Implantable cardiac resynchronisation device

Abstract

The invention relates to an implantable cardiac resynchronisation device comprising a processing unit, a right lead intended to be placed in the right ventricle of the heart, a left lead (5) intended to be placed in the left ventricle (9) of the heart, the left lead (5) being intended to be placed on an outer wall of the heart and comprising at least two electrodes: an anode (5a) and a cathode (5b). According to the invention, the right lead is a lead provided with at least one defibrillation coil (4c). The processing unit (2) is configured: - to perform at least one impedance cardiography measurement, by injecting a current between an electrode of the left lead and the defibrillation coil used as a reference earth and by measuring a current between an electrode of the left lead and the defibrillation coil used as the reference earth, the defibrillation coil being used as a reference earth for injection and measurement; and - to determine, from the at least one impedance cardiography measurement, a cardiac electromechanical delay, and / or a blood filling duration and / or a blood ejection duration.

Description

Description Title of the invention: Implantable cardiac resynchronization device Technical field

[0001] The present invention relates to an implantable cardiac resynchronization device.

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

[0003] A heart needs electrical assistance, especially 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. This disrupts the heart rhythm.

[0004] To treat this pathology, one can consider the implantation of a cardiac device, called a pacemaker, which constantly monitors cardiac activity and generates electrical impulses in the right ventricle and the left ventricle (several probes per ventricle are possible) in order to synchronize over 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).

[0005] A pacemaker is a small cardiac device implanted under the skin and consisting of a pacemaker and one or more pacing leads whose ends are connected to the heart.

[0006] The leads are flexible, insulated electrical wires capable of capturing signals from the heart and transmitting electrical impulses to the different chambers of the heart (left and / or right atria, right and / or left ventricles). The signals captured correspond to the natural electrical activity of the heart; if this natural activity proves deficient, the pacemaker can stimulate the one to four different cardiac chambers mentioned above in order to maintain a heart rate within the human norm and in accordance with the physical activity of the person at all times (depending on the pacemaker programming carried out by the expert physician).

[0007] Implanted automatic defibrillation devices are also known that can deliver life-saving shocks to terminate dangerous arrhythmias and prevent sudden cardiac death. An implantable defibrillator also serves as a pacemaker as already described above; it can therefore have a dual function (pacemaker and defibrillator or defibrillator alone).

[0008] However, the natural rhythm of the heart can vary over time depending in particular on age or any other consideration.

[0009] During installation, a pacemaker is set to match the patient's natural rhythm. This way, as the patient's natural rhythm changes over time, the pacemaker can adapt to these changes and pace the heart as needed.

[0010] 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 intracardiac pressure readings, 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.

[0011] The present invention aims at a non-invasive monitoring method.

[0012] Another object of the invention is an automatic tracking method. Statement of the invention

[0013] At least one of the objectives is achieved with an implantable cardiac resynchronization device comprising: - a processing unit, - an ear probe intended to be placed in an atrium of a heart, - a straight probe intended to be placed in a right ventricle of the heart, - a left probe intended to be placed in a left ventricle of the heart, the left probe being intended to be placed on an external wall of the heart and comprising at least two electrodes, an anode and a cathode.

[0014] According to the invention, the right probe is a probe equipped with at least one defibrillation coil, the processing unit is configured to carry out locally or have the following steps carried out remotely by an external processing unit: - carry out at least one cardiography impedance measurement by injecting a current between an electrode of the left probe and the defibrillation coil used as a reference ground, and by measuring a current between an electrode of the left probe and the defibrillation coil used as a reference ground, the defibrillation coil being used as a reference ground for the injection and the measurement, and - determining from said at least one cardiographic impedance measurement, a cardiac electromechanical delay, and / or a blood filling time in the right and / or left ventricle, and / or a blood ejection time from the right and / or left ventricle.

[0015] The right probe can advantageously further comprise two electrodes, an anode and a cathode,

[0016] With the device according to the invention, a tripolar configuration is used by injecting current between the left ventricle and the right ventricle. The coil is used as a common ground electrode for injection and for measurement. Therefore, both stimulation (for measurement) and measurement systematically have the defibrillation coil as the reference ground.

[0017] Having the coil as a reference allows the electric field lines to be distributed uniformly in the heart, this allows for better quality impedance measurements, the cardiac volume is more easily deduced from the impedance signal. In prior art systems, the impedance signal cannot be improved because the only solution would be to increase the injectable current level, but this current level is limited so as not to stimulate the heart. Prior art systems suffer from artifacts due to movements.

[0018] Another advantage of using the coil as a ground reference is to reduce an impedance gap, this reduces the risk of measurement saturation and allows the use of higher current levels (improving the quality of the collected signal).

