Method for managing a cardiac pump

Abstract

In a method for managing a cardiac pump intended to assist the heart of a patient, the cardiac pump sends pressurized blood at a flow rate proportional to the speed of rotation Vrpm of the pump through the aortic valve of the heart. The steps, during a same ventricular systole, include: detecting mitral valve closure, rotational speed Vrpm of the pump being strictly less than a maximum value Vrpm max, increasing Vrpm of the pump such that, at time t2, after the time t corresponding to the closing of the mitral valve, the speed of rotation of the pump is equal, or substantially equal, to the maximum value Vrpm max of the speed of rotation, and keeping the speed of rotation Vrpm of the pump at this maximum value Vrpm max for at least a portion of the time period T during which the aortic valve is open.

Claims

1. A method for managing a cardiac pump configured to assist the heart of a patient, said cardiac pump being configured to send pressurized blood at a flow rate proportional to the speed of rotation V.sub.rpm of said pump through the aortic valve of said heart, the method comprising: measuring electrical activity of the heart to detect a ventricular depolarization of the heart; and from an instant t.sub.o corresponding to the detecting of the depolarization, the following steps are carried out in succession, during a same ventricular systole: (a) detecting the closing of the mitral valve of said heart, the speed of rotation V.sub.rpm of said pump being strictly less than a maximum value V.sub.rpm max of the speed of rotation of said pump, (b) from an instant t.sub.1, increasing the speed of rotation V.sub.rpm of said pump such that, at an instant t.sub.2, after the instant t.sub.1 corresponding to the closing of said mitral valve, the speed of rotation of said pump is equal, or substantially equal, to said maximum value V.sub.rpm max of the speed of rotation, the time Δt separating the instants t.sub.1 and t.sub.2 being determined such that said maximum value V.sub.rpm max of the speed of rotation of the pump is reached before or at an instant t.sub.physio, t.sub.physio being the instant, after the instant t.sub.1, when opening of the aortic valve physiologically occurs, and (c) keeping said speed of rotation V.sub.rpm of said pump at the maximum value V.sub.rpm max for at least a portion of the time period T during which the aortic valve is open.

2. The method as claimed in claim 1, wherein, at an instant t.sub.3 corresponding to the closing or substantially to the closing of the aortic valve, an additional step (d) is carried out including reducing the speed of rotation V.sub.rpm of said pump to a value strictly less than the maximum value V.sub.rpm max of the speed of rotation of said pump.

3. The method as claimed in claim 2, wherein said pump is set such that a speed of rotation V.sub.rpm of the pump is equal, or substantially equal, to a setpoint value outside of the steps b) to d).

4. The method as claimed in claim 3, wherein said setpoint value corresponds to a minimum value V.sub.rpm min of the speed of rotation of said pump.

5. The method as claimed in claim 1, wherein the step of detection of the closing of the mitral valve is performed by at least one implantable accelerometer.

6. The method as claimed in claim 2, wherein, in the step (a) and/or in the step (d), the speed of rotation V.sub.rpm of said pump is varied progressively.

7. The method as claimed in claim 1, wherein, having previously determined a duration of a phase of isovolumetric contraction for said patient by echography or by magnetic resonance imaging (MRI) or even by positron emission tomography, in the step (b), the time Δt is taken that is equal to, or substantially equal to, the duration of the isovolumetric contraction phase.

8. The method as claimed in claim 1, wherein the maximum value V.sub.rpm max of the speed of rotation of said pump being adjustable, the maximum value V.sub.rpm max being varied for a patient as a function of a heart rate of the patient and/or of the content of the corresponding ventricle.

9. The method as claimed in claim 1, wherein the speed of rotation of said pump is monitored and regulated.

10. The method as claimed in claim 1, wherein, having determined from the measurement of the electrical activity of the heart a disorder of the heart rate, the steps a) to c) are carried out once in every two consecutive ventricular systoles, the speed of rotation V.sub.rpm of said pump being kept at a minimum value of V.sub.rpm min during the rest systole.

11. The method as claimed in claim 1, wherein, having determined from the measurement of the electrical activity of the heart that the patient presents a ventricular tachycardia or a cardiac arrest, the speed of rotation V.sub.rpm of the pump is kept constantly at the maximum value V.sub.rpm max, independently of the steps a) to c).

