Cardiac pump with cardiac resynchronization functions.

Abstract

The invention relates to a cardiac assist system comprising: - an intraventricularly implantable cardiac pump, - a processing unit, - at least one lead intended to be placed on an external wall of the heart. The processing unit includes a cardiac pump management function, a pacing function, and / or a defibrillation function. The processing unit is configured to: - perform cardiographic impedance measurements between said at least one lead and a metallic part of the cardiac pump in order to determine the following hemodynamic parameters: - a cardiac electromechanical delay from the cardiographic impedance measurements, - a blood filling time in the heart from the cardiographic impedance measurements, - a blood ejection time from the heart from the cardiographic impedance measurements, and - a change in right ventricular and / or left ventricular volume over time.Figure for the abridged version: Fig. 1.

Description

Title of the invention: Cardiac pump with cardiac resynchronization functions. technical field

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

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

[0003] A heart needs electrical assistance, particularly in cases of heart failure. This heart failure is a condition in which the heart muscles are no longer able to pump blood properly and sufficiently. The heart rhythm is thus disrupted.

[0004] To treat this condition, one can consider:

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

[0006] - the implantation of a cardiac pacemaker, which monitors maintains cardiac activity and generates electrical impulses at the level of the right ventricle and the left ventricle (several probes per ventricle are possible) in order to synchronize in time the contraction of all the still viable left ventricular walls (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 composed of a cardiac pacemaker and one or more pacing leads whose ends are connected to the heart.

[0008] The probes are flexible, insulated electrical wires capable of capturing signals from the heart and transmitting electrical impulses to the heart. The captured signals correspond to the heart's natural electrical activity.

[0009] We also know of implanted automatic defibrillation devices which can deliver life-saving shocks to stop dangerous arrhythmias and prevent sudden death of cardiac origin.

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

[0011] During implantation, a pacemaker is programmed according to 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, to date, hemodynamic variations caused by the pacemaker can only be identified and monitored by summoning the patient to the Cardiology department so that the patient can undergo non-invasive (echocardiography) or even invasive (arterial puncture with intracardiac pressure measurement, which is less common) examinations. In the prior art, to address this issue, the patient is encouraged to visit the hospital regularly for periodic follow-up.

[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. Description of the invention

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

[0017] - an implantable cardiac 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 cardiac pump management function and a cardiac resynchronization function, this cardiac resynchronization function comprising a pacing function (subthreshold or otherwise) and / or a defibrillation function; the processing unit being configured to:

[0021] - perform cardiography impedance measurements between said at least one probe and a metallic part of the heart pump in order to determine the following hemodynamic parameters:

[0022] - a cardiac electro-mechanical delay from impedance measurements cardiography,

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

[0024] - a blood ejection time from the heart based on impedance measurements cardiography.

[0025] Said probe can be placed opposite the left ventricle either via an epicardial and / or trans-myocardial route, or via the coronary sinus in a branch leading opposite the left ventricle, or via an 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. Parameters are automatically obtained from cardiography or cardioimpedance measurements performed using the probe as the first electrode and a metallic part of the heart as the second electrode. These parameters allow for monitoring cardiac activity by taking measurements and performing calculations at each cardiac cycle, for example. Comparing several measurements, whether consecutive or not, allows for the identification of changes in heart rhythm.

[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 echocardiogram 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 rarely used today (too invasive except in exceptional cases).

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

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

[0030] - the data is retrieved by the device and a clinician analyzes it and Reprogram the device parameters if necessary, based on the data collected.

[0031] -either an automatic mode embedded in the device allowing to automatically modify the parameters of the device with positive and negative feedback 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 changes can be checked 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 retrieve at the same time 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 which the doctor can connect to and obtain the information collected in the device implanted in the patient.

[0035] With the system according to the invention, cardiography impedance measurements are carried out advantageously using a metallic part of a cardiac pump as a reference electrode.

[0036] Preferably, a heart pump according to the invention is designed to be disposed wholly or partially inside a ventricle. The metallic part is preferably located inside the ventricle of the heart.

[0037] In operation, the presence of the heart pump in the intraventricular space is thus taken advantage of to obtain highly accurate 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 a probe placed on the wall of one 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 placed 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 feature 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 cardiography impedance is the lowest.

[0041] The moment when the cardiography impedance value is the lowest corresponds to a moment of the beginning of the opening of the aortic valve of the heart.

