FR2784585A1 - Implantable cardiac prosthesis with independent ventricular chambers has rigid shell to protect deformable sacs of biocompatible material - Google Patents

Abstract

The prosthesis has independent ventricular chambers (10, 12) with inlet and expulsion valves, an actuating motor/pump (30) on a rigid wall (28), a supple membrane and a biocompatible floating membrane operated by a compliance fluid, and deformable sacs (32) of a biocompatible material, protected by a rigid shell (34). At least some of the prosthesis surfaces which are designed to make contact with the blood are covered with a layer of biocompatible metal (titanium) micro-balls 10 - 150 microns in size. It also contains a microprocessor module to regulate heart rhythm and amplitude and a stand-by battery.

Description

IMPLANTABLE HEART PROSTHESIS WITH VENTRICULAR CHAMBERS
INDEPENDENT
The present invention relates to implantable cardiac prostheses, intended to be implanted either temporarily or permanently, in the case of ventricular deficiency.

 Numerous implantable cardiac prostheses have already been proposed.

 The invention relates more particularly to implantable cardiac prostheses, connectable to the natural atria of a patient, of the type comprising two independent ventricular chambers each provided with a blood admission valve and a blood ejection valve and '' a clean actuation device consisting of a motor-pump group carried by a rigid wall, a flexible and non-extensible mechanical membrane displaceable by an actuating fluid transferred by the pump and a floating hemo-compatible membrane , separated from the mechanical membrane by a chamber filled with physiological liquid, the biocompatible membrane moving under the action of the compliance liquid discharged by the mechanical membrane from a diastolic position to a systolic position, in response to the transfer of the fluid actuation by the pump from a deformable bag to the mechanical membrane, and vice versa from the systolic position to the diastolic position.

 Such a prosthesis is described in document US-A5135539, to which reference may be made. It has the advantage of separating the function of confinement and movement of blood from mechanical functions, which makes it possible to use, for the floating membrane, a material having good hemo-compatibility but reduced mechanical characteristics, and, for the mechanical membrane, a material with superior mechanical properties.

 The deformable bag of the cardiac prosthesis according to document FR-A-2 625 903 is directly in contact with internal organs of the body. The presence of this bag, driven by an alternating inflation and deflation movement, can have unfavorable biological effects. The present invention aims in particular to eliminate this defect. It therefore proposes a cardiac prosthesis of the type defined above also comprising a rigid protective shell enclosing each deformable bag and made of a bio-compatible material (such as for example the titanium alloy known as TA6V), at least on its external face.

 The space between the deformable bag and the shell will be occupied by gas, the pressure of which must not undergo too sudden alternating variations. To do this, this space can be connected to the ambient atmosphere by transcutaneous route, by means of a filter preventing contamination, which is less to be feared because this compartment is isolated from the internal organs. Another solution is to connect the compartment to a pocket located near the lungs.

 Current biological membranes are made from pericardium fixed with glutaraldehyde. According to one embodiment of the invention, the biocompatible membrane consists of a sheet of plastic material, covered, on the face intended to be in contact with blood, with a mat of biocompatible metal microbeads ( titanium in general) with a particle size usually between 10 and 150 μm, embedded in the surface. These microbeads constitute a network of micron-sized cavities, in which the blood deposits fibrins which reconstitute tissue in a few tens of minutes. The shell can also be made of polysulfone coated with titanium microbeads on the face in contact with the organs or in another bio-compatible material such as a titanium alloy. In general, the coating treatment can advantageously be applied to all the pieces of non-"biological" material in contact with the blood or the tissues. The body, the caps and more generally the rigid parts can be made of biocompatible metal.

 The invention also provides a device for controlling, supplying and possibly monitoring the operation of the prosthesis, comprising an internal implanted module, containing a microprocessor for adjusting the heart rate and amplitude, and a backup accumulator, allowing the wearer of the prosthesis to temporarily free himself from any external power supply, and an external module. The external module is connected to the internal module by the transcutaneous or percutaneous route and includes a rechargeable accumulator.

 The internal and external modules are advantageously provided to allow a transfer of information on the same electrical conductors as those which are used for recharging the internal accumulator, in particular by carrier currents. The external module, designed to be worn for example on a belt or in a satchel, can be provided with diagnostic and / or alarm means and with a warning light or horn.

 The external source may have sufficient capacity to require recharging only at spaced time intervals of several hours.

 Power supply by carrier currents can be provided in particular at a frequency between 100 and 500 kHz.

 The power required for an adult is generally between 20 and 50 W, depending on whether he is at rest or active. To meet these power needs, it is currently preferable to use a transcutaneous connection by a waterproof electrical connector, with two wires only when the data connections with the outside are carried out by carrier currents or another technique. not requiring additional wires. However a percutaneous connection by inductive route is also possible.

