine an instant of electrical activation in real time during a cycle N, then to deduce the hemodynamic parameters of cycle N by taking the times of opening and closing of the aortic valve of cycle N1.

[0080] The operating mode may for example be the management of the duration and / or the rotation speed of a turbine of the heart pump.

[0081] In addition in particular to all of the above, the processing unit can be configured to carry out several cardio-impedance measurements for several different positions of the probes, in particular different positions of the probe arranged outside the ventricle (right or left). A probe can be used comprising several fixing points representing different positions, the different measurements being carried out with a probe pre-installed once and for all. Depending on the cardio-impedance curves and values ​​obtained during a cardiac cycle in the absence of arrhythmia, an optimal position can be retained. Such an embodiment makes it possible to correctly position a probe so that cardiac stimulation is as effective as possible at the hemodynamic level (obtaining the best ventricular filling and ejection pressures).And for a probe with multiple addressable attachment points, one attachment point can be retained as the probe position after analyzing the cardio-impedance measurements.

[0082] Description of the figures and embodiments.

[0083] Other advantages and particularities of the invention will appear on reading the detailed description of implementations and embodiments which are in no way limiting, and the following appended drawings:

[0084] [Fig.l] [Fig.l] is a schematic view of a system according to the invention comprising a heart pump with cardiac resynchronization functions with a single probe,

[0085] [Fig.2] [Fig.2] is a schematic view of a system according to the invention comprising a heart pump with cardiac resynchronization functions with several probes,

[0086] [Fig.3] [Fig.3] is a line graph illustrating a ventricular electrogram and a cardiographic inverse impedance curve for determining electromechanical delay,

[0087] [Fig.4] [Fig.4] is a line graph illustrating a ventricular electrogram and an inverse impedance cardiography curve for determining ejection time, and

[0088] [Fig.5] [Fig.5] is a line graph illustrating a ventricular electrogram and an inverse impedance cardiography curve for determining filling time.

[0089] The embodiments which will be described below are in no way limiting; it will be possible in particular to implement variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one preferably functional characteristic without structural details, or with only a part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0090] In the figures, the elements common to several figures retain the same reference.

[0091] In [Fig.l], a system 1 according to the invention can be generally distinguished, which when in operation is intended to be associated with a core 6.

[0092] The system 1 comprises a processing unit 2 connected to a heart pump 3 via a wired connection 4 and to a single probe 5 fixed on an external wall of the left ventricle of the heart 6.

[0093] The processing unit 2 comprises hardware and software means for implementing a heart pump management function, a pacing function and a defibrillation function. It can be powered by battery and / or contactless power supply by means of an external module by magnetic flux.

[0094] The processing unit 2 may comprise:

[0095] - a current generator for generating electrical pulses to be applied to the heart via the single probe 5 or to generate the current or voltage necessary for the cardiography impedance measurement,

[0096] - a power supply,

[0097] - a microprocessor or microcontroller which controls the pump cardiac, heart rate control and the various operations to be carried out according to the invention, and

[0098] - a transmitter-receiver-transmitter for communicating with the outside world in particular.

[0099] The heart pump 6 may be such as that described in the document US 10,744,244. Other types of heart pumps may be used, such as pumps draining blood in bypass from the apex of the left or right ventricle to the aorta (ascending or descending), whether internalized, externalized, axial / centrifugal turbine, vibrating / mobile membranes, volumetric or not.

[0100] This pump comprises a motor 3a arranged outside the heart. However, this motor may be fully or partially integrated into the heart, for example in the ventricle 9.

[0101] This motor 3a is intended to drive a transmission shaft 3b carrying blades 3c. The transmission shaft 3b and blades 3c assembly has the function of propelling the blood contained in the ventricle 9 towards the aorta. To do this, the heart pump 3 comprises a metal box 3d around the transmission shaft 3b and blades 3c assembly, this box being provided with an inlet 3e and an outlet 3f. In operation, the blood contained in the ventricle 9 enters through the inlet 3e, passes through the box and then exits through the outlet 3f.

[0102] Ideally, the motor 3a operates in a pulsed mode, i.e., times of operation at high speed and times of operation at low speed.

[0103] The invention also aims to control the motor 3a so that the pulsed mode corresponds to the heart rate and takes into account the physiological characteristics of the heart.

[0104] The engine speed is controlled by the processing unit 2.