[0019] The device may be a CRT-D equipped with a defibrillation coil.

[0020] Additionally, an atrial probe may be provided for placement in an atrium of a heart.

[0021] According to the invention, the processing unit can perform the calculations locally or preferably transmit the raw data to a processing unit external to the patient, in particular by wireless means, which will perform the calculations.

[0022] Using an external processing unit allows for a small implantable part, as the computing power is moved to the external processing unit. This also prevents any heating of the implantable elements. The external processing unit is thus able to retrieve the raw data, process it, and provide the various intervals and times calculated from variations in cardiographic impedance.

[0023] When using the external processing unit, the device according to the invention is partly implantable.

[0024] With the device according to the invention, hemodynamic parameters such as, for example, the electromechanical delay, the filling time and the ejection time are determined. These parameters are obtained automatically. tic from impedance measurements cardiography or cardio-impedance carried out for example using standard probes of a cardiac resynchronization device. These parameters allow monitoring of cardiac activity by carrying out measurements and calculations at each cardiac cycle for example. The comparison between several successive or non-successive measurements makes it possible to identify changes in the heart rate.

[0025] 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 within the left ventricle remains little used today (too invasive except in exceptional cases).

[0026] The present invention therefore proposes a non-invasive solution using permanently implanted probes to carry out measurements and determine hemodynamic parameters.

[0027] According to an advantageous characteristic of the invention, the processing unit may comprise a network of programmable resistors connected to all or part of the electrodes and the defibrillation coil, this network being intended to modify the resistance of a branch carrying an electrode or the defibrillation coil for better distribution of current density during measurements.

[0028] For example, this is a programmable series resistor network. One programmable resistor for each electrode line used or defibrillation line used.

[0029] A step is planned to measure the resistance seen by the defibrillation coil and / or each electrode. Then, during an impedance measurement, the resistances are programmed, branch by branch, to balance the level of current injected per branch. Each coil and each electrode is carried by an independent branch connected to the processing unit.

[0030] The resistor network can be used to better distribute the current to the right side of the heart.

[0031] In addition, a second defibrillation coil may be provided for placement in a right atrium.

[0032] The processing unit can be configured to ground all defibrillation coils and electrodes in the right ventricle and right atrium. This allows the entire right side to be at the same potential, improving signal quality during impedance measurements, for example.

[0033]

[0034] According to an advantageous characteristic of the invention, the cardiac electromechanical delay can be the duration, in a cardiac cycle, between an instant electrical activation measured by means of the probe placed outside the heart wall and a following instant for which the cardiographic impedance is the lowest.

[0035] The instant when the cardiographic impedance value is lowest corresponds to an instant when the heart's aortic valve begins to open.

[0036] The instant when the cardiographic impedance value is highest corresponds to an instant of the beginning of closure of the aortic valve of the heart.

[0037] By "next instant" we mean here the first opening following an instant of electrical activation.

[0038] The electrical activation moment corresponds to the moment when the heart in operation generates an electrical excitation signal that will result in the opening of the aortic valve. But this opening is not immediate. There is a lag between this signal and the 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 the left or right probe, and the opening of the aortic valve is determined from the cardiographic impedance curve.

[0039] 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.

[0040] This filling time is obtained from two moments determined on the cardiography impedance curve, i.e. the measurement of the impedance mapped as a function of time.

[0041] Filling time is a hemodynamic parameter that also deserves to be monitored over successive or non-successive cardiac cycles.

[0042] Preferably, the next time at which the cardiographic impedance is lowest is determined to be the time of the next change in sign of the derivative of a cardiographic impedance curve.

[0043] Thus, the electromechanical delay or 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.

[0044] According to an advantageous characteristic of the invention, the duration of blood ejection from the heart may 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.

[0045] By "next instant" here we mean the next closure of the aortic valve.

[0046] This ejection duration is obtained from two moments determined on the impedance curve cardiography. Ejection time is a hemodynamic parameter that also deserves to be monitored over successive or non-successive cardiac cycles.

[0047] 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.

[0048] The filling volume corresponds to diastole, a phase during which the left ventricle fills in two stages: a first stage of filling with passive blood flow and a second stage of filling with active blood flow induced by atrial contraction (of the right atrium for the right ventricle, and respectively the left atrium for the left ventricle).

[0049] 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.

[0050] Stroke volume corresponds to systole, the phase during which the left ventricle empties, the QRS complex generating an ejection of blood.

[0051] Filling volume and ejection volume are also hemodynamic parameters that can be monitored and compared to successive or non-sequential measurements.