 A prosthesis of the above kind makes it possible to have both independent ventricular chambers, independent right and left actuations, surfaces in contact with biological blood or made biological and "intelligent" control of blood flow.

The above characteristics as well as others will appear better on reading the following description of a particular embodiment of the invention, given by way of nonlimiting example. The description refers to the accompanying drawings, in which:
FIG 1 is a schematic sectional view of a prosthesis according to the invention. The elements framing the central module being in place only on one side;
FIGS. 2 and 3 show a prosthesis according to the invention, respectively in elevation and in top view, without the shell;
FIG. 4 is a view on the left showing a central module of the prosthesis of FIG. 1, on which the partitions carrying the pump motors, the deformable bags and the shell are connected;
FIG. 5 is a perspective view of a possible shell shape of a prosthesis according to the invention;
FIG. 6 is a top view of the shell; and
FIG. 7 is a block diagram showing a possible constitution of the supply device;
The basic principle of the prosthesis appears in FIGS. 1 to 4. It comprises a central module 10 delimiting two independent ventricular chambers 12 and 14, the bottom of which is in the form of a spherical cap, each provided with an inlet valve 16 or 18. These valves are carried by flanges allowing the module to be connected to the atria of the natural heart muscle, for example by means of glasses or sutured monocles on the atria. Each chamber also communicates with the outside via an ejection tube, not visible in FIG. 1, intended to be connected either to the pulmonary artery or to the aorta. An ejection valve is provided between the tubes connected to the arteries and the corresponding ventricles.

 FIG. 1 shows that each ventricular cavity is limited by a floating biological membrane 20, the periphery of which is tightly retained on a shoulder formed in the central module.

 Behind each biological membrane 20 is placed a mechanical membrane 22, the periphery of which is also tightly connected to the module. The membranes 20 and 22 delimit between them a pressure transmission compartment 24. When the prosthesis is used, this compartment is occupied by physiological liquid. It can be filled using a tube 25 which is then welded. The mechanical membranes 22 are made of flexible material, but not extensible, having good mechanical properties, for example nitrile, latex or polyurthane.

 The biological membrane 20 must be hemocompatible, at least on its face in contact with the blood. For this, it can be constituted in the traditional way by a fragment of properly treated beef or pork pericardium. It can also be constituted by a membrane whose face delimiting the compartment 12 or 14 has been treated by inlaying a mat of titanium microbeads, as indicated above.

 Means are provided for detecting at least approximately the position of each membrane 22. In the case illustrated in FIG. 1, these means comprise magnets 26 fixed to the mechanical membranes and cooperating with sensors 27 placed in the central module 10. (sensors Hall effect for example).

 Each deformable membrane 22 defines a variable volume with a partition 28 which carries a motor-pump group 30. The pump of each group makes it possible to pass liquid, which will generally be a non-toxic oil, between a compartment 29 delimited by the partition 28 and the membrane 22 and a variable volume compartment delimited by the partition 28 and a bag 32 of oil reserve. This bag 32 must be able to stretch and retract and for this reason will generally be made of elastomer. The wall 28, which need not be biocompatible, could be made of a synthetic material, such as a polysulfone or a metal such as a titanium alloy (for example TA6V). It will have a thickness sufficient to be rigid.

 Each motor-pump group 30 is reversible. It can use a motor with electronic switching and integrated power circuit, achievable in a relatively small volume.

 The bags 32 are enclosed in a rigid shell 34 which is connected to the central module 10. The space between the shell 34 and each bag 32 is occupied by a gas. To limit the pressure variations in this intermediate space, during liquid transfers, it can be connected to the ambient atmosphere by means of a narrow conduit 38, fitted with a filter. These spaces can also be connected to an implanted pocket, for example under the lungs.

 Figures 2 to 4, in which the elements corresponding to those of Figure 1 bear the same reference number, show the essential parts of the prosthesis. In these figures appear tubes 36 and 38 each opening into one of the chambers 12 and 14 and intended to be sutured moon 36 to the aorta and the other 38 to the pulmonary artery. Pressure taps (fig. 4) make it possible to measure the pressure prevailing in chamber 24 and to deduce the pressure of the blood therefrom. The groups are provided with rotation sensors making it possible to know at any time the flow transferred to and from the chamber 24, therefore to constitute an input signal of a loop for regulating the blood flow. This blood flow regulation loop, or medical regulation algorithm, is based on a simulation of the heart muscle based on time, volume and above all pressure. This simulation is inspired by the Starling principle. It allows the prosthesis to automatically adapt the blood flow to the physiological needs of the patient. The sensors and the power supplies of the motors can be grouped in a connector 40 (FIG. 2).