[0042] The moment when the cardiography impedance value is highest corresponds to a moment of the beginning of closure of the aortic valve of the heart.

[0043] By "next instant" we mean here the first opening following an instant of electrical activation.

[0044] The moment of electrical activation corresponds to the instant when the beating heart generates an electrical excitation signal that results in the opening of the aortic valve. However, this opening is not immediate. There is a delay between this signal and the mechanical opening of the aortic valve; this is the electromechanical delay. This is a hemodynamic parameter that can be monitored. Advantageously, the excitation signal is measured using at least one probe, and the opening of the aortic valve is determined from the impedance cardiography curve.

[0045] According to a further feature of the invention, the duration of blood filling in the heart can be the duration, in a cardiac cycle, between a moment for which the cardiography impedance is the highest and a following moment for which the cardiography impedance is the lowest.

[0046] This filling time is obtained from two instants determined on the cardiography impedance curve, that is to say the measurement of the impedance mapping as a function of time.

[0047] The duration of filling 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 cardiography impedance is the lowest, is determined as being the instant of the next change of sign of the derivative of a cardiography impedance curve.

[0049] Thus, the electro-mechanical 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 cardiography impedance curve changes sign for the first time since the first instant.

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

[0051] By "next instant" we mean here the next closure of the aortic valve.

[0052] This ejection time is obtained from two specific instants on the curve Cardiography impedance. 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 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 left atrium for the left ventricle).

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

[0056] According to an advantageous feature of the invention, the processing unit can further be configured to determine an ejection volume and / or a change in blood volume from the heart from 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 an area calculated under or at- above the cardiography impedance curve respectively during the time of blood filling into the heart or the time of blood ejection from the heart.

[0060] This area calculation can be a velocity-time integral (VTI) calculation of the cardiography impedance curve over a defined period. This value is directly related to the stroke volume. This value also allows for the deduction of cardiac output.

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

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

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

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

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

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

[0067] Said at least one probe may comprise at least two probes; a first probe suitable for use as an electrode for cardiography 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 control of the defibrillation function.

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

[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 cardiography 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 control of the defibrillation function.

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

[0076] The use of an atrial probe intended to be connected to an atrium of the heart can also be envisaged. The function of this probe will be to transmit the detected heart rhythm to the processing unit.

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

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

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

[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 to all the above, the processing unit can be configured to perform several cardioimpedance measurements for several different lead positions, in particular different positions of the lead outside the ventricle (right or left). A lead with multiple attachment points representing different positions can be used, with the various measurements performed with a pre-installed lead once and for all. Based on the cardioimpedance curves and values ​​obtained during a cardiac cycle in the absence of arrhythmia, an optimal position can be selected. Such a configuration allows for the correct positioning of a lead so that cardiac pacing is as hemodynamically efficient as possible (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 analysis of the cardio-impedance measurements.

[0082] Description of figures and embodiments.

[0083] Other advantages and features of the invention will become apparent from the detailed description of implementations and embodiments, which are by no means limiting, and from the following accompanying drawings:

[0084] [Fig. 1] Fig. 1 is a schematic view of a system according to the invention comprising a cardiac 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 cardiac pump with cardiac resynchronization functions with several probes,

[0086] [Fig.3] The [Fig.3] is a curve graph illustrating a ventricular electrogram and an inverse impedance cardiography curve for determining the electromechanical delay,

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

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

[0089] The embodiments described below are not in any way limiting; in particular, variants of the invention may be implemented comprising only a selection of the features described below, isolated from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art. This selection includes at least one preferably functional feature without structural details, or with only a portion of the structural details if this portion alone is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

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

[0091] In [Fig.1], a system 1 according to the invention is 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 cardiac pump 3 via a wired link 4 and to a single probe 5 fixed to an external wall of the left ventricle of the heart 6.

[0093] The processing unit 2 includes 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 via an external magnetic flux module.

[0094] Processing unit 2 may include:

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

[0096] - a power supply,

[0097] - a microprocessor or microcontroller that controls the pump cardiac, heart rhythm control and the various operations to be performed according to the invention, and

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

[0099] The cardiac pump 6 may be such as that described in US document 10,744,244. Other types of cardiac pump 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, extemalized, axial turbine / centrifugal, vibrating / moving membrane, volumetric or non-volumetric.