[0105] According to the invention, the processing unit 2 uses the 3d metal box of the heart pump 3 as a reference or ground electrode for the cardiography impedance measurements.

[0106] The pacing function of the processing unit 2 is designed to help the heart maintain a proper heart rate by emitting tiny electrical impulses via one or more leads when the heart rate is deficient. Arrhythmias are irregular heart rhythms and can have various causes, such as age, genetics, medications, or others. The role of the pacemaker is to correct these arrhythmias.

[0107] However, it happens that the native heart rate drifts and renders ineffective the operation of the pacemaker which has been set according to this native heart rate.

[0108] To enable the practitioner to identify drifts in the heart rate which would render the pacemaker ineffective, the present invention proposes an automatic tracking tool.

[0109] This monitoring is made possible by the continuous measurement of hemodynamic parameters using cardiographic impedance measurement.

[0110] The defibrillation function of the processing unit 2 has the function of emitting electric shocks to restart a failing heart. This function can be automated by setting up monitoring of the hemodynamic state of the heart.

[0111] The hemodynamic parameters used to ensure these monitorings include the electromechanical delay, the filling time and the ejection time. The filling volumes and the ejection volume can also be determined. These parameters are calculated in situ, automatically and non-invasively.

[0112] By monitoring these parameters, it is possible to define duration or volume thresholds or any combination of durations and / or volumes allowing alert signals to be triggered and / or the operation of the heart pump to be optimized.

[0113] The probe 5 is placed on an external wall of the left ventricle 9 of the heart 6. It comprises for example an anode 5a and a cathode 5b useful for transmitting electrical stimulation pulses to the wall of the ventricle and for generating an electrical current for cardio-impedance measurement.

[0114] Impedance cardiography allows variations in blood volume in the heart cavities to be measured and the result to be displayed in the form of a curve as a function of time and the cardiac cycle (diastole and systole). Variations in blood volume lead to variations in thoracic and / or myocardial bioimpedance.

[0115] Impedance cardiography can allow monitoring and measurement of variations in the systolic ejection volume as well as the diastolic filling volume of the ventricle (right or left) of the patient. To do this, the probe 5 is used as a transmitter dipole and the 3d box as a receiver dipole. The patient's body is then electrically mapped by injecting a current of fixed infra-threshold amplitude and of a duration of 5 to 30ps for example. The duration of the pulse is variable and obeys Lapicque's law, known to those skilled in the art. The current can also be injected in series of pulses (from 1 to n) with the same characteristics cited above consecutively. The receiver dipole makes it possible to measure the voltage at the terminals of the thoracic cage.

[0116] The voltage across the receiving dipole makes it possible to calculate the impedance between the two dipoles.

[0117] We also distinguish a coil 5c connected to the probe 5 and placed on the external wall of the ventricle. This coil makes it possible to transmit an electric shock coming from the treatment unit when a defibrillation action is triggered.

[0118] In [Fig.2], we find the heart pump 3 as in [Fig. 1]. The processing unit 2 includes the same functions as in [Fig.l], namely pump management, stimulation and defibrillation.

[0119] The probe 5 in [Fig.2] also includes an anode 5a and a cathode 5b, but no defibrillation coil. This probe 5 is used for pacing and for cardiographic impedance measurement, considering the heart pump chamber as a reference. For defibrillation, a new probe 10 is used, equipped with an anode 10a and a cathode 10b, as well as a defibrillation coil 10c. pressed against the external wall of the right ventricle 8 of the heart 6.

[0120] A new probe 11 is also provided, equipped with an anode 11a and a cathode 11b. The probe 11 is an atrial probe arranged on the wall of the right atrium 7. This probe has the function of listening to the heart rate produced by the myocardium.

[0121] The ear probe 11 can be used with the embodiment of [Fig.l]. Without this probe in the embodiment of [Fig.l], the heart rate listening function can also be performed by the probe 5.

[0122] Overall, when a defibrillation action is initiated, a shock can be delivered between:

[0123] - the heart pump 3 and a stimulation electrode,

[0124] -heart pump 3 and a pacemaker-type heart failure terminal in abdominal position,

[0125] - the heart pump 3 and an electrode of the probe placed on the right ventricle,

[0126] - the heart pump 3 and a coil placed on a probe.

[0127] The systems of figures 1 and 2 therefore allow impedance measurements because diography using probes 5, 10, 11.