12. The method as claimed in claim 1, wherein said cardiac pump is an implantable ventricular assistance device (VAD).

13. A computer program comprising instructions suitable for implementing each of the steps of the method as claimed in claim 1, when said program is run on a computer.

14. A management unit, comprising: a power source configured to power a cardiac pump; and a central unit (17) comprising a processor, said central unit comprising a set of software instructions which, when executed by said processor, enable implementing a method for managing said cardiac pump, said cardiac pump being configured to send pressurized blood at a flow rate proportional to the speed of rotation V.sub.rpm of said pump, said method comprising: measuring electrical activity of the heart to detect a ventricular depolarization of the heart, and from an instant t.sub.o corresponding to the detecting of the depolarization, the following steps are carried out in succession, during a same ventricular systole: (a) detecting the closing of the mitral valve of said heart, the speed of rotation V.sub.rpm of said pump being strictly less than a maximum value V.sub.rpm max of the speed of rotation of said pump (13), (b) from an instant t.sub.1, increasing the speed of rotation V.sub.rpm of said pump (13) such that, at an instant t.sub.2, after the instant t.sub.1 corresponding to the closing of said mitral valve, the speed of rotation of said pump is equal, or substantially equal, to said maximum value V.sub.rpm max of the speed of rotation, the time Δt separating the instants t.sub.1 and t.sub.2 being determined such that said maximum value V.sub.rpm max of the speed of rotation of the pump is reached before or at an instant t.sub.physio, t.sub.physio being the instant, after the instant t.sub.1, when opening of the aortic valve physiologically occurs, and (c) keeping said speed of rotation V.sub.rpm of said pump at the maximum valve V.sub.rpm max for at least a portion of the time period T for which the aortic valve is open.

15. The unit as claimed in claim 14, wherein said central unit comprises one or more inputs configured to receive one or more signals, each of the inputs being linked to an audible or inaudible mechanical vibration linked to mechanical activity of the heart, a first subset of software instructions of said set of software instructions which, when executed by said processor, enables defining a time window for measuring said signal or signals, for analyzing each signal thus received at the input of said central unit during the time window to determine one or more parameters of the corresponding signal, for comparing the parameter or parameters of each signal thus determined with one or more data previously stored in a storage of said central unit in order to identify the signal corresponding to the closing of the mitral valve and the instant t.sub.1 corresponding to the closing of said mitral valve.

16. The unit as claimed in claim 14, wherein the electrical activity of the heart is measured by one or more electrodes, the measurement signal or signals being received at one or more other inputs of said central unit, said central unit comprising a second subset of software instructions of said set of software instructions which, when executed by said processor, enables determining in real time the heart rate of the heart of said patient, to monitor said cardiac pump according to a predetermined law which is a function of said duly determined heart rate, in particular a speed of rotation V.sub.rpm.

17. The unit as claimed in claim 16, wherein said software instructions of said second subset, when executed by said processor, enable determining, from the measurement of the electrical activity of the heart, each instant to at which a ventricular depolarization of said heart occurs in order to synchronize the steps a) to c) of said management method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantages, aims and particular features of the present invention will emerge from the following description, given, for explanatory and nonlimiting purposes, in light of the attached drawings, in which:

(2) FIG. 1 schematically represents the different steps of the method for managing a cardiac pump as a function of the natural mechanical activity of the heart of an individual;

(3) FIG. 2 schematically represents a setting and power supply assembly of an artificial cardiac pump according to a particular embodiment of the invention;

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(4) First of all, note that the figures are not to scale.

(5) FIG. 1 schematically shows the different steps of the method for managing a cardiac pump as a function of the natural mechanical activity of the heart of an individual, according to a particular embodiment of the present invention.

(6) It is known that the contraction of the heart at rest follows an invariable sequence that can be followed by measuring the electrical activity of the heart. A curve 10 is then obtained of electrical signal as a function of time.

(7) The curve 10 which schematically represents the normal electrical activity of a human heart, essentially shows the wave P denoting the contraction of the atria of the heart, the QRS complex embodying the contraction of the ventricles and the wave T relating to the electrical repolarization of the ventricles.

(8) This electrical activity of the heart finds its corollary in the mechanical activity of the heart which will now be described for just the left ventricle of the heart with respect to a time axis 11.

(9) Initially, the left atrium fills with blood, the pressure therein being greater than the pressure in the left ventricle. Then, the left atrium contracts (wave P) and forces the passage of the blood to the left ventricle, the mitral valve opening to free this passage. After the time interval separating P and R, the left ventricle begins to contract, the pressure increasing and exceeding the pressure in the left atrium, the mitral valve recloses at the instant t.sub.1.