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

[0101] This motor 3a is intended to drive a drive shaft 3b carrying blades 3c. The drive shaft 3b and blades 3c assembly is designed to propel the blood contained in the ventricle 9 towards the aorta. To accomplish this, the heart pump 3 comprises a metal casing 3d surrounding the drive shaft 3b and blades 3c assembly, this casing having an inlet 3e and an outlet 3f. During operation, the blood contained in the ventricle 9 enters through the inlet 3e, passes through the casing, and then exits through the outlet 3f.

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

[0103] The invention also aims to control the motor 3a so that the pulsed mode corresponds to the heart rhythm 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 metallic casing 3d of the heart pump 3 as a reference electrode or ground for cardiography impedance measurements.

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

[0107] However, it sometimes happens that the native heart rhythm drifts and renders ineffective the functioning of the pacemaker which has been programmed according to this native heart rhythm.

[0108] To enable the practitioner to identify deviations in heart rhythm that would render the pacemaker ineffective, the present invention proposes an automatic monitoring tool.

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

[0110] The defibrillation function of processing unit 2 is designed to deliver electrical shocks to restart a failing heart. This function can be automated by implementing hemodynamic monitoring of the heart.

[0111] The hemodynamic parameters used to ensure these monitorings include the electromechanical delay, the filling time, and the ejection time. Filling volumes and stroke 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 thresholds of duration or volume or any combinations of durations and / or volumes allowing to trigger warning signals and / or to optimize the functioning of the cardiac pump.

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

[0114] Impedance cardiography allows the measurement of blood volume variations in the cardiac chambers and displays the result as 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 be used to monitor and measure variations in stroke volume and ventricular diastolic filling volume (right or left) of the patient. To do this, probe 5 is used as the transmitting dipole and the 3D chamber as the receiving dipole. The patient's body is then electrically mapped by injecting a subthreshold current of fixed amplitude and duration, for example, 5 to 30 ps. The pulse duration is variable and obeys Lapicque's law, which is 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 mentioned above, consecutively. The receiving dipole allows the voltage across the thoracic cage to be measured.

[0116] The voltage across the terminals of the receiving dipole allows the impedance between the two dipoles to be calculated.

[0117] A coil 5c, connected to lead 5 and attached to the outer wall of the ventricle, is also shown. This coil transmits an electrical shock from the processing unit when a defibrillation action is initiated.

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

[0119] The lead 5 in [Fig. 2] also includes an anode 5a and a cathode 5b, but no defibrillation coil. This lead 5 is used for pacing and for impedance measurement cardiography, taking the heart pump chamber as the reference. For defibrillation, a new lead 10 is used, equipped with an anode 10a and a cathode 10b, as well as a defibrillation coil 10c, which is attached to the outer wall of the right ventricle 8 of the heart 6.

[0120] A new probe 11 equipped with an anode 1a and a cathode 11b is also planned. The probe 11 is an atrial probe placed on the wall of the right atrium 7. This probe is used to listen to the heart rhythm produced by the myocardium.

[0121] The ear probe 11 can be used with the embodiment of [Fig. 1]. Without this probe in the mode of [Fig. 1], the heart rhythm monitoring 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] - the cardiac pump 3 and a pacemaker-type heart failure terminal in an 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 in Figures 1 and 2 therefore allow impedance measurements cardiography using probes 5, 10, 11.

[0128] In [Fig. 3], a curve 12 is shown representing a signal captured 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 rhythm. Also shown is the curve of the inverse impedance cardiography 13 obtained from the impedance variations between the probe 5 and the cardiac pump 3. The processing unit 2 is configured to detect the electrical activation 14 shown in curve 12, as well as the opening 15 of the aortic valve corresponding to the beginning of blood ejection and shown in curve 13. The opening 15 can be detected as the moment when the derivative of curve 13 changes sign, from positive to negative, for the first time after time 14.

[0129] Curve 13 is a simple representation of the inverse of the cardiography impedance; it has the intuitive advantage of corresponding the rises in curve with volume increases. Calculations are performed directly from the measured cardiography impedance values.