[0052] 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 cardiographic impedance curve respectively during the blood filling time in the heart or the blood ejection time from the heart.

[0053] This area calculation can be a time-velocity integral (TVI) calculation of the cardiographic impedance curve over the defined duration. This value is directly related to the stroke volume. This value also allows cardiac output to be deduced.

[0054] Advantageously, all or part of the probes can be unipolar, bipolar, tripolar or quadripolar probes. Depending on the probe used, numerous measurement configurations are possible.

[0055] According to an advantageous embodiment, the device according to the invention constitutes a cardiac stimulator (“pacemaker” in English), the left and / or right probe being a stimulation probe.

[0056] According to an advantageous embodiment, the device according to the invention constitutes an implantable automatic defibrillator (“Implantable Cardiac Defibrillator”, ICD, in English), the left and / or right probe being a probe equipped with a defibrillation coil.

[0057] 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.

[0058] In addition to all of the above, the processing unit can be configured to perform several cardio-impedance measurements for several different positions of the probes, in particular different positions of the probe placed outside the ventricle (right or left). A probe can be used comprising several fixation points representing different positions, the different measurements being carried out with a probe pre-installed once and for all. Based on the cardio-impedance curves and values ​​obtained during a cardiac cycle in the absence of arrhythmia, an optimal position can be selected. Such an implementation 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. Description of figures and embodiments.

[0059] 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:

[0060] [Fig. 1] Figure 1 is a schematic view of a cardiac resynchronization device such as a pacemaker comprising three probes distributed in three different locations of the heart,

[0061] [Fig. 2] Figure 2 is a schematic view of a cardiac resynchronization device such as an implanted cardiac defibrillator comprising three leads distributed in three different locations of the heart,

[0062] [Fig. 3] Figure 3 is a line graph illustrating a ventricular electrogram and a cardiographic inverse impedance curve for the determination of electromechanical delay,

[0063] [Fig. 4] Figure 4 is a line graph illustrating an electrogram ventricular and inverse impedance cardiography curve for determination of ejection time,

[0064] [Fig. 5] Figure 5 is a line graph illustrating a ventricular electrogram and an inverse impedance cardiography curve for the determination of filling time, and

[0065] Figure 6 is a schematic view of the interior of a processing unit.

[0066] 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.

[0067] In the figures, elements common to several figures retain the same reference.

[0068] In Figure 1, we can generally distinguish a cardiac resynchronization device 1 comprising a processing unit which is a cardiac stimulator or pacemaker 2 and three probes 3, 4 and 5 intended to be fixed to a heart 6.

[0069] Pacemaker 2 may include:

[0070] - a current generator to generate electrical impulses to be applied to the heart via the probes,

[0071] - a power supply such as an integrated battery or cell,

[0072] - a microprocessor or microcontroller which ensures the control of the heart rate and the various operations to be carried out including the steps according to the invention, and

[0073] - a transmitter-receiver-transmitter, in particular for communicating with the outside world.

[0074] The function of a pacemaker 2 is to help the heart maintain a proper heart rhythm by sending tiny electrical impulses through the leads when the heart rate is off. Arrhythmias are irregular heart rhythms and can have various causes, such as age, genetics, medications, or other factors. The role of a pacemaker is to correct these arrhythmias.

[0075] However, sometimes the native heart rate drifts and renders the pacemaker that has been set up accordingly ineffective. native heart rate.

[0076] To enable the practitioner to identify drifts in the heart rate which would render the pacemaker ineffective, the present invention provides an automatic tracking tool.

[0077] This monitoring is made possible by the continuous measurement of hemodynamic parameters using cardiographic impedance measurement.

[0078] These parameters are 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.

[0079] By monitoring these parameters, it is possible to define duration or volume thresholds or any combination of durations and / or volumes to trigger alert signals.

[0080] In Figure 1, the probe 3 is an atrial probe arranged inside the right atrium 7 of the heart 6. It is a bipolar probe comprising an anode 3a and a cathode 3b, for example screwed onto an internal wall of the right atrium 7. The function of this probe is to listen to the heart rate produced by the myocardium.

[0081] The right lead 4 is a stimulation lead which is placed on an internal wall of the right ventricle 8 of the heart 6. It comprises for example an anode 4a and a cathode 4b.

[0082] The left lead 5 is a pacing lead that is placed on an external wall of the left ventricle 9 of the heart 6 via the coronary sinus. It comprises, for example, an anode 5a and a cathode 5b.

[0083] Probes 4 and 5 are used to transmit electrical impulses from processing unit 2 to the walls on which they are fixed.

[0084] According to the invention, probes 4 and 5 are used to carry out cardiographic impedance measurements.