(10) However, the pressure in the left ventricle is not yet sufficient to open the aortic valve, the volume of the ventricular cavity not changing, so the term isovolumetric contraction applies.

(11) The pressure then continues to rise in the left ventricle until the aortic valve opens at an instant t.sub.physio, after the instant t.sub.1, to allow the blood contained in the left ventricle to be driven to the bodily circulation during a so-called ejection phase.

(12) This contraction phase ends with the closing of the aortic valve when the pressure in the left ventricle becomes lower than the arterial pressure is called the ventricular systole (time interval situated within the portion of electrical curve Q-T on the curve 10).

(13) The heart is, here, provided with a cardiac pump 13 making it possible to assist the weakened left ventricle in projecting the blood from the left ventricle through the aortic valve.

(14) This cardiac pump 13 is intended to send pressurized blood at a flow rate proportional to the speed of rotation V.sub.rpm of this pump 13 through the aortic valve.

(15) This artificial pump 13 here comprises an impeller inserted into the left ventricle through the heart wall, a sealing membrane making it possible to ensure a tight link for the impeller and the wall of the heart, this membrane being partly sutured onto the outer wall of the heart, with a casing secured, directly or indirectly, to the sealing membrane, this casing being placed in the left ventricle and with an electric motor intended to suck and discharge the blood from the bottom of the left ventricle.

(16) A management unit 14 making it possible to control this pump 13 is linked to the impeller by a wired link 15.

(17) This management unit 14 comprises an electrical power source 16 for powering this pump 13 and a central unit comprising processor and a storage unit. This central unit 17 also comprises a set of software instructions which, when they are executed by this processor, make it possible to implement a method for managing this cardiac pump 13.

(18) This management method here comprises a first step aiming to detect the instant t.sub.1 corresponding to the closing of the mitral valve, the speed of rotation V.sub.rpm of said pump 13 being kept at a value strictly less than a maximum value V.sub.rpm max of the speed of rotation of the pump 13.

(19) As represented in the curve 12, which shows the variation of the speed of rotation of the pump 13 as a function of time t, this speed of rotation value is equal to a minimum value V.sub.rpm min of the speed of rotation, which is determined to avoid any stagnation of the blood in the ventricle while minimizing the electrical consumption of the pump 13.

(20) Then, from this instant t.sub.1, the speed of rotation V.sub.rpm of the pump 13 is increased such that, at an instant t.sub.2, after the instant t.sub.1, the speed of rotation of the pump 13 is equal, or substantially equal, to its maximum rotation speed value V.sub.rpm max.

(21) Preferably, this increase in the speed of rotation of the pump 13 is progressive so as not to draw energy abnormally from the power source 16.

(22) The instant t.sub.2 is chosen here such that it corresponds to the opening of the aortic valve, the pump 13 having thus reached its maximum rotation speed value V.sub.rpm max to eject the blood through the aortic valve.

(23) As represented in FIG. 1, the speed of rotation of the pump 13 is then kept constant, and at this maximum value V.sub.rpm max, throughout the time period T during which the aortic valve is open so as to ensure a maximum ejection of the blood present in the left ventricle.

(24) When the aortic valve closes, that is to say at the instant t.sub.3, the speed of rotation of the cardiac pump 13 is progressively reduced to its minimum value V.sub.rpm min.

(25) Preferably, all of these steps are repeated for each next ventricular systole so as to optimize the energy of the power source 16 and reduce the time between two successive recharges of this power source 16.

(26) It has been observed that this method provided a significant advance in quality of life of the patient suffering from a cardiac insufficiency.

(27) Preferably, and to adapt automatically to the physical activities of the patient, equipped with such a cardiac pump 13, the electrical activity of the heart of this patient is measured so as to detect, prior to the performance of each first step of detection of the closing of the mitral valve, a ventricular depolarization of the heart of the patient.

(28) This depolarization measurement is performed through one or more ventricular electrodes 18, 18′.

(29) Such a measurement advantageously makes it possible to synchronize the different steps of the management method relative to the heart rate of the patient.

(30) Furthermore, and to address the metabolic needs of the patient, in the event of an effort, the maximum value V.sub.rpm max of the speed of rotation of the pump is adjustable and can therefore be increased to ensure a greater blood flow when necessary.