[0128] In [Fig. 3], a curve 12 can be seen representing a signal picked up by the single probe 5 of [Fig. 1] or by the atrial probe 11 in [Fig. 2]. This signal is a ventricular electrogram representing the heart rate. Also visible is the inverse impedance cardiography curve 13 obtained from the impedance variations between the probe 5 and the heart pump 3. The processing unit 2 is configured to detect the electrical activation 14 illustrated in curve 12, as well as the opening 15 of the aortic valve corresponding to the start of blood ejection and illustrated in curve 13. The opening 15 can be detected as the instant when the derivative of curve 13 changes sign, from positive to negative, for the first time after instant 14.

[0129] Curve 13 is a simple representation of the inverse of the cardiographic impedance, it has the intuitive advantage of making the curve rises correspond to increases in volume. The calculations are carried out directly from the measured cardiographic impedance values.

[0130] The duration between the two instants 14 and 15 constitutes the electro-mechanical delay 16.

[0131] The measurement of the ejection duration is illustrated in [Fig.4]. We can again distinguish the cardiography impedance curve 13 with an identification of the opening 15 of the aortic valve. This opening 15 corresponds to the start of the passage of blood via the aortic valve. The end of this ejection phase corresponds to the moment when the heart stops contracting. This instant of end of ejection is clearly identifiable on the inverse curve of the cardiography impedance 13. This is the instant corresponding to the nadir, that is, the lowest point of the inverse cardiographic impedance curve following the opening of the aortic valve and for a given cardiac cycle. This point corresponds to the maximum cardiographic impedance value in the cardiac cycle. In [Fig.4], this is mark 17. This mark can also be detected as a change in sign of the derivative of curve 13.

[0132] The closure of the aortic valve or the opening of the mitral valve corresponds to the instant when the cardiographic impedance value is the highest (acme, i.e. the highest point of the cardiographic impedance curve but the lowest point, nadir, of the curve 13 of the inverse of the cardiographic impedance).

[0133] The opening of the aortic valve or the closing of the mitral valve corresponds to the instant when the cardiographic impedance value is the lowest (nadir, i.e. the lowest point of the cardiographic impedance curve but the highest point, acme, of the curve 13 of the inverse of the cardiographic impedance).

[0134] The duration between the two instants 15 and 17 constitutes the ejection duration 18.

[0135] The volume of blood ejected during this ejection phase can also be estimated by calculating the area contained under curve 13 between points 15 and 17. This ejected volume can be used to determine the cardiac output if we have access to the diameter of the aortic valve.

[0136] The measurement of the filling time is illustrated in [Fig. 5]. We can again distinguish the cardiography impedance curve 13 with an identification of the opening 15 of the aortic valve. This opening 15 corresponds to the start of blood passage via the aortic valve and to the end of filling of the ventricle. The start of filling corresponds to the moment when the heart stops contracting. This instant of the start of filling is clearly identifiable on the cardiography impedance curve 13. This is the instant corresponding to the nadir, that is to say, the lowest point of the cardiography impedance curve preceding the opening of the aortic valve and for a given cardiac cycle. In [Fig. 5], this is the mark 19. This mark can also be detected as a change in sign of the derivative of curve 13.

[0137] The duration between the two instants 19 and 15 constitutes the filling duration 20.

[0138] We can also estimate the filling volume during this filling phase by calculating the area contained under curve 13 between points 19 and 15. To do this, we can carry out the so-called time-speed integral calculation.

[0139] Periodic cardioimpedance measurements can provide quantitative hemodynamic monitoring.

[0140] Volume variations can be tracked over time.

[0141] Alert signals linked to threshold values ​​provided by cardio-impedance measurements can be considered when the left ventricle presents excessive unloading and / or excessive dilated volume. These thresholds can allow doctors to analyze, diagnose and then possibly modify a medical treatment, including the dosage of medication.

[0142] Monitoring cardio-impedance measurements can allow physicians to analyze and diagnose early impairment of left ventricular function before symptoms appear.

[0143] Cardio-impedance measurements can allow chronic monitoring of the hemodynamic state of patients.

[0144] These hemodynamic parameters are advantageously calculated during a cardiac cycle N, then used to modify the pump control.

[0145] Of course, the invention is not limited to the examples which have just been described. Numerous modifications can be made to these examples without departing from the scope of the present invention as described.