[0085] Impedance cardiography measures changes in blood volume in the heart chambers and displays the results as a curve over time and the cardiac cycle (diastole and systole). Changes in blood volume lead to changes in thoracic and / or myocardial bioimpedance.

[0086] Impedance cardiography can allow monitoring and measurement of changes in the patient's stroke volume and diastolic filling volume of the ventricle (right or left). For example, this can be done by using the left lead 5 as a transmitter dipole and the right lead 4 as a receiver dipole. The patient's body is then electrically mapped by injecting a current of subthreshold fixed amplitude and duration from 5 to 30 JJ.S. 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 mentioned above in a consecutive manner. The receiving dipole makes it possible to measure the voltage across the rib cage.

[0087] The voltage across the receiving dipole allows the impedance between the two dipoles to be calculated. Each of probes 4 and 5 can act as a transmitting dipole or a receiving dipole.

[0088] In Figure 2 we find the same elements as in Figure 1 with the following differences. The right probe 4 is replaced by a right probe 41 playing the same function as in Figure 1 but with the addition of the defibrillation function by means of a coil 4c intended to be placed on an internal wall of the right ventricle. The processing unit 2 can be a pacemaker equipped in addition with the defibrillation function but it can also be only an implanted automatic defibrillator. A second coil 4d is also envisaged in the right atrium.

[0089] According to the invention, the impedance measurement is tripolar: the coil or the two coils are used as a reference mass for the current injected from the electrodes 5a and / or 5b, and the current measurement from the electrodes 5a and / or 5b for the calculation of the impedance. Thus, the impedance measurement is carried out over a distance from the left ventricle to the right ventricle, having the same reference mass. The volume is thus determined with greater precision.

[0090] The devices of Figure 1 and Figure 2 therefore allow cardiographic impedance measurements using sones 4 / 41 and 5.

[0091] In Figure 3, a curve 10 is shown representing a signal captured by the ventricular probe: it is a local ventricular electrogram related to the attachment of a probe to the left ventricle or the right ventricle 3. This ventricular electrogram represents the heart rate. Also shown is the inverse impedance cardiography curve 11 obtained from the impedance variations between the two right 4 / 41 and left 5 probes. The processing unit is configured to detect the electrical activation 12 illustrated in curve 10, as well as the opening 13 of the aortic valve corresponding to the start of blood ejection and illustrated in curve 11. The opening 13 can be detected as the instant when the derivative of curve 11 changes sign, from positive to negative, immediately after instant 12.

[0092] Curve 11 is a simple representation of the inverse of the cardiographic impedance, it has the intuitive advantage of matching curve rises to volume increases. Calculations are performed directly from the measured cardiographic impedance values.

[0093] The duration between the two instants 12 and 13 constitutes the electro-mechanical delay 14.

[0094] The measurement of the ejection time is illustrated in Figure 4. We can again distinguish the cardiography impedance curve 11 with an identification of the opening 13 of the aortic valve. This opening 13 corresponds to the beginning 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 cardiography impedance curve 11. This is the instant corresponding to the nadir, that is to say, 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 Figure 4, this is the mark 15. This mark can also be detected as a change in sign of the derivative of curve 11.

[0095] Aortic valve closure corresponds to the instant when the cardiographic impedance value is highest (acme, i.e., the highest point of the cardiographic impedance curve but the lowest point, nadir, of the inverse cardiographic impedance curve 11).

[0096] The opening of the aortic valve or the closure 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 inverse cardiographic impedance curve 11).

[0097] The duration between the two instants 13 and 15 constitutes the ejection duration associated with the very short phase of isovolumic relaxation (30-60ms) 16.

[0098] The volume of blood ejected during this ejection phase can also be estimated by calculating the area contained under curve 11 between points 13 and 15. This ejected volume can be used to determine the cardiac output if the diameter of the aortic valve is available.

[0099] The measurement of the filling time is illustrated in Figure 5. We can again distinguish the cardiography impedance curve 11 with an identification of the opening 13 of the aortic valve. This opening 13 corresponds to the beginning of the passage of blood via the aortic valve and to the end of filling of the ventricle. The beginning of filling corresponds to the moment when the heart stops contracting. This instant of the beginning of filling is clearly identifiable on the cardiography impedance curve 11. 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 Figure 5, this is the mark 17. This mark can also be detected as a change in sign of the derivative of curve 11.

[0100] The duration between the two instants 17 and 13 constitutes the filling duration 18.

[0101] The filling volume during this filling phase can also be estimated by calculating the area contained under curve 11 between points 17 and 13. To do this, the so-called time-velocity integral calculation can be carried out.