 The rigid shell 34 may have the appearance shown in FIG. 5. It then has a large opening 42 for introducing the central module 10 and holes for the fixing screws of this module. Its shape can be chosen to allow it to fit into the thoracic cavity as well as possible. The shell may further comprise a titanium fork, which can be described as a spine support leg, allowing the prosthesis to be fixed on the patient's spine.

The electromechanical part of the cardiac prosthesis is supplied and controlled by a supply system which can have the constitution shown in FIG. 7. This system can be regarded as having:
-a module 50 implantable in the abdomen, supply and control,
an external power supply module 52, designed to be worn by the patient, for example over the shoulder or on the belt, connected to the module 40 by a two-wire transcutaneous connector 54.

 These modules are periodically recharged with energy by a fixed supply console 56 supplied by the sector and provided with a connector 58.

 The implantable module 50 contains a backup battery 60 and a charger 62 intended to maintain the backup battery 60 in the fully charged state as long as the connector 54 is plugged in, being able to ensure an autonomy of a few tens of minutes when the connector is disconnected. The voltages necessary for operation are obtained from the backup battery 60 or from a battery 70 belonging to the external module 52, by a direct current switch 66 and a converter 68.

 The output signals from the sensors carried by the prosthesis are used to modulate carrier currents, using means not shown. A modem 72 contained in the external module 52 makes it possible to put these signals in a form enabling them to be transmitted over a telephone or other link.

 The means of energy conversion, power supply, communication interface and monitoring can be present both in the implantable module and in the console, so that it is the console which performs the various functions when the connection is carried out. Two consoles are advantageously provided, the operation console and the patient console. The first is for the hospital. It is used in particular during implantation for starting the prosthesis, then allows the doctor to gradually adapt its operation according to the improvement in the patient's condition. The patient console is a portable module that allows the recipient to quickly diagnose the prosthesis and prevent it in the event of a problem. This console can be provided to automatically notify an emergency intervention center by radio call.

 The purpose of the monitoring function is in particular to give the wearer of the prosthesis information which can be displayed in the form of indicators on the external module. For example, the external module can be designed to include an indicator and an audible warning device which comes into action when the backup battery is partially discharged and (or) as soon as the prosthesis is powered by the internal battery 60. Faults can also be signaled by a warning light or an audible warning.

Claims (9)

 1. Implantable cardiac prosthesis comprising two independent ventricular chambers (10,12) each provided with a blood admission valve and a blood ejection valve and with its own actuation device made up of a group motor-pump (30) carried by a rigid wall (28), a flexible and non-extensible mechanical membrane displaceable by an actuating fluid transferred by the pump and a floating biocompatible membrane, separated from the mechanical membrane by a chamber (24) filled with compliance liquid, the bio-compatible membrane moving under the action of the compliance liquid discharged by the mechanical membrane from a diastolic position to a systolic position, in response to the transfer of the fluid actuation by the pump from a deformable bag to the mechanical membrane, and conversely from the systolic position to the diastolic position, characterized by a rigid protective shell (34) enclosing the deformable bags (3 2), made of biocompatible material.  2. Prosthesis according to claim 1, characterized in that at least some of the surfaces intended to be in contact with the blood are covered with a layer of microbeads of biocompatible metal, with a particle size between 10 and 150 μm, embedded in the surface.  3. Prosthesis according to claim 2, characterized in that the microbeads are made of titanium.  4. Prosthesis according to claim 1,2 or 3 characterized in that the space between the rigid shell (34) and each deformable bag (32) is connected to the environment by means of a filter or connected to an implanted pocket.  5. Prosthesis according to any one of the preceding claims, characterized in that it comprises an implanted module, containing a microprocessor for adjusting the rhythm and the cardiac amplitude and an electrical backup accumulator, as well as a portable external module. connected to the internal module by transcutaneous or percutaneous route, containing a rechargeable accumulator.  6. Prosthesis according to claim 5, characterized in that the module implements a blood flow regulation loop based on a simulation of the heart muscle based on input time, volume and pressure, allowing the prosthesis to automatically adapt the blood flow to the physiological needs of the wearer.  7. Prosthesis according to claim 5 or 6, characterized in that the internal and external modules are provided to allow a transfer of information on the electrical conductors than those which are used for recharging the internal accumulator.  8. Prosthesis according to claim 7, characterized in that the transfer of information is carried out by carrier current.  9. Prosthesis according to any one of claims 5 to 8, characterized in that the external module is provided with diagnostic and alarm means as well as an indicator or audible warning.