Claims

Claims

1. 1. Cardiac assistance system comprising: - a cardiac pump (3) implantable intraventricularly or extraventricularly, - a processing unit (2), - at least one probe (5) intended to be placed on an external wall of the heart (6) or in a branch of the coronary sinus, characterized in that the processing unit (2) comprises a function for managing the cardiac pump (3) and a cardiac resynchronization function, this cardiac resynchronization function comprising a stimulation function and / or a defibrillation function;the processing unit (2) being configured to: - carry out cardiography impedance measurements between said at least one probe (5) and a metallic part of the heart pump (3d) so as to determine the following hemodynamic parameters: - a cardiac electromechanical delay from the cardiography impedance measurements, - a duration of blood filling in the heart from the cardiography impedance measurements, and - a duration of blood ejection from the heart from the cardiography impedance measurements.;

2. 2. Device according to claim 1, characterized in that the cardiac electromechanical delay (16) is the duration, in a cardiac cycle, between an instant of electrical activation measured by means of said at least one probe placed outside the wall of the heart and a following instant for which the cardiographic impedance is the lowest.

3. 3. Device according to claim 1 or 2, characterized in that the duration of filling (20) of blood in the heart is the duration, in a cardiac cycle, between an instant for which the cardiographic impedance is the highest and a following instant for which the cardiographic impedance is the lowest.

4. 4. Device according to claim 2 or 3, characterized in that the next instant (15) for which the cardiographic impedance is the lowest, is determined as being the instant of the next change of sign of the derivative of a cardiographic impedance curve.

5. 5. Device according to any one of the preceding claims, characterized in that the duration of ejection (18) of blood from the heart is the duration, in a cardiac cycle, between an instant for which the cardiographic impedance is the lowest and a following instant for which the cardiographic impedance is the highest.

6. 6. Device according to any one of the preceding claims, characterized in that the processing unit (2) is further configured to determine a volume and / or a variation of blood filling in the heart from the cardiography impedance measurements.

7. 7. Device according to any one of the preceding claims, characterized in that the hemodynamic parameters comprise a variation in volume of the right ventricle and / or the left ventricle over time.

8. 8. Device according to any one of the preceding claims, characterized in that the processing unit (2) is further configured to determine a volume and / or a variation in volume of blood ejection from the heart from the cardiography impedance measurements.

9. 9. Device according to claim 7 or 8, characterized in that the blood filling volume in the heart or the blood ejection volume from the heart is determined from a calculated area under or above the cardiography impedance curve respectively during the blood filling time (20) in the heart or the blood ejection time (18) from the heart.

10. 10. Device according to any one of the preceding claims, characterized in that said at least one probe (5) is a unipolar, bipolar, tripolar or quadripolar probe.

11. 11. Device according to any one of the preceding claims, characterized in that said at least one probe (5) is a single probe: - capable of being used as an electrode for cardiographic impedance measurements, - capable of transmitting electrical impulses to the heart in response to a command of the stimulation function, and - comprising a coil for generating electrical shocks in response to a command of the defibrillation function.

12. 12. Device according to any one of claims 1 to 10, characterized in that said at least one probe (5) comprises at least two probes (5, 10); a first probe suitable for use as an electrode for cardiographic impedance measurements, and a second probe: - capable of transmitting electrical impulses to the heart in response to a command of the stimulation function, or - comprising a coil for generating electrical shocks in response to a command of the defibrillation function.

13. 13. Device according to any one of claims 1 to 10, characterized in that said at least one probe (5) comprises three separate probes, each intended for one of the following functions: - capable of being used as an electrode for cardiography impedance measurements, - capable of transmitting electrical impulses to the heart in response to a command of the stimulation function, and - comprising a coil for generating electrical shocks in response to a command of the defibrillation function.

14. 14. Device according to claim 12 or 13, characterized in that at least two probes (5, 10) are intended to be arranged on two different ventricles.

15. 15. Device according to any one of the preceding claims, characterized in that it further comprises an atrial probe (11) intended to be connected to an atrium of the heart.

16. 16. Device according to any one of the preceding claims, characterized in that the processing unit (2) is further configured to determine at least the cardiac electromechanical delay (16), the duration of filling (20) of blood in the heart and the duration of ejection (18) of blood from the heart, periodically and to emit an alert signal when a predetermined duration threshold is exceeded.

17. 17. Device according to any one of the preceding claims, characterized in that the processing unit (2) is further configured to determine hemodynamic parameters during a cardiac cycle N and to deduce therefrom an operating mode of the cardiac pump during a cardiac cycle N+1.

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