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

[0131] The measurement of the ejection time is illustrated in [Fig. 4]. The cardiography impedance curve 13 is again shown, with identification of the opening 15 of the aortic valve. This opening 15 corresponds to the beginning of blood flow through the aortic valve. The end of this ejection phase corresponds to the moment when the heart ceases to contract. This end of ejection is clearly identifiable on the inverse cardiography impedance curve 13. It is the instant corresponding to the nadir, that is, the lowest point of the inverse cardiography impedance curve following the opening of the aortic valve and for a given cardiac cycle. This point corresponds to the maximum cardiography impedance value in the cardiac cycle. In [Fig.4], this is the reference frame 17. This reference frame can also be detected as a change of sign of the derivative of the curve 13.

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

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

[0136] The measurement of the filling time is illustrated in [Fig. 5]. The cardiography impedance curve 13 is again shown with identification of the opening 15 of the aortic valve. This opening 15 corresponds to the beginning of blood flow through the aortic valve and the end of ventricular filling. The start of filling corresponds to the moment when the heart ceases to contract. This moment of the start of filling is clearly identifiable on the cardiography impedance curve 13. It is the moment corresponding to the nadir, that is, the lowest point of the cardiography impedance curve preceding the opening of the aortic valve for a given cardiac cycle. In [Fig. 5], this is marker 19. This marker 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] The filling volume during this filling phase can also be estimated by calculating Faire contained under the curve 13 between points 19 and 15. To do this, the so-called time-velocity integral calculation can be performed.

[0139] Periodic cardio-impedance measurements can provide quantitative hemodynamic monitoring.

[0140] Volume variations can be tracked over time.

[0141] Warning signals linked to threshold values ​​provided by cardioimpedance measurements can be considered when the left ventricle exhibits excessive unloading and / or excessive dilated volume. These thresholds can allow physicians to analyze, diagnose, and then potentially modify medical treatment, including drug dosages.

[0142] Monitoring of cardioimpedance measurements may allow physicians to analyze and diagnose early impairment of left ventricular function before the onset of symptoms.

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

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

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

Claims

Demands

1. 1. Cardiac assistance system comprising: - a cardiac pump (3), - a processing unit (2), - at least one lead (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 cardiac pump (3) is implantable intraventricularly and the processing unit (2) includes a cardiac pump (3) management function and a cardiac resynchronization function, this cardiac resynchronization function including a pacing function and / or a defibrillation function;the processing unit (2) being configured to: - perform cardiography impedance measurements between said at least one probe (5) and a metallic part of the cardiac pump (3d) so as to determine the following hemodynamic parameters: - a cardiac electro-mechanical delay from the cardiography impedance measurements, - a blood filling time in the heart from the cardiography impedance measurements, and - a blood ejection time from the heart from the cardiography impedance measurements.;

2. 2. System according to claim 1, characterized in that the cardiac electro-mechanical 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 subsequent instant for which the cardiography impedance is the lowest.

3. 3. System according to claim 1 or 2, characterized in that the time of filling (20) of blood in the heart is the time, in a cardiac cycle, between a moment for which the cardiography impedance is the highest and a following moment for which the cardiography impedance is the lowest.

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

5. 5. System according to any one of the preceding claims, characterized in that the duration of blood ejection (18) from the heart is the duration, in a cardiac cycle, between a moment for which the cardiography impedance is the lowest and a subsequent moment for which the cardiography impedance is the highest.

6. 6. System 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 cardiography impedance measurements.

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

8. 8. System 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 change in volume of blood ejected from the heart from cardiography impedance measurements.

9. 9. System according to claim 7 or 8, characterized in that the volume of blood filling into the heart or the volume of blood ejected from the heart is determined from an area calculated below or above the cardiography impedance curve respectively during the duration of blood filling (20) into the heart or the duration of blood ejection (18) from the heart.

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

11. 11. System according to any one of the preceding claims, characterized in that said at least one probe (5) is a single probe: - suitable for use as an electrode for cardiography impedance measurements, - suitable for transmitting electrical impulses to the heart in response to a command from the pacing function, and - comprising a coil for generating electrical shocks in response to a command from the defibrillation function.

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

13. 13. System 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: - suitable for use as an electrode for cardiography impedance measurements, - suitable for transmitting electrical impulses to the heart in response to a command from the pacing function, and - comprising a coil for generating electrical shocks in response to a command from the defibrillation function.

14. 14. System 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. System 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. System 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 time of filling (20) of blood into the heart and the time of ejection (18) of blood from the heart, periodically and to emit an alert signal when a predetermined time threshold is exceeded.

17. 17. System 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 a mode of operation of the cardiac pump during a cardiac cycle N+1.

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