[0102] Periodic cardioimpedance measurements can provide quantitative hemodynamic monitoring.

[0103] Volume variations can be tracked over time.

[0104] Warning signals related 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 physicians to analyze, diagnose and then possibly modify medical treatment, including drug dosage.

[0105] Monitoring cardioimpedance measurements can allow physicians to analyze and diagnose impaired left ventricular function early before symptoms appear.

[0106] Cardioimpedance measurements can enable chronic monitoring of the hemodynamic status of patients. In Figure 6, the processing unit 2 comprises a volume estimation module 19, a valve opening estimation module 20 and an electrode configuration unit. All of these elements 19-21 are connected to the impedance measurement module 22. The electrode configuration unit is connected to a programmable resistor network 24. The resistors of this network are connected to all or part of the electrodes and / or to the defibrillation coil(s). This programmable resistor network 24 is arranged between the impedance measurement module 22 and the electrodes and defibrillation coils. The resistors of the network are capable of modifying the resistance of each branch carrying an electrode or a defibrillation coil for a better distribution of current density during a measurement.

[0107] There is also an EGM 23 module for recording the electrical activity of the heart.

[0108] The electrodes are shared between EGM (action potential) and impedance. The impedance measurement is used for the estimation of volume data (e.g. ejection fraction), valve opening time. The impedance measurement is also used by the processing unit to program the resistance network by means of the electrode configuration unit 21. The probe 5 can have more than two electrodes in order to choose the stimulation vector more simply and adapt the therapy over time if necessary (e.g. development of fibrosis over time).

[0109] Of course, the invention is not limited to the examples which have just been described. Many modifications can be made to these examples. without departing from the scope of the present invention as described.

Claims

Claims

1. 1. Implantable cardiac resynchronization device (1) comprising: - a processing unit (2), - a straight probe (4) intended to be placed in a right ventricle (8) of the heart, - a left probe (5) intended to be placed in a left ventricle (9) of the heart, the left probe (5) being intended to be placed on an external wall of the heart and comprising at least two electrodes, an anode (5a) and a cathode (5b), characterized in that the right probe is a probe provided with at least one defibrillation coil (4c), the processing unit (2) is configured to carry out locally or have carried out remotely by an external processing unit the following steps: - carry out at least one cardiography impedance measurement by injecting a current between an electrode of the left probe and the defibrillation coil used as a reference ground, and by measuring a current between an electrode of the left probe and the defibrillation coil used as a reference ground, the defibrillation coil being used as a reference ground for the injection and the measurement, and - determining from said at least one cardiographic impedance measurement, a cardiac electromechanical delay, and / or a blood filling time in the right (8) and / or left (9) ventricle, and / or a blood ejection time from the right (8) and / or left (9) ventricle.

2. 2. Device according to claim 1, characterized in that the processing unit (2) comprises a network of programmable resistors connected to all or part of the electrodes and the defibrillation coil, this network being intended to modify the resistance of a branch carrying an electrode or the defibrillation coil for a better distribution of current density during a measurement.

3. 3. Device according to claim 1 or 2, characterized in that the cardiac electromechanical delay (14) is the duration, in a cardiac cycle, between an instant of electrical activation measured by means of the probe (5) placed outside the wall of the heart and an instant next for which the cardiographic impedance is the lowest.

4. 4. Device according to claim 1 or 2, characterized in that the duration of filling (18) 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.

5. 5. Device according to claim 2 or 3, characterized in that the next instant for which the cardiographic impedance is the lowest, is determined as being the instant (13) of the next change of sign of the derivative of a cardiographic impedance curve.

6. 6. Device according to any one of the preceding claims, characterized in that the duration of ejection (16) 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.

7. 7. 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.

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

9. 9. Device according to claim 6 or 7, 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 in the heart or the blood ejection time from the heart.

10. 10. Device according to any one of the preceding claims, characterized in that all or part of the probes are bipolar, tripolar or quadripolar probes.

11. 11. Device according to any one of the preceding claims, characterized in that it constitutes a cardiac stimulator ("pacemaker" in English), the left and / or right probe being a stimulation probe.

12. 12. Device according to any one of the preceding claims, characterized in that it constitutes an implantable automatic defibrillator (“Implantable Cardiac Defibrillator”, ICD, in English).

13. 13. 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, 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.

14. 14. Device according to any one of the preceding claims, characterized in that it further comprises a second defibrillation coil intended to be placed in a right atrium.

15. 15. Device according to any one of the preceding claims, characterized in that the processing unit (2) is further configured to ground all of the defibrillation coils and electrodes of the right ventricle and right atrium.

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